STUDIES AND EVALUATION OF METHODOLOGY

USED IN FERMENTATION OF BEER

Major project report submitted towards partial fulfillment of the requirements

for the degree of

BACHELOR OF TECHNOLOGY

IN

FOOD TECHNOLOGY

Submitted To

AMITY UNIVERSITY, UTTAR PRADESH

BY

MR. ARVIND PATI TRIPATHI

B.TECH FOOD TECHNOLOGY (2008-12)

ENROLMENT NO- A4312608009

Under the guidance of

MR.ANKIT PALIWAL

Assistant Professor, AIFT

AMITY INSTITUTE OF FOOD TECHNOLOGY

I-1 BLOCK, 4TH FLOOR, AMITY UNIVERSITY

SECTOR-125, NOIDA 201303, U.P.

JUNE 2012

ACKNOWLEDGEMENT

I take this opportunity to express my sincere thanks & deep gratitude to all those people who

extended their whole hearted co-operation & have helped me in completion of this project

successfully. This project is an effort to contribute towards achieving the desired objectives.

It is my heartfelt honor to thank MR. ANKIT PALIWAL faculty & project guide. This project

would not have seen the light of the day but for her sustained direction, supervision &

continuous encouragement that saw us sail through the difficulties faced.

I wish to extend my thanks to all the respected employees of MOHAN MEAKINS LTD.,

SOLAN BREWERY for their invaluable help without which, I would not have been able to

complete this project. My earnest & intense sense of gratitude to MR. S.R.S. PATHANIA

(C.E.O.), MR. J.P. DUTTA (HEAD BREWER), MR. P.K. GHOSH (BREWER), MR.

RAJNISH BEHL (QUALITY HEAD), MR. SATISH AGNIHOTRI (ASSISTANT

BREWER) & MR. YOGINDER SHARMA (FERMENTATION HEAD).

Last but not the least I would like to thank my family members & friends who stood by me &

gave constant strength & support whenever I lacked in them.

(……………..…………)

Place: Noida Arvind Pati Tripathi

Date: __\__\__ B.Tech Food Technology

(2008-2012, 8thsem)

ABSTRACT

Fermentation in brewing is the conversion of carbohydrates to alcohols and carbon dioxide or

organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions.

Fermentation happens in tanks which come in all sorts of forms, from enormous cylindro-conical

vessels, through open stone vessels, to wooden vats.

Yeast is single-celled microorganisms that reproduce by budding. They are biologically

classified as fungi and are responsible for converting fermentable sugars into alcohol and other

byproducts. There are literally hundreds of varieties and strains of yeast. In the past, there were

two types of beer yeast: ale yeast (the "top-fermenting" type, Saccharomyces cerevisiae) and

lager yeast (the "bottom-fermenting" type, Saccharomyces uvarum, formerly known as

Saccharomyces carlsbergensis). Today, as a result of recent reclassification of Saccharomyces

species, both ale and lager yeast strains are considered to be members of S. cerevisiae. 

1:TOP-FERMENTINGYEAST

Ale yeast strains are best used at temperatures ranging from 10 to 25°C, though some strains will

not actively ferment below 12°C. Ale yeasts are generally regarded as top-fermenting yeasts

since they rise to the surface during fermentation, creating a very thick, rich yeast head. That is

why the term "top-fermenting" is associated with ale yeasts.

2:BOTTOM-FERMENTINGYEAST

Lager yeast strains are best used at temperatures ranging from 7 to 15°C. At these temperatures,

lager yeasts grow less rapidly than ale yeasts, and with less surface foam they tend to settle out to

the bottom of the fermenter as fermentation nears completion. This is why they are often referred

to as “bottom” yeasts. Some of the lager styles made from bottom-fermenting yeasts are Pilsners,

Dortmunders, Märzen, Bocks, and American malt liquors.

TABLE OF CONTENT

S.NO. CONTENT PAGE NO.

1 INTRODUCTION 1

2 COMPANY OVERVIEW 2

3 OBJECTIVE 5

4 REVIEW OF LITERARURE 6

4.1.1 FERMENTATION 6

4.1.2 TYPES OF FERMENTATION 8

4.2 YEAST 10

4.2.1 BREWER’S YEAST 11

4.2.2 YEAST LIFECYCLE 14

4.2.3 YEAST NUTRITIONAL REQUIREMENTS 16

4.2.4 YEAST BY PRODUCTS 17

4.2.5 YEAST STRAIN SELECTION 19

4.2.6 PURE CULTURE MAINTENANCE 21

4.2.7 YEAST PROPAGATION & SCALEUP 23

4.2.8 YEAST CULTURE CONTAMINATION 25

4.2.9 YEAST WASHING 26

4.2.10 YEAST VIABILITY & REPLACEMENT 27

4.2.11 YEAST STORAGE 28

4.2.12 YEAST MANAGEMENT 29

4.3 BEER FERMENTATION 30

4.3.1 PITCHING BEER YEAST 32

4.3.2 LAGER FERMENATION 33

4.3.3 ALE FERMENTATION 34

4.3.4 CHANGES DURING FERMENTATION 36

4.3.5 YEAST COLLECTION 37

4.3.6 FERMENTATION SYSTEMS 38

4.4 BEER CONDITIONING 41

4.4.1 BEER MATURATION 41

4.4.2 BEER CLARIFICATION 43

4.4.3 BEER STABILIZATION 44

4.4.4 BEER CONDITIONING TANKS 45

4.5 BEER FILTRATION 46

4.5.1 FILTRATION METHODS 47

4.5.2 POWDER FILTERS 48

4.5.3 POWDER FILTER AIDS 50

4.6 BEER CARBONATION 52

4.6.1 METHODS OF CARBONATION 53

4.7 BREWERY CLEANING & SANITIZATION 54

5 MATERIALS & METHODS 59

6 RESULT & DISCUSSION 63

7 RECOMMENDATION & CONCLUSION 72

8 BIBLIOGRAPHY 73

1: INTRODUCTION

Beer is the world’s oldest and most widely consumed alcoholic beverage and the third most

popular drink overall after water and tea. It is produced by the brewing and fermentation of

starches, mainly derived from cereal grains – the most common of which is malted barley,

although wheat, maize/corn, and rice are commonly used [Rose A. H, 1961], The French

chemists Louis Pasteur was the first zymologists, in 1857 , he connected yeast to fermentation.

Pasteur originally defined fermentation as respiration without air; Pasteur performed carefully

research and concluded that alcoholic fermentation never occurs without simultaneous

organization, development and multiplication of cells.

German chemist and Zymologist, Edward Buchher, winner of 1907 Noble prize in chemistry,

later determined that fermentation is actually caused by a yeast secretion that he termed

zymase[Voet et al, 1995].

The most common Microorganism used in the fermentation of beer is the yeast

(Saccharomyces). The quality of brewing yeast is judged ultimately by the quality of the beer it

produced. It is clear that the quality of brewing yeast depends not only upon its intrinsic

characteristics but also upon the environment provided by the Brewer – Particularly the type of

wort and other fermentation condition. Thorne in 1972 has developed a scheme by which

brewing yeast can be adequately and usually described in terms of the brewing characteristics

rate and extend of growth rate, extent of fermentation, flocculence , flavor and aroma of beer

produced, Adequate growth at an adequate rate is needed for a normal fermentation [Thorne

R.S.W, 1972].

2: COMPANY OVERVIEW

Mohan Meakin is a large group of companies started with Asia's first brewery incorporated in

1855 (but established much earlier) by Edward Dyer at Kasauliin the Himalayan

Mountains in India under the name Dyer Breweries.

In the late 1820s, Edward Dyer moved from England to set up the first brewery in India (later

incorporated as Dyer Breweries in 1855) at Kasauli in the Himalayan Mountains. The Kasauli

brewery launched India's and indeed Asia's first beer, Lion, which was in great demand by the

thirsty British administrators and troops stationed in the sweltering heat of India. Lion was much

appreciated as a beer, and one famous poster featured a satisfied British Tommy declaring, "as

good as back home!".

The brewery was soon shifted to nearby Solan (close to the British summer capital Shimla), as

there was an abundant supply of fresh spring water there. The Kasauli brewery site was

converted to a distillery, which Mohan Meakin Ltd. still operates. Dyer set up more breweries at

Shimla, Murree (Murree Brewery), Rawalpindi, Mandalay, Quetta and acquired interests in

the Ootacamund Brewery (South India).

Another entrepreneur, H G Meakin, moved to India and bought the old Shimla and Solan

Breweries from Edward Dyer and added more

at Ranikhet, Dalhousie, Chakrata, Darjeeling, Kirkee and NuwaraEliya (Ceylon). After the First

World War, the Meakin and Dyer breweries merged and in 1937, when Burma was separated

from India, the company was restructured with its Indian assets as Dyer Meakin Breweries, a

public company on the London Stock Exchange.

Following independence, N.N. Mohan raised funds and travelled to London where he acquired a

majority stake in Dyer Meakin Breweries. He took over management of the company in 1949

and built new breweries at Lucknow, Ghaziabad and Khopoli (near Mumbai). The company

name was changed to Mohan Meakin Breweries in 1967 (the word "Breweries" was dropped in

the eighties as the company diversified into other industries).

On the death of N.N. Mohan in 1969, his eldest son Colonel V.R. Mohan took over as Managing

Director. He introduced a number of new products that are brand leaders today but died in 1973,

soon after taking the helm. In the 1970s the manufacturing activities of the company were

diversified into other fields including breakfast cereals, fruit juices and mineral water under the

leadership of Brigadier(Dr.)Kapil Mohan V.S.M link title (Col. V.R. Mohan's brother).

Subsequently the word brewery was dropped from the company name in 1982 to remove the

impression that the company was engaged only in beer making. New breweries were built during

the seventies and eighties at Chandigarh, Madras, Nepal and Kakinada near Hyderabad.

Today, Mohan Meakin's principal brands are Old Monk Rum and Golden Eagle Beer. Its other

products include Diplomat Deluxe, Colonel's Special, Black Knight, Meakin 10,000, Summer

Hall and Solan No 1 whiskies, London Dry and Big Ben gins, and Kaplanski vodka. Asia’s

original beer, Lion, is still sold in northern India.

Lion Beer is the main brand first sold by Dyer Breweries in the 1840s. Lion was originally an

IPA (India Pale Ale - which makes it the oldest IPA brand still in existence) but the beer style

was changed in the 1960s to a lager. Lion remained the number one beer in India for over a

century from the 1840s until the 1960s. After this another Mohan Meakin brand, "Golden

Eagle", took the number one spot until the 1980s, when Kingfisher became number one. By

2001, Lion sales had declined substantially and Lion was only available to the Indian Army

through the CSD (Canteen Services Department). Mohan Meakin then entrusted the marketing of

their original beer to International Breweries Pvt. Ltd. The brand has since been relaunched in

the north Indian market. With a new label design and marketing campaign, Lion has established

itself once more in the civilian market and is now expanding into markets across India.

Lion earns a place in history as Asia's first beer brand. Lion's popularity with the British during

the heyday of the Empire led to the start-up of other Lion beers around the world, in New

Zealand, South Africa and elsewhere. Lion remains the number one brand in neighbouring Sri

Lanka where Mohan Meakin had introduced it in the 1880s through their Ceylon brewery.

Australian is another popular 5% abv lager distributed by International Breweries (P) Ltd. The

8% abv version is called Australian MAX. Australian MAX has recently won the title of the

"World's Best Strong Lager" at the World Beer Awards. Australian MAX beat the best

strong beers from Germany, England, USA, Belgium, Denmark and from all over the

world. This is the highest honour ever awarded to a beer brewed in India.

Old Monk is a vatted Indian Rum, blended and aged for 7 years (though there is also more

expensive, 12 year old version). It is dark, with an alcohol content of 42.8%. It is produced by

Mohan Meakin, based in Mohan Nagar, Ghaziabad, Uttar Pradesh.

It is available in all parts of India. Old Monk is also the third largest selling Rum in the world.

Old Monk has been the biggest Indian Made Foreign Liquor (IMFL) brand for many years.[1]

It is sold in four size variants 180 ml (quarter), 350 ml (half), 750 ml (full), and a 1 liter bottle.

ALCOHOLIC PRODUCTS

WHISKIES BEERS

Summer Hall

Colonel's Special

Golden Eagle

Top Brass

Diplomat Deluxe

Black Knight

Solan No.1

Cellar 117

MMB

Blue Bull

BRANDIES

Triple Crown

Doctor's Reserve

No.1

D.M.

MMB

GINS

Big Ben London

(Export Quality)

Golden Eagle

Lager

Golden Eagle

Deluxe Premium

Lager

Gold Lager Beer

(Herbal Beer)

Golden Eagle

Super Strong Beer

Gymkhana

Premium Lager

Asia 72 Extra

Strong Lager

Black Knight

Super Strong

Solan No.1

Premium Beer

I Q Beer

Lion Beer

Meakins 10000

Super Strong

Old Monk Super

Strong

RUMS

Old Monk

Supreme Rum

Old Monk Gold

Reserve Rum

Old Monk XXX

Rum

Old Monk Deluxe

XXX Rum

Old Monk White

Rum

NON-ALCOHOLIC PRODUCTS

JUICES

Mohun's Gold

Coin Apple Juice

VINEGARS

Mohun's Brewed

Vinegar

Mohun's Non-

Fruit Vinegar

MINERAL

WATER

Golden Eagle

Mineral Water

Mohun's Mineral

Water

BREAKFAST

FOODS

Mohun's New

Life Corn Flakes

Mohun's Wheat

Porridge

Mohun's Wheat

Flakes

Mohun's Wheat

Dalia

MANUFACTUR

ES

Glass Bottles

EXTRACTS Malt Extract

EXPORTS Beer, Rum,

Whisky, Brandy

& Gin.

3: OBJECTIVE

1.) To Study the basic working principle of fermentation science.

2.) To Study the various equipment used in the beer fermentation.

3.) To Study problems of the existing fermentation process of Brewery.

4.) To improve the efficiency of the Existing fermentation process.

5.) To study the microorganisms (yeast) used & it affects in the fermentation of beer.

6.) To study the step by step procedure of beer fermentation.

4:REVIEW OF LITERATURE

4.1: FERMENTATION

Fermentation in food processing typically is the conversion of carbohydrates to alcohols and

carbon dioxide or organic acids usingyeasts, bacteria, or a combination thereof,

under anaerobic conditions. Fermentation in simple terms is the chemical conversion

of sugarsinto ethanol. The science of fermentation is also known as zymology, or zymurgy.

Fermentation usually implies that the action of microorganisms is desirable, and the process is

used to produce alcoholic beverages such as wine, beer, and cider. Fermentation is also

employed in the leavening of bread (CO2 produced by yeast activity), and for preservation

techniques to produce lactic acid in sour foods such as sauerkraut, dry

sausages, kimchi and yogurt, or vinegar (acetic acid) for use inpickling foods.

French chemist Louis Pasteur was the first known zymologist, when in 1856 he connected yeast

to fermentation. Pasteur originally defined fermentation as "respiration without air". Pasteur

performed careful research and concluded:

"I am of the opinion that alcoholic fermentation never occurs without simultaneous organization,

development and multiplication of cells, If asked, in what consists the chemical act whereby the

sugar is decomposed, I am completely ignorant of it."

When studying the fermentation of sugar to alcohol by yeast, Louis Pasteur concluded that the

fermentation was catalyzed by a vital force, called "ferments," within the yeast cells. The

"ferments" were thought to function only within living organisms. "Alcoholic fermentation is an

act correlated with the life and organization of the yeast cells, not with the death or putrefaction

of the cells,"he wrote.

Nevertheless, it was known that yeast extracts can ferment sugar even in the absence of living

yeast cells. While studying this process in 1897, Eduard Buchner of Humboldt University of

Berlin, Germany, found that sugar was fermented even when there were no living yeast cells in

the mixture, by a yeast secretion that he termed zymase. In 1907 he received the Nobel Prize in

Chemistry for his research and discovery of "cell-free fermentation."

One year prior, in 1906, ethanol fermentation studies led to the early discovery of NAD + .

In 1892 Delbruck give the idea of continuous fermentation A one-stage continuous primary beer

fermentation with immobilized brewing yeast was studied. The objective of the work was to

optimize the operational conditions (Aeration and temperature) in terms of volumetric

productivity and organoleptic quality of green beer. The system consisted of an internal –loop

airlift reactor and a carrier material prepared from spent grains (a brewery by –product)

industrialwortand yeast strains were used. The immobilized biomass contributed 45 % to 75 % to

the total fermentation. The volumetric productivity of the continuous system was as much as

give times higher than that of the batch fermentation [Branyik, Tomas et al, 2004] In 1857,

Pasteur published the result of his studies and concluded that fermentation is associated with the

life and structural integrity of yeast cell. Yeast cell is a living organism & the fermentation

process is essential for reproduction and survival of the cell. During the course of his study

Pasteur was also able to establish not only that alcohol which produced by yeast through

fermentation but also that souring was consequence of contamination with bacteria that were

capable of converting alcohol to acetic acid so for avoiding souring Pasteur do heat treatment at a

certain temperature for a given length of time, thus eliminated the bacteria without adversely,

affecting the organoleptic quantities of the beer is process we know as

“Pasteurization”[ E.M.T.El –Mensi al. al, 1877].

Beer is a poor and rather hostile environment for most Microorganisms, its ethanol concentration

and low PH is lower than most bacteria can tolerate for growth, Beer also contain bitter hop

compounds, which are toxic only a few bacteria are ale to grow under such inhospitable

condition and are able to spoil beer, [Adult, R.G and R.Newton, 1971]. Amaha et.al.. 1974

isolated and characterized chemical entities produced by growing mycelium ofRhizopus or

Fursariumin germinated barley.

Bacteria:[Pristet. Al. 1974], conclude that bacteria most commonly associated with barley in

the field are divided into three groups – Lactic acid bacteria, Enterobacteria& Pseudomonas,

During mashing and lautering a few thermophilic lactic acid bacteria can grow e.g.

Lactobacillus a Gram positive homofermentative, thermophilic rod with an optimum growth

temperature of 45oC, but it can grow at a temperature as high as 54oC, if the temperature of mash

tunwort should fall into this range, this organism will grow rapidly, resulting in spoilage of the

product, Similarly, Pediococcus is a gram positive homofermentative, thermophilic occurs with

and optimum temperature for growth of 40oC and a maximum temp for growth of 52oC. The

Citrobacter, Klebsiella, Hafnia, Serratia, They are gram negative rods which are non –

pathogenic. They are widely distributed in nature occurring in soil and water also spoils beer,

[Priest et. al, 1974; Van Vurenet. Al, 1978].

4.1.2: TYPES OF FERMENTATION

1: LACTIC ACID FERMENTATION

Lactic acid fermentation is a biological process by which sugars such as glucose, fructose,

and sucrose, are converted into cellular energy and the metaboli lactate. It is

an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle

cells. If oxygen is present in the cell, many organisms will bypass fermentation and

undergo cellular respiration; however, facultative anaerobic organisms will both ferment and

undergo respiration in the presence of oxygen. Lactate dehydrogenase catalyzes the

interconversion of pyruvate and lactate with concomitant interconversion of NADH and NAD + .

In homolactic fermentation, one molecule of glucose is ultimately converted to two molecules of

lactic acid. Heterolactic fermentation, in contrast, yieldscarbon dioxide and ethanol in addition to

lactic acid, in a process called the phosphoketolase pathway.

the process of lactic acid fermentation using glucose is summarized below. In homolactic

fermentation, one molecule of glucose is converted to two molecules of lactic acid:

C6H12O6 → 2 CH3CHOHCOOH

In heterolactic fermentation, the reaction proceeds as follows, with one molecule of glucose

converted to one molecule of lactic acid, one molecule of ethanol, and one molecule of carbon

dioxide:

C6H12O6 → CH3CHOHCOOH + C2H5OH + CO2

Before lactic acid fermentation can occur, the molecule of glucose must be split into two

molecules of pyruvate. This process is called glycolysis.

2: ALCOHOLIC FERMENTATION

Ethanol fermentation, also referred to as alcoholic fermentation, is a biological process in

which sugars such as glucose, fructose, and sucrose are converted into cellular energy and

thereby produceethanol and carbon dioxide as metabolic waste products. Because yeasts perform

this conversion in the absence of oxygen, ethanol fermentation is classified as anaerobic.

Ethanol fermentation occurs in the production of alcoholic beverages and ethanol fuel, and in the

rising of bread dough.

The chemical equations below summarize the fermentation of sucrose, whose chemical

formula is C12H22O11. One mole of sucrose is converted into four moles of ethanol and four moles

of carbon dioxide:

C12H22O11 +H2O + invertase →2 C6H12O6

C6H12O6 + Zymase → 2C2H5OH + 2CO2

C2H5OH is the chemical formula for ethanol. Before fermentation takes place,

one glucose molecule is broken down into two pyruvate molecules. This is known

as glycolysis. Glycolysis is summarized by the chemical equation:

C6H12O6 + 2 ADP + 2 Pi + 2 NAD+ → 2 CH3COCOO− + 2 ATP + 2 NADH + 2 H2O + 2H+

The chemical formula of pyruvate is CH3COCOO−. Pi stands for the inorganic phosphate. As

shown by the reaction equation, glycolysis causes the reduction of two molecules

of NAD +  to NADH. TwoADP molecules are also converted to two ATP and two water

molecules via substrate-level phosphorylation.

4.2: YEAST

Yeast is single-celled microorganisms that reproduce by budding. They are biologically

classified as fungi and are responsible for converting fermentable sugars into alcohol and other

byproducts. There are literally hundreds of varieties and strains of yeast. In the past, there were

two types of beer yeast: ale yeast (the "top-fermenting" type, Saccharomyces cerevisiae) and

lager yeast (the "bottom-fermenting" type, Saccharomycesuvarum, formerly known as

Saccharomycescarlsbergensis). Today, as a result of recent reclassification of Saccharomyces

species, both ale and lager yeast strains are considered to be members of S. cerevisiae. 

FIG: YEAST CELL

FIG: BUDDING

BIOLOGY OF YEAST

LIFE CYCLE

There are two forms in which yeast cells can survive and grow: haploid and diploid.

The haploid cells undergo a simple life cycle of mitosis and growth, and under

conditions of high stress will, in general, die. The diploid cells (the preferential 'form' of

yeast) similarly undergo a simple life cycle of mitosis and growth, but under conditions

of stress can undergo sporulation, entering meiosis and producing a variety of

haploid spores, which can proceed on to mate.

MATING

Yeast has two mating types, a and α (alpha), which show primitive aspects of sex

differentiation, and are, hence, of great interest. For more information on the biological

importance of these two cell types, where they come from (from a molecular biology

point of view), and details of the process of mating type switching, see Mating of yeast.

CELL CYCLE

Growth in yeast is synchronised with the growth of the bud, which reaches the size of the

mature cell by the time it separates from the parent cell. In rapidly growing

yeast cultures, all the cells can be seen to have buds, since bud formation occupies the

whole cell cycle. Both mother and daughter cells can initiate bud formation before cell

separation has occurred. In yeast cultures growing more slowly, cells lacking buds can

beseen, and bud formation only occupies a part of the cell cycle. The cell cycle in yeast

normally consists of the following stages – G1, S, G2, and M – which are the normal

stages of mitosis.

4.2.1: BREWERS YEAST

1: ALE YEAST

Ale yeast strains are best used at temperatures ranging from 10 to 25°C, though some strains

will not actively ferment below 12°C. Ale yeasts are generally regarded as top-fermenting

yeasts since they rise to the surface during fermentation, creating a very thick, rich yeast head.

That is why the term "top-fermenting" is associated with ale yeasts. Fermentation by ale

yeasts at these relatively warmer temperatures produces a beer high in esters and higher

alcohols, which many regard as a distinctive character of ale beers.

EXAMPLE: Saccharomycescerevisiae is a species of yeast. It is perhaps the most useful yeast,

having been instrumental to baking and brewing since ancient times. It is believed that it was

originally isolated from the skin of grapes (one can see the yeast as a component of the thin

white film on the skins of some dark-colored fruits such as plums; it exists among the  waxes of

the cuticleIt is the microorganism behind the most common type

of fermentation.S. cerevisiae cells are round to ovoid, 5–10 micrometres in diameter. It

reproduces by a division process known as budding.

Saccharomyces cerevisiae is currently the only yeast cell that is known to have Berkeley

bodies present, which are involved in particular secretory pathways.

"Saccharomyces" derives from Latinized Greek and means "sugar mold" or "sugar

fungus", saccharo- being the combining form "sugar-" and myces being

"fungus". Cerevisiae comes from Latin and means "of beer". Other names for the organism are:

S. cerevisiae short form of the scientific name

Brewer's yeast , though other species are also used in brewing

Ale yeast

Top-fermenting yeast

Baker's yeast

Budding yeast

This species is also the main source of nutritional yeast and yeast extract.

Saccharomycescerevisiae is used in brewing beer, when it is sometimes called a top-

fermenting or top-cropping yeast. It is so called because during the fermentation process its

hydrophobic surface causes the flocs to adhere to CO2 and rise to the top of the fermentation

vessel. Top-fermenting yeasts are fermented at higher temperatures than lager yeasts, and the

resulting beers have a different flavor than the same beverage fermented with lager yeast. "Fruity

esters" may be formed if the yeast undergoes temperatures near 21 °C (70 °F), or if the

fermentation temperature of the beverage fluctuates during the process. Lager yeast normally

ferments at a temperature of approximately  5 °C (41 °F), where Saccharomyces

cerevisiae becomes dormant. Lager yeast can be fermented at a higher temperature to create a

beer style known as "steam beer".

2: LAGER YEAST

Lager yeast strains are best used at temperatures ranging from 7 to 15°C. At these

temperatures, lager yeasts grow less rapidly than ale yeasts, and with less surface foam they

tend to settle out to the bottom of the fermenter as fermentation nears completion. This is why

they are often referred to as "bottom" yeasts. The final flavor of the beer will depend a great

deal on the strain of lager yeast and the temperatures at which it was fermented but lager

yeasts generally produce greater quantities of hydrogen sulfide and other sulfur compounds.

EXAMPLE: Saccharomyces pastorianus is ayeast, used industrially for the production

of lager beer. It is a synonym of the yeast species Saccharomyces carlsbergensis, which was

originally described in 1883 by Emil Christian Hansen, who was working for

the Danish brewery Carlsberg.

The genomic difference between S. pastorianus and S. cerevisiae is responsible for a number of

phenotypic traits which S. pastorianus shares with S. bayanus, but not S. cerevisiae. The ability

of S. pastorianus to break down melibiose is dependent on up to ten MEL genes, which are

exclusive to strains metabolisingmelibose such as S. bayanus. S. pastorianus never grows

above 34 °C (93 °F), whereas S. cerevisiae will grow at 37 °C (99 °F). S. pastorianus exhibits a

higher growth rate than S. cerevisiae at 6 to 12°C.

4.2.2:YEAST LIFE CYCLE

The life cycle of yeast is activated from dormancy when it is added (pitched) to the wort.

Yeast growth follows four phases, which are somewhat arbitrary because all of the phases

may overlap in time: 1) the lag period, 2) the growth phase, 3) the fermentation phase, and 4)

the sedimentation phase.

1: LAG PHASE

Reproduction is the first great priority upon pitching, and the yeast will not do anything

else until food reserves are built up. This stage is marked by a drop in pH because of the

utilization of phosphate and a reduction in oxygen. Glycogen, an intracellular carbohydrate

reserve, is essential as an energy source for cell activity since wort sugars are not

assimilated early in the lag phase. Stored glycogen is broken down into glucose, which is

utilized by the yeast cell for reproduction – the cell’s first concern. Low glycogen levels

produce abnormal levels of vicinal diketones (especially diacetyl) and result in longer

fermentations.

2: GROWTH PHASE

The growth phase, often referred to as the respiration phase, follows the lag phase once

sufficient reserves are built up within the yeast. This phase is evident from the covering of

foam on the wort surface due to the liberated carbon dioxide. In this phase, the yeast cells

use the oxygen in the wort to oxidize a variety of acid compounds, resulting in a

significant drop in pH. In this connection, some yeast strains will result in a much greater

fall in pH than others within the same fermenting wort.

3: FERMENTATION PHASE

The fermentation phase quickly follows the growth phase when the oxygen supply has

been depleted. Fermentation is an anaerobic process. In fact, any remaining oxygen in the

wort is "scrubbed," i.e. stripped out of solution by the carbon dioxide bubbles produced by

the yeast. This phase is characterized by reduction of wort gravity and the production of

carbon dioxide, ethanol, and beer flavors. During this time period, yeast is mostly in

suspension, allowing itself dispersal and maximum contact with the beer wort to quickly

convert fermentable. Most beer yeasts will remain in suspension from 3 to 7 days, after

which flocculation and sedimentation will commence.

4: SEDIMENTATION PHASE

The sedimentation phase is the process through which yeast flocculates and settles to the

bottom of the fermenter following fermentation. The yeast begins to undergo a process that

will preserve its life as it readies itself for dormancy, by producing a substance called

glycogen. Glycogen is necessary for cell maintenance during dormancy and, as mentioned,

is an energy source during the lag phase of fermentation.

4.2.3: YEAST NUTRITIONAL REQUIREMENTS

To grow successfully, yeast requires an adequate supply of nutrients-fermentable

carbohydrates, nitrogen sources, vitamins, and minerals-for healthy fermentation. These

nutrients are naturally present in malted barley or developed by enzymes during the

malting and mashing process.

1: CARBOHYDRATES

Carbohydrates are available for yeast growth in wort as low-molecular-weight sugars such

as the mono-, di- and oligosaccharides are available for yeast growth. Polysaccharides are

not used by the yeast. The sugars are, in order of concentration, maltose, maltotriose,

glucose, sucrose, and fructose, which together constitute 75 to 85% of the total extract.

The other 15 to 20% consists of non-fermentable products such as dextrins, beta-glucans,

pentosans, and oligosaccharides.

2: NITROGEN

Nitrogen is available for yeast growth in wort as amino acids, peptides, and ammonium

salts. Yeast prefers to use ammonium salts, but these are present in wort only in very small

amounts. Amino acids and peptides are therefore the most important wort constituents.

Amino acids collectively referred to as "free amino nitrogen (FAN)," are the principal

nitrogen source in wort and are an essential component of yeast nutrition. It is the amino

acids that the yeast cells use to synthesize more amino acids and, in turn, to synthesize

proteins.

3: VITAMINS

Vitamins such as biotin, panthotenic acid, thiamin, and inositol are essential for enzyme

function and yeast growth. Biotin is obtained from malt during mashing and is involved in

carboxylation of pyruvic acid, nucleic synthesis, protein synthesis, and synthesis of fatty

acids. Biotin deficiencies will result in yeast with high death rates.

4:MINERALS

Yeasts are unable to grow unless provided with a source of a number of minerals. These

include phosphate, potassium, calcium, magnesium, sulfur, and trace elements. Phosphate

is involved in energy conservation, is necessary for rapid yeast growth, and is part of many

organic compounds in the yeast cell. Potassium ions are necessary for the uptake of

phosphate.

Zinc

The most important trace element is zinc, and at least 0.10 to 0.15 mg/l should be present

in the wort. Zinc assists in protein synthesis in yeast cells and controls their nucleic acid

and carbohydrate metabolism. Fermentations are accelerated by adding zinc chloride (0.2-

0.3 mg/l) to the wort.

4.2.4: YEAST BYPRODUCTS

The flavor and aroma of beer is very complex, being derived from a vast array of

components that arise from a number of sources. Not only do malt, hops, and water has an

impact on flavor, so does the synthesis of yeast, which forms byproducts during

fermentation and conditioning. The most notable of these byproducts are, of course,

ethanol and carbon dioxide; but in addition, a large number of other flavor compounds

such as esters, higher alcohols, and acids are produced, all of which contribute to the taste,

aroma, and other characteristics of the beer.

1: ESTERS

Esters are considered the most important aroma compounds in beer. They make up the

largest family of beer aroma compounds and in general impart a "fruity" character to beer.

Esters are more desirable in most ales, and in some dark or amber lagers, lower levels are

preferred in pale lagers.

2: DIACETYL AND 2,3-PENTANEDIONE

Diacetyl and 2,3-pentanedione, which are classified as ketones, are important contributions

to beer flavor and aroma. Often these two ketones are grouped and reported as the vicinal

diketone (VDK) content of beer, which is the primary flavor in differentiating aged beer

from green beer. Of the two, diacetyl is more significant because it is produced in larger

amounts and has a higher flavor impact than 2,3-pentanedione. A "buttery" or

"butterscotch" flavor usually indicates the presence of diacetyl, while 2,3-pentanedione has

more of a "honey" flavor.

3: ACETALDEHYDES

There are many flavor-active acetaldehydes present in beer that are formed at various

stages in the brewing process. They are produced by oxidation of alcohols and various

fatty substances. Acetaldehyde levels peak during the early to mid-stages of primary

fermentation or immediately after kraeusening, then decrease in concentration.

4: ORGANIC AND INORGANIC SULFUR VOLATILES

Sulfur-containing compounds in beer arise from organic sulfur-containing compounds

such as some amino acids and vitamins. They are also formed from inorganic

wortconstituents such as hydrogen sulfide, dimethyl sulfide, sulfur dioxide, and thiols

make significant contributions to beer flavor. When present in small concentrations, sulfur

compounds may be acceptable or even desirable (for example Burton ales), but in excess

they give rise to unpleasant off-flavors, e.g., rotten-egg flavors.

5: DIMETHYL SULFIDE

Another major compound responsible for sulfury flavors in beer is dimethyl sulfide

(DMS), which is a desirable flavor component in lager beer but not in ales. Dimethyl

sulfide in lagers it will lead to a malty/sulfury note. The taste threshold for DMS is

considered to be from 50-60 µg/liter. If the concentrations are too high, it has a relatively

objectionable taste and aroma of cooked sweet corn.

6: FUSEL ALCOHOLS

Fusel alcohols are a group of byproducts that are sometimes called "higher alcohols." They

contribute directly to beer flavor but are also important because of their involvement in

ester formation. Fusel alcohols have strong flavors, producing an "alcoholic" or "solvent-

like" aroma. They are known to have a warming effect on the palate. About 80% of fusel

alcohols are formed during primary fermentation. The yeast strain is very important, with

some being able to produce up to three times as much fusel alcohols as others . Ale strains

generally produce more fusel alcohols than lager strains.

7: ORGANIC ACIDS

The most important organic acids found in beer are acetic, citric, lactic, malic, pyruvic and

succinic. They confer a "sour" or "salty" taste to beers. Some of these organic acids are

derived from malt and are present at low levels in wort, with their concentrations

increasing during fermentation.

8: FATTY ACIDS

Fatty acids are minor constituents of wort and increase in concentration during

fermentation and maturation. They give rise to "goaty", "soapy", or fatty flavors and can

cause a decrease in beer foam stability. They are recognized as common flavor

characteristics in both lagers and ales but are more prevalent with lager yeast strains.

9: NITROGEN COMPOUNDS

Yeast also excretes some nitrogen compounds during fermentation and maturation as

amino acids and lower peptides, which contribute to the rounding of the taste and an

increase in palate fullness.

4.2.5: YEAST STRAIN SELECTION

Selection of a yeast strain with the required brewing characteristics is vital from both a

product quality and economic standpoint. The criteria for yeast selection will vary

according to the requirements of the brewing equipment and the beer style, but they are

likely to include the following:

• Rapid fermentation

• Yeast stress tolerance

• Flocculation

• Rate of attenuation at the desired temperature

• Beer flavor

• Good yeast storage characteristics

• Stability against mutation

• Stability against degeneration

1: RAPID FERMENTATION

A rapid fermentation without excessive yeast growth is important, as the objective is to

produce a beer with the maximum attainable ethanol content consistent with the overall

flavor balance of the product.

2: YEAST STRESS TOLERANCE

The yeast strain should be tolerant to alcohol, osmotic shock, and temperature. Another

stress point for yeast can be the collection, separation (centrifuging/pressing), and transfer

(pumping) throughout the plant.

3: FLOCCULATION

The flocculation characteristics of yeast are of great importance. The term "flocculation"

refers to the tendency to form clumps of yeast called flocs. The flocs (yeast cells) descend

to the bottom in the case of bottom-fermenting yeasts or rise with carbon dioxide bubbles

to the surface in the case of top-fermenting yeasts. The flocculation characteristics need to

be matched to the type of fermentation vessel used-a strongly cropping strain will be ideal

for skimming from an open fermenter but unsuitable for a cylindroconical fermenter.

4: RATE OF ATTENUATION

Attenuation refers to the percentage of sugars converted to alcohol and carbon dioxide, as

measured by specific gravity. Most yeasts ferment the sugars glucose, sucrose, maltose,

and fructose. To achieve efficient conversion of sugars to ethanol (good attenuation)

requires the yeast to be capable of completely utilizing the maltose and maltotriose.

Brewing yeasts vary significantly in the rate and extent to which they use these sugars.

5: BEER FLAVOR

The selection of the yeast strain itself is perhaps one of the most important contributors to

beer flavor. Different strains will vary markedly in the byproducts they produce: esters,

higher alcohols, fatty acids, hydrogen sulfide, and dimethyl sulfide. The yeast strain must

also be capable of reproducible flavor production.

6: STORAGE CHARACTERISTICS

The storage characteristics of yeast are very important for maintaining viability during

storage between fermentations and rapid attenuation when repitched.

7: MUTATION OF YEAST

Yeast mutations are a common occurrence in breweries, but their presence may never be

detected. Usually the mutant has no adverse effect since it cannot compete with normal

yeast and generally disappears rapidly. In some cases, though, mutant yeast will overcome

the normal brewing yeast and may express itself in many different ways. For example, a

mutation could affect the fermentation of maltotriose, or there could be a continuous

variation in the fermentation rate.

8: DEGENERATION OF YEAST

Yeast degeneration refers to the gradual deterioration in performance of the brewing

yeast. Yeast degeneration has a harmful effect on the course of brewing fermentations. It

is characterized by some of the following symptoms: sluggish fermentations, premature

cessation of fermentation (resulting in high residual fermentable levels in beer), gradual

lengthening of fermentation times, and poor foam or yeast head formation. Some brewers

have noticed that the flavor of beer becomes increasingly "dry" as a result of yeast

degeneration.

4.2.6: PURE CULTURE MAINTENANCE

Once yeast has been selected, accepted, and fully proven for use in brewing, it is essential

that a pure culture (working master culture) is maintained in the laboratory yeast bank for

prolonged periods. Some small breweries do not maintain a master culture but rather

purchase fresh slants for each in-house propagation cycle or hold stock cultures at

independent third party institutions. Some of the more common methods brewers can use

for maintaining the purity and characteristics of their yeast strains are sub-culturing,

desiccation, lyophilization, and freezing in liquid nitrogen.

1:SUB-CULTURING

SUB-CULTURING ON AGAR SLANTS

A popular method of sub-culturing involves maintaining the cultures on a medium suitable

for yeast growth. Yeast cultures are best kept on agar slopes in 28 ml screw-capped

McCartney bottles. Aluminum caps with rubber liners are preferred since bottles fitted

with plastic caps suffer from poor survival rates.

SUB-CULTURING ON AGAR SLANTS WITH AN OIL OVERLAY

Alternatively, if the agar slants are overlayed with sterile mineral oil, the known shelf life

increases to at least two years. After inoculation and incubation for 3 days at 25°C, the

culture is overlaid with a layer of sterile B.P. mineral oil.

2: DESSICATION

This method uses purified silica gel as a desiccant, or squares ofWhatman No. 4 filter

paper. It is more suitable for strains used by collection curators or for research rather than

for industrial strains. The shelf life can be up to 3 to 6 years.

3: LYOPHILIZATION

Lyophilization or freeze-drying is another popular technique among research laboratories

and culture collections. Cultures are rapidly frozen followed by drying under vacuum.

4: FREEZING IN LIQUID NITROGEN

With this method pure cultures are kept in vials and submerged in liquid nitrogen (196°C),

thereby maintaining viability and genetic integrity for tens of years.

FIG: YEAST SUPPLY PROCESS

4.2.7: YEAST PROPAGATION AND SCALE-UP

The objective of propagation is to produce large quantities of yeast with known

characteristics for the primary role of fermentation, in as short a time as possible. Most

brewers use a simple batch system of propagation, starting with a few milliliters of stock

culture and scaling up until there is enough yeast to pitch a commercial brew. Scale-up

introduces actively growing cells to a fresh supply of nutrients in order to produce a crop

of yeast in the optimum physiological state.

1: LABORATORY PHASE

The process initially begins in the laboratory when cultures are taken from the "working"

master culture and grown in a progression of fermentations of increasing size until enough

yeast is produced to transfer to the propagation plant. The number of transfer steps in the

laboratory varies according to the final weight of yeast required for the propagation plant.

Of course, the more transfers, the greater the risk of infection. Most yeast culturing is done

in a laminar flow hood.

2: PLANT PHASE

After rigorously cleaning the yeast-propagation vessel (in the case of smaller breweries, a

production fermenter) it is then filled with hot or cold wort and aerated with sterile air.

Preferably the wort should be of the same quality as that used in fermentation. During

propagation, temperature is maintained at a set level and the propagating yeast is

intermittently aerated. When the yeast has reached the required cell concentration, it is

pitched into an intermediate fermenter or directly to a production fermenter. As in the

laboratory, yeast is grown in a progression of fermentations until there is enough to pitch a

commercial-size brew.

3: AERATION

As mentioned, air or oxygen is passed continuously into the vessel through an efficient gas

sterilizer to encourage yeast growth. Oxygen is preferable since it is sterile, whereas an air

supply may contain impurities that must be removed before the air enters the vessel. The

optimum rate of oxygenation for a system must be found by experiment, as the rate will

affect the total crop produced.

After cooling the wort is aerated to increase yeast activity and to start the fermentation

process. The amount of oxygen required depends on yeast strain, wort temperature, wort

gravity, amount of trub in the wort, and a number of other factors.

OXYGEN REQUIREMENTS

The oxygen requirements for individual brewing strains can range from 3 to 30 mg O2/l

but usually it is in the range of 7 to 18 mg O2/l. Yeast strains with low oxygen

requirements can be aerated using sterile air since it contains approximately 8 mg O 2/l,

while strains with high oxygen requirements must be aerated with pure gaseous oxygen.

POINT OF INJECTION

The point of injection of oxygen has been the subject of many debates, and the choice is

largely a matter of tradition. Many brewers believe that gas injected into the hot wort prior

to cooling improves cold break formation. However, when injected into wort at the hot end

of a cooler the wort allows oxidation of wort components, resulting in darker-colored

worts. In addition, according to Moll, oxygenation of hot wort contributes to off-flavors in

the beer, e.g., garlic flavor.

METHODS OF OXYGENATION

Wort oxygenation is most commonly achieved by direct injection of either sterile air or

oxygen at the time it exits the wort cooler. Devices used to aerate the wort are:

1: CERAMIC OR SINTERED METAL ELEMENTS

With ceramic or sintered metal elements, air is injected as very small bubbles through fine

pores into the flowing wort.

2: VENTURI TUBES

With Venturi tubes, there is a substantial increase in flow velocity, and the air is

thoroughly mixed in the wort.

3: TWO-COMPONENT JETS

Brewers employing two-component jets inject the air (or oxygen) as very small bubbles

under high pressure into the wort stream, which is then forced through a small orifice and

into an expansion chamber.

4: STATIC MIXERS

In static mixers, the initial mixing of the wort and air is achieved in a reaction section with

built-in angle bands.

5: CENTRIFUGAL MIXERS

If a centrifuge mixer is employed, air can be introduced into the wort stream via the

centripetal pump impeller, which results in very fine bubbles.

OPTIMUM PROPGATION TEMPERATURES

There is a wide variety of recommendations in this instance as well. Some brewers prefer

to propagate their yeast at temperatures identical to those employed during fermentation in

order to prevent temperature shock to the yeast.

PROPAGATION PLANTS

The propagation plant usually consists of anywhere from one, two or more closed stainless

steel vessels of increasing volume, which are usually situated in a separate room to

minimize contamination of risk.

4.2.8: YEAST CULTURE CONTAMINATION

It frequently happens that brewing yeasts carry a persistent low level of contaminants such

as Obesumbacteriumproteus, acetic acid bacteria, and slow-growing Torula-type yeasts.

These organisms are generally regarded as harmless because their numbers never reach a

point where they are likely to have adverse effects on the beer. On the other hand, L.

pastorianus, Z. anaerobia, andS. carlsbergensis are strains considered harmful at low

levels.

MICROSCOPIC EXAMINATION

Microscopic examination of the yeast culture can be useful in assessing the overall health

of the population. Abnormal-looking or irregularly shaped yeast cells are signs of cell

stress, possibly indicating potential problems with wort composition, aeration, poor yeast

handling, or fermentation conditions. Microscopic examination is also useful in detecting

extraneous particles such as diatomaceous earth, trub, grain particles, etc. that may

interfere with proper yeast performance.

4.2.9: YEAST WASHING

Pitching yeasts collected from brewery fermentations are never absolutely free of

microbiological infection. In spite of whatever care and sanitary precautions are taken,

some bacteria and wild yeast will contaminate the pitching yeast. The pitching yeast can

contain healthy yeast cells and trub (dead yeast cells and organic residues) and may

contain 5 to 15% dry solids. To minimize microbiological infection, brewery yeast can be

washed using the following procedures:

1: DISTILLED OR STERILE WATER WASH

In the first method, the yeast slurry and cold, distilled or sterile water are mixed

thoroughly in a decantation tank. The yeast is allowed to settle and the supernatant water is

decanted, taking with it dead cells, trub, grain, and hop particles.

2: ACID WASH

The second method is to wash the yeast with acids, e.g., tartaric, citric, sodium

metabisulfite, sulfuric, or phosphoric acid which is typically the most commonly used

acid. Acid washing lowers the pH of the yeast slurry to the point at which bacteria and

weak yeast cells are killed off, but it does not harm the healthy yeast cells.

ACID WASH WITH AMMONIUM PERSULFATE

Some brewers use an acid-persulfate combination rather than just acid claiming that it is a

more effective treatment than treatment with acid alone. Briggs et al. recommend the

addition of a strong oxidizing agent as ammonium persulphate (0.75% w/v) with

phosphoric acid.

CHLORINE DIOXIDE

Chlorine dioxide, an alternative to distilled water or acid washing, is relatively new to the

brewing industry and is gaining acceptance as a method for washing yeast. It kills via

microbes by reacting chemically with sulfur-containing amino acids, the building blocks of

protein which are used to form cell membranes.

YEAST HANDLING PRACTISES

Yeast Holding in the Fermentor after Full Cooling at a temperature of 4 to 5˚C,

appreciably for not more than 24 hours

Yeast Cropping from the Fermentor to the Yeast Storage Vessel at a temperature of 4 to 5

˚C appreciably within 24 hours of Full Cooling

Yeast Storage in the Yeast Storage Vessel at a temperature of 3 to 4 ˚C appreciably for

not more than 24 hours

Storage of Acid Washed Yeast ready for pitching in the Yeast Pitching Tank at a

temperature of 3 to 4 ˚C for not more than 2 hours

Yeast Acid Washing always at a temperature of 3 to 4 ˚C

Use of Food Grade Ortho Phosphoric Acid only for Yeast Acid Washing

Yeast Acid Washing is recommended only as a preventive measure, and not as a

corrective measure

Yeast Acid Washing is recommended only to eliminate minute or low levels of Bacterial

Contamination.

Yeast with High Levels of Bacterial Contamination are not to be used, rather discarded

Yeast with Wild Yeast Contamination are also not to be used, rather discarded

Pitching Yeast should be used for not more than 6 to 8 Generations

An Ideal Pitching Yeast should have a Viability more than 98% and a Solid

Concentration of 60 to 65% by weight or 40 to 45% by volume

4.2.10: YEAST VIABILITY AND REPLACEMENT

YEAST VIABILITY

Viability is a measure of yeast's ability to ferment-a property not possessed by dead cells.

Yeast viability is determined by selective staining, by the standard-slide culture method, or

by more advanced methods such as the Slide Viability Method, and fermentation tests.

SELECTIVE STAINING

A more objective result of yeast viability is obtained by selective staining using buffered

methylene blue or methylene violet. These stains show dead cells as blue or pink,

respectively, on microscopic examination. Various other dyes have been recommended

from time to time, such as methyl green, acridine orange, neutral red, and erythrosine.

STANDARD-SLIDE CULTURE METHOD

A more accurate method in determining the viability of yeast is the standard slide-culture

method that consists of three steps: perform a hemacytometer count on a suspension of

cells, plate a measured quantity on a wort gelatin medium, and then incubate and count the

resultant colonies.

SLIDE VIABILITY METHOD

In the Slide Viability Method, cells are suspended in a growth medium containing 6%

gelatin, and the suspension is placed on a hemacytometer slide.

FERMENTATION TESTS

Although the above methods can assess whether a cell is alive or viable, they cannot

readily assess the vigor of the yeast and whether they can produce a normal fermentation.

YEAST REPLACEMENT

Most brewers discard yeast after a successive number of fermentations because it may be

intermixed with other yeasts, contaminated with wild yeast and bacteria, or mutated to less

desirable strains. Depending on their yeast-handling facilities and procedures, some

brewers use their yeast in production for less than three generations, while others only

discard their yeast after 5 to 10 successive fermentations. However, there are exceptions to

the rule, with some brewers routinely discarding yeast after 30 brewery fermentations.

Those brewers who employ high pitching rates will probably have to replace their yeast

more often because continuous use and high pitching rates tend to increase the average age

of the yeast, thus reducing their vigor.

4.2.11: YEAST STORAGE

In most breweries, yeast is stored during the period between cropping and re-pitching.

Pitching yeast may be stored within the brewery as slurry in a yeast collection vessel, or as

slurry stored under a layer of water or beer, or as pressed cake.

YEAST COLLECTION VESSELS

Most modern breweries store their yeast in sophisticated collection vessels under filtered

sterile air or inert sterile gas pressure with external cooling and equipped with low shear

stirring devices.

SLURRIED STORAGE SYSTEMS

Slurried storage systems are usually self-contained, thereby reducing the risks of

contamination. Slurry yeast has the advantage over pressed yeast in that it gives more

vigorous fermentations, requires lower pitching rates, and can be stored for longer periods

(usually fewer than 4 weeks) without affecting viability.

PRESSED CAKE

Alternatively, yeast can be stored as pressed cake. The yeast recovered is stored at 0°C

before re-suspension in wort for pitching.

4.2.12:YEAST MANAGEMENT

FIG: YEAST MANAGEMENT

PARAMETER INFORMATION SHOULD BE AVAILABLE

YEAST IDENTITY Which strain

AGE Generation number (number of fermentation cycles)

YEAST PITCHING From which storage vessel to which fermenter

YEAST CROPPING From which fermenterto which storage vessel

FERMENTATION EFFICIENCY

Calculated yeast growth (from pitch:crop ratio)

YEAST CROP Total yeast available for pitchingPrompt for disposal at maximum generation numberPrompt for propagation

4.3:BEER FERMENTATION

Fermentation is the process by which fermentable carbohydrates are converted by yeast into

alcohol, carbon dioxide, and numerous other byproducts. It is these byproducts that have a

considerable effect on the taste, aroma, and other properties that characterize the style of beer.

WORT RECEIVED IN WASHED YEAST PEACHED PRIMARY FERMEN.

R.V.(2 UNITS, 20995 LTS.) & AIR INCOR.(8 HRS. HOLD) (8-12 DAYS)(15 NO.)

(23,365 LTS.)(1.5 HR.)

SECONDARY FERME. (7-15 DAYS) WASHING CENTRIFUGATION

CHEMICALS ADDED IN S.V. (3 HR.) (CO2) (1440 R.P.M.)(3 HR)

(16 UNIT, 16,700 LTS.) (9 NO., 8493 LTS.)

FILTRATION (1.5 HR) RECEIVED IN B.B.T. CARBONATION (1.5 HR.)

(6 NO., 8170 LTS.)

FIG: BEER FERMENTATION PROCESS

FERMENTATION

STAGE

APPEARANCE AT THE TOP

INITIAL The young beer becomes covered by a white layer of fine bubble

foam ,(i.e. becomes white all over)

YOUNG OR LOW

KRAUSEN

The fine bubble foam becomes deeper & has brown caps. The foam

cover should looks as uniform as possible & be creamy.

HIGH KRAUSEN Fermentation has entered his most intensive stage. The ridges or crests

in the foam become higher & the bubbles coarser.

KRAUSEN

COLLAPSING

The fermentation has become less vigorous & the high crests slowly

collapse since not much carbon dioxide is formed. The foam looks

browner.

COLLAPSED

FOAM

Because the rate of fermentation continues to decrease the foam

continues to collapse & finally forms only a loose, dirty brown layer,

which is removed before transfer of the beer so that it does not sink

down & dirty the yeast.

4.3.1: PITCHING BEER YEAST

STRAIN

The yeast strain itself is a major contributor to the flavor and character of the beer. Thus the

choice of yeast strain depends on such things as the oxygen requirements, cropping methods,

attenuation limits, fermentation rate, fermentation temperatures, flocculation characteristics,

and the flavor profile (sulfur compounds, esters, fusel alcohols, etc.).

PITCHING RATES

The brewer's ability to pitch the correct number of yeast cells to initiate fermentation is

crucial to consistently producing a product of superior and constant quality. Pitching rates are

governed by a number of factors, including yeast strain, fermentation capacity of the yeast,

yeast viability, flocculation characteristics, previous history of the yeast, and desired beer

flavor characteristics. Other considerations when choosing pitching rates include wort gravity,

wort constituents, fermentation temperature, and the degree of wort aeration. For example,

highly flocculent yeast strains may settle prematurely, requiring the brewer to either over-

pitch or to mix and aerate the yeast by "rousing."

VIABILITY

The pitching rates should be adjusted to account for the number of viable cells rather than the

total number of cells. Dead cells can be determined by staining with methylene blue and

counting with a hemacytometer.

METHODS FOR DETERMINING PITCHING RATES

Traditionally, brewers determined pitching rates on the basis of either the volume or the

weight of yeast slurry to a known quantity of wort. Today most breweries determine pitching

rates by a number of alternative methods including the use of a counting chamber

(hemacytometer), centrifugation of the yeast slurry, electron cell counting, or of in-line

biomass sensors.

DOSING

Yeast can be directly added to the fermenters (batch), mixed with the wort in a starter tank

prior to transfer to the fermenter, or continuously metered into the cold, aerated wort stream

on the way to the fermenter.

MICROBIOLOGICAL CONTAMINATION

Uninoculatedwort is liable to contamination by many types of mold; bacteria such

as Pediococcus, spp. and Lactobacillus spp.; and wild yeasts such

as Hansenula, Dekkera, Brettanomyces, Candida, andPichia. Other Saccharomyces species

may be present.

4.3.2: LAGER FERMENTATIONS

STARTER TANKS

Traditional European lager brewers, especially in Germany and Scandinavia, use starter tanks

in which yeast is added to the cooled wort and the contents then allowed to stand for a period

of up to 24 hours before racking. Traditionally, starter tanks were open vessels, but nowadays

they are generally designed like regular closed-in fermenters.

TOPPING UP (DARAUFLASSEN)

If the brewer doesn't have enough yeast or if the brewer has a smaller mash tun and kettle

than the fermenter, the brewer can employ a technique called topping up or darauflassen.

Topping up, a technique common among German lager brewers, is the infusion of wort into a

tank with strongly fermenting young beer (high kraeusen).

TRADITIONAL LAGER FERMENTATION

While vertical cylindroconical fermenters are used to make the majority of the world's lager

production, open square fermenters are still commonly used (especially in Eastern Europe) in

traditional lager fermentation. In recent years, some major brewers have started fermenting

their lagers in open square fermenters for quality reasons.

MODERN LAGER FERMENTATION

Today modern lager fermentation typically uses vertical cylindrodroconical fermenters

achieving similar flavor profiles compared to traditional fermentation systems. In modern

fermentation systems, the yeast is pitched at higher temperatures between 7 and 8°C, and after

a couple of days the temperature is increased to 10 to 11°C. After 3 to 4 days, at peak

fermentation, the fermentation temperature is allowed to ramp up in order to facilitate a rapid

reduction in diacetyl. Some brewers use the same starting temperature for pitching but then

increase the temperature between 14 and 15°C. Other breweries are known to pitch between

10 and 13°C and then increase the temperature to as high as 17°C, with a short diacetyl rest.

4.3.3:ALE FERMENTATIONS

STARTER TANKS

Like lager brewers, some ale brewers initiate fermentation in starter tanks in which the

residence time may be as short as 3 hours or as long as 36 hours.

TRADITIONAL ALE FERMENTATION

The brewing of traditional cask ale is fermented in shallow vessels that could be round,

square or rectangular often referred by the type of fermentation system (e.g., Yorkshire

square, the Burton Union, the ale top-skimming system, and the ale dropping system). The

Burton Union system is now confined to a single brewery in Burton-on-Trent, and the

Yorkshire square system is found in Yorkshire and Midland breweries.

MODERN ALE FERMENTATION

Today modern ale fermentation typically uses vertical cylindrodroconical fermenters

achieving similar flavor profiles compared to traditional fermentation systems. Typically, the

yeast is pitched between 15 and 22°C, and the temperature is allowed to rise gently to 18 to

25°C, depending on the yeast strain. At the end of fermentation a diacetyl rest may be

incorporated, although some popular ales (e.g., Irish stouts) have a perceptible diacetyl

character that is are part of the flavor profile. Once fermentation is complete, the contents are

cooled to about 4°C to settle the yeast in the cone of the fermenter. The settling time is

dependent on the flocculation characteristics of the yeast. Typically, brewers will wait for an

additional 24 hours for the yeast to further settle before cropping. Changes in yeast handling

are required since collecting yeast off the surface is no longer possible.

4.3.4: CHANGES DURING FERMENTATION

As the fermentation proceeds various substances accumulate on the surface of the

medium ,Including hop resins, Yeast cells and proteinaceous materials This scum may be

removed after the fermentation starts to recede in order to improve the quality of the beer.

Certain very definite change takes place in the wort during fermentation at a particular

point near the end of the fermentation the yeast flocculates and commences to settle . This

change is known as “break” and depend in part upon the pH for initiation. A large proportion of

the fermentable sugars are transformed to ethyl alcohol ,co2 , glycerol and acetic acid, higher

alcohols and acid are produced from protein and fat derivatives . Esters are formed from

organic acids and alcohols the pH of the mash drops gradually, insoluble products precipitate

out the fermentation of a bottom fermenting yeast which is usually carried out at 6 degree C to

12 degree C is ordinarily completed in 8 to 10 days. While that of top fermenting yeast is

completed in a shorter time 5 to 7 days beer at this stage is known as “green” or young beer. The

beer from fermentation vessel the so called green beer is fed to a centrifuge for complete

separation of green beer from the impurities in it and sent to the co2 washing tank. The beer

is sparged with co2 for reducing off flavours and substances which make the beer non –

palatable the characteristic feature of beer are obtained by removal of off flavoring substances

by washing the beer by co2 rather than by development of other substances during the period

of storage. The washing process consists in passing a current of finely divided co 2 under a

pressure of 0.35 to 0.4 atm . The standing time is given to beer in lagering vessels before racking

or bolting.

The bottom fermented beer is usually lagered or stored for the period of time after the

completion of primary fermentation slow changes occur which may be comprised in the term

maturation these include- continuation of fermentation under condition which remove air and

undesirable flavoring substances from the beer and ultimately leads to its saturation with co 2 .

Promotion of changes in the colloidal constituents of beer resulting in aggregation and

precipitation of protein and in removal of hop resin under effect of increasing acidity,

clarification through deposition of Yeast and suspended matter.

Improvement of flavour occurs by production of minute quality of ester acids and other

secondary products of fermentation. Digestibility is help to be increased at same time by changes

in the protein and other beer constituents. Usual storage temp.is between 0.5 degree to 2 degree

C but too long storage of beer makes it flavour empty.

During fermentation the yeast converts the sugar in the wort chiefly to alcohol and co2 plus

small amount of glycerol and acetic acid , proteins and fat derivatives yield small amount of

higher alcohols and acid . Organic acids and alcohols combine toform aromatic esters. As the

co2 is evolved in increasing amount, the foaming increases later it decreases to none when the

fermentation has concluded. At a later stage the bottom yeast break that is flocculate and

settle .Bacterial growth isnot desired during the fermentation and subsequent aging of the beer

[Barney,M.C and Helbert.1976].

C6H12O6 2CH3 CH2 OH + 2CO2

4.3.5: YEAST COLLECTION

Aside from the need to remove most of the yeast from the beer prior to conditioning, yeast

recovery for reuse in subsequent fermentations is an important process in the brewery. The

total amount of yeast produced is dependent upon not only the yeast strain but also the level

of aeration, the fermentation temperature, the specific gravity of the wort, and the pitching

rate. Increases in any of these variables will lead to greater yeast crops.

FERMENTATION SYSTEMS

1: TRADITIONAL LAGER FERMENTATION SYSTEM

The traditional method of collecting lager yeast is to decant the "green" (unconditioned) beer

from the settled yeast on the bottom of the open fermenters. The yeast is collected manually

from the middle layer of the sediment on the floor.

2: TRADITIONAL ALE FERMENTATION SYSTEM

Traditionally, top-cropped ale yeast was harvested by skimming the head of yeast/foam that

formed on top of the beer in the shallow, flat-bottomed fermentation vessel. Generally, the

second crop that forms towards the end of fermentation is the one that is harvested since the

yeast is pure, with very high viability.

3: CYLINDROCONICAL FERMENTERS

Today, with the advent of cylindroconical fermenters, the differentiation on the basis of

bottom and top cropping has become less distinct. Cylindroconical tanks allow improved

yeast separation and collection strategies for both lager and ale yeast. The angle at the bottom

of the tank allows the yeast to settle into the base of the vessel at the completion of primary

fermentation. This aids in yeast collection from the bottom of the cone without exposing the

yeast to outside air, leaving the beer comparatively free of yeast.

YEAST STORAGE

Upon harvesting, the yeast can be transferred directly to another fermenter, transferred to a

yeast brink and held for the next fermentation, or stored with its own beer at 0°C. The yeast

will remain healthy while held at refrigerated temperatures, especially if the cells are kept

suspended by gentle agitation so that "hot" spots do not accelerate cell death and autolysis.

Small craft breweries may use nothing more than a white food-grade tub with a snap lid for

storing the yeast.

4.3.6: FERMENTATION SYSTEMS

There are many different fermentation systems that are used worldwide that have evolved

based on available technology, brewing materials, and perceived product quality. The

following is a brief description of some of the more common fermentation systems in use

today.

CYLINDROCONICAL

Cylindroconical fermenters are the most commonly used fermentation systems used today to

produce both lagers and ales. As the name implies, the enclosed vessels are vertical cylinders

with a conical base and, normally, a dished top, as shown in Figure. This design allows for

easy yeast collection and CIP cleaning. They range in size between 100 and 7,000 hl, have

from a 1:5 to a 3:1 ratio of height to diameter, and work under pressures of from 1 to 1.3 bars

above atmospheric pressure. In fermentation vessels with a ratio greater than 3:1, there is a

tendency for increased production of higher alcohols at the expense of esters (5). Vessel

geometry plays an important role in fermentation. As the height-to-diameter ratio increases,

so does the mixing of yeast and wort, as well as the fermentation rate.

FIG: CCV

TRADITIONAL ALE TOP-SKIMMING SYSTEM

This is the traditional ale skimming system used in the United Kingdom. It utilizes top-

fermenting yeast cropped for re-pitching by skimming from the surface. The vessels are

normally shallow and flat-bottomed and may be round, square, or rectangular. Traditionally,

these vessels are open-topped to facilitate skimming and are located in a well-ventilated room

to disperse the carbon dioxide evolved during fermentation.

TRADITIONAL ALE DROPPING SYSTEM

This is a variation of the ale top-skimming system, whereby the wort is pitched, collected, and

partially fermented in one vessel (the settling tanks) and then dropped or transferred to a

second vessel after 24 to 36 hours to complete the fermentation .Trub and cold break are left

behind in the first vessel, and the transfer also rouses the fermentation.

YORKSHIRE SQUARE SYSTEM

Thissystem is used in the north of England to produce ales with a clean, round palate. It is a

variation of the ale fermentation system adapted to enable the use of a flocculent yeast strain

or a two-strain system with one of the yeasts being flocculent. The vessels are normally

square or rectangular in shape, and constructed of stainless steel. The Yorkshire square

system consists of a lower compartment with a gently sloping upper deck located just above

the fill level of the vessel.

BURTON UNION SYSTEM

This system was commonly used in Burton-on-Trent and produces pale ales with a fruity

character by using "powdery" non-flocculent yeast. The wort is collected and pitched in a

separate vessel and then transferred to the union set after 24 to 48 hours. The union set

consists typically of 2 rows of wooden casks, 24 to 50 in number and each of 7 hl capacity,

positioned under a cooled trough. Each cask is fitted with a swan neck that overhangs a

slightly inclined trough mounted above the casks.

OPEN SQUARE FERMENTERS

Traditional lager systems in Continental Europe and still common in Eastern Europe utilize

open square fermenters similar to those used in the traditional ale top system.

DUAL PURPOSE VESSEL SYSTEM

The vessel characteristics that make cylindroconicals so suitable for fermenting vessels also

make them ideal for conditioning tanks. This has led to the installation of dual-purpose

vessels where primary fermentation and conditioning are carried out in the same vessel. Dual-

purpose vessels have cooling jackets located high in the vessel for fermentation and low in the

vessel for conditioning. Other differences are that conditioning tanks are normally required to

be top-pressured to maintain carbonation levels, which is not required in fermenters.

4.4:BEER CONDITIONING

Following primary fermentation, the "green" or immature beer is far from finished because it

contains suspended particles, lacks sufficient carbonation, lacks taste and aroma, and it is

physically and microbiologically unstable. Conditioning reduces the levels of these

undesirable compounds to produce a more finished product. The component processes of

conditioning are:

MATURATION

CLARIFICATION

STABILIZATION

4.4.1: BEER MATURATION

Maturation techniques vary from brewery to brewery but generally they can be divided into

two general schemes for finishing beer after primary fermentation called secondary

fermentation and cold storage.

SECONDARY FERMENTATION

Traditionally, maturation involves secondary fermentation of the remaining fermentable

extract at a reduced rate controlled by low temperatures and a low yeast count in the green

beer. During secondary fermentation, the remaining yeast becomes re-suspended utilizing the

fermentable carbohydrates in the beer. The carbohydrates can come from the residual gravity

in the green beer or by addition of priming sugar or by kraeusening. Yeast activity achieves

carbonation, purges undesirable volatiles, removes of all residual oxygen, and chemically

reduces many compounds, thus leading to improved flavor and aroma.

LAGERING

Lagering was developed in Germany for bottom-fermented lagers, and it involves a long, cold

storage at low temperatures. Although lagering refers to bottom-fermented beers, some top-

fermented beers such as Kölsch and Alt beers also require periods of lagering.

KRAEUSENING

"Kraeusen" is the German word used to describe the infusion of a strongly fermenting young

beer into a larger volume of beer that has undergone primary fermentation. Traditionally, the

wort used for kraeusening is obtained from the high 'kraeusen' stage of primary fermentation

and added in small portions (5-20% by volume) to the green beer to start a secondary

fermentation. MacDonald suggests adding a volume of kraeusen equal to 10 to 12% of the

"green" beer, containing approximately 2% (w/w) residual extract with a cell count of

between 10 and 15 million. Usually, higher gravity beers require a larger proportion of

kraeusen. Kraeusen may also be made from wort and a yeast culture, or from a sugar solution

together with yeast.

CASK-CONDITIONED BEERS

Casking has its origins in the British Isles and is most widely used to make pale ales (bitters),

porters, and stouts. Beer is racked either directly from fermenting vessels into casks when

fermentation is judged sufficiently complete (a residual extract of 0.75 to 2°P) or when the

correct charge of yeast is present (0.25-4.00 million cells/ml) . If too little yeast is present in

the beer, secondary fermentation is too slow and insufficient carbon dioxide is dissolved in

the beer. However, if too much yeast is suspended in the beer, secondary fermentation may to

violent. Although traditionally beer was racked directly to the cask, some brewers pass the

beer through a rough filtration to improve clarity.

BOTTLE-CONDITIONED BEERS

The practice of using priming sugars for bottle-conditioning has been refined by British

brewers and is still followed by some craft brewers as well as a few larger British brewers.

Belgian brewers are also known for using this method to add unique flavors. Bottle-

conditioning usually involves a short time in the conditioning tanks to improve overall

stability and flavor before adding priming sugars. Some brewers allow some yeast to pass

through for secondary fermentation, while others prefer to completely remove the primary

fermentation yeast and re-pitch with ale or lager yeast. Some brewers use lager yeast because

it generally has a smaller cell mass, is less likely to leave an autolyzed flavor, and flocculates

and settles better than ale yeast.

COLD STORAGE

Today with the use of modern equipment for refrigeration, carbonation, and filtration,

obviates the need for secondary fermentation and a long cold storage. The green beer

undergoing cold storage is fully attenuated and virtually free from yeast, which is achieved

because of higher fermentation temperatures and a diacetyl rest. Cold storage comprises

relatively short-term storage at temperatures - 2 to 4°C for several weeks or less compared to

secondary fermentation and subsequent cold storage that took several months.

4.4.2:BEER CLARIFICATION

Although much of the suspended yeast will settle to the bottom of the storage tank by gravity

sedimentation, it can be very time consuming in preparing beers for filtration. Consequently,

the brewer can add fining agents at the onset or during storage to speedup the sedimentation

process. Alternatively, the brewer can use centrifugation to remove yeast and other solids

after fermentation. Each of these processes is described in the following sections.

FINING AGENTS

Although good clarity can be obtained from simple sedimentation, better results can be

obtained in less time by using fining agents-isinglass and gelatin. The use of finings is not

universal. They find their widest employment in the United Kingdom with some ale brewers

but there has been renewed interest in North America.

1: ISINGLASS

Isinglass is a traditional "real ale" clarifier used in the United Kingdom, where the style of

beer benefits from a 48 hour clarification before or after casking. It is also used for fining

chilled and filtered beers. Isinglass is a gelatinous substance derived from the internal

membranes of fish bladders and comes in many different forms. The currently accepted

mechanism involves a direct interaction of positively charged isinglass with negatively

charged yeast to form flocs, which precipitate. Its effectiveness in settling ale yeast varies

with the strain of yeast, and it is generally not recommended for precipitating lager yeast.

CENTRIFUGATION

Centrifuging is a popular method of reducing the yeast content of beer and is often used

where fining agents are not used or are used in conjunction with fining agents. Many brewers

who practice accelerated cold conditioning use centrifuges, as they offer a greater degree of

control over yeast count and eliminate the time needed for maturation and fining. The yeast

count in beer ex-centrifuge can be controlled to a level of 0.05 x 106 cells/ml. The flocculation

characteristics of the yeast are of less importance as long as the yeast remains in suspension

for most of the fermentation. Optimal yeast separation is achieved at temperatures between 3

and 5°C . There are two principal ways to use centrifuges for yeast removal after

fermentation.

4.4.3: BEER STABILIZATION

In addition to clarification (i.e., removing yeast), beer must display physical stability with

respect to haze. Colloidal instability in beer is caused mainly by interactions between

polypeptides and polyphenols. Amino acids make up polypeptides which, in turn, make up

proteins. Polypeptides and polyphenols combine to produce visible haze that reduces a

product's physical shelf life. Reducing the levels of one or both of the precursors using

suitable stabilizing treatments will extend physical stability.

Polypeptides responsible for haze formation originate mainly from barley. Polyphenols in

beer originate from barley and hops. Polyphenols are mostly lost throughout the brewing

process, particularly during mashing, boiling, wort cooling, and maturation.

To remove polypeptides or polyphenols and to improve its physical stability, a number of

methods are employed for reducing chill haze. This procedure is often referred to as

"chillproofing."

1: CHILLPROOFING AGENTS

Over the years a number of chillproofing agents have been used to enhance beer haze stability

(i.e., reduction of beer proteins and/or polyphenols). Each agent has its pros and cons, and

many are used in combination, to suit the brewers own requirements and plant constraints.

4.4.4:BEER CONDITIONING TANKS

Conditioning tanks or commonly referred to as bright beer tanks are either horizontal or

cylindroconical and are usually constructed of AISI 304 stainless steel. Horizontal tanks

usually range in size of 100 to 500 hl while vertical cylindroconical tanks can be up to 6,500

hl in size. The greater ratio of surface area to beer depth for horizontal tanks provides a

distinct advantage over vertical tanks in the conditioning of beer. Although horizontal tanks

use more floor space per barrel of capacity, they offer quicker clarification, and the sediment

has a shorter distance to fall, than in upright vessels. Horizontal tanks are usually located

within the brewery in a temperature controlled room while cylindroconical tanks can either be

located in the brewery or outdoors. Tanks are normally fitted with impellers for mixing.

VESSEL SIZE

If the sole purpose of the tank is for conditioning, there is no restriction on the height of the

tank. However, if the tank is also used for fermentation the height can't exceed 15 m. This has

to do with the hydrostatic pressure on the yeast during fermentation. Tank diameters and the

cone angle can vary but generally fall within the range of 3.5-4.75 m and 60° to 75°,

respectively.

TEMPERATURE CONTROL

1: COOLANTS

For temperature control of cylindroconical tanks the brewer can either use direct or indirect

cooling:

2: COOLING JACKETS

The coolant is circulated through the conditioning tanks (i.e., cooling jackets) and then

returned to the plant.

4.5:BEER FILTRATION

Although conditioning-maturation, clarification, and stabilization-plays an important role in

reducing yeast and haze loading materials, a final beer filtration is needed in order to achieve

colloidal and microbiological stability. The beer must be rendered stable so that visible

changes do not occur during its shelf life.

FIG: BEER FILTRATION PROCESS

4.5.1:FILTRATION METHODS

1: DEPTH FILTRATION

Depth filtration removes particles from beer within the depth structure of the filter medium

itself. The particles are either mechanically trapped in the pores or absorbed on the surface of

the internal pores of the filtration medium. The filter media can be pre-made sheet filters or

fine powder made of, for example, diatomaceous earth (DE), also known as kieselguhr, which

is introduced into the beer and re-circulated past screens to form a filtration bed.

2: SURFACE FILTRATION

Surface filtration can be either absolute or nominal with a minimal depth capacity. Surface

filtration consists of a thin membrane or a thin membrane covered with polypropylene or

polyethersulfone in which particles are trapped in pores in the filter medium. Prior filtration

with a depth filter is usually required to prevent clogging the surface of a cartridge membrane

filter.

3: SINGAL- OR DOUBLE-PASS FILTRATION

The beer can undergo a single- or a double-pass filtration process. The double-pass filtration

consists of two steps: a primary (rough) filtration, and a secondary (polish) filtration. Primary

filtration removes the bulk of yeast and suspended material and the secondary filtration

produces a brilliantly clear beer. Filtered beer is subsequently stored in a finishing tank.

Double-pass filtration can be achieved with two sets of sheet filters of decreasing pore size or

more commonly with a powder filter followed by a sheet filter. If sterile filtration is required

the beer is filtered through a cartridge membrane filter too.

4.5.2: POWDER FILTERS

Many brewers employ powder filters for single pass filtration and are able to produce beers

that are suitable for packaging. In a powder filter, filtration is achieved with the use of filter

aids that form a filter bed on stainless wire mesh inside a pressurized vessel; or, on cellulose

sheets in a plate and frame filter; or, in the form of small holes in a candle filter. While the

screens and/or cellulose do not filter at all, but act as septum for the filter aids, it is the applied

"cake" of filter aid which does the filtration. The mechanics are very similar to those of sheet

filters.

TYPES OF POWDER FILTERS

There are several types of powder filters, namely: (a) plate and frame filters in which the

support is a cloth, (b) horizontal leaf or vertical leaf filters in which the support screen is a

wire mesh, and (c) candle filters which support the filter aid on a long thin perforated rod.

1: PLATE AND FRAME FILTERS

The plate and frame filter, has been the workhorse in breweries around the world for many

decades. It is robust and reliable, consistently filtering beer to the specified standards. Plate

and frame filters consist of a series of chambers enclosed within a metal frame. Between

adjacent frames is a double-sided porous filter plate covered with a cellulose filter sheet

folded at the top of the plate so that both sides of the plate are covered.

2: HORIZONTAL AND VERTICAL LEAF FILTERS

Leaf filters have a series of stainless steel leaves that are arranged either vertically or

horizontally inside a filter body. The filter leaf consists of a stainless steel mesh septum

attached to a stainless steel support plate. Screen septums are made with openings ranging

from 45 to 70 microns. Unfiltered beer enters the pressure vessel, passes through the filter

cake established on the leaf, and exits through the hollow shaft connecting the leaves.

FIG: HORIZONTAL LEAF FILTER

3: CANDLE FILTERS

Candle filters utilize a series of candles, containing a number of rings that are hung from a

rigid horizontal plate. The candles can be of porous ceramic, but they are usually perforated

or fluted stainless tubes covered or surrounded by a stainless steel support of various types.

The candles and support plate are housed within a vertical cylindrical vessel with a conical

base. The beer and filter aid is fed into the base of the filter case, forming a cake on the

outside of the candles. Beer flows into the candles and is collected through the dished end

cavity.

FIG: CANDLE FILTER

4.5.3: POWDER FILTER AIDS

TYPES OF FILTER AIDS

There are two types of filter aids used in conjunction with powder filters, which are

diatomaceous earth and perlite.

1: DIATOMACEOUS EARTH

The most popular powder used for filtration is diatomaceous earth (DE), which consists of

skeletal remains of single-celled plants called "diatoms" that contain silicon dioxide. The

three classifications of diatomaceous earth are natural, calcined, and flux-calcined. The

natural product is referred to as "diatomaceous earth" and the name "kieselguhr" is used only

for the calcined grades of diatomaceous earth.

2: PERLITE

Perlite is alumino-silicate rock that has been expanded by heat treatment and later crushed

and graded.

SAFETY AND DISPOSAL

Diatomaceous earth is very dangerous when inhaled; it can lead to irritation of the lungs and

even long-term lung damage. It is considered carcinogenic to human beings and can also

cause silicosis, a progressive and sometimes fatal lung disease, following long exposure to

silica dust.

4.6:BEER CARBONATION

The next major process that takes place after filtration and prior to packaging is carbonation.

Carbon dioxide not only contributes to perceived "fullness" or "body" and enhances foaming

potential it also acts as a flavor enhancer and plays an important role in extending the shelf

life of the product.

The level of dissolved carbon dioxide in beer following primary fermentation varies as a

result of a number of parameters such as temperature, pressure, yeast, type of fermentation

vessel, and initial wort clarity. Typically, carbon dioxide levels range from 1.2 to 1.7 volumes

of carbon dioxide per volume of beer (v/v) for non-pressurized fermentations. Consequently,

carbon dioxide levels need adjustment, unless the beer has undergone secondary fermentation.

Common practice is to raise the carbon dioxide level between 2.2 and 2.8 v/v and possibly

more prior for bottled and canned products. The carbon dioxide levels for kegged beer

typically range from 1.5 to 2.5 volumes.

PRINCIPLES OF CARBONATION

The time required to reach a desired carbon dioxide concentration depends on a number of

physical factors. Temperature and pressure play an important role in determining the

equilibrium concentration of carbon dioxide in solution. Increasing the pressure leads to a

linear increase in carbon dioxide solubility in beer. Decreasing the temperature gives a

nonlinear increase in carbon dioxide solubility in beer. Consequently, the equilibrium

concentration cannot be attained without either increasing the pressure or decreasing the

temperature. Thus, the closer the carbonating temperature is to 0°C and the higher the

pressure, the greater the carbon dioxide absorption. The amount of carbon dioxide that

dissolves is a function of time, with the rate decreasing exponentially as equilibrium is

approached.

Carbon dioxide levels are stated as volumes of gas at standard temperature and pressure per

volume of beer. Fixing the temperature and pressure at appropriate settings will bring about

the desired carbon dioxide concentration. This relationship between pressure, temperature,

and carbon dioxide volumes is given shown in the Carbon Dioxide Volume Table in

Appendix B. To use this carbonation chart, look up the volume of CO2 that you wish to

dissolve in the beer, cross reference it to the temperature your beer is at, and this will tell you

the gas pressure needed. For example, if you want 2.1 volumes of carbon dioxide in your beer

and the temperature of your beer is at 0°C you need to adjust the psi to 8.0.

SAFETY PROCEDURES

The brewer should only use pressure-rated vessels for carbonation and must know the

maximum working pressure of the tanks. Pressure-rated tanks are certified by the American

Society of Mechanical Engineers (ASME) certifying its ability to withstand normal operation

pressures. Tanks are equipped with pressure relief valves as a precaution against over-

pressurization. Relief valves should always be mounted directly to the highest point on the

tank. It is very important that no beer or foam come in contact with the relief valve, as contact

can affect the operation of the relief valve, causing it to fail to blow off at the set pressure.

Pressure relief valves should be inspected and tested on a regular basis, and they should be

regularly cleaned to avoid buildup that can lead to malfunction. To avoid buildup from beer

or beer foam, never fill tanks completely.

4.7: BREWERY CLEANING AND SANITATION

Cleaning and sanitation are an integral part of a brewery and should be taken into

consideration at every phase of the beer brewing process. Cleaning proceeds sanitation and

prepares the way for sanitation treatment by removing organic/inorganic residues and

microorganisms from the brewery equipment. Sanitation reduces the surface population of

viable microorganisms after cleaning and prevents microbial growth on the brewery

equipment.

CLEANING AND SANITATION

CLEANING DETERGENTS

There are two types of cleaning detergents: alkaline-based or acid-based detergents that are

often formulated with surfactants, chelating agents, and emulsifiers to enhance the

effectiveness of the detergents. A detergent must be capable of wetting surface(s) to allow it

to penetrate the soil deposits in order to act more quickly and efficiently. The detergent must

have the capacity to break the soil into fine particles and to hold them in suspension so that

they do not redeposit on the cleaned surface. Detergents also must have good sequestering

power to keep calcium and magnesium salts (beerstone) in solution.

1: ALKALINE-BASED DETERGENTS

Alkaline detergents are most effective in removing organic soils, i.e., oils, fats, proteins,

starches, and carbohydrates encountered in brewing. Alkaline detergents work by hydrolyzing

peptide bonds and breaking down large, insoluble proteins into small, more easily soluble

polypeptides. Alkaline detergents will not remove calcium oxalate and other inorganic

compounds that lead to a buildup of beerstone.

SODIUM HYDROXIDE

Of the cleaning agents, sodium hydroxide (NaOH), otherwise known as caustic soda, is

widely used in breweries worldwide. Its effectiveness in dissolving proteinaceous soils and

fatty oils by saphonification is virtually unsurpassed. This makes it a natural choice for

cleaning sludge off the bottoms of boilers and for cleaning beer kegs. Sodium hydroxide is an

acutely excellent emulsifier too. It is unrivaled in its ability to dissolve protein and organic

matter if used in conjunction with chlorine, surfactants, and chelating agents.

SODIUM HYDROXIDE/HYPOCHLORITE SOLUTIONS

Caustic/hypochlorite mixtures are particularly effective in removing tannin deposits, but are

used for a great variety of cleaning tasks. These mixtures can be used in CIP systems for

occasional purge treatments or to brighten stainless steel.

2: ACID-BASED DETERGENTS

Acid detergents are often used in a two-step sequential cleaning regime with alkaline

detergents. Heavy soils, tannins, hop oils, resins, and glucans are unaffected by acid

detergents. Acid detergents are also used for the prevention or removal of beerstone, water

scale (calcium and magnesium carbonates), and aluminum oxide. Acid detergents are more

effective against bacteria than are alkaline detergents.

PHOSPHORIC ACID

Phosphoric acid is used widely in the removal of beerstone and similar deposits on surfaces

such as protein material resins and yeasts. Its performance is greatly enhanced by adding an

acid-stable surfactant, which promotes penetration of surface deposits and also assists in the

process of rinsing at the end of the cleaning process. Phosphoric acid is not effective in

removing beerstone until it reaches 16°C.

NITRIC ACID

Nitric acid not only is used to remove beerstone and other inorganic deposits, it also has

biocidal properties when used either as a pure acid or in more stable, less hazardous mixtures

with phosphoric acid. In addition, nitric acid attacks protein.

SANITIZING AGENTS

Sanitizing agents (often called disinfectants) are used to reduce the number of

microorganisms to acceptable levels in brewing. Sanitizing may be accomplished by physical

methods or through the use chemical sanitizers. Physical methods include the use of either hot

water or steam to kill bacteria. Chemical sanitizing generally involves either immersing the

object in a sanitizing solution for a specific amount of time or spraying/wiping the object with

the solution and allowing it to air-dry. Chemical sanitizers differ in their effectiveness on

certain microorganisms and in the concentration, temperature and contact time required to kill

bacteria. Common chemical sanitizers include chlorine compounds, quaternary ammonium

compounds, hydrogen peroxide, peroxyacetic acid, anionic acids, and iodophores."

PHYSICAL SANITATION

Some brewers favor steam or hot water for brewery sanitation on the grounds that chemical

sanitizers can taint the beer with objectionable odors. To be effective, steam must be wet (not

superheated) and free from air.

PHYSICAL VERSUS CHEMICAL SANITATION

The advantage of physical sanitation is the elimination of chemical sanitizing agents;

however, its application is limited due to the energy required to produce steam or hot water,

and its suitability and effectiveness for some applications is limited. Chemical sanitation is

therefore predominantly used in the beer brewing industry.

ALKALINE-BASED SANITIZERS

1: CHLORINE

Chlorine based sanitizers are widely used in the beer brewing industry. Chlorine compounds

are broad spectrum germicides which act on microbial membranes, inhibit cellular enzymes

involved in glucose metabolism, have a lethal effect on DNA, and oxidize cellular protein.

Chlorine has activity at low temperature, is relatively inexpensive, and leaves minimal residue

or film on surfaces. In properly blended products, chlorine based sanitizers are relatively non-

toxic, colorless, non-staining, and easy to prepare and apply.

2: QUATERNARY AMMONIUM

Quaternary ammonium compounds, commonly referred to as "quats" or "QACs," are used

extensively in breweries because of their stability and non-corrosiveness. They have rapid

bactericidal action at very low concentrations but selective biocidal activity. QACs are

efficient against gram-positive bacteria but less effective against gram-negative bacteria. They

are very effective against yeast and mold too.

ACID-BASED SANITIZERS

1: HYDROGEN PEROXIDE

Hydrogen peroxide (HP) has a broad spectrum with slightly higher activity against gram-

negative than gram-positive organisms.

2: PEROXYACETIC ACID (PAA)

Peroxyacetic acid (peracetic, PAA) has been known for its germicidal properties for a long

time. One of the advantages of peroxyacetic acid is that, once it is dosed into water, there are

no vapor issues as with chlorine-based compounds. Its other advantages include the absence

of phosphates and foam, and its biodegradability. PAA is relatively stable at use strengths of

100 to 200 mg/l.

3: ANIONIC ACIDS

Anionic acids are one of the fastest growing sanitizing groups in the craft brewing industry.

They are chemicals composed of two functional groups-a lipophilic portion and a hydrophillic

portion-which results in a negative charge. The negatively charged anionic acid sanitizers

react with positively charged bacteria by attraction of opposite charges.

4: IODOPHORES

Iodophores have a wide biocidal spectrum, react directly with the cell, and are not subject to

immune species of yeast, bacteria, or molds. These are iodine-containing formulations are

usually composed of elemental iodine, a surfactant, and an acid such as phosphoric acid. The

surfactant reduces the staining and corrosive properties of iodine, which is stated to be a more

effective sanitizer than chlorine at comparable concentrations.

MATERIAL AND CORROSION RESISTANCE

1: STAINLESS STEEL

Many types of stainless steel are used in brewing beer. The type of stainless steel used in

brewing and fermentation equipment is the nonmagnetic 300 series, which includes several

types. Those more common to brewing are 304 and 316L stainless steel. Types 304 and 316L

have very good corrosion-resistant properties and are easily welded. Most brewery equipment

is constructed from Type 304 stainless steel. Type 316L, which has better corrosion resistance

properties, is often used but the material cost is much higher. Other 300 series metals are to be

avoided for brewery use, especially 303.

CHEMICAL AGENTS

Acid Detergents - Some acids can be used for a variety of stainless steel cleaning and

removing beerstone.

Alkaline Detergents - Sodium hydroxide, commonly used in the CIP systems of commercial

breweries, is quite effective for removing organic deposits from stainless surfaces.

Alkaline Disinfectants - Alkaline disinfectants, e.g., sodium hypochlorite, do not corrode

stainless steel Type 316.

PASSIVATION

As mentioned, stainless steel's resistance to corrosion and discoloration is in part due to a

passive oxide layer that protects the metal. The oxide forms naturally on clean surfaces

exposed to the atmosphere, but this formation can take up to two weeks, which is too long for

breweries. A technique known as passivation, using acid mixtures containing oxidizing

agents, can be used to enhance the formation of the passive oxide layer.

1: COPPER

Copper generally is more acid-resistant than alkaline-resistant. Copper is usually resistant to

non-oxidizing acids such as acetic, hydrochloric, and phosphoric, but is not resistant to

oxidizing acids such as nitric and sulfuric or to non-oxidizing acid solutions that have oxygen

dissolved in them.

2: ALUMINUM

Caustic cleaners react with aluminum, actually dissolving the metal and pitting the surface.

The reaction with aluminum can produce a potentially dangerous situation, in that flammable

hydrogen gas is produced. Proper ventilation is necessary under these conditions.

5: MATERIAL & METHODS

PHYSICAL PARAMETERS OF BEER:

1: ESTIMATION OF PH:pH of the sample was measured with pH meter. It is very essential to

check the pH in every step of beer production for the better Quality of beer. A good beer should

have pH=3 - 4.8

2: ESTIMATION OF SPECIFIC GRAVITY:The initial and final gravity of the sample of

beer was measured with hydrometer.

FIG: HYDROMETER

3: ESTIMATION OF TEMPERATURE:

Temperature: Initial and final temperature was noted by using thermometer.

YEAST ANALYSIS METHODS

1: YEAST CELL COUNT

Collect the sample and if required, dilute it to 10 times using 0.85% normal saline i.e.,

1ml sample + 9 ml saline

Count the no. of yeast cells using haemocytometer counting chamber in 5 medium

squares (4 corner and the central square)

Use the NEUBAUER improved counting chamber for yeast cell count, which contains 01

big square, 25 medium squares & 400 small squares (16 small squares in each medium

square)

The area of each small square is 0.0025 sq.mm, the total area of 400 small squares or the

counting chamber being 01 sq.mm

The depth of the counting chamber is 0.10 mm, the total volume of the counting chamber

being 0.10 cu.mm or 0.0001 ml / cc.

Neglect the budding cells smaller than half of the mother cell and count the budding cells

equal or more than half of the mother cell as individual cells

Count the cells on the lower and left margins, while neglect the cells on the upper and

right margins

Report the results as x million cells per ml of sample , where x = No. of cells counted in

the 5 medium squares / 02

2: YEAST VIABILITY

Collect the sample and mix it with 0.01% methylene blue stain in the ratio of 1:1, say 2

ml sample + 2ml stain

Count as many as 200 cells in approximately 4 to 5 medium squares of haemocytometer

counting chamber containing uniformly distributed yeast cells

The blue stained cells are reported as dead while the cells which do not take up any stain

are reported as viable

Report the results in terms of percentage as Total

no. of cells counted – no. of dead cells * 100

Total no. of cells counted

3: YEAST SOLIDS BY VOLUME

Suitable volume of sample, say 15 to 25 ml in a graduated centrifuge tube

Centrifuge the sample at 3000 rpm for 10 minutes

Determine the total volume contained in the tube and also the volume that has sedimented

in the tube

Calculate the yeast solids by volume asSedimented Volume * 100

Total Volume

and report the results in terms of percentage

4: YEAST SOLIDS BY WEIGHT

Weigh out a 50 ml centrifuge tube

Dispense approximately 50 ml of yeast sample into the preweighed centrifuge tube and

weigh it again

Weight of the tube with yeast – empty weight = weight of the slurry

Centrifuge the tube at 3000 rpm for 10 minutes

Decant the supernatant and reweigh the centrifuge tube with the sediment

Weight of the tube with the sediment – empty weight = weight of the yeast

Calculate the yeast solids by weight as Weight of the Yeast * 100

Weight of the Slurry

and report the results in terms of percentage

5: YEAST ATTENUATION

Collect 100 ml wort post – chiller and add 10 grams of pressed yeast to it

Leave it at 20 C for 24 hours with constant shaking in an orbital shaker

Filter the sample using glass fibre filter and determine the specific gravity at 20 C

Present gravity / End gravity – Limit gravity gives the Free Fermentables in the beer

6: YEAST PITCHING RATE

Yeast Pitching Rate is calculated in litres as follows:

Brew Length (in Hl.) * 0.0259 * Reqd. Pitching Cell Count * 100 * 100

S * V

Where, S is Solids% (by weight) & V is Viability%

7: YEAST FOOD DOSING

For Yeast Food, Zinc SulphateHepta Hydrate is used and its dosing is calculated in grams

of ZnSO4.7H2O as follows:

Brew Length (in kl) * Zinc Dosing Rate (in ppm) * 4.41

A dosing rate of 0.25 to 0.35 ppm , i.e., 0.25 to 0.35 mg per litre of wort is adequate

Sterilized solution of Zinc Sulphate is always recommended to be added only in cold

wort just before pitching.

8: YEAST ACID WASHING

Take about 250 ml of Yeast Slurry from Yeast Storage / Pitching Tank ready for pitching

and note its initial pH using a pH meter

Bring down the pH of the yeast slurry to 2.20 using 2.5 N ortho phosphoric acid (56.184

ml of 85% H3PO4 diluted to 1000ml with distilled water)

Note the titre reading i.e., volume of 2.5 N H3PO4 used to bring down the pH of the

yeast slurry to 2.20

Calculate the volume of 85% H3PO4 in ml, required to be added to ensure complete

yeast washing as follows:

Titre Reading (in ml) * Yeast Volume (in litres) * 56.184

Volume of Yeast sample (in ml)

6: RESULT& DISCUSSION

Numerous parameters influence the result. They can be divided in the followinggroups:

• COMPOSITION OF THE WORT:

– Original gravity

– FAN > 230 mg/l

– Ca 10 – 20 mg/l

– Mg > 40 mg/l

– Zn 0.10 – 0.15 mg/l

TEMPERATURE COURSE:

– speed of fermentation start influences the total fermentation time

– Fermentation byproducts

– CO 2 counter - pressure on top of the fermenter

• YEAST CELL COUNT:

– Yeast viability

– Yeast vitality

– Yeast strain

• AERATION:

– Rate of reproduction

– Sulfur dioxide formation

Sulfur dioxide is a highly antioxidative substance that is positive to the shelf -life of the beer. SO

2has come into focus as an ingredient that can be an allergen to some people. Therefore, if a

concentration above 10 mg/l is reached, ithas to be declared on the label. Formation during

fermentation depends mostlyon the yeast strain. In addition, it can also be influenced by

technologicalparameters during pitching. Lower aeration, high original gravity and poor

yeastvitality lead to higher sulfur dioxide contents; however, yeast count at pitchingis also

important, as higher extract and lower oxygen per cell can increase sulfurdioxide .

• TOPPING - UP METHOD:

– pitching and aerating each brew

– pitching and aerating the first brew and aerating only the followingbrews

• GEOMETRY OF THE FERMENTER:

– Open or closed fermentation

– Hydrostatic pressure

CHANGES DURING FERMENTATION

The dissolved extract substances of the wort are fermented to ethanol and CO 2 bythe activity of

yeast enzymes. This metabolic pathway is exothermic and is called glycolysis. Yeast hydrolyses

hexose and sucrose first (startingsugar), then takes maltose (main fermentation sugar) and

afterwards maltotriose(secondary sugar).

Fermentation byproducts are formed on metabolic sideways. They can be characterized into six

groups:

• Higher aliphatic and aromatic alcohols.

• Multivalent alcohols.

• Esters.

• Carbonyl compounds.

• Sulfur - containing compounds.

• Organic acids.

All these compounds have different taste and odor thresholds. Their combined contributions

make up the flavor or off - flavor of the beer; the amounts produced can be influenced to some

degree by brewing technology.

During the main fermentation, the pH decreases by one unit because volatile(acetic, formic) and

non - volatile organic acids (pyruvic, malic, citric, lactic) areformed from amino acids by

deamination. The final pH of the beer ranges from4.3 to 4.6. The intensity and speed of acid

formation is determined by the bufferingcapacity of the wort, amount of easily assimilated

nitrogen, yeast strain and fermentationmethod used. The pH has a direct influence on the flavor

and thesparkle of the beer.

Short - chain fatty acids are formed at the beginning of the main fermentationprocess: butyric,

isovaleric, hexanoic, octaoic and decanoic acids. Their amountscan be controlled by the wort

composition, aeration, yeast strain and generalfermentation conditions. During pressure

fermentation, increased levels ofthese compounds can be expected. They cause a yeasty odor and

impair headretention.

The higher aliphatic alcohols (1 - propanol, 2 - methyl - 1 - propanol, 2 - methyl - 1 -butanol and

3 - methyl - 1 - butanol) and the aromatic alcohols (especially 2 - phenyl - 1 -ethanol) represent

the largest fraction of the compounds responsible for the aromaof the beer. They are formed

during the first 2 – 3 days of the fermentation; lateron there is only a slight increase. In

concentrations above 100 mg/l, however, theywill adversely affect taste and quality. Their levels

can be controlled to some extentby the content of free amino nitrogen, wort concentration,

pitching rate and yeaststrain, but mainly by the pitching temperature and the fermentation

temperature.

The formation of higher alcohols is decreased by cold pitching temperatures,colder fermentation

temperatures and the use of pressure as early as a degree ofattenuation of about 50% is reached.

Owing to their low threshold values, esters strongly influence the organolepticproperties of beer

to interesting fruity notes. Esters are the products of the enzymaticcatalysis of organic acids and

alcohol (mainly ethanol, but also higher alcohols).

Their formation is closely related to yeast propagation and lipid metabolism.Beer contains more

than 50 different esters, from which six are of greater importance for the beer flavor:

• Ethylacetate.

• Iso - amylacetate.

• Iso - butylacetate.

• β - Phenylacetate.

• Ethylcaproate.

• Ethylcaprylate.

Bottom - fermenting beers contain up to 60 mg esters/l, top - fermenting beers upto 80 mg

esters/l. Ester production is increased by:

• Increasing the original gravity above 13%.

• Restricting wort aeration.

• Higher fermentation temperatures.

• Increased movement during fermentation and maturation.

Pressure during fermentation decreases ester formation in the same way as thehigher alcohols.

Higher alcohols and esters in defined concentrations are necessary for the aroma profile of a high

- quality beer. Once formed, they stay in beer and are notremoved in later fermentation

stages.Methylthio- 1 - propanol and thiols] are not desirable in beer because of their strong

vegetableodor and taste even in very low concentrations. Apart from efficient trubremoval, the

most important factor in the formation and reduction of these flavor -active substances is the

yeast strain and the absence of spoiling microorganisms in beer. Mercaptans are thioalcohols,

compounds in which the OH group of the alcohol lis replaced by a SH group. They can strongly

impair beer flavor and are alsoresponsible for the so - called lightstruck flavor in beer.DMS is

not affected by yeast. DMS in beer depends on the amount present inwort.

Glycerol, a multivalent alcohol, is formed during glycolysis; its concentrationdepends on the

amount of fermented sugars (1300 – 2000 mg/l) and is thereforeproportional to the gravity of the

wort.

Aldehydes and ketones are responsible for the aroma of the green beer and for the stale flavor.

Acetaldehyde is formed in the green beer during the first 3 daysand gives beer an unripe,

unbalanced taste. Since it vanishes in later fermentationstages, it presents no technological

difficulties. In the green beer phase the acetaldehyde content is about 20 – 40 mg/l; in the

finished beer values of 8 to 10 mg/lare found.

Off - flavors in beer are usually caused by high levels of the vicinal diketonesdiacetyl and 2,3 -

pentandione. They impart an unfavorable, rancid and cheesy/buttery odor and taste to beer. The

taste threshold of diacetyl depends onbeer type and ranges from 0.08 to 0.2 mg/l; that of 2.3 -

pentandione from 0.5to 0.6 mg/l. The vicinal diketones are transferred to the

correspondingmultivalent alcohols and they are seen to be indicators of the stage ofmaturation.In

addition to the formation of byproducts, a number of other reactions andchanges take place

during the fermentation.

CHANGES IN THE COMPOSITION OF NITROGEN COMPOUNDS

Yeast converts nitrogen compounds from wort to synthesize its own cellular substances.The free

amino nitrogen ( FAN ) content is reduced from 200 – 250 to 100 –120 mg/l. High - molecular -

weight polypeptides become insoluble and are later filtered out of the beer.

pH DROP

The pH decreases from 5.4 – 5.6 in wort (biological acidified wort 5.2 – 5.0) to avalue of 4.3 –

4.6 and then remains constant. A rapid fermentation is advantageousfor the precipitation of

protein – polyphenol complexes. The beer matures quicker, can be filtered without problems and

has an excellent non - biological stability.Lower pH values, for instance below 4.2, must be

avoided because they impairan acidic beer taste. An increase in pH after fermentation indicates

yeastautolysis.

CHANGES IN THE REDOX PROPERTIES OF BEER

The redox properties indicate the relationship between the reducing andoxidizing power in a

solution. The increase of the reducing potential is closelyrelated to the uptake of dissolved

oxygen by the yeast at the beginning of thefermentation.

The redox potential in beer can be measured by the rH value, the Indicator TimeTest or the

oxygen content in beer. The rH value of wort ranges between 20 and30; in green beer between 8

and 12.The oxygen of the aerated wort is absorbed by the yeast some hours after pitchingand

then reaches values of 0.0 mg O 2 /l beer. The oxygen content must be kept low during filtration

and filling.

BEER COLOR

In the first days of fermentation the color of the beer becomes 2 – 3 EuropeanBrewery

Convention ( EBC ) color units lighter. Some substances change their coloraccording to the pH

drop; some are adsorbed on the surface of the yeast and areremoved with the settling yeast.

PRECIPITATION OF BITTER SUBSTANCES AND POLYPHENOLS

As a further result of the pH drop a number of colloidally dissolved bitter substancesand

polyphenols reach their isoelectric point (pI) and then precipitate. Therest of the non - isomerized

α - acids and some isohumulones are captured fromascending CO 2 bubbles and carried ahead to

the foam. The loss of bitter substancesranges from 25 to 40% during fermentation.

CO 2 CONTENT

According to the desired CO 2 content, CO 2 is enriched in fermenting beer. TheCO 2 content can

range from 4.3 to 5.5 g CO 2 /l for bottom - fermented beers and 6to 10 g CO 2 /l for top -

fermented beers. The solubility of CO 2 in beer depends ontemperature and pressure. Most of the

CO 2 produced during fermentation is,however, recovered.

ROUTINE CHECK RESULT OF SPECIFIC GRAVITY & TEMPERATURE:

Primary fermentation is the fermentation stage proper in which yeast, throughcontrolled growth,

is allowed to ferment wort to generate alcohol andthe desired spectrum of flavors. Increasingly

brewery fermentations areconducted in cylindro-conical vessels. The fermentation is regulatedby

control of several parameters, notably the starting strength of thewort (◦Plato, which

approximates to percentage sugar by weight, or Brix),the amount of viable yeast (‘pitching rate’),

the quantity of oxygen introducedand the temperature. Fermentation is monitored by measuring

the decrease in specific gravity (alcohol has a much lower specific gravity thansugar).

TABLE: RESUL OF SP.GR. & TEMP.

DATE F.V. NO. 12 13 14 15 16 17 18 19 20 23 24 27 28 29 31

15/3 SP.GR. 52 50 58 7 6 58

TEMP. 11 11 11 2 1 11

16/3 SP.GR. 37 36 50 5 51 58 58

TEMP 12 11 11 1 11 11 11

17/3 SP.GR. 30 30 40 40 50 52

TEMP. 11 11 11 11 11 11

18/3 SP.GR. 20 20 30 30 41 41

TEMP. 12 12 11 11 11 11

19/3 SP.GR. 13 12 19 21 29 29

TEMP 13 13 12 11.

5

11 11

20/3 SP.GR. 10 8 12 12 20 20 58 58

TEMP. 12 2 13.5 13.

5

12 12 11 11

21/3 SP.GR. 9 8 8 9 14 13 58 58 52 54

TEMP 2.

5

0 8.5 2.5 13.5 13 11 11 11.5 11

22/3 SP.GR. 7 7 7 7 12 9 52 54 45 46

TEMP. 0.

5

0.5 1 0 13 12 11 11 11 11

23/3 SP.GR. 9 7 7 7 6 52 55 43 43 33 40

TEMP 0 0 0.5 1.5 3 11 10 11 11 11 11

24/3 SP.GR. 6 31 36 19 15 14 18

TEMP. 2 14 13 13 13 13 13

TABLE: RESUL OF SP.GR. & TEMP.

DATE F.V. NO. 1 13 14 15 16 17 18 19 20 23 24 2 28 29 31

2 7

1/5 SP. GR. 1

0

10 10 25 28 9 10 9 10

TEMP. 1 1 1 11 11 1 1 1 1

2/5 SP.GR. 1

0

10 58 58 16 27 10 9 10

TEMP 1 1 11 11 12 12 1 2 1

3/5 SP.GR. 1

0

10 58 58 52 54 10 23 10 9 10

TEMP. 1 1 11 11 11 11 14 13 1 1 1

4/5 SP.GR. 52 54 42 46 40 10 19 10 9 10

TEMP. 11 11 11 11 11 1 14 1 1 1

5/5 SP.GR. 5

8

58 42 47 32 36 30 10 14 9 10

TEMP 1

1

11 11 11 11 11 11 1 15 1 1

6/5 SP.GR. 5

0

55 31 37 23 28 17 10 11 8 10

TEMP. 1

1

11 11 11 11 11 11 1 5 1 1

7/5 SP.GR. 4

1

50 23 29 26 20 9 10 11

TEMP 1 11 11 11 11 12 12 1 2

1

8/5 SP.GR. 3

1

42 15 21 12 15 9 10 11 5

8

58

TEMP. 1

1

11 14 14 14 14 4 1 1 1

1

11

9/5 SP.GR. 2

2

32 10 13 10 10 9 10 11 5

5

56 58 58

TEMP 1

1

11 14 13 13 14 2 1 1 1

1

11 11 11

10/5 SP.GR. 1

6

25 10 9 10 10 9

TEMP. 1

4

11 4 14 2 5 2

CONTROL OF FERMENTATION

Control of fermentation and maturation needs to measure temperature, extractand diacetyl. In

addition, pH drop, cell count during fermentation, turbidity,decrease in color, redox potential or

CO 2 content also need to be checked once perfermentation or from time to time.

7: RECOMMENDATION:

1. Use cylindroconical (Unit Tank) vessels for the fermentation.

2. Change the old thermometers & pressure meter & use the advanced & automatic meters.

3. Use the hand gloves, hair cap & special during yeast pitching, yeast collection, yeast

washing & washing of the fermentation vessels &equipment.

4. Sanitize the hands with formaline to prevent the microbial contamination in beer.

5. Do the microbial examination of the yeast & yeast culture for example SPC, TPC&

viability test.

6. Use the advanced & new laboratory equipment for the testing.

7. Proper room is needed for the yeast cultivation, storage & propagation.

7.1: CONCLUSION

Fermentation is a decisive step to obtain a well - balanced and high - quality beer.The main goals

of the fermentation are to reach:

• Constant fermentation times.

• Vigorous extract degradation and pH drop.

• A desired degree of fermentation.

• A constant beer quality.

• A long shelf - life.

• Maintain the analysis parameters.

The in plant training was very interesting and useful to me. I was able to understand some of the

processes about which I had learnt from the text book. This training also gave me an opportunity

to understand the practical problems.

In this Industry arrangement has made to get the staff medically examined once in six month.

Any person who is suffering from infections disease is not permitted to work in the production

hall until the completion of medical treatment allow for work.

As a trainee I got that individual attention of managers and their team of different workers of

complete plant and my association with the company will be ever-lasting in my memory.

8: BIBLIOGRAPHY

BOOKS:

1: Charles W. Bamforth, Food, Fermentation & Microorganism, Blackwell Publishing, 2005

2: Wolfgang Kunze, Technology Brewing And Malting, Vlb Berlin, Isbn 3-921690-49-8

3: C. W. Bamforth, Brewing New Technologies, Wood Head Publishing,2006

4: Alan J. Buglass, Alcoholic Beverages, Wiley,2011

5: Hans Michael Eblinger, Handbook Of Brewing, Wiley Vch,ISBN: 978-3-527-31674-8,2009

WEB SOURCE:

1. en.wikipedia.org/wiki/Yeast

2. en.wikipedia.org/wiki/Fermentation_(food

3. en.wikipedia.org/wiki/Fermentation_(biochemistry)

4. en.wikipedia.org/wiki/Brewing

5. en.wikipedia.org/wiki/Beer

6. http://www.beer-brewing.com

7. en.wikipedia.org/wiki/Saccharomyces_pastorianus

8. en.wikipedia.org/wiki/Saccharomyces_cerevisiae