Beer fermentation

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Microbiology in Microbiology in society:society:

Eat, Drink & Sleep MicrobesEat, Drink & Sleep Microbes

Kevin F. KellyKevin F. KellyDepartment of BiologyDepartment of BiologyMcMaster UniversityMcMaster University

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Microbes in Society:Microbes in Society:The Power of NumbersThe Power of Numbers

Microbes are EVERYWHERE, you are probably inhaling them right now.

5 broad classes:

1. Bacteria (>5000 sp.!)2. Fungi (moulds, yeast)3. Algae4. Viruses5. Protozoa (amoeba)

rod-shaped bacteria

budding yeast

threadlike algae

amoeba

viral particles

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Slide 3 Many, Many disease-Many, Many disease-causing foodborne causing foodborne

MicrobesMicrobes

Most common, caused by bacteria:

1. Campylobacter: fever, diarrhea, abdominal cramps. Lives inthe gut of healthy birds (E.g. chicken).

2. Salmonella: more fever, diarrhea, abdominal cramps. If entersbloodstream, can be fatal. Present in or on birds, reptiles and mammals.

3. E. coli O157:H7: Bloody diarrhea, painful abdominal cramps.Present in cattle and other animals; often ingested through cow feces.

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Many, Many Many, Many Beneficial foodborne MicrobesBeneficial foodborne Microbes

Microbes are used in the generation of various foods, including:

1. Hams (involved in the curing process)2. Beans, other veggies (N2 fixation)3. Pickles4. Chocolate5. Milk and Cheese

and on and on…

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Beer & Yogurt

using Yeast using Bacteria

Making

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Making BeerMaking Beer

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The Making of The Making of BeerBeer

Four, and only four, ingredients required:

Hops, water, yeast, and barley.

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Step 1: Sprouting the Step 1: Sprouting the BarleyBarley

Barley

•Soak barley in water for several days

•drain, hold barley at 60 degrees F for 5 days

•husks will open and barley will sprout

•now called “green malt”

•now ready for “the mash”

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Slide 10 Step 1.1: grinding the Step 1.1: grinding the BarleyBarley

“The Mash”“The Mash”

The Mash

•Converts the barley starches into “fermentable” sugars

•malted barley is crushed throughrollers

•heated water is sprayed onto the barleygrains as they enter the mash

•wet grains stay in the mash for 1 hourat 150 degrees F.

•Optimal temperatures and mashing releasesenzymes capable of converting starches tosugars

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Step 2: Time for the Wort Step 2: Time for the Wort (“wert”)(“wert”)

•Liquid drained off of mash is added to ahuge brew kettle

•brought to a vigorous boil for 90 mins.

Brew Kettle

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Step 2.1: “Hop to Step 2.1: “Hop to it”it”

Hops

•At start of boil, hops are added

•member of the hemp family

•contain acid, give beer its bitter flavour

•inhibits growth of ‘unwanted’bacteria

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Step 3: Separate the Step 3: Separate the SolidsSolids

•Wort is pumped from the kettle, then forced back into kettle through a jet nozzle

•The unique flow of liquid initiates a whirlpool; all of the hops and other solids move to the centre of the kettle

•The liquids (wort) are drained out, leaving the solids (in a cone shape) behind

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Slide 14 Step 4: The Beauty of Step 4: The Beauty of Biochemistry:Biochemistry:

Yeast FermentationYeast Fermentation

•Cooled wort is transferred to fermentation vessel already containing the yeast

•Type of yeast ultimately determines the ‘type’ of beer

Lager – kept at 48 degrees F for 6 weeks!Ale – kept at 68 degrees F for two weeks

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Step 4: Using Yeast for Step 4: Using Yeast for Alcohol FermentationAlcohol Fermentation

Alcohol DehydrogenaseThe source of

alcohol in beer!

released toatmosphere

C6H12O62(CH3CH2OH) + 2(CO2)

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Yeast Fermentation in a brewery

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Step 5: Cooling to Step 5: Cooling to bottling/Keggingbottling/Kegging

•Most important thing is to maintain sterility: limit exposure toyeasts, microbes in the environment prior to packaging

•empty bottles are sterilized with a chlorine solution and rinsed

•beer added to CO2-pressurized bottles

•bottles are capped

WHAT IS THE MOST DIFFICULT PART OF ALL THIS?

rinsing

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Getting the label to stick

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Processing of Yeast amino acids yields various compounds affecting the scent and taste of beer

(aromas)

(aromas)

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Over 1,000 chemical compounds in beer

Some of these compounds are generatedwhen beer becomes exposed to light –creating “skunky” aromas

3-methylbut-2-ene-1-thiol is one culprit

“Studying the chemical constituents of beer is "like looking at the night sky," he says. "The closer you look, the more stars you can see."

Morten C. Meilgaard

““A Skunk walked A Skunk walked into a bar…”into a bar…”

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Bring the milk to 85°C (185°F) over a stove and keep it there for two minutes, to kill any undesirable microbes.

Pour the re-pasteurised milk into a tall, sterile container and allow to cool to 43°C (110°F)

Mix in 120ml of warmed yogurt and cover tightly.

After about six hours of incubation at precisely 43°C (110°F); the entire mixture will have become a very plain but edible yogurt with a loose consistency.

Making yogurt:Making yogurt:Doing It at HomeDoing It at Home

*

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Streptococcus thermophilus and

Lactobacillus bulgaricus

Making yogurt:Making yogurt:the co-operation of two the co-operation of two

bacteriabacteria

S. thermophilus

L. bulgaricus

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Bacterial Lactic Acid Bacterial Lactic Acid FermentationFermentation

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Streptococcus thermophilus produces lactic acidlowers the pH, changing the form of the milk proteins and causing the mixture to thicken

Lactobacillus bulgaricus produce acetaldehyde, acetic acid, volatilefatty acids, ethanol, carbon dioxide and various other products which influence flavor and aroma

If Streptococci outgrow the Lactobacilli, the result is a harsh, sour yogurt due to overproduction of lactic acid relative to flavor components.

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Neat Yogurt Facts

-a good source of calcium, riboflavin and protein.

-has a fine curd which makes it more easily digestible than sweet milk.

-lactose is converted to lactic acid; this makes digestion easier on lactose- intolerant people

-lactic acid bacteria fight pathogenic organisms: Salmonella typhi die, E. coli are unable to develop, and S. paratyphi and Corynebacteriae diphtheriae lose their pathogenic properties.

-fermented milk cultures have been reported to help treat peptic ulcer, diarrhea, and dysentery.

-Freshly prepared yogurt contains 10,000,000,000 (109) bacteria per gram!!

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Other FoodborneOther FoodborneMicrobesMicrobes

Bifidobacteria are beneficial to the gastro-intestinal tract. Also called probiotic bacteria.

Streptococcus lactis and other lactic acid bacteria are used to make cheese. They ripen the cheese and provide characteristic flavour.

Streptococcus thermophilus is one of the major yogurt-forming bacteria. The other is Lactobacillus bulgaricus

Campylobacter jejuni is one of the major causes of diarrhea in humans

Listeria monocytogenes are psychrotropic food pathogens which can grow even in refrigerated Foods.

Salmonella infection of meat is one of the major causes of food poisoning.

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Slide 27 Conclusions:Conclusions:The good & bad of The good & bad of

microbesmicrobes

•We exploit microbes for the purpose of bettering our food industry,creating medicines etc…

•Also, at times, microbes exploit us for bettering their livingenvironments

•Important to understand which microbes are beneficial, and whichare undesirable

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Glycolysis

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What is Cenosillicaphobia the fear of? Answer: Fear of an empty glass

Answer: Prohibition lasted 13 years, 10 months, 19 days, 17 hours, 32 1/2 minutes

Answer: Brahma Beer. It is brewed in Sao Paulo, Brazil.

What was the length of Prohibition?

What is the best selling brand in the Western Hemisphere outside of the United States? What country is it brewed in?

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While in some countries the penalty for driving while intoxicated can be death (yes, death), in Uruguay intoxication is a legal excuse for having an accident while driving. "Please believe me officer, I really was drunk.”

There are more breweries in the US than any other country in the world.

There is more than 200 styles of beer produced throughout the world today.

Anheuser-Busch consumes about 15% of the entire U.S. rice crop for brewing beer.

The average American annually consumes 23.1 gallons of beer.