PRESENTED BY,

NIMISHA.K

MSC FST 2ND SEM

KUFOS

WHAT IS PASTEURIZATION ??

Pasteurization is a heat treatment involves heating food to a

temperature that kills disease causing micro organisms and

substantially reduces the levels of spoilage organisms

Pasteurization is not intended to kill all micro organisms in the

food. Instead pasteurization aims to reduce the number of viable

pathogens so they are unlikely to cause disease

The heating may be by means of steam, hot water, dry heat, or

electric currents, and the products are cooled promptly after the

heat treatment

Heating also destroy enzymes that make milk spoil, so

pasteurized milk drinkable for long time

HISTORY OF PASTEURIZATION

The French scientist Louis Pasteur

invented pasteurization

To remedy the frequent acidity of the

local wines he found out experimentally

that it is sufficient to heat a young wine to only about 50-60˚C (122-140˚F) for a brief time to kill the microbes

Pasteurization was originally used as away of preventing wine and beer from souring, and it would be many years before milk was pasteurized

Pasteurization of milk was suggested by Franz von soxhlet in 1886

FOODS USED FOR PASTEURIZATION

Milk

Milk products

Dried fruits

Cream

Eggs

Fruit juices

PASTEURIZATION IS USED FOR;

1.When more rigorous heat treatments might harm the quality of products

2.When one aim is to kill pathogens, as with market milk

3.When the main spoilage organisms are not very heat resistant, such as the yeasts in fruit juices

4.When any spoilage organisms will be taken care of by additional preservative methods to be employed

When competing organisms are to be killed

DIFFERENT METHODS OF PASTEURIZATION

PASTEURIZATIO

N

HTSTUHT

LTLTVAT

VAT PASTEURIZATION

The first widely used pasteurization process

for milk involved heating the milk in large

tanks or vats to 60˚C for at least 20 minutes

The holding method was subsequently

changed to 61.7˚C for 30 minutes

This was not a continuous process and was

referred to as vat pasteurization

ULTRA HIGH TEMPERATURE (UHT)

Heat treatment processes in excess of

pasteurization for milk and milk products

have been designated as very high

temperature (VHT) and ultra high

temperature (UHT)

UHT processes usually refer to

pasteurization techniques with temperature

of at least 130˚C in a continuous flow, with

holding times of approximately 1 sec.

UHT SYSTEM

Steam injection

technique

steam is

injected into milk

Steam infusion

technique

milk is

injected into steam

BATCH PASTEURIZATION (LTLT)

Milk is heated at 63˚C for 30 minutes

Can heat milk in vat or outside the vat

Here milk is heated in plate heat exchanger and send to the vat

Agitator is provided in the vat to prevent cream formation and to ensure uniform heat distribution

Then the milk is cooled and again passed through the plate heat exchanger and cooled using chilled water

HIGH TEMPERATURE SHORT TIME (HTST)

Stages in HTST

1. REGENERATIO

N

2.HEATING

SYSTEM

3.HOLDING

SECTION

4.COOLING

SECTION

PROCESS

1) cold raw milk is fed into the pasteurization plant and passes into the

regeneration heating system of the plate heat exchanger

2) The plate heat exchanger is basically a series of stainless steel plates

stacked together with some space in between forming chambers to hold

the milk as it passes through

3) In the regeneration section cold milk is pumped through the A chambers,

while milk that already been heated and pasteurized is pumped through

the B chamber

4) The heat from the hot milk passes to the cold milk through the steel

plates5) This warms the milk to 57-68˚C 6) Next the milk is passes into the heating section of plate heat exchange. Here

hot water in the B chamber heats the milk at least 72˚C which is the goal temperature for HTST

7) Hot milk is then passed though a holding tubes, it takes milk about 15 sec to pass through the tube

8) Milk is officially pasteurized once its passes through the holding tube9) Now the pasteurized milk is sent back through the regenerative section, where

it warms the incoming cold milk10) This cools the pasteurized milk to about 32˚C

TEMPERATUE TIME PASTEURIZATION TYPE

63˚ C 30 min Vat pasteurization

72˚ C 15 sec HTST

89˚ C 1 sec HHST

90˚ C 0.5 sec HHST

94˚ C 0.1 sec HHST

100˚ C 0.01 sec HHST

138˚ C 2 sec UHT

PASTEURIZATION TEMPERATURE

The sensible heat required to raise the temperature of a liquid during pasteurization is;

Q=mc(T₁-T₂)

Q= Specific rate of heat transfer

m= mass flow rate

c= specific heat capacity

T₁-T₂= Temperature difference