Pasteurization v Introduction Name Louise Pasteur study during

Pasteurization v Introduction: Ø Name: Louise Pasteur – study during 1860 -1864 Ø First attributed : Dr. Soxhlet – Germany – 1886

Definition 2 Ø Pasteurization refers to the process of heating every particle of milk or milk of the different classes to atleast 630 C (1450 F) for 30 minute or 720 C (1610 f)for 15 seconds or an approved temperature and time combination that will serve to negative phosphatase test, the milk is immediately cooled to 50 C (41 o. F) or below. Ø The temperature-time requirement for pasteurization was fixed as 61. 7 0 C for 30 minute on the basis of destruction of Mycobacterium tuberculosis, which was considered as the most heat resistant organism. Ø Later, it was changed to 62. 8 0 C for 30 minute based on the time- temperature required for destruction of Coxiella burnetii, which is more heat tolerate than Mycobacterium tuberculosis.

Objective of pasteurization 3 Ø Public health aspect: Safe for human consumption by destroying all bacteria that may be harmful to health. Ø Keeping quality aspect: Improve the keeping quality – destroyed some undesirable enzymes and many spoilage bacteria.

Disadvantages of pasteurization: 4 Ø The nutritive value of milk is to some extent adversely affected. Ø It affect the cream line. Ø Increase the cost of milk due to processing charge. Ø Does not destroy bacterial toxins in milk.

Various methods of pasteurization 5 Ø Batch pasteurization / low temperature long time pasteurization (LTLT) ü Water jacketed type ü Water spray type ü Coil vat type Ø High temperature short time pasteurization (HTST) ü Tubular heat exchanger ü Plate heat exchanger. Ø Vacuum pasteurization

6 Ø Flash pasteurization Ø Ultra high temperature treatment (UHT) ü Direct ü Indirect Ø Ultra pasteurization (Uperisation) Ø Stassanization

Batch / LTLT: 7 Ø Every particle of milk is subjected to a temperature of 630 C for 30 min followed by prompt cooling to 50 C or below. Ø It is 3 types: ü Water jacketed type: Steam or hot water – passing through double jacket of vat. Foam heater is used to prevent surface cooling. ü Water spray type: Spraying of the hot water ü Coil vat type: Heated and cooling by horizontal and vertical turning coil.

Advantages 8 Ø It is useful for handling small quantity of milk. Ø It does not involve sophisticated equipment. Ø Technically trained persons are not required as its operation is easy. Ø Milk is not wasted during this process.

Disadvantages 9 Ø There is possibility of outside contamination. Ø Time taken for pasteurization is too long as there is no regenerative heating and cooling. Hence growth of thermophilic organisms is encouraged. Ø Automatic control to check the operation is not possible. Ø This occupies more space and in place-cleaning is not convenient. Ø It can not handle large quantity of milk and operation cost per litre of milk handle is more.

HTST: 10 Ø Heating of milk - 720 C for 15 sec. - cooling to 50 C or below. 1) Tubular heat exchanger: Shell-and tube and concentric tubes. ü In shell-and –tube heat exchanger: No. of small tubes carrying milk – passing to large tubes where heating/cooling medium circulated. ü Concentric tube heat exchanger: Inner and outer tube carrying the heating/cooling medium and middle tube carrying the product. 2) Plate heat exchanger: The corrugated stainless steel plates held (3 mm) aprat are joined together by non-absorbant rubber gaskets or seal.

Advantages 11 Ø This is useful for handling large quantity of milk. Ø The capacity can be increase by increasing the number of plate heat exchanger. Ø The energy required for heating and cooling is saved by the regenerative process of this method.

Disadvantages 12 Ø This not suitable for handling small quantity of milk. Ø Gaskets used between the plates must be given constant attention. Ø Complete drainage is not possible as approximately 10% milk retained in between the plates. Ø There are chances of formation and accumulation of milk stones. Ø Margins of safety in the product sanitary control are narrow. Ø It required trained operator. Ø Survival of thermoduric organisms is possible.

UHT: 13 Ø Every particle of milk is subjected to a temperature time combination of 1350 C – 1500 C without holding. Ø The success of this treatment depend upon aseptic packaging in tetra pack. Ø UHT is 2 types. ü Direct heat treatment: either the steam is injected into the milk or milk is infused into the steam. ü Indirect heat treatment: either by plate heat exchanger or tube heat exchanger

Vacuum pasteurization 14 Ø Pasteurization of milk/cream under vacuum - Vacreation. Ø The advantage of this process is to remove off flavour from milk as well as cream. Ø The process has been found more suitable pasteurization of cream meant for butter making. for Ø The machine used for vaccum pasteurization is known as vacreator which is invented in New Zealand by M/s. Murry Deodorizers Ltd.

Flash pasteurization: 15 Ø The temperature of milk is raised to 80 0 C for practically no holding period. Ø This process destroyed all pathogenic organisms that might be present in milk. Ø The major advantages of this process are the reduction in nutritive value of milk is less in this methods as compared to other methods.

Ultra pasteurization (Uperisation): 16 �The process of uperization is one of the recent inventions of the market milk industry. �The process has been developed in Switzerland. �In this process milk is heated with a direct steam up to 150 0 C for a fraction of a second.

Stassanization: 17 Ø The credit of developing this process of pasteurization goes to a French scientist Henri Stassno who invented the process in France. Ø The process is now in use to a considerable extent in milk plants of France, Denmark, Italy and certain other countries. Ø The principle of its operation is heating of milk to the desired temperature by passing it through two water heated pipes, through narrow space of 0. 6 to 0. 8 mm. Ø The milk is force through the narrow space which comes in contact with heating surface. The temperature of milk is raised to about 74 0 C for 7 seconds and immediately cooled to 4 to 5 0 C.

Milk preservation methods 18 v Lactoperoxidase (LP) system v Chilling v Concentration process v Drying

Lactoperoxidase (LP) system: 19 Ø The milk can be preserved by addition of preservatives such as H 2 O 2. Ø The permissible limits recommended by FAO (1957) for use of H 2 O 2 in milk is less than 800 ppm. Ø However, the used of H 2 O 2 is not permitted by PFA, 1954 because the flavour , body and texture of milk products made from the milk is unsatisfactory. Ø Besides, the marginal loss in biological value of sulphur containing A. A in H 2 O 2 treated milk is also observed.

20 Ø The three essential components of LP-system are ü ü ü Lectoperoxidase (enzyme) Thiocyanate (substrate) Hydrogen peroxide (promoter) Ø If any one of these is absent, the LP-system fails to get activated in milk. Ø IDF (1988) recommended the use of LP-system for temporary preservation of raw milk during collection and transportation to the processing plant. Ø They have recommended the addition of thiocyanate (14 mg) and sodium percarbonate (30 mg) per litre of milk within 3 hrs of its production.

21 Ø Lactoperoxidase is normally synthesized within the mammary gland is always present in bovine milk (30 ug/ml). The level needed for the LP-system to get activated in milk is 0. 5 – 1. 0 ug/mg. Ø Sodium thiocyanate and hydrogen peroxide when added @ 30: 30 mg/litre improves the keeping quality of milk to 10 hrs. at 370 C. Ø LP-system is bactericidal to gram negative organisms and bacteriostatic to gram positive organisms.

Chilling: 22 Ø Chilling of milk to 50 C or below and holding it at such a temperature will preserve the milk by preventing the multiplication of microorganisms but it does not destroy them as in pasteurization.

Concentration process: 23 Ø Milk, skim milk, whey and other milk products can be concentrated, i. e. , part of the water can be removed. Ø This is applied to diminish the volume and to enhance the keeping quality. Ø Water can be removed from by evaporation. Ø In addition to water, volatile substances, especially dissolved gases, are removed as well. Ø Evaporation is usually done under reduced pressure- hence, decrease temperature- to prevent damage caused by heating. Water can also removed by reverse osmosis.

Drying: 24 Ø Drying is usually applied to make a durable product that is easy to handle and after reconstitution with water, is very similar in properties to the original material. Ø Drying is applied to products like milk, skim milk, whey, cream, ice cream mix, protein concentrates, infant foods, all of which have high water content.

25 Thank you