7 Safe Methods of Milk pasteurization

Methods of Milk pasteurization

  1. Pasteurization refers to the process of heating every particle of milk or milk of the different classes to at least 63°C (145°F) for 30 minute or 72°C (161°F) for 15 seconds or an approved temperature and time combination that will serve to negative phosphatase test, the milk is immediately cooled to 5°C (41°F) or below.
  2. Milk pasteurization
    Milk pasteurization

  3. 1. Batch pasteurization / low temperature long time pasteurization (LTLT)
  • Every particle of milk is subjected to a temperature of 63°C for 30 min followed by prompt cooling to 5°C or below.
  • It has 3 types:

    • Water jacketed type: Steam or hot water passing through double jacket of vat. Foam heater is used to prevent surface cooling

    • Water spray type: Spraying of the hot water

    • Coil vat type: Heated and cooling by horizontal and vertical turning coil

  • Advantages

    • It is useful for handling small quantity of milk.
    • It does not involve sophisticated equipment.
    • Technically trained persons are not required as its operation is easy.
    • Milk is not wasted during this process.
  • Disadvantages
    • There is possibility of outside contamination.
    • Time taken for pasteurization is too long as there is no regenerative heating and cooling. Hence growth of thermophilic organisms is encouraged.
    • Automatic control to check the operation is not possible.
    • This occupies more space and in place-cleaning is not convenient.
    • It can not handle large quantity of milk and operation cost per litre of milk handle is more.
2. High temperature short time pasteurization (HTST):
Heating of milk – 72°C for 15 sec. – cooling to 5°C or below.
i) Tubular heat exchanger: Shell-and tube and concentric tubes.
  • In shell-and –tube heat exchanger: No. of small tubes carrying milk – passing to large tubes where heating/cooling medium circulated.
  • Concentric tube heat exchanger: Inner and outer tube carrying the heating/cooling medium and middle tube carrying the product.
ii) Plate heat exchanger: The corrugated stainless steel plates held (3 mm) aprat are joined together by non-absorbant rubber  gaskets or seal.
  • Advantages

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

    • This not suitable for handling small quantity of milk.
    • Gaskets used between the plates must be given constant attention.
    • Complete drainage is not possible as approximately 10% milk retained in between the plates.
    • There are chances of formation and accumulation of milk stones.
    • Margins of safety in the product sanitary control are narrow.
    • It required trained operator.
    • Survival of thermoduric organisms is possible.
3. Vacuum pasteurization
  • Pasteurization of milk/cream under vacuum – Vacreation.
  • The advantage of this process is to remove off flavour from milk as well as cream.
  • The process has been found more suitable for pasteurization of cream meant for butter making.
  • The machine used for vaccum pasteurization is known as vacreator which is invented in New Zealand by M/s. Murry Deodorizers Ltd.
4. Flash pasteurization
  • The temperature of milk is raised to 80°C for practically no holding period.
  • This process destroyed all pathogenic organisms that might be present in milk.
  • The major advantages of this process are the reduction in nutritive value of milk is less in this methods as compared to other methods.
5. Ultra high temperature treatment (UHT)
  • Every particle of milk is subjected to a temperature time combination of 135°C – 150°C without holding.
  • The success of this treatment depend upon aseptic packaging in tetra pack.
  • UHT is of 2 types:
    • Direct heat treatment: either the steam is injected into the  milk or milk is infused into the steam.
    • Indirect heat treatment: either by plate heat exchanger or tube heat exchanger.
6. Ultra pasteurization (Uperisation)
  • 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°C for a fraction of a second.
7. Stassanization
  • The credit of developing this process of pasteurization goes to a French scientist Henri Stassno who invented the process in France.

  • The process is now in use to a considerable extent in milk plants of France, Denmark, Italy and certain other countries.

  • 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.

  • The milk is force through the narrow space which comes in contact with heating surface. The temperature of milk is raised to about 74°C for 7 seconds and immediately cooled to 4 to 5°C.

Post a Comment

share your words ...

Last Article Next Article