Raw Milk Heat Treatment Application

Microorganisms in milk change the qualities of milk under optimum conditions, rendering it unusable. For this reason, raw milk must be subjected to certain temperature processes before consumption. In other words, in order to destroy the pathogenic microorganisms in the milk and to prolong the shelf life, a certain temperature is a rule that must be strictly followed. For this purpose, boiling, pasteurization and sterilization processes are applied.

Boiling

It is not a widely used modern method in the dairy industry.Because with this method, all the qualities of the milk, especially the natural taste and smell, change in an undesirable way and there is a great loss in nutritional value.In addition, as a result of the high temperature applied during boiling, a pale brownish color is formed by the breakdown of lactose in milk.

Pasteurization

It is a temperature process applied below 100ºC with the aim of inactivating of all vegetative forms of pathogenic microorganisms, a large part of other microorganisms  , resulting in minimal physical, chemical and sensory changes that extend the shelf life of milk. There are different pasteurization methods applied to milk.

Continuous pasteurization (L.T.L.T.(low temperature – long time))

Raw milk is kept at 63 – 65 ºC for about 30 minutes in pasteurization performed at a low temperature.Steam or hot water is used as a heating medium.A suitable mixer should be available to ensure that the heat is spread homogeneously on all sides.Milk is cooled below 10 ºC immediately after heat treatment.With this method, pathogenall microorganisms are killed and the properties of milk are preserved.Since this method is very time consuming and there is no continuity in the process, it is preferred by businesses that process very little milk.

Short time pasteurization (H.T.S.T.(high temperature – short time))

In a high degree of pasteurization in a short time, the milk is kept at 72 - 75 ºC for 15-20 seconds.It is immediately cooled below 10 ºC.Plate heaters are used for pasteurization with this method.The heat exchangers plates are designed in a way to best transmit the heat from both the heating medium and the cooling medium. High heat pasteurization at 85 ºC for 1 minute is also a heat treatment. Immediately after the heat treatment, the milk is immediately cooled below 10 ºC. Pasteurized milk is filled in Tetra Pak filling machines and presented to the consumer in glass bottles or in boxes made of Tetra Pak. Pasteurized milk should be stored at 4 ºC.It should be consumed within the specified time. The shelf life of pasteurized milk varies between 1 and 5 days; Moreover in order for pasteurized milk to show this resistance, it must be stored in the cold (4 ºC).