Process of Pasteurization

Process of Pasteurization
This is a comparatively low order of heat treatment generally done at temperature below the boiling point of water.

Two primary objective are achieved by pasteurization.

1. Destruction of majority of but not necessarily all pathogenic and other spoilage microorganisms in liquid foods such as milk and liquid egg. In the case of milk used for cheese making, pasteurization destroys all microorganism that would compete with the desired fermentation process at a later stage.

2. Extending the product shelf life from a microbial and enzymatic points of view.

The second objective is more of relevance in the pasteurization of beer, wine, fruit juice. Pasteurization will also inactive the natural enzymes present in the food.

Pasteurized food will contain many living organism capable of growth thus limiting the storage life of the foods compared to commercially sterile foods.

Pasteurized foods must be stored under refrigerated conditions, e.g. pasteurized milk may be stored in a refrigerator for a week or so without developing significant off flavours.

Pasteurization may be carried out in batch or continuous mode. Bulk foods such as milk and fruit juices may be pasteurized in batches in stirred, jacketed stainless steel vessels using steam or hot water.

Rapid cooling of pasteurized food is necessary to limit the growth of thermophilic organisms and hence the food is passed though a cooler.

Foods sealed in containers may batch pasteurized in water or steam baths followed by water spray cooling.

Continuous pasteurization of bulk foods is carried out by passing them though plates heat exchangers in four stages viz. preheating, heating, holding and cooling.

The choice of temperature and time pasteurization depends on the type of food.

For example, milk is pasteurized at 62,8 degree C for 30 minutes or by high temperature short time (HTST) pasteurization at 72 degree for 15 seconds, while whole egg is pasteurized at 64.4 degree C for 205 minutes.
Process of Pasteurization