Wednesday, June 23, 2021

Butter processing: Pasteurization

The pasteurization of cream for butter making has for its primary object the elimination of the normal bacteria of the cream to enable the butter maker by controlling the ripening of the cream to secure a uniform product.

Butter processing begins with the clarification and separation of milk. The cream is cooled and kept in a transitional storage tank where the fat content is analyzed, and if necessary adjusted to the desired value.

Cream with a concentration of 30 to 45 percent milkfat (depending on the method of churning) is then pasteurized and cooled.

For vat pasteurization the cream is normally pasteurized at 74° C for 30 minutes; for the high temperature short time method cream is pasteurized at 85° C for 15 seconds.

The high temperature is needed to destroy enzymes and micro-organisms that would impair the keeping quality of the butter and to help lengthen butter’s shelf life.

Pasteurization of cream for making ripened cream butter is commonly carried out at higher temperature than for sweet cream butter e.g., 90-95° C for 15 or 105-110° C with no holding. Severe heat treatment denatures whey proteins, particularly lactoglobulins, exposing-SH groups which act as antioxidants and can enhance starter growth.

Several factors are involved in the determination of this temperature, among the most important of which are the uniform destruction of a large proportion of the bacteria of the cream; the destruction of the enzymes inherent in the milk; the avoidance of imparting scorched, metallic, or other undesirable flavors to the cream; and the possible increased loss of fat in the buttermilk.

Pasteurization causes the fat in the fat globules to liquefy. And when the cream is subsequently cooled a proportion of the fat will crystallize. If cooling is rapid, the crystals will be many and small; if gradual the yield will be fewer but larger crystals.

By modifying the cooling program for the cream, it is possible to regulate the size of the crystals in the fat globules and in this way influence both the magnitude and the nature of the important continuous fat phase.
Butter processing: Pasteurization

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