VACREATION

Heat treatment of cream is necessary to destroy organisms that may be pathogenic or cause spoilage and inactivate enzymes. Lactic acid produced by bacteria, causes souring and coagulation of cream. Proteolytic enzymes may produce bitter peptides and also cause coagulation.

Lipolytic enzymes will break down the lipids to produce free fatty acids which give a rancid flavor. Cream can be pasteurized by conventional means and the principles of heat treatment of milk can be applied to cream.

Cream is more viscous and somewhat more susceptible to mechanical break down, and this should be borne in mind when choosing equipment for cream pasteurization. Pasture feeding of animals can produce flavor taints through herbage derived substances dissolved in the fat.

As most of the tainting substances are relatively volatile, a process was devised in New Zealand both to pasteurize the cream and to remove the volatiles through what is essentially a steam distillation process.

The piece of equipment is known as a Vacreator, which was the trade name adopted for the Murray Vacuum Pasteurizer (present manufacturers and agents NDA Engineering Group, Auckland, New Zealand).

The process is known as vacreation. Vacreation has been used in a number of countries, and not only it improves the flavor of creamery butter, but also extends the shelf-life significantly when compared with butter derived from plate-pasteurized cream.

In the Vacreator, steam is intimately mixed with cream and the condensed vapor plus volatiles are removed by flash evaporation under vacuum.

The typical pressure and temperature conditions pertaining to each vessel are shown on the diagram.

Raw cream is preheated in a tubular heat exchanger by vapors exiting from vacuum vessels 3 and 4. The cream is mixed with steam and vapors.