Observations on the Freezing of Milk and Cream II. The Destruction of the Fat Emulsion in Frozen Cream

Abstract

Cream which has been partially frozen or frozen to apparent solidity for the purpose of storage, almost invariably shows evidence, upon thawing, of a partial destruction of the fat emulsion. This phenomenon has been noted and studied by several investigators (1, 2, 3, 4). Recently Webb and Hall (5) have shown this separation of free f a t to increase with the fat content of the cream and suggest that it is dependent on several factors, the most important being, the freezing point of the aqueous phase, the protection afforded the emulsified fat by adsorbed protein, and the size of the fat globules themselves. Sommer (6) atributes the breakdown of the fat emulsion to the destabilization of the protein adsorption film, around the fat globules, brought about by freezing. However, it has been shown that the protein of frozen milk and cream is not appreciably affected until after a considerable interval of holding in the frozen condition (1, 5) whereas the fat emulsion is immediately affected (1, 3, 5). Mack (7), Price (8), and also Webb and Hall have found that additions of sugar to cream before freezing markedly decrease the amount of oiling off of the fat after thawing.