INSTABILITY AND PARTIAL COALESCENCE IN WHIPPABLE DAIRY EMULSIONS

Dairy emulsions must be stabilized by an adsorbed layer to prevent flo cculation or phase separation during quiescent storage. In the product ion of products such as whipped cream and ice cream, however, a contro lled destabilization or partial coalescence of the emulsion is needed during further processing to develop an internal structure of agglomer ated fat, which favorably alters the texture and physical appearance o f the product. Several requirements must be met to induce partial coal escence, including a partially crystalline emulsion (implying refriger ated temperatures for milk fat), a weak adsorbed layer, and usually th e presence of air, agitation, or both. Milk fat that is homogenized in the presence of a blend of caseins and whey proteins normally produce s an emulsion that is too stable to undergo partial coalescence. Thus, small molecule surfactants (e.g., monoglycerides, diglycerides, and p olysorbates) are added to protein-stabilized emulsions to promote part ial coalescence by displacing proteins from the surface, resulting in a reduced surface concentration. However, it may be possible to contro l the adsorbed protein layer, hence promoting partial coalescence with out the use of such surfactants, by selectively homogenizing the emuls ion in the presence of only those milk proteins that would produce an interfacial layer that would be weak yet sufficient to maintain stabil ity of the emulsion during storage but not sufficient to maintain stab ility during a whipping process.