Some Observations on the Physical-Chemical Stability of Sterile Concentrated Milks

Summary Gelation of sterilized concentrated milk appears to be a complex phenomenon. It may be influenced by as many as four or five variables. Heat treatment given the concentrated milk, composition of the milk, concentration, and storage temperature influence the gelation rate most. The first three variables influence gelation rate in a regular manner, but storage temperature influences gelation rate in an irregular manner; storage at 100F promotes gelation at a rate about four times as great as that at 40, 60, and 70F, which are about equivalent; storage at 50F promotes gelation at a rate approximately 50% greater than at 40, 60, and 70F. Conventional evaporated milk, under certain circumstances, will gel the same as HTST milks, but because of its much more severe heat treatment, gelation is delayed beyond normal storage, and it is almost never found in commerce. Homogenization at elevated temperatures increases viscosity and this, in turn, accelerates the gelation rate. However, we do not know if homogenization at lower temperatures will affect the gelation rate.