Gelation of Concentrated Skimmilk: Electron Microscopic Study

Concentrated skimmilks (26% solids), high-temperature, short-time sterilized and aseptically canned, with or without the addition of polyphosphate, were examined at weekly intervals by electron microscopy. In the control concentrated skimmilk, incipient gelation (aggregation of casein particles) was observed after nine weeks of storage and six weeks before gelation was observed visually. Micelles from concontrated skimmilks were smooth textured and twice the diameter of those of skimmilk. The addition of sodium tetrapolyphosphate retarded gelation, for which a number of possible explanations are presented.