Milk gel Structure: II. Relation between firmness and ultrastructure of heat-induced skim-milk gels containing 40–60% total solids

Abstract

SummaryMilk gels varying widely in firmness were examined by both scanning and transmission electron microscopy, and a close correlation was found between their ultrastructure and firmness. In gels containing 40 and 50% total solids (14 and 17% protein respectively), casein micelles appeared as individual entities linked by some bridging material. At 60% total solids (20% protein), the micelles were fused and offered a considerably higher resistance to a penetrometer probe. Likewise some additives to gels, such as ammonium persulphate and CaCl2, caused the micelles to fuse. These chemicals appreciably increased firmness of such gels. In gels containing hexametaphosphate, a known inhibitor of gelation, most of the casein micelles were disintegrated; these gels were soft.