Mechanism of pressure-induced gelation of milk

The pressure-induced gelation of concentrated skimmed milk, and milk-sugar mixtures was studied to discover the main components responsible for gelati on. The major protein component responsible for gelation is micellar casein . Gelation occurs at similar pressures to casein micelle disintegration in dilute milk, and both can be prevented by inclusion of excess calcium chlor ide. Transmission electron micrographs show that the protein network is for med from particles with diameters approximately an order of magnitude small er than those of intact casein micelles. Gelation occurs on decompression a nd is found to be baroreversible. Concentrations of sugar up to 30% reduce the critical concentration of casein required for gelation, but higher suga r concentrations inhibit gelation. A mechanism of gelation based on the agg regation of casein submicelles formed by pressure-induced disintegration of casein micelles is proposed. Observations on the effect of sucrose on gela tion are discussed in terms of the influence of sugars on the solvent quali ty in aqueous casein systems.