The high-solids mix is given a higher heat-treatment than for conventional pasteurization. Generally, milk is heat-treated at 85-95°C and then held for 10-40 min. At these temperatures, bacteriophages and vegetative bacterial cells are inactivated and the growth of starter bacteria improves. Up to 60°C, there is no effect on whey protein. At 60° to 100°C, the whey proteins interact with each other and n-casein. This interaction decreases dissociation of as- and h-casein and increases n-casein dissociation (51). When skim milk was pre-heat-treated at 85°C for 30 min and 90°C for 2 min, whey protein denaturation was 76.5% and 55.0%, respectively (52). This heat-treatment and resulting interactions increase the water-binding capacity of the protein system.
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