Effects of Phosphates Added to Concentrated Milks before Sterilization at Ultra-High Temperatures

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Abstract
Polyphos-phates added to concentrated milks before sterilization at 303 [plus or minus] 2 F delayed gelation, whereas orthophosphates speeded gelation. Concentrated milks containing 0.05% added polyphosphate stored at 100 F browned and developed undesirable flavors before gelation. Viscosities of concentrated milks increased with increased additions of polyphos-phates, and the size of microscopically visible particles became more uniform in the size range 0.7-1.4 [mu] diameter, compared with 0.1-.5[mu]. diameter in the controls. These aggregates of protein and fat (regardless of phosphates added) dissociated rapidly in 6[image] urea at pH 8, very slowly in 6[image] urea at pH 6.7, rapidly in 0.1 N potassium-oxalate and ammonium -oxalate; but not to a great extent when diluted one part of concentrated milk to 50 parts of dilute acetic-acid at pH 3.88. Gel structure was similar in the phosphate containing samples and the controls. Disulfide bonds were involved in the gel structure.