The effects of high pressure on colloidal calcium phosphate and the structural integrity of micellar casein in milk. Part 2. Kinetics of casein micelle disintegration and protein interactions in milk

Schrader, K.; Buchheim, W.

Kieler Milchwirtschaftliche Forschungsberichte 50(1): 79-88

1998


ISSN/ISBN: 0023-1347
Accession: 003303861

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Abstract
The effects of varying pressure treatments (100, 200, 300, 400 and 500 MPa), temperatures (5, 10, 20 and 40 degrees C) and holding times under pressure (1, 5 and 10 min) on pH and turbidity of pasteurized skim milk and UHT skim milk were investigated. Turbidity decreased and pH increased in both milk types as pressure of treatment increased, with increasing pressures resulting in increased disintegration of native micellar casein (pasteurized milk) and casein-whey protein aggregates (UHT milk). Pressure treatments at lower temperatures resulted in greater and more rapid increases in pH and disintegration of micellar casein. Increases in pH of UHT milk were greater than those of pasteurized milk due to the presence of additional insoluble calcium phosphate resulting from UHT treatment. At >20 degrees C and at >200 MPa, pressure-related whey protein denaturation overlaid the casein disintegration process, insofar as this whey protein denaturation had not already taken place during UHT treatment. The degree of reversibility of pressure-related increases in pH and decreases in turbidity differed significantly with different types of heat treatment. In pasteurized milk, increases in pH were almost completely reversible, whereas decreases in turbidity remained unchanged after 24 h storage at room temperature. In UHT milk, decreases in turbidity were almost completely reversible, but increases in pH were partly maintained.