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Thermal Denaturation and Aggregation of Whey Proteins
M. Donovan and D. M. Mulvihill
Irish Journal of Food Science and Technology
Vol. 11, No. 1 (1987), pp. 87-100
Published by: TEAGASC-Agriculture and Food Development Authority
Stable URL: http://www.jstor.org/stable/25558155
Page Count: 14
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The denaturation of whey protein in a rennet casein whey, as measured by protein rendered insoluble at pH 4.5 and reactive thiol groups, increased slowly on heating at 60 and 70°C and increased very quickly on heating at 80 and 90°C. This shows that whey protein denaturation is a co-operative process with a large thermal coefficient. Electrophoresis showed that the relative denaturation rates of the individual whey proteins differed. The order of heat resistance found was proteose peptone >α-lactalbumin>β-lactoglobulin>bovine serum albumin >immunoglobulin. The contribution of the individual whey proteins to the total protein denaturation is shown. The thermodenaturation of the total whey protein increased with increasing pH in the range 4.5-7.0 and electrophoresis showed that the thermal response of the individual whey proteins to pH differed. Greatest denaturation of β-lactoglobulin occurred at high pH, bovine serum albumin was most resistant at high pH while the thermal denaturation of α-lactalbumin was relatively independent of pH. Thermal precipitation was also found to be pH dependent with greatest aggregation occurring in the pH range 4.5-5.5. That thermal precipitation of whey proteins is influenced mainly by electrostatic charge is shown by the increased precipitation at high pH on the neutralization of the high negative charge of denatured protein molecules by the addition of Ca²⁺
Irish Journal of Food Science and Technology © 1987 TEAGASC-Agriculture and Food Development Authority