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The denaturation of α-lactalbumin and β-lactoglobulin in heated milk

Published online by Cambridge University Press:  01 June 2009

R. L. J. Lyster
R. L. J. Lyster
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
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Summary

The rates of denaturation by heat of α-lactalbumin and β-lactoglobulin in skim-milk were measured by an immunodiffusion method over a wide range of temperatures. Both reactions showed an unusual temperature dependence.

The denaturation of α-lactalbumin is a first-order reaction; between 90 and 155 °C the kinetic constant k1 in s−1 is given by the equation

where T is the temperature in °K.

The denaturation of β-actoglobulin in skim-milk is second order with respect to time, and the kinetic constant k2 in 1g–1 s–1 is given by 2 equations, valid for different temperature ranges. Between 68 and 90 °C,

Between 90 and 135 °C

Results obtained by the immunodiffusion method agreed well with those found by salt fractionation of the milk proteins. The denaturation rates decreased when a specific reagent for sulphydryl groups was added, suggesting that such groups are involved in the denaturation of both proteins.

Type
Original Articles
Information
Journal of Dairy Research , Volume 37 , Issue 2 , June 1970 , pp. 233 - 243
Copyright
Copyright © Proprietors of Journal of Dairy Research 1970

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