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Determination of the proportion of κ-casein hydrolysed by rennet on coagulation of skim-milk

Published online by Cambridge University Press:  01 June 2009

Brian Chaplin  and
Margaret L. Green
Brian Chaplin
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
Margaret L. Green
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading, RG2 9AT
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Summary

A method has been developed for quantitative determination of para-κ-casein, involving spectrophotometric scanning of stained protein bands following polyacrylamide gel electrophoresis. The rate of hydrolysis of κ-casein in skim-milk at pH 6·6 and 30 °C was compared with that in EDTA-treated skim-milk under the same conditions. This showed that at the visually observed clotting time, at least 90% of the total κ-casein in milk had been hydrolysed. The time course of the reaction was consistent with all the κ-casein molecules being hydrolysed with the same efficiency. The results strongly suggest that essentially all of the κ-casein in milk is equally accessible to rennet action. This is consistent with the casein micelle being porous, or having all the κ-casein on the surface.

Type
Original Articles
Information
Journal of Dairy Research , Volume 47 , Issue 3 , October 1980 , pp. 351 - 358
Copyright
Copyright © Proprietors of Journal of Dairy Research 1980

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