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Application of polymer cross-linking theory to rennet-induced milk gels

Published online by Cambridge University Press:  01 June 2009

Donald E. Johnston
Donald E. Johnston
Affiliation:
Department of Agricultural and Food Chemistry, The Queen's University of Belfast, Belfast BT9 5PX, Northern Ireland, Department of Agriculture for Northern Ireland
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Summary

A general theory of gel formation by cross-linking of polymer molecules, orginally developed for the study of rubber vulcanization, is proposed as a model for milk gel formation. The model divides gel formation and development into 4 stages, an enzymic and a non-enzymic stage preceding gelation, then a stage of material transition from the sol to the gelled state and a stage of increase in gel strength due to internal cross-link formations. The 2 post-gelation stages overlap to a variable degree depending upon particular circumstances. Gel formation and properties are interpreted in terms of the number of initial units which combine to form the gel and the number of cross-links eventually formed by each unit. When combined with a kinetic expression for the rate of cross-link formation the time course of gel shear modulus development or of the incorporation of material into the gel may be predicted. The classical asymmetric sigmoid shape of gel shear modulus development curves results from the third stage of material transition into the gel, which in turn depends upon the number of cross-links eventually formed by each initial unit. The modulus of mature gels is found to depend upon the square of material concentration, and gel breaking strength is found to be proportional to the modulus, in agreement with the predictions of the theory.

Type
Original Articles
Information
Journal of Dairy Research , Volume 51 , Issue 1 , February 1984 , pp. 91 - 101
Copyright
Copyright © Proprietors of Journal of Dairy Research 1984

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References

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