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Effects of thermization and cold storage on some properties of rennet-induced milk gels

Published online by Cambridge University Press:  01 June 2009

Donald E. Johnston ,
Robert J. Murphy  and
Norah R. Whittaker
Donald E. Johnston
Affiliation:
Department of Agricultural and Food Chemistry, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX Northern Ireland, †Agricultural and Food Chemistry Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX Agricultural and Food Chemistry Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX
Robert J. Murphy
Affiliation:
Agricultural and Food Chemistry Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX
Norah R. Whittaker
Affiliation:
Department of Agricultural and Food Chemistry, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX Northern Ireland, †Agricultural and Food Chemistry Research Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX
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Summary

The effects of thermization (a sub-pasteurization heat treatment), followed by cold storage at 7 °C for up to 3 d on the post-gelation behaviour of rennet-induced gels from alternate-day collected milks, pasteurized before testing, were investigated. Observations of the time course of gel rigidity modulus development and of the syneresis of cut curds were fitted to a general exponential relationship to aid interpretation. Milk performance was assessed by measurements of rennet coagulation time at pH 6·5, various gel rigidity and syneresis parameters and losses of protein and Ca to the whey. A small but significant reduction in protein losses to the whey (mean 0·05%) was the only effect resulting from thermization. Cold storage gave rise to significantly weaker gels than those from unstored controls. The gels from cold-stored milks attained 50% of their maximum rigidity modulus in significantly less time and lost significantly more protein (mean 0·11%) to the whey. Samples cold stored for 1, 2 or 3 d were not significantly different from each other and no other parameters were affected. No significant interactions between thermization and cold storage were found.

Type
Original Articles
Information
Journal of Dairy Research , Volume 50 , Issue 2 , May 1983 , pp. 231 - 236
Copyright
Copyright © Proprietors of Journal of Dairy Research 1983

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References

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