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Studies on the heat stability of milk: II. Association and dissociation of particles and the effect of added urea

Published online by Cambridge University Press:  01 June 2009

Douglas G. Dalgleish ,
Yves Pouliot  and
Paul Paquin
Douglas G. Dalgleish
Affiliation:
Hannah Research Institute, Ayr, KA6 5HL, UK
Yves Pouliot
Affiliation:
Sciences et Technologie des Aliments, Université Laval, Québec, Canada
Paul Paquin
Affiliation:
Sciences et Technologie des Aliments, Université Laval, Québec, Canada
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Summary

The sizes of the casein particles in milk heated at 130°C were measured as functions of heating time and of initial pH. The effect of adding 10 mM-urea to the milks was also studied. Turbidities of the milks before and after dispersing the caseinate particles in 8 m-urea/EDTA/β-mercaptoethanol were measured, the latter measurement giving an indication of the extent of covalent cross-linking. Urea was found to modify the behaviour of the milk: diameters of the caseinate particles were considerably altered, and the extent of covalent cross-linking was diminished. These results agree with the observation that more protein is solubilized from the casein micelles when urea is present, indicating that a competitive reaction scheme involving cross-linking in opposition to micellar dissociation may be responsible for the ultimate precipitation of milk by heat.

Type
Original Articles
Information
Journal of Dairy Research , Volume 54 , Issue 1 , February 1987 , pp. 39 - 49
Copyright
Copyright © Proprietors of Journal of Dairy Research 1987

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References

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