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Heat-induced changes in sodium Caseinate

Published online by Cambridge University Press:  01 June 2009

Mingruo Guo ,
Patrick F. Fox ,
Albert Flynn  and
Kais S. Mahammad
Mingruo Guo
Affiliation:
Department of Food Chemistry, University College, Cork, Ireland
Patrick F. Fox
Affiliation:
Department of Food Chemistry, University College, Cork, Ireland
Albert Flynn
Affiliation:
Department of Nutrition, University College, Cork, Ireland
Kais S. Mahammad
Affiliation:
Department of Food Chemistry, University College, Cork, Ireland
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Summary

Chemical and physical changes that occur in Na caseinate (at 1 or 2% in water, pH 7·0) on heating in the range 120–150 °C were investigated by polyacrylamide gel electrophoresis, ion-exchange and gel-permeation chromatography, light scattering, u.v. spectroscopy, amino acid analysis, and the formation of pH 4·6 and 12% TCA-soluble N and 12% TCA-soluble P. The electropherograms of heated samples were smeared and indistinct suggesting intermolecular aggregation which was not reversed by 6 M-urea or SDS and indicating covalent bond formation; αs2-casein was especially sensitive. Aggregation was confirmed by ion-exchange chromatography and light scattering. Fragmentation of the caseins also occurred on heating, as indicated by the formation of pH 4·6 and 12% TCA-soluble N and by gel filtration. Formation of soluble N and dephosphorylation followed first-order kinetics. Concentrations of available lysine and available methionine were reduced by 10–15% on heating at 140 °C for 30min; chemical assays for arginine and tryptophan indicated increases, suggesting interference. Ultraviolet spectroscopy indicated a slight apparent increase in aromatic residues after heating at 140 °C for up to 60 min.

Type
Original Articles
Information
Journal of Dairy Research , Volume 56 , Issue 3: Special Issue: Proceedings of the Hannah Research Institute Casein Conference , May 1989 , pp. 503 - 512
Copyright
Copyright © Proprietors of Journal of Dairy Research 1989

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References

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