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Dissociation during dialysis of casein aggregates cross-linked by colloidal calcium phosphate in bovine casein micelles

Published online by Cambridge University Press:  01 June 2009

Takayoshi Aoki ,
Nagisa Yamada ,
Yoshitaka Kako  and
Tsuneaki Imamura
Takayoshi Aoki
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan
Nagisa Yamada
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan
Yoshitaka Kako
Affiliation:
Department of Animal Science, Faculty of Agriculture, Kagoshima University, Kagoshima 890, Japan
Tsuneaki Imamura
Affiliation:
Department of Applied Biochemistry, Faculty of Applied Biological Science, Hiroshima University, Fukuyama 720, Japan
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Summary

Casein micelles separated by ultracentrifugation of raw skim milk were dispersed at a casein concentration of 2·5% in simulated milk ultrafiltrate and dialysed against 10 mM-imidazole buffer (pH 7·0) at 5 °C. The amounts of colloidal Ca and inorganic P decreased from 77 to 11 mg and from 31 to 2 mg respectively in 100 ml during 72 h of dialysis. Micellar casein content was reduced to 43 and 11% after 48 and 72 h of dialysis respectively. In high-performance gel chromatography of casein micelles in the presence of 6 M-urea, fraction 1, consisting of the casein aggregates cross-linked by colloidal Ca phosphate (CCP) decreased during dialysis and the retention time of the peak of fraction 1 was prolonged, suggesting that the cross-linkage between CCP and casein molecules was disrupted. The dissociation rates of the individual casein constituents from the casein aggregates cross-linked by CCP during dialysis were in the order β-> αs1 - > αs2-casein. The higher the ester phosphate content, the slower was the dissociation rate of the individual casein constituent. It is suggested that the strength of interaction between CCP and casein molecules depends on the ester phosphate content.

Type
Original articles
Information
Journal of Dairy Research , Volume 55 , Issue 2 , May 1988 , pp. 189 - 195
Copyright
Copyright © Proprietors of Journal of Dairy Research 1988

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References

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