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Effect of calcium on the hydration of casein. I. Water vapour sorption and fine structure of calcium caseinates compared with sodium caseinates in the pH range 4·6–8·0

Published online by Cambridge University Press:  01 June 2009

Max Rüegg  and
Ursula Moor
Max Rüegg
Affiliation:
Federal Dairy Research Institute, CH-3097 Liebefeld, Switzerland
Ursula Moor
Affiliation:
Federal Dairy Research Institute, CH-3097 Liebefeld, Switzerland
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Summary

Hydration of Ca and Na caseinates which were prepared from whole casein at different pH levels (range 4·7–8·0) was determined by means of water vapour sorption measurements in the water activity (aw) range 0·58–0·95. Water uptake of Ca caseinates was systematically lower than that of Na caseinates prepared at equal pH, the differences increasing with increasing pH and aw. Plots of the water content ν. the amount of added hydroxide at constant aw revealed a linear relationship between water uptake and cation content, suggesting that the increase in water uptake is mainly determined by the amount and type of cations associated with the caseins. In the aw range tested, Ca2+ adsorbed about 2–7 and Na+ 3–18 mol water/mol of cation. This implies that replacement of one mol of casein-bound Na+ by Ca2+ is accompanied by a displacement of 1–11 mol water at aw 0·58–0·95. The loss of water is a consequence of conformational changes induced by the chelating and cross-linking effects of Ca2+, which also lead to micelle formation.

Type
Original Articles
Information
Journal of Dairy Research , Volume 51 , Issue 1 , February 1984 , pp. 103 - 111
Copyright
Copyright © Proprietors of Journal of Dairy Research 1984

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References

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