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Effect of Minerals on Casein Micelle Stability of Cows' Milk

Published online by Cambridge University Press:  12 February 2007

Alexandros Tsioulpas ,
Michael J Lewis  and
Alistair S Grandison
Alexandros Tsioulpas
Affiliation:
School of Food Biosciences, The University of Reading, Whiteknights, PO Box 226, RG6 6AP, Reading, UK
Michael J Lewis
Affiliation:
School of Food Biosciences, The University of Reading, Whiteknights, PO Box 226, RG6 6AP, Reading, UK
Alistair S Grandison
Affiliation:
School of Food Biosciences, The University of Reading, Whiteknights, PO Box 226, RG6 6AP, Reading, UK
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Abstract

The effects of minerals on casein micelle stability of individual cows' milk, throughout a complete lactation, were investigated. Calcium and calcium ions, magnesium, phosphorus, sodium, potassium and citrate contents were analysed, together with the following physical properties of milk; pH, ethanol stability, rennet clotting time and coagulum firmness. There was an inverse non-linear relationship between free calcium ion concentration and ethanol stability (ES; r=0·84). Rennet coagulation time showed a weaker relationship with free calcium ion concentration (r=0·44) but a stronger relationship with pH (r=0·66). In addition, samples containing higher amounts of free calcium ions produced a firmer gel. Citrate in natural samples acts as a stabilizing factor, as it slightly improves milk stability. Potassium, on the other hand, exhibited a negative correlation, but only with rennet clotting time (r=−0·52). Throughout lactation the average values were; free Ca2+ concentration 1·88 mM, pH 6·63, ES 83·2% and clotting time 13·6 min. The equilibrium relationship between pH and free Ca2+ concentration was investigated by adjusting milk pH from 5·9 to 7·1, using acid and alkali. There was a good inverse linear relationship between pH and log (free Ca2+) for individual milk samples, with a gradient of −0·62 and a standard deviation of 0·042.

Keywords

ionic calciumcasein micelle stabilityethanol stabilitymineral composition
Type
Research Article
Information
Journal of Dairy Research , Volume 74 , Issue 2 , May 2007 , pp. 167 - 173
Copyright
Proprietors of Journal of Dairy Research 2007

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