Effect of minerals on casein micelle stability of cows' milk.
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.
Tsioulpas
Alexandros
A
School of Food Biosciences, The University of Reading, Whiteknights, RG6 6AP, Reading, UK.
Lewis
Michael J
MJ
Grandison
Alistair S
AS
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002364:Caseins / Q000737:chemistry* / Q000187:drug effects; D002417:Cattle; D005260:Female; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D008892:Milk / Q000187:drug effects / Q000502:physiology*; D008903:Minerals / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
D002364:Caseins; D008823:Micelles; D008903:Minerals; D012964:Sodium; D011188:Potassium; D002118:Calcium