Chemical composition, rennet coagulation properties and flavour of milks from cows grazing ryegrass or white clover

Abstract

SUMMARY: Milks from two groups of dairy cows grazing either white clover or ryegrass swards were compared to determine whether their acceptability in terms of flavour, composition and rennet coagulation properties was affected by these differences in the cows' diet.The concentrations of Ca and Mg were slightly higher and that of inorganic phosphorus was slightly lower in milks from the animals on the ryegrass pasture compared with those grazing clover, but the levels of Na, K and citrate were the same. The clover milks contained more α_s- and β-casein and a greater proportion of small micelles but had similar contents of κ-casein to the ryegrass milks. Following addition of rennet at pH 6·4, the clover milks gave rise to firmer curds but the clotting times and rates of syneresis were not consistently different from the ryegrass milks. The clover milks contained a greater proportion of short-chain (C₄–C₁₀) fatty acids, but lower proportions of long-chain (C₁₈₊) and unsaturated acids than the ryegrass milk.The different pastures did not give rise to any differences in the flavour of the milk.