Effect of κ-casein glycosylation on cheese yielding capacity and coagulating properties of milk

Abstract

The effects of the average degree of glycosylation of milk κ-casein on rennetclotting time, rate of curd firming and curd firmness 30 min after the addition of chymosin were measured on 55 blended-milks by a Formagraph. The degree of glycosylation, which is reflected by the N-acetylneuraminic content of κ-casein ( NANA κ-CN ) varied from 43 to 93 μg/mg of κ-CN during the study. Significant ( p < 0·01) variations in the rate of firming and curd firmness in relation to the NANA κ-CN ratio were observed, suggesting that a firmer curd can be obtained with milk having a high NANA κ-CN value. To study the effect of the degree of glycosylation of κ-casein on cheese yielding capacity, laboratory-scale Cheddar-type cheese was prepared from 45 blended-milks. No significant ( p > 0·1) difference in the 37% moisture-adjusted cheese yield was observed. It is concluded that the improvement of the coagulating properties of milk brought about by the increase in the average degree of glycosylation of κ-casein did not result in a greater cheese yield.