Effects of β-lactoglobulin and κ-casein genetic variants and concentrations on syneresis of gels from renneted heated milk

Abstract

Milk protein genetic polymorphism has a major influence on the composition of milk, and on its processing properties, including yield of cheese (see Schaaret al.1985; McLeanet al.1984, 1987; McLean, 1987). However, there appears to be little information on the effects of milk protein genetic variants on syneresis of cheese curd. The effect of casein composition on syneresis was studied by Pearseet al.(1986), who found that syneresis was affected only by the level of β-casein. Syneresis is an essential requirement in cheese making from renneted or acidified milk, but is undesirable during the storage of products such as yogurt. Milk for yogurt manufacture is preheated to minimize syneresis and to give maximal firmness of the yogurt coagulum (Tamime & Deeth, 1980). Pearseet al.(1985) showed that the reduction of one-third in the extent of syneresis caused by heating artificial micelle milk (AMM) containing βlactoglobulin (β-lg) in natural concentrations was due to sulphydryl-mediated complex formation between β-lg and micellar κ-casein which appeared to interfere with the micelle–micelle interactions responsible for syneresis. The results presented here were part of a study which investigated the effects of κcasein and κ-lg genetic variants and concentrations on syneresis of curd formed from renneted heated AMM.