Effect of manipulation of milk composition and curd-forming conditions on the formation, structure and properties of milk curd

SummaryMilks whose compositions had been altered by deliberate manipulation or by contact with various environmental conditions relevant to cheesemaking were treated with rennet in such a way as normally to give a constant coagulation time. Rates of curd formation and whey loss, curd structure and fat retention were determined. Ca depletion in concentrated milks reduced firming and syneresis rates and gave curds with finer protein networks. Increased temperature of curd formation increased the curd-firming rate and curd coarseness, but decreased the syneresis rate at 30 °C. Prior treatment of concentrated milk with rennet in the cold gave a much finer protein network which retained fat better than curd formed normally. Despite increasing firming and syneresis rates, acidified milk gave a slightly finer curd with a better fat retention than normal. Addition of cationic materials stimulated aggregation and the curd retained fat better than normal, although the curd structure was unaffected. The results indicate that the processes of firming and syneresis have related mechanisms, and that the curd structure is not simply dependent on curd-forming conditions, but on the number of aggregating particles and the forces between them.