Effects of pH, temperature, CaCl_2 and enzyme concentrations on the rennet-clotting properties of milk: a multifactorial study

摘要

The effects of pH, coagulation temperature, CaCl_2 and enzyme concentrations on the rennet clotting properties of milk were assessed. Rennet coagulation time, coagulum firmness, curd firmness and gel firming rate were the coagulation parameters measured using a gelograph. A multifactorial design, considering two levels of coagulation temperature (28 and 44℃), pH (6.0 and 6.8) and concentration of CaCl_2 (10 and 18 mM), was applied. pH showed the most important influence on rennet coagulation time and gel firming rate, while coagulation temperature showed the highest contribution to predict the firmness parameters. The effects of the interactions among pH, coagulation temperature and CaCl_2 concentration were significant, except for curd firmness. Rennet coagulation time was the parameter most affected by two- and three-factor combinations. The interaction between pH and CaCl_2 concentration was the only combination of factors that affected coagulum firmness and gel firming rate. However, curd firmness was affected only by coagulation temperature.