Combined effect of renneting pH, cooking temperature, and dry salting on the contraction kinetics of rennet-induced milk gels

A model system was optimised to monitor rennet curd contraction during cooking under quiescent conditions. Small milk samples (5 g) were renneted and cooked in polyallomer tubes that reduced adherence to the wall and increased repeatability. Curd mass fraction was measured as a function of cooking time and fitted to a second-order decay equation to obtain kinetic parameters. The combined effect of renneting pH (6.2–6.6) and cooking temperature (40–50 °C) on gel contraction was studied. Salt-induced contraction was also evaluated by adding dry salt to the curd after cooking. Temperature was the main factor influencing the contraction kinetics. Curd mass fraction and curd moisture before and after salting decreased as renneting pH was reduced and cooking temperature was increased. The influence of renneting pH on curd mass fraction before salting increased at lower temperature. A positive correlation between curd moisture and final salt concentration in the curd was observed.