RHEOLOGICAL PROPERTIES AND CUTTING TIME OF RENNET GELS - EFFECT OF PHAND ENZYME CONCENTRATION

The subjectively evaluated cutting time of rennet gels was compared to the rheological moduli measured by oscillation at different rennet co ncentrations and different milk pHs. We found no unique value of the r heological moduli at cutting time but a linear correlation between the cutting time and the time of the maximum rate of increase of G' indic ating that the properties evaluated empirically by the cheesemaker are related to fundamental rheological properties. G was 7-10 Pa at the cutting time at pH 6.7 and decreased with decreasing pH. Plotting the maximum rate of increase of G' vs. the enzymatic reaction rate we foun d a linear relationship with a positive intercept at the y-axis. This shows that the rate of gelfirming is not determined by the enzymatic r eaction rate alone. Both the slope and the intercept increased with de creasing pH, demonstrating that the effect of pH on the rate of gelfir ming was not only caused by the change in the enzymatic reaction rate. The results indicated that the rate of structural rearrangements of t he gel increased when the pH was lower. (C) 1998 Elsevier Science Ltd. All rights reserved.