Viscosity changes during rennet coagulation of Murciano-Granadina goat milk

The viscosity changes during coagulation of raw, and pasteurized Murciano-G ranadina goat milk with 10 rennets and coagulant enzymes were studied using a cylindrical rotational viscometer. The effect of three shear rates (7.32 , 14.68, 73.42 s(-1)) was analysed in reconstituted milk using 60% chymosin rennet and different enzyme concentrations. The shear rate selected (14.68 s(-1)) corresponded to that in which the coagulation time was not modified At a sheer rate of 73.42 S' there was a significant difference (p < .05) i n the milk clotting time determined compared with the shear rates of 7.32 a nd 14.68 s(-1). At the beginning of the coagulation process there was a dec rease in the viscosity value, which was higher in raw milk (22%) than in th e two heat treated samples (17%) in milk pasteurized at 65 degrees C for 30 min, low temperature long time, and 19% in milk pasteurized at 75 degrees C for 15 s, high temperature short time). After this period the viscosity r ose rapidly and reached a value 2.89 times greater than at time 0. A highly significant Pearson correlation (0.952-0.994) was found between the coagul ation rime determined by the Berridge method and viscometric measurement in raw and pasteurized milk.