Effect of Starter and Enzyme Additions on Clotting Time of Milks for Mish Manufacture

Cows milk samples were subjected to changes in their physical and chemical properties when different additions of Starter, Rennet, Starter/ Rennet combinations and their effects on the rate of coagulation were studied. The milk samples were first pasteurized and then coagulated with different additions of enzyme and acid starter combinations. Time from the enzyme and starter additions to the onset of gelation as indicated by the first visible floccules was measured. The results showed that the longest clotting time of milk recorded (22.7 min) was in samples containing 0.25 ml of rennet enzymes solution (1ml = 20 mg rennet), while the shortest time was (4.65 min) in samples containing 1.5 ml of enzyme. Other samples ranged intermediate. Using starter alone, the longest clotting time of milk recorded (19.69 min) was in the samples containing 0.25 ml inoculum of lactic acid starter mother culture, while the shortest time (6.87 min) was in samples containing 1.5 ml of starter. Other samples ranged intermediate. Furthermore, the additions of different mixtures of starter and rennet significantly (P??????? 0.05) affected the clotting time of milk. The longest clotting time recorded (10.05 min) was in the sample containing a mixture of 0.5 ml starter and 0.5 ml rennet, while the shortest clotting time (9.43 min) was in the samples containing a mixture of 0.5 ml starter and 1.0 ml rennet enzyme. The longest clotting time (13.55 min) was when renetting the samples at pH (5.9), while the shortest clotting time (6.87 min) was at pH (5.7). Viscosity changes in the coagulated milk samples were followed during the coagulation process. At zero time, the viscosity was (4.1) Poise and was highest (49.8) Poise at the end of incubation time using the mixture of enzyme and starter. These experiments were done to establish a guideline for Mish manufacture, a popular Sudanese fermented milk product.