Vol. 5, Issue 12, Part A (2019)

Abstract
The growing demand for natural coagulants led to an increased necessity for rennet substitutes. Many attempts have been made to find new proteases. A novel protease with milk-clotting activity was isolated and purified from tuna fish stomach. The aim of this study was to investigate the protease enzyme as a novel milk-clotting in the development of cheese. The milk coagulating time for tuna protease was studied at pH (3.0–12.0) with the optimum at 4.0 and showed its maximum activity at 50 °C when casein was used as a substrate. The enzyme showed the highest activity and purification when precipitated at 20-40% ammonium sulphate and dialyzed effectively improved specific activity of enzyme. The cheese manufactured by using the purified tuna protease showed similar textural properties as compared to cheese produced using commercial rennet. This research was carried out for the utilization of tuna fish by-products for producing enzymes and also to the reduction of waste disposal problems. Considering the special characteristics, including high milk-clotting activity, considerable stability over wide ranges of pH and temperature, the results revealed that the tuna protease might be the promising candidate for the dairy industry as well as other food and biotechnological industries.