.The .coagulation of milk is fundamental to cheese manufacturing, and is initiated by the addition of proteolytic enzymes ta milk causing hydrolysis of K-casein into para-K-casein and glycomacropeptide. The suitability of a coagulant enzyme depends not only on its clotting activity but also on the influence that enzyme may exercise on curd rheology, particularly through its influence on the proteolytic processes of ripening (1). The principal disadvantage of some rennet substitutes is their high protertlytic activity which produces a bitter taste and can even lead to poorer cheese yields (2). Separation by size of molec~ules and use of only the clotting fractions for cheesemaking is an appropriate way to improve the milk clotting to general proteolysis ratio of some commercial milk clotting preparations, although this is not an appropriate technique for microbial coagulant enzymes derived from Mucor miehei since preparations with a high coagulant power are correlated with high rates of proteolysis (3). The rate of milk coagulation, the overall yield of cheese from milk, and the quality of cheese produced are affected by the enzymatic hydrolysis phase. The extent of enzymic reaction is determined by measuring the concentration of either para-K-casein or macropep tide. To determine the glycomacropeptide (GMP) the most frequently used method is to determine the non protein nitrogen (NPN) during proteolysis, which gradually increases, although VAN HOOYDONK et al. (4) consider that the sensitivity of this rapid and easily used method is insufficient to determine the initial reaction rate. An alternative, more specific and sensitive technique, which can be easily applied in the laboratory, is to use spectrofluorimetry (5); variations of the order of 5% in the final level of K-casein in milk could be detected in this way. This method has been modified by ROLLEMA etal. (6), to determine proteolytic activities of lactic bacteria in sterilised milk. Other methods which have been developed include high pressure liquid chromatography in a reverse phase column (7) or liquid chromatography through gel filtration (4,8), the interest of this latter technique lying in its rapidity and simple pre-treatment of the samples. Both methods permit pre-treatment with trichloroacetic acid to eliminate residual components. Other indirect methods for determining proteolytic activity are based on the dir . inution of viscositv or turbiditv. These methods give logical suitability of each enzyme for a particular substrate is studied, taking calf rennet as a reference (9). A detailed understanding of the intricate renneting process therefore requires a separate study of the enzymic and coagulation reaction. For this reason the present paper reports the results of the kinetic study on the action of 8 rennets and coagulant enzymes in pasteurised goat milk and correlates the enzymatic constant value with some technological parameters such as viscosity evolution and cheese yield. ,