(1998)*. This suggests that casein micelles are formed because of two binding mechanisms namely hydrophobic attraction and colloidal calcium phosphate bridging. The mineral content of cheese is largely determined by the quantity of calcium phosphate lost from the curd, which is mainly dependant upon the pH of the whey at drainage; the pH of the whey at this point is dependant on starter activity. The latter depends on several factors including: concentration of starter starter type time which has elapsed since starter addition temperature. It is this loss of calcium phosphate, and its effect on the properties of protein aggregates in cheese, that is critical to the development of cheese type. At the other extreme Cheshire cheese has a low mineral content and has very small protein aggregates. This cheese has virtually no elasticity; it is 'crumbly' and will break easily. Electron microscopy reveals a very weak internal protein matrix. Cheddar is intermediate between Gouda and Cheddar with regard to the size of protein aggregates and the density and strength of the internal protein matrix. The basic structure of a cheese affects proteolysis and influences cheese flavour In general proteolysis in cheeses made with calf rennet is dependent on the activity of two major proteases, chymosin and plasmin. Chymosin is one of several enzymes present in rennet. Plasmin is a native milk protease. Chymosin is active at low pH whereas plasmin is active at higher pH, pH optimum ca. 7.5. For this reason chymosin activity during ripening is highest in