Properties of the Esterase Produced by Mucor miehei to Develop Flavor in Dairy Products

The development of Italian cheese flavor is attributed in large part to the action of animal pregastric esterases added to the milk prior to coagulation. Comparable flavor in Fontina and Romano cheese can be developed with an esterase preparation derived from Mucor rniebei. The unique ability of this esterase to replace the animal-derived enzymes prompted a study of its properties. Esterase and microbial rennet are produced by Mucor rniebei in the same fermentation. The enzymes are separated by filtration at pH 5.0. The insoluble esterase then is recovered by extraction of the filter cake at pH 10.5. The enzyme has a pH optimum of 7.0 on tributyrin, has a temperature optimum of 50 C, and is stable over the pH range of 4.0 to 10.0 and up to 55 C at pH 5.3. The enzyme will hydrolyze a number of synthetic triglycerides, with optimum activity on tributyrin and trioctanoin. Higher molecular weight fatty acid containing triglycerides are hydrolyzed less readily. Sorbitol esters of fatty acids also are attacked. The esterase will hydrolyze a number of animal fats and vegetable oils and is relatively unaffected by high concentrations of various salts, ethylene diamine tetraacetate, or sulfhydryl inhibitors.