Role of Xanthine Oxidase in the Development of Spontaneously Oxidized Flavor in Milk

Abstract

The role of xanthine oxidase in the development of spontaneously oxidized flavor was considered. The study included: (1) the relationship of xanthine oxidase activity to the development of off-flavor, (2) a multiple-enzyme system versus a single enzyme in the development of the off-flavor, and (3) the effect of inhibitors upon the development of spontaneously oxidized flavor. Results of the study indicated that: (1) The occurrence of a spontaneously oxidized flavor in milk was dependent upon a high level of xanthine oxidase activity, (2) a single enzyme (xanthine oxidase) was involved, and (3) inhibitors of xanthine oxidase were effective in preventing flavor development. A brief discussion of the peroxidatic action of xanthine oxidase was included. In 1943, Roberts (19) reported significant correlations between the oxidizing enzymes normally present in milk and the development of oxidized flavor in milk. Dorn (6) stated that a peroxide action upon the milk fat could be traced to the action of xanthine oxidase and aseorbic acid oxidation. He co'ncluded that riboflavin was mainly responsible for the development of oxidized flavor; whereas, ascorbic acid was only secondarily so. Greenbank et at. (11) suggested that xanthine oxidase could be of great significance in problems of oxidative deterioration of milk and milk products, tlecently, it has been reported (2) that an enzyme is involved in the development of spontaneously oxidized flavor and that the enzyme so involved may be xanthine oxidase. Studies were initiated, therefore, to determine the role of xanthine oxidase in oxidized off-flavor development.