Xanthine Oxidase and Incidence of Spontaneous Oxidized Flavor in Milk

Abstract

A Thunberg tube technique and the vanillic acid method were used to determine xanthine oxidase in milk samples from cows on an alfalfa hay-grain concentrate ration. No relation was found between xanthine oxidase activity and incidence of spontaneous.oxidized flavor in the milks. This result is inconsistent with recent reports. Data for changes in xanthine oxidase activity during refrigerated storage indicated that the discrepancy probably is not attributable to increases in activity of the enzyme during storage. Experiments based on addition of xanthine oxidase preparations to milk were conducted in an attempt to establish a possible role for xanthine oxidase in catalysis of spontaneous oxidized flavor. This approach proved unsatisfactory because of difficulty in controlling several variables. It is concluded that spontaneous oxidized flavor cannot be differentiated from non-spontaneous flavor on the basis of catalytic activity of xanthine oxidase.