Hormonal Control of Oxidized Flavour in Milk

Abstract

IN two recent papers the importance of natural copper in producing oxidized flavour in milk has been stressed^1,2. The pronounced effect of adding copper salts to induce oxidized flavour, as well as the inhibiting effect of a great many compounds with copper-binding abilities, has been recognized for a long time. Contamination with copper occurs easily in metal equipment with which the milk has been in intimate contact³. Contribution from equipment was considered to be the main origin of copper in milk, and thus the importance of natural copper for development of oxidized flavour may have been overlooked. High copper values are found in carefully sampled milk^1,4, and particularly high values in milk from the early lactation period¹. Elevated content of natural copper in this period seems to indicate a hormonal regulation of copper metabolism. The copper-catalysed oxidation in milk may be enhanced or depressed, and factors of this kind will combine to give the final result. The addition of copper sulphate to milk is a method used to evaluate these factors, or the so-called susceptibility, and is of practical importance. The relative effect of natural copper contents is lessened. Indications of hormonal influence on oxidized flavour in milk are reported here.