J.S. Timmons*, W.P
Weiss1*, D.L. Palmquist*, and W.J.
Harper#
*The Ohio State University Department of Animal Sciences
#The Ohio State University Department of Food Science and Technology
Abstract
Milk from bulk tanks from 20 commercial dairy farms near Wooster, OH was sampled approximately once monthly for four months to determine relationships among milk composition, dietary ingredients, and the development of spontaneous oxidized flavor in milk. The herds were chosen so that a wide range in dietary concentrations of roasted whole soybeans was represented. The concentrations of polyunsaturated fatty acids (linolenic and linoleic acids) in milk fat was positively correlated with the concentration of roasted soybeans in the diet. Similarly, the development of spontaneous oxidized flavor in milk was positively correlated with the concentrations of linolenic, linoleic, and total polyunsaturated fatty acids in milk fat. Milk most susceptible to developing oxidized flavor was milk with high concentrations of polyunsaturated fatty acids and copper. Multiple regression equations were developed that quantified the relationship between concentrations of certain milk fatty acids and copper and milk flavor score.
Introduction
During storage, some milk can develop an oxidized flavor often described as "metallic", "carboardy", or "tallowy" which can reduce the acceptability of dairy products to the consumer. The development of oxidized flavor is complex but depends on the relative concentrations of pro- and anti-oxidants and on the concentration of oxidizable substrates. Antioxidants found in milk include vitamin E and vitamin C; pro-oxidants include copper and iron. Polyunsaturated fatty acids are easily oxidized and upon oxidation can produce compounds that cause oxidized flavor. Full fat soybeans have high concentrations of linoleic and linolenic acids, and cows fed whole soybeans produce milk with elevated concentrations of those two fatty acids. High concentrations of those two polyunsaturated fatty acids in milk are related to spontaneous oxidized flavor. The objective of this experiment was to quantify relationships between dietary whole roasted soybeans, milk composition, and milk flavor using milk produced under typical Ohio feeding and management systems.