: Oxidative stability of milk fats from cows o †ered naked oats-and barley-based diets were compared in shelf-life tests using the Schaal Oven Test at 63¡C, and determination of peroxide and thiobarbituric acid values. Milk fat from cows o †ered the diet containing naked oats, although containing a higher proportion of monounsaturated fatty acids, had a signiÐcantly longer oxidation induction period (13 days) than milk fat from cows o †ered the control (barleybased) diet (9 days). However, sensory testing of the milk fats indicated that a perceptible odour di †erence was apparent between stored (63¡C) and unstored milk fats after 3 days of storage irrespective of the diet fed. It is possible that the odours perceived may have originated from the cowsÏ diets or from hydrolytic rancidity reactions. The difficulties of relating chemical and sensory testing of the oxidative deterioration of milk fat or butter are underlined.1998 SCI. ( J Sci Food Agric 76, 546È552 (1998)

Oxidative stability of milk fats from cows offered naked oats‐ and barley‐based diets were compared in shelf‐life tests using the Schaal Oven Test at 63°C, and determination of peroxide and thiobarbituric acid values. Milk fat from cows offered the diet containing naked oats, although containing a higher proportion of monounsaturated fatty acids, had a significantly longer oxidation induction period (13 days) than milk fat from cows offered the control (barley‐based) diet (9 days). However, sensory testing of the milk fats indicated that a perceptible odour difference was apparent between stored (63°C) and unstored milk fats after 3 days of storage irrespective of the diet fed. It is possible that the odours perceived may have originated from the cows' diets or from hydrolytic rancidity reactions. The difficulties of relating chemical and sensory testing of the oxidative deterioration of milk fat or butter are underlined. © 1998 SCI.

Dairy cows were offered diets containing three commercially available lipid supplements to determine their effect on milk fat composition and melting properties. Changes in fatty acid composition were observed. These were similar irrespective of supplement and agreed with the general trends reported in the literature. Changes in triglyceride composition were also found and these again were similar irrespective of supplement. However, the melting behaviour of the milk fats was different and may possibly be explained by changes in triglyceride structure. Compatibility of the dietary modified milk fats in mixtures with cocoa butter was examined using iso-solid diagrams produced by a computer-aided modelling technique. The differences in compatibility observed were small in magnitude but may still be important to the chocolate manufacturer.