EFFECT OF NAKED OATS IN THE DAIRY-COWS DIET ON THE OXIDATIVE STABILITY OF THE MILK-FAT

Oxidative stability of milk fats from cows offered naked oats-and barl ey-based diets were compared in shelf-life tests using the Schaal Oven Test at 63 degrees C, and determination of peroxide and thiobarbituri c acid values. Milk fat from cows offered the diet containing naked oa ts, although containing a higher proportion of monounsaturated fatty a cids, had a significantly longer oxidation induction period (13 days) than milk fat from cows offered the control (barley-based) diet (9 day s). However, sensory testing of the milk fats indicated that a percept ible odour difference was apparent between stored (63 degrees C) and u nstored milk fats after 3 days of storage irrespective of the diet fed . It is possible that the odours perceived may have originated from th e cows' diets or from hydrolytic rancidity reactions. The difficulties of relating chemical and sensory testing of the oxidative deteriorati on of milk fat or butter are underlined. (C) 1998 SCI.