Effect of rancidity ofLupinus albus protein-concentrate-based diets on food intake and growth of Wistar rats

Abstract

The organoleptic properties of a diet are influenced by technological processes and have to be taken into account in food intake studies. The authors studied the food intake suppression associated with rancidity occurring during the storage of diets based on casein or heated or lyophilised lupin protein concentrates, and with or without ascorbic acid supplementation in five groups of 10 weanling Wistar rats for 21 or 26 days. After 15 days of storage, the unsaturated fatty acids were oxidised in heated lupin-protein-based diet without ascorbic acid. Compared to casein, food intake was decreased slightly during the first 10, 16 or 20 days for, respectively, heated lupin protein diet without ascorbic acid, heated lupin protein diet with ascorbic acid, and lyophilised lupin protein diet with or without ascorbic acid. After these periods, food intake decreased strongly. Body weight gain variations did not exactly follow food intake variations. The storage at 20°C could induce first an accumulation of free radicals, which were not detectable in measurement of fatty acids but perceived by rats, and then a fast oxidation of unsaturated fatty acids that increased rancid smell, modified nutritional quality and caused a dramatic decrease of rat food intake. Supplementing ascorbic acid into the diet could diminish the formation of free radicals at the beginning of storage, and consequently could delay food intake decrease. © 1997 SCI.