Effect of diet handling on nutritional studies with used frying fats.

A four-week experiment to study the significance of careful diet handling was carried out with weanling rats fed purified rations containing 15% of various fats. Fresh soybean oil was the fat in the control diet and the other fats, which had been used to prepare food by a commercial-type deep-frying operation, were soybean oil, partially hydrogenated soybean oil with iodine value (I.V.) 70, partially hydrogenated soybean oil with I.V. 108, and cotton-seed oil. A purified diet was fed ad libitum.Treatment of the dietary groups in regard to preparation and handling of the rations proved to be highly significant. That is, as opposed to weekly mixing and twice weekly feeding of the diets, daily preparation and feeding along with the use of antioxidants and refrigeration of the ingredients resulted in a much superior growth rate and a higher efficiency of feed conversion. Since this very significant response became apparent in less than four weeks, the importance of careful handling to minimize secondary effects within the diet must be emphasized. The fresh soybean oil control, and all of the used frying fats gave similar results.