Thermoxidation in a sunflower oil used in 75 deep fat frying of potatoes. Effects of its inclusion in rat-diet upon growth and food intake

The alteration of a sunflower oil used in 75 repeated deep fat frying of potatoes performed with addition of unused oil every 4-5 fryings with the aim to keep constant the proportion food/oil in 500 g / 3 liters, was evaluated by column and high performance size exclusion chromatographies. The polar components increased from 5.09 ± 0.21 (unused oil) to 19.11 ± 0,40 mg/100 mg oil mainly due to the formation of polymers and dimers of triacylglycerides, and to oxidized triacylglycerides. Oils, unused and from the 75 frying, were included at a rate of 15% on rat-diets. Dietary food intakes were similar, however body weight gain was a 22.3% lower in rat fed with the used oil-diet. Apparent digestibility ratios of fat and protein were similar in both groups of rats, however both. Alimentary and Protein Efficiency ratios decreased on the 75 frying oil fed rats.