The chemical and functional properties of cottonseed oil as a deep-fat frying medium

The purpose of this research study was to determine if unhydrogenated cottonseed oil was suitable for the deep-fat frying process and to determine the nutritional characteristics of the cottonseed oil and the french fries cooked in the oil. Cottonseed oil, partially hydrogenated canola oil and partially hydrogenated soybean oil were subjected to a temperature of 177°C for 8 hours per day and 6 batches of french fries were fried per day for 5 consecutive days. French fries were weighed prior to frying, cooked for 5 minutes, allowed to drain, and reweighed. Oil was not replenished, filtered once per day, and weighed daily before and after frying. Both the oil and the french fries were evaluated to determine color, fatty acid profiles, trans fatty acids, crude fat, and moisture. The french fries were analyzed for total polar materials and the oil was analyzed for iodine values, peroxide values, p-anisidine values, free fatty acids and totox values. No significant differences were found among oil types for loss of oil during cooking, weight of french fries before and after cooking, color, moisture, and crude fat. Iodine values for all three oil types were significantly different. Both canola oil and soybean oil had significantly lower iodine values than cottonseed oil due to being partially hydrogenated. Free fatty acid values were not significantly different for the three oil types. Cottonseed oil, regardless of days of frying, had higher peroxide values, p-anisidine values and totox values compare to canola oil and soybean oil, indicating an increased presence of primary and secondary oxidation products. However, as days of frying increased, values for all three oils trended closer together. There were no significant differences in total polar materials for french fries cooked in the three oils. Fatty acid profiles for both the french fries and the oil remained relatively stable as frying days increased. The analytical tests indicated that none of the three oil types reached a highly deteriorated state. Cottonseed oil was significantly lower in trans fatty acids than the other oils, as were the french fries prepared in the oil. Cottonseed oil appeared to be as stable as canola oil and soybean oil, however the oils would need to be stressed to a much greater degree to confirm this. In regard to dietary components associated with potential negative health effects, french fries cooked in cottonseed oil were slightly higher in saturated fatty acids, but markedly lower in trans fatty acids than those cooked in canola oil and soybean oil.