Deep fat frying of frozen foods in sunflower oil. Fatty acid composition in fryer oil and frozen prefried potatoes

The fatty acid pattern was used to evaluate the alteration of a sunflower o il that had been used 20 times to fry various frozen foods with frequent re plenishment (FR) or without replenishment (NR) of the used oil with fresh o il during frying. Furthermore, the fat extracted horn potatoes fried in the sunflower oil from fryings 1, 5, 8, 12, 16 and 20 was also analysed by gas -liquid chromatography to compare its fatty acid profile with that of the c orresponding fryer oil. The amount of unaltered fatty acids decreased from 96.2 mg per 100 mg oil in the unused sunflower oil to 89.6 mg per 100 mg oi l after 20 fryings in the FR oil and to 88.9 mg per 100 mg oil in the NR oi l, following a linear adjustment (r>0.97; p<0.001). Linoleic acid also decr eased while palmitic and oleic acids increased in the bath oil. Fatty acid variations were more pronounced in NR than FR oil for major fatty acids and not only related to the degradation of unsaturated fatty acids but also to the interactions between the bath oil and the fried food fat. Thus the inc rease in palmitic acid of the fryer oil could be due to migration of this f atty acid from the prefried frozen potatoes as revealed by the composition of the fat extracted from those potatoes. Although the fatty acid variation (eg myristic, palmitic, oleic, trans-cis isomers of linoleic and linoleic acids) was not equivalent in FR or NR fryer oil and in the fat of the potat oes, the changes in total unaltered fatty acids were not significantly diff erent in oil and potatoes. Present data suggest that frequent addition of f resh oil throughout the frying process minimises the fatty acid changes, co ntributing to the obtainment of fried foods with a healthy fatty acid profi le. (C) 2000 Society of Chemical Industry.