Changes in Fatty Acid Composition and Quality of Three Kinds of Vegetable Oils during Frying

The effect of frying on the quality of soybean oil,camellia oil and palm oil was evaluated by determining acid value and peroxide value by the national standards and analyzing fatty acid composition(especially trans fatty acids,TFA) using a highly polar column(CP-Sil 88).The results showed that cis-linoleic acid(53.06%),cis-oleic acid(82.26%) and palmitic acid(49.7%) were predominant in soybean oil,camellia oil and palm oil,respectively.During low-temperature frying,the total TFA contents in soybean oil and palm oil had no significant change at an average level of 15.51 mg/g and 1.35 mg/g.The content of trans-oleic acid in camellia oil revealed an increase by 63.82% with extended frying time.In decreasing order of acid value,the vegetable oils were camellia oil,palm oil and soybean oil.During frying,the peroxide values of soybean oil and palm oil initially increased and then decreased.Within 8 h of continuous use,neither acid value nor peroxide value exceeded the national food hygiene standards.Taken together,the above results suggest that palm oil has the lowest total TFA content and therefore is more suitable for short-term repeated use in food processing.