Quality Change Of Soybean Oils During Flying And The Research Of Improving The Number Of Flying

In this paper, soybean oil was taken as raw material, wherein TBHQ, BHT and 18 degrees palm oil were added into two oil samples. The changes of oil color, acid value, peroxide value, carbonyl value, fatty acid, glycerides’ composition and the content of trans fatty acid of the five soybean samples went with the frying times had been examined during the(190±5)℃ frying process. At the same time, the loss of antioxidants and tocopherol were also been checked. Results show that: the quality of soybean oil in the frying process changed significantly. The color deeper with the increasing frying times, acid value, carbonyl value,the content of diglycerides and the types of volatile component increased, the peroxide value fluctuated, while triglycerides decreased. Monoglycerides and trans fatty acids content, fatty acids compsition showed no significantly change, while unsaturated fatty acids showed a slightly decreased.Adding antioxidants, adding fresh soybean oil in frying process can improve the frying performance of the soybean oil. Adding antioxidants can improve the frying number s from 3 to 5 times, namely frying performance is the initial soybean oil 1.67 times. Adding new oil in the process of frying could improve frying number 1 time; When the unsaturated fatty acid content of soybean oil was 3.55% lower, also can effectively improve the performance of frying on the soybean oil, fry number can be increased from three to six times; In the process of frying antioxidants will loss, typically in fried three hours, the loss was 100%, and the function mainly reflects in the fried twice before; In the frying process, with the increase of the number of frying, the loss rate of TBHQ faster than BHT, 1.5 to 1.8 times that of BHT; Adding fresh soybean oil in the process of frying, BHT and TBHQ loss rate is relatively slow; With the increase of frying times, tocopherol in soybean oil obviously loss, the loss rate of α-, γ-and δ-tocopherol in turn is a->γ->δ-tocopherol.To verify the validity of the method to improve soybean oil frying times, choose the blend oil of fried good performance on the market to contrast test. The results proved that the soybean oil with unsaturated fatty acids reduce 3.55% compared to sold fried blend oil have enough performance, fried soybean oil of only add antioxidants have disparity compared with commercial blend oil. That can be promote further by tracing raw material and improve the process of bleaching and deodorization.