Factors affecting Trans fatty acid content in Chinese fried dough

Abstract

This study aimed to evaluate the factors affecting trans fatty acid in deep fried food by the attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) method. Chinese fried bread (or Pa-tong-ko in Thai), the well-known fried food in Thailand, was chosen to be a representative of fried food in this study because the repeated used of frying oil was mostly found in this kind of food. The factors which were investigated in this study were frying time without refilling new oil added and vitamin E added in frying oil. Chinese fried bread was made following the instant wheat powder package label. 80 g dough was prepared and was separated into 10 equal pieces for once frying. Then they were fried with 6,000 g palm oil, at 170°C temperature controlled for 3 minutes. Therefore ten pieces of dough were fried every 10 minutes continually until reach 5 hours without refilling new oil added. Samples were divided into 3 groups; 1) control group 2) 0.23% (w/w) vitamin E added oil group and 3) 0.45% (w/w) vitamin E added oil group. The fried sample of each group was collected every 1 hour including the first of frying. So after 5 hours frying, there were total 6 times collected. The results showed that adding of vitamin E in frying oil (at dose of 0.23% and 0.45%) could not prevent the formation of trans fatty acid in oil that was repeated used. Moreover, this study showed that frying time affects trans fatty acid content in fried food. It was found that trans fatty acid content (% of total fat) of Chinese fried bread at first time frying (hr0) was significantly lower than those at hr4 and hr5. Therefore, consumers should avoid consuming food that used repeated frying oil.