| Deep-fat frying is a popular method of food preparation, especially in fast food restaurants. During deep-fat frying, the fat is exposed to high temperatures in the presence of moisture from food and air and a variety of reactions such as autoxidation, thermal polymerization, thermal oxidation, isomer cyclization, and hydrolysis can occur producing numerous decomposition products, both volatile and nonvolatile. Hydrolysis of frying fat results in the formation of diacylglycerols, monoacylglycerols and fatty acids. Monoacylglycerols (MG) are commonly used as emulsifiers in margarine and table spreads, and their addition to frying oils has been reported to decrease the interfacial tension (IFT) between frying oil and water. Reduction in IFT of frying oils was reported to highly correlate with increased fat absorption. The purpose of the present study is to understand the role of MG during frying using a model food system based on starch gel. A gas chromatographic method, using short-length packed columns, has been adapted to follow the increase in concentration of fatty acids, mono- and diacylglycerols during frying. A model food system based on corn starch gel has been developed and evaluated for its performance during frying. The model food system was noted to have features that mimic the characteristics of many foods undergoing deep-fat frying (moisture loss, fat absorption, crust formation etc.). High correlation has been determined between fat absorption and frying time (r = 0.96), and between concentration of MG and IFT of soybean oil with water. Use of the model food system to study the effect of MG concentration on fat absorption indicated a poor correlation between fat absorption and MG concentration at frying times of 3 and 5 minutes. However, a significant correlation between MG concentration and fat absorption was determined at a longer frying time of 8 minutes. These results suggest that reduction in IFT due to MG is not the sole reason for increased fat absorption of foods fried in degraded oils. |
