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Repeated thermal processing during cooking, as well as overcooking of food may affect the fatty acids by acting on the carbon double bonds or hydroxyl bonds which may further affect the quality of oil. The process of cooking can lead to various physiological and chemical changes in the oil, making the oil unfit for consumption. The aim of present study is to observe the effects of selected repeated thermal processes on the oil quality and to set aside the oil most suitable for cooking. Five major oils/fats consumed in India: mustard oil, soybean oil, palm oil, hydrogenated fat (vanaspati) and desi ghee (clarified butter) were selected to observe the effects of different thermal processes (frying, heating, and microwaving) which are common in households during cooking. The parameters investigated during this study are free fatty acid (FFA), peroxide value, iodine value, total polar compound (TPC), anisidine value and diene value of oils/fats. Based on the obtained results it was found that frying treatment significantly affect the quality of oils followed by microwave and heat treatment. Among the selected oils/fats maximum variation in FFA was found for clarified butter. However for TPC and peroxide value maximum variation was observed in mustard oil and soybean oil respectively.
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