Changes in quality characteristics of coconut oil during deep frying

Abstract

Reuse of coconut oil, especially for deep frying of various foods is a common practice in domestic and commercial food preparations in Sri Lanka. A study was carried out to find out whether there are any changes of quality characteristics of repeatedly deep-fried coconut oil. Reused coconut oil (18 samples) used for deep frying were collected from home kitchens, street food outlets and commercial food outlets. Simultaneously fresh coconut oil samples as reference samples were also collected. Moisture content, free fatty acids content (FFA), peroxide value and iodine values of fresh and deep-fried coconut oil samples were determined using AOAC methods. Results showed that all the fresh coconut oil samples (FCO) had moisture contents higher than 0.4 %, while 22 % FCO has a FFA contents higher than 0.8 %, and were not within the SLS standards (0.8%). Iodine values of 88 % FCO confirmed to the SLS standards indicating most of the commercially available coconut oils are not adulterated and 83% of FCO had Peroxide values below 2meq/kg. Coconut oil samples used for deep frying (DFCO) showed significantly lower moisture contents than respective FCO, and 80% of DFCO had FFA contents confirming to SLS Standards. However, peroxide and iodine value of DFCO showed significantly increased values compared to corresponding FCO. This may be due to the contribution of the unsaturated fatty acids from food material used for frying.