A comparative study on stability of different types of coconut (Cocos nucifera) oil against autoxidation and photo-oxidation

摘要

This study aimed to compare the stability of five types of coconut (Cocos nucifera) oil available in Sri Lanka. The types of coconut oil studied were coconut pairing oil (CPO), white coconut oil (WCO), refined bleached and deodorized coconut oil (RBDCO), virgin coconut oil (VCO) and coconut oil (CO). Oils were exposed to elevated temperature (60±5°C) in the presence of excess air or oxygen to induce autoxidation and florescent light (2650 lux) to induce photo-oxidation in 28 days of storage. Samples were taken on 0, 1, 3, 5, 7, 14, 21 and 28 days to assess the level of oxidation by peroxide value (PV), conjugated dienes (CD), conjugated trienes (CT) and thiobarbituric acid reactive substances (TBARS) with time. WCO and VCO possessed the highest oxidative stability against autoxidation followed by CO and CPO, while, RBDCO showed the lowest stability. WCO and VCO possessed highest stability against photo-oxidation. CO was more susceptible to photo-oxidation among the oils examined followed by CPO and RBDCO. WCO and VCO possessed similar stability against both autoxidation and photo-oxidation. VCO has highest monounsaturated fatty acid: polyunsaturated fatty acid ratio (4.28) and suitable n63 ratio (5:1); hence applicable as whole purpose oil which is resistant to processing and storage conditions with good nutritive value.