Frying Performance Of Palm Olein With Added Natural Antioxidant Mixtures And Acceptability Of Fried Potato Chips

A comprehensive study on the feasibility of use of natural antioxidants, namely rosemary and sage, together with citric acid acting as a synergist during repeated deep-fat frying process of potato chips in palm olein was carried out. The study was inclusive of evaluation of oxidative behaviour of these antioxidants, monitoring of physico-chemical changes of oil during frying, development of some new instrumental methods for detecting quality parameters of used oil, effect of addition of the antioxidants on organoleptic properties of fried product and relationship between quality indices of the oil and sensory acceptability of the fried product.Results showed that rosemary and sage extracts are feasible to be used in retarding the palm olein deterioration during repeated deep-fat frying of potato chips. The two natural antioxidants were proven to significantly (P<0.05) lower the rate of oxidation of the oil during frying, while having very good thermal resistance. Organoleptically, both rosemary and sage extracts could improve acceptability of fried potato crisps. There were significant correlations between sensory attributes of fried potato chips and quality parameters of palm olein used. Optimization study on the effect of use of the natural antioxidants during deep-fat frying on fatty acid composition of palm olein revealed that C 1 8:2 and C 16:0 fatty acids were the most important fatty acids for predicting changes in oil quality after frying. However, for optimization purposes, the use of the C 18:2/C 16:0 ratio best predicted the efficacy of natural antioxidants in preserving palm olein during deep-fat frying. This study also successfully developed instrumental methods for monitoring the physico-chemical changes of palm olein during repeated deep-fat frying. The alkaline contaminant materials (ACM) contents in palm olein could be determined spectrophotometrically at 540 nm, whereas the use of Fourier transform infrared (FTIR) spectroscopy to monitor changes in the iodine value, peroxide value and free fatty acid contents in palm olein during frying was found to be a viable alternative to the wet chemical methods, with FTIR providing rapid results taking less than 2 min per sample and minimum use of solvent and labour.