Optimization of physicochemical changes of palm olein with phytochemical antioxidants during deep-fat frying

Response surface methodology (RSM) was used to optimize the amounts of rose mary and sage extracts together with citric acid as synergist antioxidants in stabilizing refined, bleached, and deodorized palm olein during repeated deep-fat frying of potato chips. For all physicochemical properties studie d, these phytochemical antioxidant treatments significantly (P < 0.05) redu ced the oxidation rate of the oil. During 5 d of frying, anisidine value, p eroxide value, free fatty acid, polymer content, color units, viscosity, an d absorbances at 232 and 268 nm gradually increased, whereas iodine value a nd ratio of 18:2/16:0 decreased. Further statistical analyses, including co efficient of determination (R-2) and probability of F values, indicated tha t mathematical models for each physicochemical parameter could be developed confidently in this study, with R2 for all parameters greater than 0.90. T hese results suggested that an optimal mixture of phytochemical antioxidant s derived from rosemary and sage together with citric acid could be produce d using RSM for stabilizing thermally processed oil. For many physicochemic al parameters examined, the use of moderate levels of antioxidants could re sult in optimal responses.