A new method to determine oxidative stability of vegetable fats and oils at simulated frying temperature

A new procedure at simulated frying conditions in our laboratory was develo ped to monitor frying stability of fats and oils. Water-conditioned silica was prepared and added to the fresh vegetable oil, which was heated for two hours at 170 degreesC. The oil stability at frying temperature was then ev aluated by determining the amount of formed dimeric triglycerides The results obtained showed that the stability of the vegetable oils at fry ing temperature could not be explained by the fatty acid composition alone. Corn oil was observed to be more stable than soybean oil, and rapeseed oil was better than olive oil. It was also observed that crude, non-refined oils were found to have a bett er heat stability than refined oils. To estimate the effectiveness of synth etic and naturally occurring antioxidants, namely various tocopherols, toco pherol acetate and phytosterol fractions, phenolic compounds like quercetin , oryzonol, ferulic acid, gallates, BHT; BHA and other compounds like ascor bic acid 6-palmitate and squalene were added to refined sunflower and rape seed oil, and their oxidative stability at elevated temperature (OSET) valu es determined. Both linoleic and oleic rich oils gave comparable results for the activity of the various compounds. cr-tocopherol, tocopheroi esters and BHA had low effects on oil stability at frying temperature, while ascorbyl palmitate an d some phytosterol fractions were found to have the most stabilizing activi ty under frying conditions.