Abstract
A new procedure at simulated frying conditions in our laboratory was developed 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°C. The oil stability at frying temperature was then evaluated by determining the amount of formed dimeric triglycerides The results obtained showed that the stability of the vegetable oils at frying 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 better heat stability than refin-ed oils. To estimate the effectiveness of synthetic and naturally occurring antioxidants, namely various tocopherols, tocopherol acetate and phytosterol fractions, phenolic compounds like quercetin, oryzanol, ferulic acid, gallates, BHT, BHA and other compounds like ascorbic acid 6-palmitate and squalene were added to refined sunflower and rape seed oil, and their oxidative stability at elevated temperature (OSET) values determined. Both linoleic and oleic rich oils gave comparable results for the activity of the various compounds. alpha-tocopherol, tocopherol esters and BHA had low effects on oil stability at frying temperature, while ascorbyl palmitate and some phytosterol fractions were found to have the most stabilizing activity under frying conditions.
Highlights
To estimate the effectiveness of synthetic and naturally occurring antioxidants, namely various tocopherols, tocopherol acetate and phytosterol fractions, phenolic compounds like quercetin, oryzanol, ferulic acid, gallates, BHT, butylated hydroxyanisole (BHA) and other compounds like ascorbic acid 6-palmitate and squalene were added to refined sunflower and rape seed oil, and their oxidative stability at elevated temperature (OSET) values determined
In the classic Swift test [2] or the Active Oxygen method (AOM) (AOCS CD 12-57 - 1981) air is passed through a sample of oil heated at 98°C and peroxide value (PV) is determined at various intervals
The results show that OSET index, total polar materials (TPM) or % TPG gives good correlation with sensory data collected from actual frying tests of French fries in these oil blends
Summary
To estimate the effectiveness of synthetic and naturally occurring antioxidants, namely various tocopherols, tocopherol acetate and phytosterol fractions, phenolic compounds like quercetin, oryzanol, ferulic acid, gallates, BHT, BHA and other compounds like ascorbic acid 6-palmitate and squalene were added to refined sunflower and rape seed oil, and their oxidative stability at elevated temperature (OSET) values determined. Both linoleic and oleic rich oils gave comparable results for the activity of the various compounds. The PV is plotted against time and the induction time or period is calculated as time between the start-point and the point of intersection obtained by the baseline and the tangent drawn from the curve's inflection
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