Bicarbonates and carbonates as antioxidants in vegetable oils at frying temperatures

Antioxidant activity of bicarbonates and carbonates including NaHCO₃ , Na₂ CO₃ , KHCO₃ , and K₂ CO₃ was evaluated in soybean oil (SBO) at 180°C. KHCO₃ and K₂ CO₃ had stronger activity than NaHCO₃ and Na₂ CO₃ . KHCO₃ (5.5 mEq/L, 0.060 wt.%) and K₂ CO₃ (5.5 mEq/L, 0.041 wt.%) were more effective than 0.02 wt.% tert-butylhydroquinone (TBHQ) in preventing oxidation of SBO. While the antioxidant activity of KHCO₃ and K₂ CO₃ increased with increasing their concentrations up to 5.5 mEq/L, it decreased at 11 mEq/L. KHCO₃ and K₂ CO₃ were also effective in preventing oxidation of other vegetable oils including avocado, canola, corn, high oleic soybean, and olive oils. Correlation tests conducted with the results from the six oils showed that KHCO₃ and K₂ CO₃ had weak to moderate positive correlations with γ- and δ-tocopherols. In a separate study in stripped SBO, it was found that KHCO₃ had a synergistic effect with α-tocopherol, but not with γ- and δ-tocopherols. KHCO₃ had additive or synergistic effect with rosemary extract, epigallocatechin gallate, ascorbic acid, and ascorbyl palmitate. Antioxidant activity of KHCO₃ was confirmed in frying of potato cubes in SBO and canola oil. Although more studies should be conducted for better understanding of the mechanisms and factors affecting the antioxidant activity of bicarbonates and carbonates, this study demonstrated that they could serve as antioxidants or co-antioxidants of other antioxidants in frying. PRACTICAL APPLICATION: Inorganic salts including NaHCO₃ , KHCO₃ , Na₂ CO₃ , and K₂ CO₃ hadstrong antioxidant activity in vegetable oils at frying temperatures when they wereadded as powder. Antioxidant activity of 0.06 wt.% KHCO₃ was higherthan that of 0.02 wt.% TBHQ in soybean oil and canola oil during frying potato. KHCO₃ had additive orsynergistic effect with rosemary extract, epigallocatechin gallate, ascorbicacid, and ascorbyl palmitate indicating that these inorganic salts can be usedas co-antioxidants to enhance the antioxidant activity of existing antioxidantswhile they can be used alone as well.