Bicarbonates and carbonates as antioxidants in vegetable oils at frying temperatures

Authors: Hwang, Hong-Sik; Moser, Jill

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2022
Publication Date: 12/28/2022
Citation: Hwang, H., Moser, J.K. 2022. Bicarbonates and carbonates as antioxidants in vegetable oils at frying temperatures. Journal of Food Science. 88(2):717-731. https://doi.org/10.1111/1750-3841.16442.
DOI: https://doi.org/10.1111/1750-3841.16442

Interpretive Summary: Although vegetable oils rich in unsaturated fatty acids have many health benefits, they are less stable and oxidize faster than highly saturated fats such as palm oil at high temperatures. For this reason, palm oil and other tropical oils are widely used for frying by the food industry and restaurants. Strong antioxidants are needed to use healthy vegetable oils for frying. In this study, sodium bicarbonate (baking soda) and its analogues were evaluated as antioxidants in soybean oil heated at a frying temperature (180 °C). It was found that potassium carbonate and potassium bicarbonate had strong antioxidant activity in soybean oil heated at 180 °C. This result indicates that synthetic antioxidants, which are strong antioxidants, but potentially toxic, can be replaced by these materials. They were also very effective in preventing oxidation of other vegetable oils including avocado, canola, corn, high oleic soybean, and olive oils at 180 °C. Potassium bicarbonate was tested in frying experiments where potatoes were fried in soybean oil and in canola oi, and its strong antioxidant activity was confirmed in the frying experiments. It was also found that potassium bicarbonate further increased the antioxidant activity of other antioxidants when it was added with these antioxidants indicating that it can be used co-antioxidant of other antioxidants for enhanced activity. This study revealed that baking soda and its analogues can replace the potentially toxic synthetic antioxidants used in frying oils and that unhealthy palm oil and other tropical oils can be replaced with healthy vegetable oils by using these materials as antioxidants.

Technical Abstract: Antioxidant activity of bicarbonates and carbonates including NaHCO3, Na2CO3, KHCO3, and K2CO3 was evaluated in soybean oil (SBO) at 180 °C. All the four bicarbonates and carbonates at 5.5 mEq/L had significant antioxidant activity, and KHCO3 and K2CO3 had stronger activity than NaHCO3 and Na2CO3. KHCO3 (5.5 mEq/L, 0.060 wt.%) and K2CO3 (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 K2CO3 increased with increasing their concentrations up to 5.5 mEq/L, it decreased at 11 mEq/L. KHCO3 and K2CO3 were also effective in preventing oxidation of other vegetable oils including avocado, canola, corn, high oleic soybean, and olive oils at 180 °C. Correlation tests conducted with the results from the six oils showed that KHCO3 and K2CO3 had weak to moderate positive correlations with g- and d-tocopherols. In a separate study in stripped SBO, it was found that KHCO3 had a synergistic effect with a-tocopherol, but not with g- and d-tocopherols. KHCO3 had additive or synergistic effect with other antioxidants including 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 commercial natural antioxidants in frying.