Although vegetable oils have many health benefits, these oils are easily oxidized due to the high content of unsaturated fatty acids during frying, resulting in deterioration of oil quality and formation of toxic substances. To reduce the oxidation rate of healthy vegetable oils such as soybean oil during frying, strong antioxidants are needed. Recently, our research group found that amino acids containing a thiol, a thioether, or an extra amine group such as arginine, cysteine, lysine, methionine, and tryptophan had strong antioxidant activity. At 5.5 mM, these amino acids had stronger antioxidant activities than 0.02% (1.1 mM) <i>tert</i>-butylhydroquinone (TBHQ). The synergistic interaction between amino acids and tocopherols seemed to be the most important mechanism for their antioxidant activity in soybean oil. Our research group also examined the derivatives of amino acids, in which the carboxylic acid group was converted to a carboxylate group (-COONa or -COOK). The heating study conducted with 5.5 mM amino acid salts in soybean oil at 180 °C revealed that sodium salts of amino acids including alanine, phenylalanine, and proline and disodium glutamate had significantly stronger antioxidant activity than the corresponding amino acids. Potassium salts had stronger antioxidant activity than sodium salts. One reason for the improved antioxidant activity of amino acid salts was found to be better retention of tocopherols in soybean oil compared to the corresponding amino acids during heating. Amino acid salts also more effective than the corresponding amino acids in preventing oxidation of other vegetable oils including olive, high oleic soybean, canola, avocado, and corn oils. A frying study with potato cubes confirmed the results and showed that phenylalanine potassium salt at 5.5. mM had significantly stronger antioxidant activity than 0.02% TBHQ.

Amino acids and their derivatives preventing oxidation of frying oil: Promising natural antioxidants

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.