Abstract:The antioxidant efficiency of gallic acid (GA) and its alkyl esters including ethyl gallate (GA-C2), butyl gallate, octyl gallate, lauryl gallate, hexadecyl gallate, and octadecyl gallate in walnut oil and its oil-in-water emulsion were evaluated. The determination of peroxide value (POV), conjugated dienes, thiobarbituric acid (TBA) value as well as p-anisidine value assays in walnut oil-in-water emulsion showed that the antioxidant activity of GA and its alkyl esters increased with the increase of alkyl chain length, and GA-C2 showed the strongest antioxidant activity and then descended, which was called "cut-off effect". The results of POV and TBA in walnut oil indicated that the antioxidant activity of GA and its alkyl esters tended to decrease with the increase of alkyl chain length, which was consistent with "polarity paradox". The effects of alkyl chain length on antioxidant activity of GA and its alkyl esters in different oil systems were discussed to provide basis for selecting antioxidants suitable for walnut oil and walnut oil-in-water emulsion.
