Interaction effect of tocopherol homologs with peppermint extract on the iron-catalyzed oxidation of soybean oil-in-water emulsion

초록

Interaction between tocopherol homologs and peppermint extract added to oil-in-water emulsions was studied during iron-catalyzed oxidation. Emulsions consisted of tocopherol-stripped soybean oil and citrate buffer (4:6, w/w) with/without addition of peppermint extract (400 mg/kg) and alpha-, gamma-, or delta-tocopherol (600 mg/kg), and were oxidized in the iron presence at 25 degrees C. Lipid oxidation of emulsions was evaluated based on hydroperoxide contents and p-anisidine values. Lipid oxidative stability of emulsions was improved by added peppermint extract, and co-added gamma- and delta-tocopherols further reduced lipid oxidation, however, alpha-tocopherol increased it. Tocopherol contents did not change during oxidation. Polyphenol degradation in the emulsion with added peppermint extract was lower and slower by gamma- and delta-tocopherols, however, alpha-tocopherol showed opposite results. The results suggest that co-addition of tocopherols to the emulsion containing peppermint extract shift a major role of polyphenols as antioxidants from scavenging lipid (peroxy) radicals to tocopherol radical scavenging.

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