Effect of pH on Antioxidant Activity of α-Tocopherol and Trolox in Oil-in-Water Emulsions

Shu Wen Huang, Edwin N. Frankel, Karin Schwarz, J. Bruce German

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


The pH had a more significant effect on the antioxidant activity of Trolox than α-tocopherol in corn oil emulsified with Tween 20 at 60 °C. Although with increasing pH the oxidative stability of corn oil emulsions decreased, the antioxidant activity of α-tocopherol increased. Initially, Trolox and α-tocopherol were similar in inhibiting hydroperoxide formation with or without phosphate buffers at pH 3-7, but at later stages α-tocopherol was more effective than Trolox at pH 3, 4, 5, and 7 but not at pH 6. In contrast, α-tocopherol inhibited hexanal formation better than Trolox during the entire oxidation period. Trolox was more stable than α-tocopherol in bulk corn oil but less stable in Tween 20 solutions at different pH. Both antioxídants in Tween 20 solutions were most stable at pH 3 and least stable at pH 7. Although more Trolox partitioned into the oil phase and the oil-water interfaces at pH 3-4, its antioxidant activity was lower than at pH 5-6. The overall antioxidant activities of α-tocopherol and Trolox depend on their hydrogen-donating ability, relative stability, and distribution in emulsions.

Original languageEnglish (US)
Pages (from-to)2496-2502
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Issue number9
StatePublished - Sep 1996


  • α-tocopherol
  • Antioxidant mechanism
  • Antioxidants
  • Corn oil triglycerides
  • Emulsion
  • Hexanal
  • Hydroperoxides
  • Interfacial oxidation
  • Oxidative stability
  • Partition coefficient
  • Trolox

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Food Science
  • Chemistry (miscellaneous)


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