Effect of pH on antioxidant activity of alpha-tocopherol and trolox in oil-in-water emulsions
1996
Huang, S.W. | Frankel, E.N. | Schwarz, K. | German, J.B.
The pH had a more significant effect on the antioxidant activity of Trolox than alpha-tocopherol in corn oil emulsified with Tween 20 at 60 degrees C. Although with increasing pH the oxidative stability of corn oil emulsions decreased, the antioxidant activity of alpha-tocopherol increased. Initially, Trolox and alpha-tocopherol were similar in inhibiting hydroperoxide formation with or without phosphate buffers at pH 3-7, but at later stages alpha-tocopherol was more effective than Trolox at pH 3, 4, 5, and 7 but not at pH 6. In contrast, alpha-tocopherol inhibited hexanal formation better than Trolox during the entire oxidation period. Trolox was more stable than alpha-tocopherol in bulk corn oil but less stable in Tween 20 solutions at different pH. Both antioxidants 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 alpha-tocopherol and Trolox depend on their hydrogen-donating ability, relative stability, and distribution in emulsions.
显示更多 [+] 显示较少 [-]