Stability of Edible Oils Containing Triacylglycerol and Diacylglycerol in the Presence of Tocopherol and/or Vitamin C

Autoxidation of triacylglycerol (TG) oil occurred most rapidly, whereas oils containing tocopherol (Toc) showed a slower increase compared to the ordinary TG oil. Autoxidation of oils was apparently delayed by addition of Toc and vitamin C (VC), and the effect of these antioxidants was greater in diacylglycerol (DG) oil than in TG oil. On the other hand, there was no apparent difference between DG and TG oils in the presence of Toc only. The ΔE values (color difference) of TG oils were higher than those of DG oils, and the values were lower in the oils containing both Toc and VC than in those containing only Toc. The carbonyl value (COV) of TG oil increased with aeration time and tended to be lower without Toc than with Toc. The peroxide value (POV) of DG oil did not change with aeration time, whereas POV of TG oil increased with aeration time and the amount of Toc. COV and the p-anisidin value (ANV) increased with the number of uses, however, the values of DG oils containing Toc tended to be lower than those of the other samples. The dehydration rate, weight decrease and moisture content tended to decrease with the number of uses, which might contribute to the oily or greasy taste of fried food. COV, ANV and the acid value (AV) showed significant correlation with each other, but not with oil absorption, dehydration rate, weight decrease or moisture content.