Oxidation in fish oil-enriched mayonnaise: 4. Effect of tocopherol concentration on oxidative deterioration

The effect of the water-dispersible tocopherol preparation, Grindox 1032, a nd the oil-soluble tocopherol preparation, Toco 70, on oxidative stability in fish oil-enriched mayonnaise was examined. The two commercial antioxidan t preparations were supplemented in different levels corresponding to 20-28 0 ppm tocopherol in addition to the 600 ppm present in the oils used for th e mayonnaise. The oxidative stability was assessed by sensory analysis, the tendency of formation of free radicals, and concentrations of lipid hydrop eroxides and volatile oxidation products. The effect of tocopherol on oxida tion depended on the nature and the concentration of the tocopherol prepara tion employed, and it also depended on the parameters evaluated. Addition o f high levels of Grindox 1032 (similar to 140-280 ppm tocopherol) thus decr eased the intensity of rancid off-flavor, but increased the formation of fi shy off-flavors, the tendency of free radical formation and the concentrati on of certain volatiles. In contrast, low levels of Grindox 1032 (< 70 ppm tocopherol) reduced the concentration of some volatiles, but did not seem t o influence the off-flavor profile of the mayonnaise. Toco 70, which was on ly supplemented in low levels (<40 ppm tocopherol) increased the tendency f or free radical formation, changed the profile of volatiles, and did not ha ve a clear effect on the fishy and rancid off-flavor formation. Thus, addit ional tocopherol did not appear to be an efficient antioxidant in fish oil- enriched mayonnaise, perhaps because it cannot prevent the metal-catalyzed decomposition of peroxides, which we previously suggested to play an import ant role in mayonnaise.