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Different tocopherols and the relationship between two methods for determination of primary oxidation products in fish oil

Kulas, E., Ackman, R.G.
Journal of agricultural and food chemistry 2001 v.49 no.4 pp. 1724-1729
alpha-tocopherol, tocopherols, menhaden oil, anchovies, fish oils, peroxide value, organic compounds, eicosapentaenoic acid, gamma-tocopherol, antioxidant activity, delta-tocopherol
The effectiveness of 2.32 mmol/kg (approximately 1000 ppm) of alpha-, gamma-, or delta-tocopherol (TOH), as well as different levels of alphaTOH, on the formation of hydroperoxides in fish oil was studied by monitoring the peroxide value (POV) and the formation of conjugated dienes (CD) during storage at 30 degrees C. The same order of antioxidant activity was observed by both methods. Linear regression of POV on CD showed that these data were strongly correlated (r2 greater than or equal to 0.98). The value of the slope of the regression lines, however, differed substantially and decreased with increasing hydrogen-donating ability of the different tocopherols and with increasing alphaTOH concentration. It is suggested that this is due, at least in part, to the contribution from hydroxy compounds to the CD measurements and a greater contribution from hydroperoxy epidioxides (two peroxide groups per conjugated diene unit) to the POV than to the CD value. The degrees of formation of both these groups of oxidation products are expected to be influenced by the rate of scavenging of lipid peroxyl and alkoxyl radicals by tocopherol (alphaTOH > gammaTOH > deltaTOH).