Effect of synthetic antioxidants on the oxidative stability of cold pressed walnut oil

Abstract

Article deals with evaluation of the efficacy of antioxidants on quality indices, related to oxidative stability of walnut oil. Properties of cold pressed walnut oil were monitored under storage conditions of darkness and room temperature over 2 months. A Full Factorial Experiment design, FFE 23, was applied to estimate the effects of n-Octyl Gallate (OG), DL-α-Tocopherol (DLTP) and L-Ascorbic Acid 6-Palmitate (AAP). A statistical study of the peroxide contents, p-anisidine index values and UV-Vis spectra of walnut oil added with antioxidants demonstrate increasing of the antioxidant activity in the series of DLTP << AAP < OG. Accordingly to the independent spectral and analytical data, DLTP which has been added in the walnut oil, shows itself as pro-oxidant, rather than antioxidant for this food product, and thus is not suitable for it. The linear regressions demonstrate synergetic super-addition effect of AAP-OG compositions, beneficial for increasing of walnut oil stability by safety amounts of antioxidants. A joint use of these antioxidants in small amounts significantly reduces lipid oxidation and increases the shelf life of walnut oil.