Enhanced Oxidative Stability of Walnut Kernels by Lipid-Soluble Antioxidant Combinations: From Individual Screening to Ternary Formulation.

Walnut kernels are highly susceptible to lipid oxidation because of their high content of unsaturated fatty acids. This study screened five lipid-soluble antioxidants-tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), propyl gallate (PG), dilauryl thiodipropionate (DLTP), and ascorbyl palmitate (AP), and further evaluated binary and ternary formulations based on BHT. Treated walnut kernels were subjected to accelerated oxidation, and the oxidative stability was assessed using peroxide value, thiobarbituric acid-reactive substances (TBARS), DPPH radical scavenging activity, electron spin resonance, fatty acid composition, thermogravimetric analysis, and sensory evaluation. Among the individual antioxidants evaluated at their respective maximum permitted concentrations, BHT showed the most consistent protective effect, with the lowest oxidation indices, the strongest DPPH radical scavenging activity, and the weakest thermally induced radical signal. The BHT + TBHQ formulation performed significantly better than BHT alone in several oxidation indices (p < 0.05). The ternary BHT + TBHQ + DLTP formulation showed the best overall performance, with antioxidant activity comparable to that of the commercial antioxidant blend and significantly lower TBARS values than the BHT + TBHQ group (p < 0.05). Linoleic, oleic, and α-linolenic acids remained at 58.78-62.54%, 17.62-21.33%, and 10.64-11.31%, respectively. No significant differences in aroma or flavor were observed among treatments (p > 0.05). These findings indicate that BHT + TBHQ + DLTP effectively improves the oxidative stability of walnut kernels during accelerated storage.