Estimation of oxidative indices in the raw and roasted hazelnuts by accelerated shelf-life testing

To estimate the oxidative stability of the raw and roasted hazelnuts, accelerated shelf-life testing (ASLT) was used at elevated temperatures (55, 65 and 75 °C) at water activity (a_w) of 0.43. Chemical parameters, including peroxide value (PV), para-anisidine value, and total oxidation value were measured to estimate the oxidative stability of the samples using Arrhenius model. In addition, the samples were maintained for 8 months in a real condition at 20-30 °C (long-term shelf-life testing) for validating the results obtained from short-term ASLT. The maximum activation energy (E_a, 78.76 kJ/mol °K) and Q₁₀ (1.871) was obtained for PV in raw hazelnuts, while the minimum E_a (53.36 kJ/mol °K) and Q₁₀ (1.552) were recorded for PV in roasted hazelnuts, indicating the negative effect of roasting process on the oxidative stability of the samples. In order to validate the estimations, the values predicted by short-term ASLT for each oxidation index were plotted versus their corresponding values in actual storage. The results showed good correlation coefficients (R² = 0.91-0.98), confirming the fitness of the Arrhenius model to predict the oxidative indices of the samples during normal storage.