Evaluation of kinetic parameters in prevention of quality loss in stored almond pastes with added natural antioxidant.

Oxidative stability and loss of nutritional values during storage are the major problems that are encountered in the nut spreads and nut pastes affecting the commercial value. In this study, kinetic behavior of lipid oxidation and depletion of the phenolic antioxidants in the black carrot juice supplemented almond pastes stored at the temperature range of 4-60 °C were studied. Kinetic models were employed to quantify the observations. Lipid oxidation was modeled with the logistic equation. Addition of black carrot juice delayed lipid oxidation, and decreased the maximum peroxide value attained. Being different than the results of the previous studies performed with the similar pastes, the rate constants of peroxide formation reactions in the black carrot juice supplemented pastes decreased with increasing temperature (from 0.60 to 0.27 d-1 ); possibly due to capturing of the lipid oxidation intermediaries by the antioxidants at higher rates at higher temperatures. Depletion of phenolics agreed with a unimolecular first order apparent kinetic model. At the end of the storage period, phenolic losses in the pastes were 5.4, 31.8, 36.9 and 38.2% at 4, 20, 30 and 60 °C, respectively. The results showed that incorporation of the black carrot juice might have an effect on the mechanism of the lipid oxidation and its temperature dependency, and improve the shelf life of the almond pastes.