Determination of water activity corresponding to the proper quality of peanut kernels

Abstract

Oxidative indices including peroxide value (PV), para-anisidine value (p-AnV), and extinction coefficients K232 and K268, instrumental texture attributes (hardness and chewiness) and colour parameters (L, a, b, and total colour difference) were measured to find the proper water activity (aw) corresponding to the proper quality of peanut kernels during a certain period of storage. The highest and lowest oxidation rates were recorded for the samples kept in aw values of 0.11 and 0.32–0.43, respectively. The stress required to obtain 25% deformation (MPa) decreased significantly (p < .05) with the increasing moisture content of the samples. In summary, less hardness, colour properties closer to fresh kernels as well as slower oxidation progress were measured for the samples stored at a higher aw, especially those stored at 0.32–0.43 at 40°C (equivalent to 0.33–0.43 at 25°C). Practical applications Peanuts (Arachis hypogaea) are grown in tropical, subtropical, and warm temperate climates in more than 70 countries. Like other nuts, peanuts are being consumed as snack foods after roasting or are used as chopped ingredients in cereal bars, confectionery, and breakfast cereals. Therefore, controlling peanut storage conditions (specially aw and temperature) should be considered before use for different purposes. In this study, color, texture, and oxidative changes of peanuts grown in northern Iran, as affected by aw were investigated in order to determine the best aw corresponding to proper quality during storage before being used in various applications at industrial scales.