Refractance window drying of walnut kernel (Juglans regia L.)

Abstract

The present study aimed to determine the effect of refractance window (RW) drying and compare it with sun drying for various physicochemical properties of walnut kernels. Physical properties such as moisture content, texture, color analysis, and water activity were analyzed and results were found to be better than sun drying. The ΔE value of kernels was found lowest (4.36) at 70 °C and texture profile results were found better than those of walnut kernels obtained by sun drying. The total phenolic content, and the antioxidant activity of the RW-dried product were found significantly higher than the sun-dried sample. The TPC value of the RW dried sample obtained at 90 °C was found maximum to be 2710 ± 2.75 mg GAE/100 g. The IC50 value of RW dried walnut kernel was found lowest (4.12 ± 0.45 µg/mL) at 50 °C. The LOX activity of all samples was significantly lower in the case of RW drying. The lowest value was obtained (0.065 ± 0.015 µkat) at 50 °C. The CHNO(S) test depicted lower lipid oxidation in the case of RW-dried samples.