Characteristics of mechanical strength and water absorption in almond and its kernel

Abstract

The rupture force and energy were measured at different loading velocities, loading direction and almond size for the Mamaei variety of almond. In addition to the rupture properties, the water absorption characteristic of almond kernels was determined. Three mathematical models (Weibull, Peleg and Exponential) for describing the water absorption kinetics of almond kernels were investigated. In this study, a new model based on the time dependent viscoelastic properties of food products was proposed to describe absorption behaviour of almond kernels. The results showed that loading velocity, loading direction and almond size had significant effects on cracking force and energy. The mean values of cracking force and energy were 539 N and 443 mJ, respectively. Almond size had increasing effects on cracking force and energy. Almonds loaded from side ruptured at a lower force and energy than the ones loaded in the front orientation. The studies on water immersion showed that the rate of water uptake was maximum during the initial phase of soaking, with the moisture content of kernel increasing from 5.26% to 22.1% (dry basis) after one hour of soaking. The determined water absorption capacity (WAC, %) of almond kernels was of 1338%. Peleg, the newly developed model, and Weibull models were more accurate for describing the water absorption characteristics of almond kernels. At the very beginning times of soaking, the water absorption velocity was of 0.32 (%/min). The rate of relaxation (Kret in the new developed model) was of 0.0082 (%/min).