The Effect of Temperature on Water Absorption (Hydration Kinetics) of Three Varieties of Rice (Oryza sativa L.) In Sierra Leone

Abstract

In this study we examined the effect of temperature on the absorption of water (hydration) by some rice varieties grown in Sierra Leone. This study was carried out at Rokupr Agricultural Research Centre (RARC) laboratory of the Sierra Leone Agricultural Research Institute (SLARI). Dry samples of paddy from three rice varieties (Nerica-19, Nerica-21 and Rok-24) were hydrated in a water bath at temperatures of 30, 50 and 70°C respectively. Model parameters for Peleg’s equation (k1 and k2) were estimated from experimental data and used to fit the equation for the three cultivars at different temperatures. Results suggest that the initial absorption rates, saturation moisture content as well as water absorption capacities increased for all three varieties with increasing temperatures. Values of both Peleg’s constants show temperature and varietal dependence. Both constants appeared to decrease linearly with rising temperature conditions. The key difference noted among rice varieties was that whereas for Nerica-19 and Rok-24, which took up moisture slowly, k1 and k2 had fairly similar values, (ranging from 7.248 to 1.273 for k1, and 0.039 to 0.025 for k2), Nerica-21, which took up moisture more rapidly, had significantly lower values (ranging from 3.972 to 0.814 for k1, and 0.025 to 0.019 for k2). The results show that Peleg’s equation can provide a satisfactory mathematical model of hydration phenomena in rice grains although its applicability for different rice grain varieties might require variety-specific or grain-type-specific grain-class-specific calibration.