Modeling of Water Absorption Behaviour of Black Gram and Dhal during Soaking

The hydration kinetics of black gram and black gram dhal was studied by soaking in water at temperatures of 30, 40, 50, 60 and 70 °C in water bath up to 180 min during the year 2012-13. The amount of water absorbed was high at the early stage of hydration followed by a decreased rate. Peleg's equation adequately described the hydration characteristics of samples under the experimental condition (R² = 0.95). The Peleg's rate constant, k₁, decreased from 4.80 ×10^-2 to 1.17 × 10^-2 for black gram and 3.11 × 10^-2 to 0.77 × 10^-2 for dhal. Peleg's capacity constant, k₂ decreased from 1.32 × 10^-2 to 0.393 × 10^-2 from 30 to 50 °C and then increased to 0.476 × 10^-2 up to 70°C for black gram while k₂ for dhal was increased from 7.2 × 10^-3 to 8.0 × 10^-3 with an increase in temperature from 30 to 70 °C, demonstrating that the water absorption rate increased and water absorption capacity decreased with increase in temperature. Both the Peleg's constants were expressed by a polynomial function (R² = 0.9) for relating to the temperature. The temperature dependence of 1/k₁ followed an Arrhenius type relationship. The activation energy was 20.78 kJ/mol and 31.57 kJ/mol for black gram and dhal, respectively.