HYDRATION KINETICS OF ROASTED LUPIN (LUPINUS ALBUS) SEEDS

Abstract

Hydration kinetics of roasted lupin (Lupinus albus) seeds was studied by soaking in water at 25, 35, 45 or 55C for 5–8 h. Water absorption rate was high at the early stage of hydration (60–180 min) followed by a decreased rate and finally approached equilibrium. Peleg's equation and first order kinetic model described the hydration characteristics adequately (R2 = 0.95−0.99 and 0.97−0.99). The Peleg rate constant k1 decreased from 1.498 to 0.375 min %-1 while Peleg capacity constant, k2 increased from 0.005 to 0.0068/% (P < 0.05) with increase in temperature. The hydration rate constant k in the first order kinetic model increased from 0.0046 to 0.017/min while the equilibrium moisture content Medecreased from 137.44 to 121.06%. Arrhenius type equation described the temperature-dependence of k1 and k (R2 = 0.98 and 0.97) giving activation energy Eapand Eaeof 39.23 and 37.78 kJ/mol, respectively. The first order kinetic model described the hydration characteristics better than Peleg's equation resulting in lower root mean square error. PRACTICAL APPLICATIONS Soaking beans and peas is an integral part of processing operations like cooking, germination and fermentation. In view of long cooking time required, soaking is predominantly meant to facilitate faster cooking. Soaking or hydration is an essential operation to remove the alkaloids that are responsible for bitter taste of lupin seeds. Optimizing the hydration conditions in order to control and predict the process is vital since hydration governs the subsequent operations and the quality of the final product. Such optimization, process control and prediction primarily call for an in-depth understanding, description and quantification of hydration kinetics of lupin seeds under different soaking conditions.