Sorption isotherms of ready-to-puff preconditioned brown rice: Development of classical models and artificial neural network approach

Moisture sorption isotherm data of ready-to-puff preconditioned brown rice shall enable in finding solutions for prolonging the period between preconditioning and puffing. Designed full factorial experiments were conducted with ready-to-puff preconditioned brown rice at five different salt concentrations (SC) ranging 0-4%, varying temperature (T), 20-30 degrees C within eight levels of moisture content (MC), and 3-25% to obtain sorption isotherms. Preconditioning was carried out at 75(+/- 3)degrees C using a fluidized bed dryer to attain a final MC of 11%, optimum for puffing. Water activity (a(w)) of the sample increased with increasing T and decreased with increasing SC. The individual and interaction effects of T, SC, and MC on a(w) are highly significant (p < .001). The experimental sorption data at each SC were fitted with the traditional model at a given temperature. All the models were statistically (p < .001) significant. A feedforward artificial neural network model was developed with three input variables T, SC, and MC as the input layer and a(w) as the output layer. Inter-relationship among the process variables is explained better by artificial neural network (R-2 = 0.991) and second-order model (R-2 = 0.973) as compared with traditional models, which are limited in their ability to express the relationship among the variables. Practical Applications The key to quality puffed rice is the preconditioning process during its manufacture. During preconditioning, salts and moisture penetrate the rice matrix to give a desirable product. The preconditioned rice should be immediately processed, else absorption or desorption of moisture from the atmospheric air takes place. This leads to finished puffed rice with compromised quality. Liberty of using the preconditioned rice for further processing will wrest upon the processor if suitable packaging is provided to this rice. Extensive knowledge of moisture sorption isotherms is required for designing such packaging material and conditions. The present study is carried out to study the sorption isotherm of ready-to-puff preconditioned brown rice. The information available in the present study is useful for food industries to develop a suitable packaging material for time-independent use of preconditioned rice.