Modeling rice and corn hydration kinetic by Nicolin-Jorge model

Empirical characterization of hydration behavior of Indian paddy varieties by physicochemical characterization and kinetic studies

Temperature is an important factor in the determination of hydration kinetics in paddy, and it varies with variety. To understand this hydration behavior, the current study analyses the hydration kinetics of 12 different paddy varieties of India that were exposed to different soaking temperatures. The protein content of the paddy samples was found to be in the range of 6.13 to 9.19%; whereas, starch content was between 67.79 and 84.88%. The physicochemical composition of paddy varieties as well as variation in time-temperature of hydration was found to be decisive in ascertaining the hydration behavior. An increased hydration rate was observed with increasing hydration temperature as well as with higher amylose content of paddy. Among the varieties studied, the ratio of amylose to amylopectin was between 0.37 and 0.77. For all samples, the gelatinization temperature was in the range of 65.60 to 83.10 °C, which in turn was negatively correlated with amylose content, and influenced the hydration behavior of paddy. The optimum time-temperature condition range for hydration for each paddy variety was between 50 and 60°C for 2 to 3.5 hr, depending upon the variety. The activation energy for the paddy samples in this investigation was found to be in the range of 8.70 to 23.10 kJ/mol. The kinetic modeling of hydration was conducted using Peleg's model, with a good fit. The data indicated that with increment in hydration temperature, the rate of hydration was enhanced in all varieties with a decrease in the Peleg's rate constant (K₁ ) and capacity constant (K₂ ). These constants indicate a direct temperature-dependence of water absorption in paddy. PRACTICAL APPLICATION: The hydration of paddy is an important procedure in paddy processing, and across the world, many industries are working on it. Irrespective of the variety, paddy processing globally has remained tricky. Knowledge about the hydration behavior of paddy would enable food processors to better understand the effect of process parameters and to model their experimental setup to obtain the desired physicochemical attributes, as well as process yield. Customers would benefit from adequately processed paddy with better digestibility for which industry would have to invest less in terms of time and resources, thereby making the hydrated paddy more affordable.

Modelling the physical properties change of canned glutinous rice porridge during cooking

In this study, we modeled the water absorption, softening and shear viscosity change kinetics of canned rice porridge during cooking as well as estimated the thermodynamic properties involved in hydration. Moreover, the internal microstructure of rice kernels was observed under different hydrothermal conditions. During cooking, the water absorption and shear viscosity alteration rate increased with temperature, whereas the softening rate decreased. However, the temperature did not significantly affect the equilibrium value of the physical properties. The variation tendencies of the moisture content and hardness of the kernels could be expressed satisfactorily by the exponential and the generalized exponential models. The porridge shear viscosity variations fitted the sigmoidal and its generalized models. Thermodynamic parameters (enthalpy, entropy and Gibbs free energy) revealed that the hydration process was non-spontaneous and exothermic. Furthermore, scanning electron microscopy images and the results of the X-ray diffraction analysis showed the microstructure of the kernels during cooking, and the kernels formed a homogeneous mesh structure at earlier times during the initial stage at higher temperatures. These findings would provide valuable information for the optimization of canned rice porridge production.