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

Abstract

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 (K 1) and capacity constant (K 2). These constants indicate a direct temperature-dependence of water absorption in paddy.

Effect of soaking temperature on the physical properties of Paddy (Variety: PS-5)

“…The highest value was found 6.306 (210 min) at ambient temperature on the other side the lowest value was 5.458 (180 min) at 60 0 C. The result demonstrate that the aspect ratio of paddy increases as the soaking temperature increased. Similar result reported by(15).…”

“…According to (14), ageing of rice influences the volume expansion of rice when it is cooked or soaked and also freshly harvested rice shows low volume expansion compared to aged rice. (15). The surface area of the TKW paddy grain was calculated by using the equation of surface area.…”

Microstructure of rice (Oryza sativa L.) and kinetics in hydrothermal process

“…Rice (Oryza sativa L.) is one of the main food crops produced globally (Aruva et al, 2020). It is consumed in various forms, including consumption of whole grains (brown, polished, or parboiled), as flour, or in fermented products (Oli et al, 2014).…”

“…Empirical models are useful due to their ability to solve equations quickly without the need to represent the fundamental laws of the phenomena involved, such as mass transfer (Balbinoti et al, 2018b). Among these, the Peleg model (Peleg, 1988) is one of the most frequently used in the literature for grain hydration, having shown a good fit to experimental data, as may be seen in the hydration studies involving wheat (Mattioda et al, 2018), oats (Anthero et al, 2019) and rice (Aruva et al, 2020).…”