Evaluation of water diffusivity in wheat hydration (Triticum spp): Isothermal and periodic operation

Abstract

In this study, kinetic and diffusivity of water in the isothermal and periodic hydration of the BRS220 wheat cultivar, were investigated. The isothermal hydration tests were carried out for 600 min at 30, 40, 50, and 60 °C. The periodic operation experiments were performed considering the temperature of 40 °C. The periodic hydration of 20 °C amplitude, which was performed in 40‐min periods, was more efficient in comparison with the isothermal at 40 °C, since the former presented 84% moisture absorption in Phase I of the hydration, and increased the diffusion coefficient (D) in 26.7%. The diffusion model and the generalized equation presented good fit to the experimental data, with p values from 1.28 to 3.04% and RMSE from 5.28 × 10−2 to 12.5 × 10−2%. The hydration tests with colorants indicated that the water enters the wheat grain through the micropyle and then through the grain pericarp, by capillarity. Practical applications This research presents kinetics and water diffusivity in isothermal and periodic hydration of wheat. Periodic hydration is efficient compared to isothermal hydration due to the increased water absorption rate in the grain. This influences directly the reduction of time and energy savings of the industrial process. The results presented can be used by industries interested in increasing the efficiency of grain processing with lower energy expenditure. In addition, this work reveals the water uptake behavior inside the wheat grain, which until now has not been in depth presented in previous literature.

Modeling of maceration step of the oat (Avena sativa) malting process

“…The activation energy (E a ) represents the energy required to occur the diffusive mass transfer process during the hydration process. The E a (10-35 C; Table 3) for oat hydration was 17.88 kJÁmol −1 , lower than that found for wheat (Mattioda et al, 2018) and rice (Balbinoti, Jorge, & Jorge, 2018a). However, it was an expected result since some cereals may present different sizes and composition.…”

“…The diffusive coefficient of the hydration process for rice was 5.6 × 10 −9 (m 2 ·s −1 ) at 25°C (Kashaninejad, Maghsoudlou, Rafiee, & Khomeiri, ), which was higher than that found in this study. In the study of Mattioda et al (), the diffusive coefficient for wheat grain hydration at temperatures of 30 and 40°C were lower than those found for maceration of oats. The differences between the comparative studies can be justified by the structure and size of each grain, with oats being slightly larger than the wheat cultivar.…”

“…Based on previous studies, which used diffusion model for hydration process of the rice (Bello, Tolaba, & Suarez, ) and for wheat grain soaking process (Mattioda et al, ), the analytical solution for Equation (8) can be represented by Equation (9) according to the following considerations: Theoretical geometry is a sphere; Volume variation and grain size during the process are negligible; Known moisture balance on the grain surface; Diffusion coefficient ( D ef ) independent of concentration …”

“…Based on previous studies, which used diffusion model for hydration process of the rice (Bello, Tolaba, & Suarez, 2004) and for wheat grain soaking process (Mattioda et al, 2018), the analytical solution for Equation (8) can be represented by Equation (9) according to the following considerations:…”

“…In addition, with the kinetic parameters, it is possible to know the energy involved in the hydration process through the thermodynamic properties obtained. Some interesting studies report the hydration process through the thermodynamic properties obtained, including wheat, soybeans, and rice (Balbinoti, Jorge, & Jorge, 2018b;Borges, Jorge, & Jorge, 2017;Mattioda, Jorge, & Jorge, 2018).…”