Modeling heat and mass transfer–induced stresses in germinated brown rice kernels during fluidized bed drying

Abstract

A study of stress distribution inside a germinated brown rice (GBR) kernel during drying is important to understand the fissure formation of GBR and hence control the drying process in order to improve the quality of GBR. In this study, a finite element method performed in three dimensions in conjunction with the heat and mass balance of the drying system was developed to describe moisture, temperature and stress distributions inside GBR kernels during fluidized bed drying. The modelling was carried out using the couple of heat and mass transfer and validated with the experimental data at 90-150C.The results of moisture and temperature predictions agreed well with the experiments.During drying, tensile stress occurred at the layers close to surface while compressive stress occurred at the inner portion of a kernel. The tensile and compressive stresses increased to the highest value at about 30 s of drying, corresponding to the highest moisture gradient, and then decreased afterwards. The tensile and compressive stresses were higher at a higher drying temperature. These stress prediction results corresponded Downloaded by [New York University] at 01:36 31 July 2015 2 to the experiments which show more severity of GBR fissuring at higher drying temperatures.

Top‐spray fluidization coating of paddy rice with zinc oxide nanoparticles to reduce infection fromAspergillussp

“…When there is a crack in the rice kernel, it cannot withstand the shear force of the husker and the percentage of husking will decrease accordingly. The thermal gradient will only affect cracks when the difference between the temperature at the surface and that inside the rice kernel is more than 34.4°C (Srisang et al., 2016).…”

“…If the stress is greater than the failure strength of the material, cracks will occur. A crack on the grain's surface is caused by a tensile stress and that inside the grain is caused by a comprehensive stress.Stresses are caused by two factors: moisture gradient and thermal gradient(Jia, Yang, Siebenmorgen, Bautista, & Cnossen, 2002;Rattanamechaiskul & Junka, 2020) Srisang, Soponronnarit, Thuwapanichayanan, and Prachayawarakorn (2016). studied the cracks of germinated brown rice that occurred during the fluidization technique drying procedure and found that the cracks caused by moisture gradient would occur at the thickest part of the grain because this was where the moisture could diffuse from inside the grain over the shortest distance Palamanit et al (2013).…”

Effect of Drying Method and Hydrothermal Treatment on Physicomechanical Properties of Parboiled Rice

“…When the rice is placed under high temperature, cracking occurs inside of the kernel and extends vertically along the axis of the rice grain. It also seems that the rapid transfer of moisture from the core of kernels and the effect of temperature on the grain, will cause a high stress and breakage in the grain (Odek et al, 2017;Srisang et al, 2016). In fact, cracking in the grains occurs by creation of stress.…”

Experimental study on drying characteristics of rice by low‐field nuclear magnetic resonance

“…When the drying rate falls, water evaporates from inside the rice, with the diffusion of water determining the drying behavior of rice (Bourassa, Ramachandran, Paliwal, & Cenkowski, 2015). Therefore, the drying process plays an important part in the process of rice treatment (Srisang, Soponronnarit, Thuwapanichayanan, & Prachayawarakorn, 2015).…”

“…LF-NMR is referred to as a sort of non-destructive, non-invasive measurement technique capable to reveal the pattern of moisture in a specific sample at the microscopic level (Ishida, Kano, Kobayashi, & Yoshida, 2014). Existing studies have demonstrated that not only can LF-NMR be applied to analyze the changes in the distribution and state of water during heat treatment, it also plays an essential role in the freezing and fermentation of grains, fruits, seafood and meat (Celma, L opez-Rodríguez, & Bl azquez, 2009;Shao & Li, 2011;Tan, Lin, Zu, Zhu, & Cheng, 2018;Zhang et al, 2017). Additionally, LF-NMR can be relied on to detect maturity, internal bruising, infection or cold damage suffered by horticultural products (Butz, Hofmann, & Tauscher, 2006).…”