Location: Healthy Processed Foods ResearchTitle: Moisture diffusivity in rice components during absorption and desorption Author
|Pan, Zhongli - John|
Submitted to: Drying Technology: An International Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2011
Publication Date: 6/8/2011
Publication URL: http://dx.doi.org/10.1080/07373937.2011.561942
Citation: Prakash, B., Bingol, G., Pan, Z. 2011. Moisture diffusivity in rice components during absorption and desorption. Drying Technology: An International Journal. doi: 10.1080/Drying Technology, 29: 8, 939 — 945. Interpretive Summary: Moisture diffusivity is one of the very important parameters affecting rice milling quality. Fully understanding the moisture movement and determining the moisture diffusivity can provide guideline for post-harvest handling and drying to reduce the fissure caused by the moisture gradient in rice kernels. In this research, we have determined moisture diffusivity values of different rice components, endosperm, bran, and husks during different adsorption and desorption conditions and provided recommendations on improving rice milling quality.
Technical Abstract: Moisture diffusivity values of different rice kernel components namely, endosperm, bran and husks are required to solve mathematical models describing absorption and desorption processes. In addition to the rice variety and temperature, the moisture diffusivity also depends on its instantaneous moisture content or water activity (aw) and whether rice is absorbing or desorbing moisture. This research was undertaken to determine moisture diffusivity values of rough rice components in different aw ranges during absorption and desorption. Experiments were performed to measure sorption rates of different rice forms, including white rice, brown rice and rough rice kernels. Mathematical models were developed to predict their moisture distribution during moisture sorption processes. These models were solved by a finite element method using Comsol Multiphysics® simulation program. Moisture diffusivity values of different rice components were calculated and found to be different during absorption and desorption. Diffusivity of rice endosperm was higher during desorption than absorption at aw higher than 0.20 and increased with an increase in aw in 0.20 – 0.80 aw range. Diffusivity of bran remained almost the same with aw while diffusivity of husk decreased with an increase in aw. Results obtained in this research demonstrated that the moisture diffusivity of different rice components vary significantly with the change in water activity or moisture and should be accounted for in the mathematical models.