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KINETICS OF HYDRATION AND DIMENSIONAL CHANGES OF BROWN RICE
Author(s) -
CHEEVITSOPON EKKAPONG,
NOOMHORM ATHAPOL
Publication year - 2011
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/j.1745-4549.2011.00537.x
Subject(s) - brown rice , thermal diffusivity , activation energy , diffusion , arrhenius equation , absorption of water , chemistry , kinetics , absorption (acoustics) , moisture , water content , thermodynamics , materials science , analytical chemistry (journal) , composite material , food science , chromatography , physics , geology , quantum mechanics , geotechnical engineering
Hydration kinetics and dimensional changes of brown rice kernels during soaking at below gelatinization temperature, 30 to 60C, were studied. Image analysis was implemented to determine changes in length, width, perimeter and projected area of kernels as a function of time. Water absorption was described by the Fick's second law of diffusion. The effective diffusivity varied from 5.30 × 10 −11 to 1.56 × 10 −10 m 2 /s. The temperature dependence of the effective diffusivity was described by an Arrhenius‐type relationship and the activation energy for moisture diffusion was 30.46 kJ/mol. The dimensional changes were first‐order kinetic and the activation energy values for changes in kernel length, width, perimeter and projected area were 25.27, 23.01, 26.39 and 31.05 kJ/mol, respectively. Five semi‐theoretical models including the Lewis, Page, Modified Page, Henderson and Pabis, and Two term models were proposed to describe the soaking behavior of brown rice kernels. It was noted that the Page model presented the best fit and represented an excellent tool for estimating moisture content and dimensions of brown rice kernels at any soaking time. PRACTICAL APPLICATIONS Soaking is one of the hydrothermal processes and it is an essential step of the brown rice process. The present study was undertaken to investigate the hydration characteristics and dimensional changes of brown rice kernels during soaking. The results of processing variables are needed for practical applications to optimize and characterize the soaking condition, design grain processing equipment, and predict water absorption as a function of time and temperature. Thus, a suitable mathematical model was applied to predict accurately the water absorption and dimensional changes of brown rice kernels during soaking.