Effect of temperature and pressure on moisture diffusion characteristics of paddy (Cv. MTU 1075)
2015
Bakhara, Chinmaya K. (Orissa University of Agriculture and Technology, Odisha (India). College of Agricultural Engineering and Technology, Department of Agricultural Processing and Food Engineering) | Dash, Sanjaya K. (Orissa University of Agriculture and Technology, Odisha (India). College of Agricultural Engineering and Technology, Department of Agricultural Processing and Food Engineering) | Pattnaik, Aditya (Orissa University of Agriculture and Technology, Odisha (India). College of Agricultural Engineering and Technology, Department of Agricultural Processing and Food Engineering) | Panda, Manoj K. (Orissa University of Agriculture and Technology, Odisha (India). College of Agricultural Engineering and Technology, Department of Agricultural Processing and Food Engineering)
Parboiling is an important and energy intensive unit operation in rice processing. Proper management of parboiling can reduce the energy requirement during parboiling and the associated cost. Soaking and steaming are the two major steps in parboiling. Soaking of paddy is usually carried out under atmospheric pressure, which takes more time. The temperature of soak water affects the rate of moisture adsorption and diffusion. The pressure during soaking and steaming also affects the process and consequently, affects the overall economics of parboiling. The hydration characteristic of paddy (Cv. MTU 1075) was studied at different conditions with the basic objective to standardize parameters for these unit operations. Soaking was carried out at four levels of soaking temperature under atmospheric pressure. Similarly hydrostatic soaking at pressure levels of 2.0, 4.0 and 6.0 kg∙cm-2 was studied at a constant soak water temperature of 70°C. Steaming was carried out at 0.5, 1.0, 1.5, 2.0 and 2.5 kg∙cm-2 pressure levels. The initial moisture content of paddy was varied at three levels. It was observed that the soaking temperature and pressure and steaming pressure affected the rate of moisture absorption by the grain and thus the time requirement. The diffusion coefficient was independent of initial moisture content and showed Arrhenius type relationship with temperature of soaking and steaming. The diffusion coefficient of paddy ranged between 8.939 x 10-5 to 2.678 x 10-4 cm²∙min-1 for steaming under pressure, 7.01 x 10-6 to 1.399 x 10-5 cm²∙min-1 for hydrostatic pressure soaking at 70°C and 1.898 x 10-6 to 1.11 x 10-5 cm²∙min-1 for soaking under atmospheric pressure at different temperature. The diffusion constant was calculated as 0.01345 m²∙min-1 and activation energy for moisture diffusion was 35.19 kJ∙g-mol-1.
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