Effect of two different rice dehusking procedures on total arsenic concentration in rice

Pollution of subterranean water by arsenic (As) in Asia has resulted in the worst chemical disaster in human history. For populations living on subsistence rice diets, As contamination of rice grain contributes greatly to dietary As exposure. The main objectives of this study were to compare two dehusking processes: (a) wet process (soaking of rice, boiling and mechanical hulling) and (b) dry process (mechanical hulling), and recommend the method leading to a lower As content in commercial rice. In general, hulling of paddy rice (373 μg As kg⁻¹) significantly decreased As content in rice grain (311 μg As kg⁻¹). The final As concentrations in boiled rice (final product of the wet process) and atab rice (dry process) were 332 and 290 μg kg⁻¹. Thus, the dry method is recommended for dehusking paddy rice if not As-free water is available. However, villagers can reduce the As content in the wet system by discarding the soaking water and using new water for the light boiling. Finally, it is not recommended to use rice husk for feeding animals because the As concentration is very high, approximately 1,000 μg As kg⁻¹.     

Optimization of process parameters and mathematical modelling for dehulling of pigeonpea

In this study, hulling efficiency and hulling losses were optimised for pigeonpea. Effects of hulling time, moisture content and cottonseed oil as pre-milling agent were studied and optimised using response surface methodology. A quadratic model satisfactorily described the hulling efficiency with an R ² value of 0.93. It predicted maximum dehulling efficiency of 89.98% at 9.82% moisture content (wet basis), 12.05-s time of hulling and 0.28% cottonseed oil treatment. Linear model developed for hulling loss showed significant effect of time of hulling whereas effect of oil treatment and moisture content were non-significant. The model predicted hulling loss of 2.92% on optimum conditions. The results of the model were validated experimentally and were within the range.