Environmental Conditions and Grain Cooling Affecting Milling Quality of Brown Rice

摘要

A humidifying and cooling chamber was developed to mill long-grain Pusa Basmati rice to minimize broken content. The effect of grain and milling chamber temperature on the polishing of Pusa Basmati variety, at constant high humidity condition was investigated. Brown rice of different initial temperatures (5, 10, 15, 20 and 25℃) was milled for different milling durations (60, 90,120,150 and 180 s) at 11, 18 and 25℃ milling chamber temperatures and 95 + 2% RH conditions. The optimized values of the parameters were done using Solver, Microsoft EXCEL 2000. It was used to minimize the specific energy consumption and broken percentage, while keeping the optimum degree of milling to a minimum value of 10%. The responses obtained from the experiments were analyzed using a second order polynomial (SOP) model. The overall quality such as cooking and textural attributes, broken content, specific energy consumption and degree of milling were used to assess the product quality. The optimum conditions which were attained for a minimum of 10% degree of polish, specific energy consumption (8 kJ/degree of milling, %) were temperature of polishing chamber (18℃), initial temperature of grain (20℃). Two trials were taken at the optimized conditions of milling, i.e. 20℃ milling chamber temperature and at 15℃ of initial grain temperature for a milling duration of 170 s using the derived optimum milling conditions to check the validity of the second order polynomial (SOP) model. The cooking, textural and milling qualities were determined for the abovementioned samples. The experimental values were found to be close to the predicted values within acceptable.