Efeitos da secagem intermitente e do beneficiamento na qualidade física, físico-química e morfológica do arroz polido

Abstract

The quality of paddy rice can determine the type of processing in the industry and the price of the product paid to the producer, while the drying stage is one of the most important and can influence the quality of the grains. Among the forms of drying, intermittent drying is the most used in rice because it reduces the tensions in the grain due to the processes of mass transfer (water) from the interior of the grain to the periphery and, consequently, can mitigate the abrupt effect of the drying temperature, during the period that the grain mass remains at rest in the flashing chamber. However, the increase in drying time can increase the temperature of the grain mass and collaborate negatively on the quality of the grains, when submitted to the intermittent process. Thus, this study aimed to evaluate the effects of drying-intermittance time and processing on the physical, physicochemical and morphological quality of polished rice. The experiment was carried out in a grain storage unit at farm level in the municipality of Cachoeira do Sul-RS. The batches of rice grains from mechanized harvesting, with grain moisture content between 24 and 20% (w.b.), were immediately submitted to pre-cleaning and drying operations. The samples collected were analyzed at the Postharvest Laboratory (LAPOS) of the Federal University of Santa Maria-Campus Cachoeira do Sul. The treatments analyzed were drying (mean temperature of the grain mass of 41 °C), the intermittence (mean temperature of the grain mass of 40 °C) and the drying time of 14 hours at an average temperature of the drying air of 107 °C. For each drying time, grain sampling was carried out in the drying chamber and at intermittence to evaluate the physical, physicochemical and morphological quality of the polished rice. Among the results obtained, it was observed that the cumulative effects of the 14-hour drying-intermittance time influenced the increase in the temperature of the mass of rice in husk to 49 °C. During the eight initial hours of drying, the maximum yield and quality of the grains was reached. In the physical evaluation, there was a reduction in the whole grain yield and in the physical classification. The percentages of protein and crude fiber, fat and ash were altered, while the morphology of the starch was affected, as well as the mineral composition in the polished rice. It was concluded that the intermittence stage prolonged the drying time of paddy rice, being the determining factor for the quality of the grains.