Efeitos do método de secagem sobre a qualidade e o desempenho industrial de grãos de arroz armazenados em ambiente controlado com temperatura reduzida

Abstract

We studied effects of the drying system and the storage time at low temperature, with evaluation of industrial performance and quality parameters conservability consumption in rice grains harvested with moisture content around 20% and dried up to 13% by three methods drying: (a) classic intermittent, (b) intermittently scaled and (c) by dry-airing. Going to make use of the pilot scale equipment in a laboratory scale, equipped with electric heaters to heat the air, was operated in order to obtain drying grain according to the method. In the classic intermittent air temperature had increased from 70+5ºC, 90+5ºC e 100+5ºC, respectively in the 1st, 2nd and 3rd hours until the penultimate, with a gradual reduction temperature in the last minute. In method intermittent scaled, with the same thermal management of method intermittent air classic, the operation took place in two stages: the first by 15-16% humidity, and the second supplementary drying, after 30 days of the first stage, the grain stored under cooling. In the third method, dry-airing, the first step was made in column dryer with air at 100°C in the two chambers and the grains were removed with 15-16% humidity and transferred to a silo dryer and rested for six hours before turning on the aeration with ambient air to supplement the drying. Once dried, the grains were stored at room temperature reduced to 17 ° C. In the first and twelfth months of storage were evaluated humidity, volume and weight of thousand grains, whole grain yield, incidence of defects, Texture profile, profile branquimétrico and cooking parameters in grains by conventional processes and parboiled. Was also studied consumer preference insect Sitophilus sp in paddy, full and white, putting - 12 - them in an arena and being evaluated after 60 days with counts of insects and consumption. It was concluded that: (1) drying methods intermittent fever, intermittent and staggered by drought-airing show similarities in the effects of physical parameters, performance industrial and cooking, both for industrialization by the conventional process like white rice by parboiling; (2) the parboiling and increased storage time cause increased incidence of grains with defects in the acidity of the oil and color in rice, irrespective of drying method used, (3) Texture parameters are affected by the ongoing storage and by the industrialization process, regardless of drying method, (4) storage in an environment with low temperatures preserves the quality of rice for at least a year, (5) the insect Sitophilus sp. has greater preference for their reproduction and consumption of grains of rice than the grain shell and polished grains, in that order.