Secagem de arroz (Oryza sativa L.) em escala piloto: avaliação de parâmetros do processo

Abstract

Rice (Oryza sativa L.) is a worldwide consumption cereal and, as a seasonal product, its conservation and storage are justified. Brazil is the biggest rice producer of South America, concentrating 64,4% of its production in the South area of the country. Rice is an agricultural product that has its marketing value depending on the quality of the grains verified after its processing. The percentage of the whole grains is the most important parameter for the rice industry. In this situation, the drying operation is essential, but, because of the very high temperature used, it can affect the quality of the produced grains. In the rice supply chain, the production cost is getting higher and higher and the final price is stable or getting lower. In this context, studies in different levels of the chain are necessary, in order to find alternatives to decrease the cost and, consequently, make the products more competitive without decreasing its quality. This paper has had the objective of evaluating the process of drying the rice during its processing in a local rice industry, in order to improve it. The drying process was done in a discontinuous drying tray in the temperatures of 50, 60 and 70°C, occurring in the first and second period of a decreasing rate with a moisture transition of 0,135, 0,140 and 0,123 kgwater/kgdry solid of the respective temperatures. The balance moisture obtained by the dynamic method were of 0,12, 0,11 and 0,09 kgwater/kgdry solid (dry base, b.s.), in the temperatures of 50, 60 and 70°C, respectively. The drying results were analyzed through the semi-empirical theorical models of Lewis, Henderson and Pabis, Page and Overhults, in which the last two models were the ones that obtained the best adjustments of the experimental data (R2>0,98). Therefore, in the rice drying process in a discontinuous drying machine, the temperature of 60°C is the most appropriate, for presenting the best results and lower grain breakage.