Avaliação de métodos para determinação de umidade em grãos: arroz (Oryza sativa L.), feijão (Faseolus vulgaris) e milho (Zea mays)

Abstract

The analysis of the moisture of grains is a determining factor in the control of deterioration, so the need to analysis of moisture influences the process from harvesting, storage and processing. The aim of this study was to compare the efficiency between rapid methods and the standard method (oven) to determine the moisture of grains (rice, common bean and maize). Samples of grains of rice, beans and maize were adjusted to different moisture levels (11, 14, 17, 20, and 23%) as those widely observed in the processing of grains. The samples were subjected to four different methods to determine of moisture: (I) official method in oven; (II) Microwave oven, applying the power of 400 W for different times (10, 12, and 14 minutes); (III) Grain moisture meter for the principle of transmittance and (IV) Grain moisture meter for the principle of capacitance. The results indicates that for the rice the moisture content determined by transmittance, showed no significant difference with those observed in the official method, while those obtained by capacitance varied significantly, indicating the need for calibration. The variation of time of microwave was influenced by moisture, where grains with 11% of moisture needs 10 min for time of exposition and the range of 14 to 23% moisture needs 12 min, to obtain results similar to those in oven. For beans and maize no significant variation (p <0.05) were observed between results obtained by rapid methods and the oven. The use of rapid methods such as microwave, transmittance or capacitance proved to be efficient and reliable, besides being obtained in less time, facilitating routine and logistics of food processing industries.