Secagem natural de milho e os efeitos sobre propriedades físicas de grãos

Abstract

Maize harvest in the northern Mato Grosso (Brazil) matches with beginning of dry season, in order to the most producers opt for the natural drying (in the field), as the conditions being favorable. However, being dependent of the weather conditions, there is not process control and neither the effects caused on the grain properties. Therefore, this work was realized with the purpose of determining the effects on the physical properties of natural drying of maize grain (mass, volume, geometric mean diameter, circularity, sphericity and surface area), and obtain the drying curve of two cultivars: TF2550 and SW5560. The sample were collected between May and July, to achieve a water content of 0.17 (decimal dry basis). It was observed grain maturation process to start collecting samples, it has started from 0.38 decimal d.b. Five cobs were collected periodically from each 3 subsections demarcated in each plant variety’s area. After collecting, we threshed grains manually, and submitted to physic analyses of size and shape, and humidity levels. To determine variation in size and shape’ characteristics, we obtained three grain’s characteristics dimensions and mass. Therefore, we took 20 random grains by each section. After, we determined water content using oven standard method (105 °C for 24 hours), to establish maize natural drying curves and equations adjustment. Thus, we concluded to reduce humidity from 0.38 to 0.18 decimal d.b. was necessary 25 and 20 days to plant’s variety TF2550 and SW5560, respectively. Third order’ polynomial equation adjusted satisfactorily to data analyzed. Grain mass reduction was 23% to TF2550 and 17% to SW5560. Shape characteristics reduced during the process making grain more irregular. Grain volume variated more significantly to SW5560 than to TF2550.