CINÉTICA DE SECAGEM DOS GRÃOS E CARACTERIZAÇÃO FÍSICA E QUÍMICA DURANTE O ARMAZENAMENTO DE FARINHA DE SORGO GRANÍFERO

Abstract

This work aimed to study the kinetics of sorghum grains under different conditions of initial moisture contents 0.49; 0.40; 0.31; 0,23 (kg of dry matter kg-1 water) at temperatures of 40, 60, 80 and 100 ºC; determine the effective diffusion coefficient during drying; To evaluate centesimal composition, apparent specific mass, color, mineral content, total phenolic compounds, antioxidant capacity, microstructure analysis, absorption indices (water, milk and oil) and solubility indices (water and milk) of sorghum flour at different drying conditions 40, 60, 80, 100 ° C and during storage. The drying kinetics of sorghum grains in different moisture contents and temperature can be described by the Midilli model. The effective diffusivity of sorghum grains increases at the same drying initial grain moisture content increases. The activation energy was higher for grain sorghum grains with higher initial water content, being 27.32; 26.75; 22.55 and 20.94 kJ mol-1 for initial water contents of 0.49; 0.40; 0.31; and 0.23 kg water kg-1 dry matter, respectively. The drying of sorghum grains for flour production reduced the initial moisture content, protein, pH, water and milk solubility indices and antioxidant activity, except for the 100 ºC treatment. It caused the increase of the total phenolic values, acidity and water absorption index, promoted the reduction of the intensity of the red and yellow tones, increase of the tone and darkening of the samples. Drying did not alter the content of lipids, carbohydrates, absorption index in milk and oil, phosphorus, calcium, magnesium and iron contents. They presented significant levels of iron, zinc and copper. The storage was made for the dry flour at 60 ºC, because it kept the analyzed characteristics better. During storage sorghum flour promoted significant changes, although not significant, could be observed from the sixth month of storage on almost all evaluated characteristics, except for moisture content, soluble solids and protein.