Determinação da qualidade imediata e latente de café secado com baixas umidades relativas do ar

Abstract

The objective of this work was to study the immediate and latent effects on the quality of dried coffee fruits in low relative humidity and to evaluate the drying kinetics and sorption isotherms of the coffee fruits. Coffee fruits (Coffea arabica L.) were harvested and separated into two stages of maturation: immature and mature. For the mature stage, the sample was divided into three parts: the first one was taken directly from the dryers, thus constituting the "natural" portion of coffee (dry processing), the second was peeled and the third benefited, drying only the grain. The immature coffee was taken from the dryers. Drying was performed in a fixed layer dryer (SCAL) with a composite air-conditioning coupled system, with airflow of 20 m3.min1.m-2, air temperature of 40 °C and relative humidity of 10%; 17.5%; 25% and 32.5%. The drying curve, the physical and physiological properties and hygroscopicity of the coffee were determined. The samples were stored in permeable packs for six months, conducting analyzes of electrical conductivity, potassium leaching and color every two months. The experiment was set up in a 4x4x4 factorial scheme (4 relative humidity of drying air, 4 types of mature [1-natural, 2-natural green, 3-peeled and 4-wetted coffee] and 4 storage times) in DIC with 4 replicates. For the adjustment of the mathematical models, non-linear regression analyzes were performed by the Gauss-Newton method, using the software STATISTICA 7.0® (Statsoft, Tulsa, USA). For the other results the statistical program Sisvar 5.6 was used for the analysis of variance. There was no immediate damage in the physical and physiological quality of the natural mature, natural green, peeled and wetted coffee. The latent damage was perceived after 60 days of storage for the natural ripe and peeled coffees and after 120 days for the natural coffees green and benefited wet. The Midilli model was the one that had the best fit to represent the drying kinetics for the natural green coffee, for all UR. For the equilibrium water content, the best adjustments to the experimental data were obtained by the Copace model for the natural green coffee.