Abstract
ABSTRACT This work aimed to study the immediate and latent effects of different relative humidities on the quality of dried coffee fruits, describe the drying kinetics of natural immature coffee (Coffea arabica L.), and evaluate the mathematical model that best fits the experimental drying data. The drying was carried out in a fixed layer dryer coupled to a composite air conditioning system in which the drying air was controlled with an air flow of 20 m3.min1.m−2, at a temperature of 40 °C, and at relative humidities of 10%, 17.5% and 32.5%. Manually harvested coffee fruits were used and dried to a mean water content of 0.120 dry basis (d.b). After drying, the kinetic curve and the physical and physiological properties were determined. The coffee was stored in permeable packs for 6 months. The electrical conductivity, potassium leaching, and colour analysis were performed every 2 months. For the modelling adjustment, the models were tested, and the Midilli model had the best fit with the drying kinetics of the immature coffee. No immediate damage was observed in the physical and physiological quality of the coffees, and latent damage was perceived after 120 days of storage for the natural immature coffees.
Highlights
IntroductionStrip harvesting is the predominant coffee harvesting method in Brazil, and it yields a very heterogeneous product consisting of ripe (cherry), unripe (green) and overripe (raisins and dried-on-trees) berries; foreign materials; and impurities (Borém, 2014)
Strip harvesting is the predominant coffee harvesting method in Brazil, and it yields a very heterogeneous product consisting of ripe, unripe and overripe berries; foreign materials; and impurities (Borém, 2014)
During the wet processing stage, ripe berries are separated from unripe berries by peeling, with the ripe berries being peeled, and the whole unripe berries being directed down a different path, generating two different coffee portions (Borém, 2008)
Summary
Strip harvesting is the predominant coffee harvesting method in Brazil, and it yields a very heterogeneous product consisting of ripe (cherry), unripe (green) and overripe (raisins and dried-on-trees) berries; foreign materials; and impurities (Borém, 2014). Coffee has a high water content at the time of harvest compared to other grains (Botelho et al, 2016). Drying is a critically important post-harvest step and should be started soon after harvesting to quickly reduce the high water content of the berries and prevent fermentation, which may impair coffee quality (Resende et al, 2009). During the wet processing stage, ripe berries are separated from unripe berries by peeling, with the ripe berries being peeled, and the whole unripe berries being directed down a different path, generating two different coffee portions (Borém, 2008). According to Borém (2014), the coffee processing stage aims to separate the berries into more homogeneous lots.
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