Hygroscopic equilibrium and physical properties evaluation affected by parchment presence of coffee grain

Abstract

Physical properties are essential for the development of silos, transport calculations, separation and classification of grain and seeds. The present work evaluates the influence of the parchment on the drying and physical properties of coffee grains. The true density (ρ t ), bulk density (ρ b ) and porosity (ε) were evaluated for coffee grains (cv. Catuaí Amarelo) with and without parchment. Four mathematical models (Chung-Pfost, GAB, Modified Henderson and Oswin) were fitted to the experimental data to acquire desorption isotherms. The drying treatment was conducted in a factorial scheme with four levels of temperature (20, 35, 45 and 55°C) and five levels of relative humidity of the drying air (30, 40, 50, 60 and 80%) in a completely randomized design. The respective equilibrium moisture contents of the coffee grains were measured for each drying condition. No differences were observed among the products on the desorption isotherms. The pulped coffee with parchment (PP) had higher ε values than the pulped coffee without parchment (PR). The true density was higher for the PP coffee, but as the moisture content (X) increased, the true densities became more similar for the two samples. The ρ b was higher for the PP coffee than for the PR coffee. Higher initial and final values of ρ b were found for the PR and PP coffee, respectively. The Guggenheim-Anderson-de Bôer model was the model that best represented the experimental data for the drying process.Additional key words: density, drying, porosity, sorption isotherms. ResumenEvaluación del equilibrio higroscópico y de las propiedades físicas afectadas por la presencia de pergamino en los granos de café Las propiedades físicas son esenciales para el desarrollo de los silos y cálculos de transporte, separación y clasificación de granos y semillas. El presente trabajo evaluó la influencia del pergamino en el secado y en las propiedades físicas de los granos de café. Se evaluaron la densidad real (ρ t ), la densidad aparente (ρ b ) y la porosidad (ε) para los granos de café (cv. Catuaí Amarelo) con y sin pergamino. Se ajustaron cuatro modelos matemáticos (Chung-Pfost, GAB, Henderson Modificado y Oswin) a los datos experimentales para obtener isotermas de desorción. El tratamiento de secado se realizó en un esquema factorial con cuatro niveles de temperatura (20, 35, 45 y 55°C) y cinco niveles de humedad relativa del aire de secado (30, 40, 50, 60 y 80%) en un diseño completamente al azar. Se midió el contenido de humedad de equilibrio de los granos de café para cada condición de secado. No se observaron diferencias entre los productos en las isotermas de desorción. El café despulpado con pergamino (PP) presentó mayores valores de ε que el café despulpado sin pergamino (PR). La densidad real fue mayor para el café PP, pero según se incrementó el contenido de humedad (X), la densidad real se hizo más similar para ambas muestras. El ρ b fue mayor para el café PP que para el café PR. Los valores más altos iniciales y finales de ρ b se observaron en el café PR ...

Determination and modeling of physical and aerodynamic properties of coffee beans ( Coffea arabica ) during the drying process

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Drying kinetics and thermodynamic properties of Uzun pistachios dried by convective drying

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