Combined microwave-fluidized bed drying of parchment coffee

REYES CHAPARRO, JOSÉ; TRUJILLO, LIZETH; DURÁN BARÓN, RICARDO; ARBALLO, JAVIER RAMIRO; CAMPAÑONE, LAURA ANALÍA; MASCHERONI, RODOLFO HORACIO

Sitges

Conferencia; 31th EFFoST International Conference; 2017

Universitat Autònoma de Barcelona

In the last years, the technologies applied to the production of the coffee have had a great development in the world. Drying is the most important stage due to the economic impact on the finished product, so research has been carried out to make it more efficient and less polluting. In this study, we investigated the application of combined microwave-fluidized bed technologies for the drying of wet parchment coffee beans. The coffee beans were characterized as being Geldart D type particles and for the fluidization in the drying chamber we used a plate (34 cm x 35 cm) with a hole size of 4 mm with a distance of 7 mm between them. In turn, microwave heating was coupled using a magnetron (1000 W). The temperature, the color of the grain and the final moisture content between 10-12% (wb) were used to establish the end point of the process. The air speed in the fluidization and the power of the magnetron are determining factors for the drying of the wet parchment coffee. The lowest drying time was reached with the condition of: 2 m / s with 100% power. Also, as a quality parameter, the antioxidant capacity and determination of the total phenol content were investigated, showing that the drying affected the chemical composition of the coffee beans, increasing the content of phenols, but decreasing the antioxidant activity. In this sense, the best quality condition was: air velocity greater than 4 m / s with 100% microwave power in 72 minutes, with a reduction in moisture content of up to 11.3% wb. In addition, the effective diffusivity of the water was determined using the second Fick law and a variation between 9.19x10-12 and 1.33x10-11 m2 / s was observed for samples of wet parchment coffee.