Quality of natural and pulped coffee as a function of temperature changes during mechanical drying

Abstract

This research evaluated the sensory quality of processed and dried coffee beans in different ways. Two types of processing were used: dry and wet, besides seven drying methods: drying in yard and mechanical drying with heated air at 50 oC until coffee reached 30% (w.b.) moisture content, followed by drying with air heated to 35 oC until reaching 11% (w.b.) moisture content; drying in fixed-layer dryers with heated air at 45 °C until coffee reached 30% moisture content, followed by drying with heated air at 35 °C until reaching 11% (w.b.) moisture content; and drying in fixed-layer dryers with heated air at 40 °C until coffee reached 30% (w.b.) moisture content, followed by drying with heated air at 35 °C until reaching 11% (w.b.) moisture content; drying in fixed-layer dryers with heated air at 35 °C until coffee reached 30% (w.b.) moisture content, followed by drying with heated air at 50 °C until reaching 11% (w.b.) moisture content; drying in fixed-layer dryers with heated air at 35 °C until coffee reached 30% (w.b.) moisture content, followed by drying with heated air at 45 °C until reaching 11% (w.b.) moisture content; drying in fixed-layer dryers with heated air at 35 °C until coffee reached 30% (w.b.) moisture content, followed by drying with heated air at 40 °C until reaching 11% (w.b.) moisture content. The mechanical drying system consisted of three fixed-layer dryers, allowing the control of temperature and drying flow. Coffee was tasted according to the evaluation system proposed by the Specialty Coffee Association of America (SCAA). Physicochemical composition and physiological quality of the beans were analyzed, involving: grease acidity, potassium leaching, electrical conductivity, color and germination. The results show that pulped coffee is more tolerant to drying than natural coffee, regardless of how it was dried.Objetivou-se neste trabalho avaliar a qualidade de grãos de café processados de duas formas diferentes (via seca e via úmida) e sete métodos de secagem: secagem em terreiro; e secagem mecânica com ar aquecido em secadores: a 50 oC até o café atingir 30% de teor de água (TA), prosseguindo-se com ar aquecido a 35 oC até atingir 11% (b.u) de TA; a 45 oC até o café atingir 30% (b.u) de TA, prosseguindo-se com ar aquecido a 35 °C até atingir 11% (b.u) de TA; a 40 oC até o café atingir 30% (b.u) de TA, prosseguindo-se com ar aquecido a 35 oC até atingir 11% (b.u) de TA; a 35 oC até o café atingir 30% (b.u) de TA, prosseguindo-se com ar aquecido a 50 °C até atingir 11% (b.u) de TA; a 35 oC até o café atingir 30% (b.u) de TA, prosseguindo-se com ar aquecido a 45 °C até atingir 11% (b.u) de TA; a 35 oC até o café atingir 30% (b.u) TA, prosseguindo- se com ar aquecido a 40 °C até atingir 11% (b.u) de TA. A análise sensorial foi realizada utilizando-se a metodologia proposta pela Associação Americana de Cafés Especiais (SCAA). As demais análises realizadas foram composição físico-química e acidez graxa, lixiviação de potássio, condutividade elétrica, cor e germinação. Para a análise estatística utilizou-se o programa computacional Assistat 4.0. A secagem em terreiro proporcionou melhor qualidade fisiológica e sensorial dos grãos de café, quando comparada com a secagem em secadores, mas o uso das temperaturas 35/40 °C e 40/35 °C apresentou resultados semelhantes à secagem em terreiro. Além disso, o café despolpado apresentou melhor qualidade fisiológica que o café natural.