咖啡豆的热风干燥特性及其干燥过程中风味成分变化规律研究

Research on Characteristics and Volatiles Changes During Hot-air Drying of Green Coffee Beans

以海南当地的咖啡鲜果为原料,测定其干基含水率和干燥速率,探索咖啡豆在不同干燥温度和载重量条件下热风干燥对干燥速率的影响,以及干燥过程中咖啡豆挥发性成分的变化规律,并建立咖啡豆热风干燥的动力学模型。结果表明:干燥速率随温度的升高而升高,初始阶段干燥速率较快;由于咖啡鲜果单层摆放,不同载重量对干燥速率影响不显著;挥发性物质的种类随水分含量的降低而增多,其中醛类化合物相对百分含量逐渐降低,而酯类、酸类、醇类化合物相对百分含量均逐渐增加,烃类化合物略有增加;采用3种模型进行非线性回归拟合以模拟咖啡豆的干燥过程,结果表明单项扩散模型(Henderson and Pabis)的拟合度最好。

In this study, hot-air drying was applied to the Hainan coffee beans to investigate the effect of drying temperatures and load capacity on the drying rate of samples with the initial moisture content of drying base as the evaluation index, explore the change regularity of volatile compounds during the process of drying, and establish the drying kinetics model of green coffee beans. It could be observed that the drying rate increased with the increase of drying temperature, the drying rate was fast in the initial stage of drying process, while the effect of loads was not significantly because of the single place. The number of volatile flavor compounds increased with the decreasing of the moisture content, the relative percentage of aldehydes gradually decreased, while the percentage of esters, acids and alcohols all increased by degrees, and hydrocarbons increased slightly. The experimental data of coffee beans was used to fit three available drying models by applying Matlab R2010a, results showed that the Henderson and Pabis model obtained satisfied performance and could model the drying process of green coffee beans.