咖啡豆红外喷动床干燥对其粉末物性品质、干燥能耗及挥发性成分的影响

Effects of infrared-assisted spouted bed drying on physical properties,drying energy consumption,and volatile components of coffee beans powder

为获得高品质干燥咖啡豆,采用红外喷动床组合干燥技术对咖啡豆进行干燥处理,研究不同进口温度和进口风速对咖啡粉色泽、堆积密度、休止角、得粉率、持水能力和水溶性指数、微观结构、干燥能耗及挥发性成分的影响。结果表明,提高进口温度和进口风速可以加快干燥速率,缩短干燥时间,降低干燥能耗。采用顶空固相微萃取-气相色谱质谱联用共检测出7大类(酸类、酯类、醛类、醇类、酮类、杂环类及其他类)挥发性化合物,其中酸类、酯类、醇类、杂环类4类为咖啡豆主要挥发性化合物且含量较高。综合对比得出最佳干燥条件为进口温度75℃,进口风速7.5 m/s,在此条件下,L*值和堆积密度取得最大值,分别为106.59和0.65 g/mL,休止角取得最小值36.87°,得粉率、持水能力和水溶性指数取得最大值,分别为43.43%、5.4 g/g和41.27%,干燥能耗取得最小值336.53 kJ/g,形态结构保存较为完整,壁面光滑平整,检测到的挥发性成分种类最高达70种,含量为38 487.028 49 ng/g(以干基计),咖啡豆综合品质最佳。该研究可为红外喷动床干燥技术在咖啡豆干燥加工及工业化生产中的应用提供参考。

To obtain high-quality dried coffee beans,the combined drying technology of an infrared-assisted spouted bed was used to dry coffee beans,and the effects of different inlet temperatures and inlet air speeds on coffee powder color,bulk density,rest angle,powder yield,water holding capacity and water solubility index,microstructure,drying energy consumption,and volatile components were investigated.Results showed that increasing the inlet temperatures and inlet air speeds could accelerate the drying rate,shorten the drying time,and reduce the drying energy consumption.Seven categories of volatile compounds(acids,esters,aldehydes,alcohols,ketones,heterocycles,and others)were detected by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry(HSSPME/GC-MS),among them,acids,esters,alcohols,and heterocycles were the main volatile compounds of coffee beans with high content.By comprehensive comparison,the optimum drying conditions were that the inlet temperature was 75℃and the inlet air speed was 7.5 m/s.Under these conditions,the maximum values of L∗and bulk density were 106.59 and 0.65 g/mL,respectively,the minimum value of rest angle was 36.87°,the maximum values of powder yield,water holding capacity and water solubility index were 43.43%,5.4 g/g,and 41.27%,respectively,the minimum value of drying energy consumption was 336.53 kJ/g,the cell structure was preserved,the wall surface was smooth and flat,the highest number of volatile components detected was 70,and the content was 38487.02849 ng/g DW.The comprehensive quality of coffee beans was the best.This study could provide a reference for the application of infrared-assisted spouted bed drying technology in the drying and processing of coffee beans and industrial production.