超声波辅助冷萃制备咖啡液工艺优化及其理化特性分析

咖啡作为世界三大饮料之一,中国咖啡主要分布在海南和云南地区。本研究以海南兴隆咖啡豆为原料,探究超声波辅助冷萃技术（以下简称超声冷萃）制备咖啡液的最优条件,并测定咖啡因、葫芦巴碱、绿原酸含量以及咖啡渣的微观结构。以超声时间、超声温度和超声功率为单因素,咖啡液总可溶性固形物提取率为评价指标,在单因素试验的基础上,利用Box-Behnken原理设计3因素3水平响应面试验,对超声冷萃提取条件进行优化得到最佳提取工艺,并以传统冷浸法为对照,采用超高效液相色谱法测定咖啡液葫芦巴碱、咖啡因、绿原酸的含量,扫描电子显微镜测定咖啡渣微观结构。结果表明,适当增加超声功率、超声时间和超声温度,咖啡液总可溶性固形物随之增加,影响咖啡液总可溶性固形物的提取率的主次因素为超声功率>超声时间>超声温度,超声冷萃制备咖啡液的最佳工艺参数为：超声功率500 W、超声时间35 min、超声温度20℃,在优化条件下,总可溶性固形物提取率为22.92%±0.16%,与响应面优化试验回归模型预测值（22.85%±0.12%）基本吻合。与传统冷浸法相比,超声冷萃制备所得咖啡液葫芦巴碱、咖啡因和绿原酸（3-CQA、4-CQA、5-CQA）含量分别为175.19 mg/L、317.71 mg/L和257.77 mg/L,均有所提高,咖啡渣表面微观结构更为破碎,说明超声冷萃破坏了植物细胞壁,从而释放出更多的可溶性物质,且超声冷萃显著缩短萃取时间。本研究优化制备咖啡液的超声冷萃提取工艺,结果表明超声波冷萃是一种有效的咖啡液提取技术,为咖啡精深加工及高值化产品研发提供理论依据和技术支撑。

Optimization of Ultrasonic-assisted Cold Extraction Process for Coffee Liquor Preparation and Its Physicochemical Characteristics

Coffee is one of the three major beverages in the world, and it is mainly distributed in Hainan and Yunnan in China. In this paper, we investigated the optimal conditions for the preparation of coffee liquor by the ultrasonic-assisted cold extraction technology using Hainan Xinglong coffee beans as the raw materials, and determined the contents of caffeine, trigonelline, chlorogenic acid and the microstructure of coffee grounds. The extraction time, ultrasonic temperature and ultrasonic power were used as the single factors, and the extraction rate of total soluble solids from coffee liquor was used as the evaluation index. Based on the single-factor test, a 3-factor, 3-level response surface test was designed using the Box-Behnken principle to optimize the extraction conditions for ultrasound-assisted cold extraction to obtain the best extraction process, and the content of trigonelline, caffeine and chlorogenic acid in coffee liquor was determined by the ultra performance liquid chromatography and the microstructure of coffee grounds was determined by a scanning electron microscopy using the traditional cold extraction method as the control. The total soluble solids of coffee liquor increased with the appropriate increase of ultrasonic power, ultrasonic time, and ultrasonic temperature, and the main factors affecting the extraction rate of total soluble solids of coffee liquor were ultrasonic power > ultrasonic time > ultrasonic temperature, and the optimal process parameters for the preparation of coffee liquor by ultrasound-assisted cold extraction were: ultrasonic power 500 W, ultrasonic time 35 min, and ultrasonic temperature 20℃, and under the optimized conditions, the total soluble solids extraction rate was 22.92%±0.16%, which was basically consistent with the predicted value of the response surface optimization test regression model (22.85%±0.12%). Compared with the traditional cold infusion method, the content of trigonelline, caffeine, and chlorogenic acids in the coffee liquor prepared by ultrasound-assisted cold extraction was 175.19 mg/L, 317.71 mg/L and 257.77 mg/L, respectively, all were increased, and the microstructure on the surface of coffee grounds was more fragmented, indicating that ultrasound-assisted cold extraction broke the plant cell walls, thus releasing more soluble substances, and ultrasound-assisted cold extraction time was significantly shortened. This study optimized the extraction process of ultrasound-assisted cold extraction for the preparation of coffee liquor, and the results showed that ultrasound-assisted cold extraction is an effective extraction technique, which would provide a reference for the application of ultrasound-assisted technology in coffee processing industry.