Abstract：
The utilization of coffee leaves in kombucha production has intrigued researchers; however, the lack of understanding regarding the characteristics of coffee leaf kombucha (CK) and its differentiation from black tea kombucha (BK) has impeded its application in the beverage industry. Therefore, this study aimed to characterize and compare the physiochemical properties, phytochemical compositions, antioxidant activity, and α-glucosidase inhibitory ability of kombucha prepared from the leaves of Coffea arabica (CK) and black tea (Camellia sinensis, BK) and their extracts (CT and BT). After fermentation, pH and the contents of total sugars, reducing sugars, and free amino acids of BK and CK were decreased, whereas the levels of total acids and organic acids, such as gluconic, lactic, and acetic acid were increased. Notably, the concentration of vitamin C in CK was 48.9% higher than that in BK. HPLC analysis exhibited that 5-caffeoylquinic acid in CT was significantly decreased by 48.0% in CK, whereas the levels of 3-caffeoylquinic acid and 4-caffeoylquinic acid were significantly increased after fermentation. The content of caffeine was significantly (p < 0.05) reduced by 9.5% and 22.0% in BK and CK, respectively, whereas the theobromine level was significantly increased in CK. Notably, CK has superior total phenolic and flavonoid contents and antioxidant activity than BK, whereas BK possesses higher α-glucosidase inhibitory capacity. Electronic nose analysis demonstrated that sulfur-containing organics were the main volatiles in both kombuchas, and fermentation significantly increased their levels. Our study indicates that coffee leaves are a promising resource for preparing kombucha. PRACTICAL APPLICATION: This article investigates the differences in physicochemical properties, bioactive constituents, antioxidant activity, and α-glucosidase inhibitory activity of kombucha preparation from black tea and coffee leaves. We have found that after fermentation BK had brighter soup color and higher α-glucosidase inhibitory capacity, whereas CK had higher levels of total phenols, flavonoids, vitamin C, and antioxidants and lower contents of sugars. This study provides valuable information for the preparation of CK with high-quality attributes and antioxidant activity.
摘要：
在红茶菌生产中利用咖啡叶引起了研究人员的兴趣；然而，对咖啡叶红茶菌（CK）的特性及其与红茶菌（BK）的区别缺乏了解，阻碍了其在饮料行业的应用。因此,这项研究旨在表征和比较理化性质，植物化学成分，抗氧化活性，和从阿拉伯咖啡（CK）和红茶（山茶，BK）及其提取物（CT和BT）。发酵后,pH值和总糖含量，减少糖，BK和CK的游离氨基酸减少，而总酸和有机酸的水平，如葡萄糖酸，乳酸，和乙酸增加。值得注意的是,CK中维生素C的浓度比BK高48.9%。HPLC分析表明,5-咖啡酰基奎尼酸在CT中显著降低,CK中降低了48.0%,而发酵后3-咖啡酰基奎尼酸和4-咖啡酰基奎尼酸的水平显着增加。BK和CK中咖啡因的含量显着降低了9.5％和22.0％（p<0.05），分别,而CK的可可碱水平显著升高。值得注意的是,CK具有优于BK的总酚和黄酮含量和抗氧化活性，而BK具有较高的α-葡萄糖苷酶抑制能力。电子鼻分析表明，含硫有机物是两种kombuchas中的主要挥发物，发酵显著提高了它们的水平。我们的研究表明，咖啡叶是制备红茶菌的有前途的资源。实际应用：本文研究了物理化学性质的差异，生物活性成分，抗氧化活性，红茶菌和咖啡叶红茶菌的α-葡萄糖苷酶抑制活性。我们发现发酵后的BK具有更亮的汤色和更高的α-葡萄糖苷酶抑制能力,而CK的总酚含量较高，黄酮类化合物，维生素C,抗氧化剂和较低的糖含量。本研究为制备具有优质属性和抗氧化活性的CK提供了有价值的信息。
