Huang Yuanyuan, Sun Yu, Cao Qingwei, Chen Dongyan, He Ronghai, Chen Xiumin
School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu, P.R. China.
Institute of Food Physical Processing, Jiangsu University, Zhenjiang, Jiangsu, P.R. China.
J Food Sci. 2025 Jul;90(7):e70400. doi: 10.1111/1750-3841.70400.
Coffee leaves, known for their health-promoting phytochemicals, have emerged as a potential functional tea ingredient. However, the effect of infrared drying (IFD) on its properties and sensory quality remains unexplored, limiting its industrial utilization. This study systematically elucidated the impact of IFD on drying kinetics, chemical compositions, Maillard reaction products (MRPs), flavor formation, and sensory characteristics of coffee leaves. IFD significantly reduced drying time by more than 50% and decreased protein loss by more than 5.79% compared to hot-air drying, while increasing total phenolic content (27.86% increase at 1300 W) and antioxidant activity (more than 50% increase). However, IFD resulted in higher levels of 5-hydroxymethylfurfural and α-dicarbonyl intermediates (glyoxal and methylglyoxal) compared to freeze-drying. Volatile analysis using HS-SPME-GC-MS revealed distinct aroma profiles: freeze-dried leaves showed a grassy aroma primarily characterized by hexanal, whereas IFD generated a more fruity-floral aroma with elevated levels of (E)-2-hexen-1-ol, octanal, and thermally derived pyrazine/pyridine. Key flavor markers such as 2,3-pentanedione and 6-methyl-5-hepten-2-one were uniquely elevated in IFD blades. The sensory evaluation confirmed that IFD-processed tea leaves received a score of 71.18 ± 3.04 and were characterized by a black tea-like flavor with caramel and fermented undertones. These findings suggest IFD as a time- and energy-efficient method to produce coffee leaf tea with dual advantages: (1) enhanced retention of bioactive compounds and (2) targeted generation of consumer-desired sensory attributes through controlled MRPs. These findings establish a scientific basis for scaling up IFD processing, offering the tea industry a sustainable approach to valorizing coffee leaves into value-added functional products. PRACTICAL APPLICATION: Infrared drying offers coffee leaf tea producers a faster, energy-saving method to create flavorful functional teas. It enhances antioxidant activity while developing appealing caramel and fruity notes similar to black tea, providing consumers with a nutritious beverage option. This technique enables sustainable upcycling of coffee leaves into premium tea products with consistent quality for commercial markets.
咖啡叶因其具有促进健康的植物化学物质，已成为一种潜在的功能性茶成分。然而，红外干燥（IFD）对其特性和感官品质的影响仍未得到探索，这限制了它的工业应用。本研究系统地阐明了IFD对咖啡叶干燥动力学、化学成分、美拉德反应产物（MRPs）、风味形成和感官特性的影响。与热风干燥相比，IFD显著缩短了干燥时间50%以上，并减少了5.79%以上的蛋白质损失，同时增加了总酚含量（在1300W时增加27.86%）和抗氧化活性（增加50%以上）。然而，与冷冻干燥相比，IFD导致5-羟甲基糠醛和α-二羰基中间体（乙二醛和甲基乙二醛）的含量更高。使用顶空固相微萃取-气相色谱-质谱联用（HS-SPME-GC-MS）进行的挥发性分析揭示了不同的香气特征：冷冻干燥的叶子呈现出以己醛为主的青草香气，而IFD产生了更具果香花香的香气，（E）-2-己烯-1-醇、辛醛和热衍生的吡嗪/吡啶含量升高。关键风味标志物如2,3-戊二酮和6-甲基-5-庚烯-2-酮在IFD叶片中独特地升高。感官评价证实，经IFD处理的茶叶得分为71.18±3.04，具有类似红茶的风味，带有焦糖和发酵的底色。这些发现表明，IFD是一种省时节能的方法，可生产具有双重优势的咖啡叶茶：（1）增强生物活性化合物的保留，（2）通过控制MRPs有针对性地产生消费者期望的感官属性。这些发现为扩大IFD加工规模奠定了科学基础，为茶叶行业提供了一种将咖啡叶转化为增值功能产品的可持续方法。实际应用：红外干燥为咖啡叶茶生产商提供了一种更快、节能的方法来制作美味的功能性茶。它增强了抗氧化活性，同时产生了类似于红茶的诱人焦糖和水果香气，为消费者提供了一种营养丰富的饮料选择。这项技术能够将咖啡叶可持续地升级为优质茶产品，为商业市场提供质量一致的产品。
