烘焙度对冷萃咖啡理化指标与风味成分的影响

以亚洲咖啡豆为研究对象，分别选取浅、中、深3 种烘焙度的中国云南和印度尼西亚苏门答腊产的卡蒂姆种咖啡豆，比较分析冷萃与热萃方式对萃取浓度、萃取率、可滴定酸、总酚、总糖、咖啡因、葫芦巴碱、绿原酸、抗氧化活性与挥发性成分的差异，并进行主成分分析，从而探究烘焙度对冷萃咖啡理化指标与风味成分的影响规律。结果表明，随着烘焙度增加，冷萃咖啡的萃取浓度、萃取率均显著上升，可滴定酸、总酚、葫芦巴碱、绿原酸、抗氧化活性均显著下降（P＜0.05）。冷萃咖啡较热萃咖啡拥有更高的萃取浓度、萃取率与总糖含量（P＜0.05），而可滴定酸、总酚含量、抗氧化活性较热萃显著偏低（P＜0.05）。经顶空固相微萃取-气相色谱-质谱检测分析发现，浅烘咖啡豆萃取液中的挥发性成分含量显著低于烘焙度高的咖啡萃取液，深烘咖啡豆萃取液中挥发性成分种类与总含量最多。进一步通过主成分分析能较好区分冷萃和热萃咖啡，两者挥发性成分贡献率具有较大差异。2-丁酮、2-丁烯醛等花香类物质对浅烘冷萃咖啡贡献率更高，而2-甲基吡嗪、糠醇等呈现烘焙坚果类香气物质对浅烘热萃咖啡贡献率更高；2,6-二乙基吡嗪、川芎嗪等烘焙坚果类香气物质对中烘冷萃和热萃咖啡具有较高的贡献率；2-乙烯基呋喃、甲基糠硫醇、2,5-二乙基吡嗪、糠基甲基硫醚等物质对深烘冷萃咖啡有较高贡献率，二甲基二硫、对甲酚、1-甲基吡咯等物质对深烘热萃咖啡贡献率更高。相对于热萃咖啡，烘焙度对冷萃咖啡抗氧化能力与挥发性成分的影响更大。

Effect of Roasting Degree on Physicochemical Indexes and Flavor Components of Cold Brew Coffee

In this study, light, medium, and dark roasted Catimor coffee beans from Yunnan, China and Sumatra Indonesia were selected to compare the differences in the extract concentration, extraction efficiency, titratable acid, total phenols, total sugar, caffeine, trigonelline, chlorogenic acid, antioxidant activity and volatile components of cold and hot brew coffee. Principal component analysis (PCA) was carried out to explore the effect of roasting degree on the physicochemical indexes and flavor components of cold brew coffee. The results showed that with the increase of roasting degree, the extract concentration and extraction efficiency of cold brew coffee increased significantly, and the levels of titratable acid, total phenols, total sugar, trigonelline, chlorogenic acid, and antioxidant activity decreased significantly (P < 0.05). Cold brew coffee had higher extract concentration, extraction efficiency and total sugar levels than hot brew coffee, while the levels of titratable acid, total phenolic content, and antioxidant activity were significantly lower than those of hot brew coffee (P < 0.05). The headspace solid phase microextraction combined with gas chromatography (HS-SPME-GC-MS) analysis showed that the content of volatile components in light roasted coffee was significantly lower than that in medium roasted coffee, and dark roasted coffee had the highest number and amount of volatile components. Furthermore, PCA could distinguish between cold and hot brew coffee, and the contribution rate of volatile components was quite different between them. 2-Butanone, 2-butenal and other substances responsible for floral aroma had a higher contribution rate to cold brew light roasted coffee, while compounds contributing to roasted nut-like aroma including 2-methylpyrazine and furfuryl alcohol had a higher contribution rate to hot brew light roasted coffee. 2,6-Diethylpyrazine, ligustrazine and other compounds contributing to roasted nut-like aroma had a higher contribution rate to both cold and hot brew middle roasted coffee. 2-Vinylfuran, methylfurfuryl mercaptan, 2,5-diethylpyrazine, and furfuryl methyl sulfide had a higher contribution rate to cold brew dark roasted coffee, and cresol and 1-methylpyrrole had a higher contribution rate to hot brew dark roasted coffee. Compared with hot brew coffee, roasting degree had a greater impact on the antioxidant capacity and volatile components of cold brew coffee.