Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
J Agric Food Chem. 2011 Apr 13;59(7):3220-6. doi: 10.1021/jf104980d. Epub 2011 Mar 22.
In this feasibility study, Fourier transform infrared (FTIR) spectroscopy and chemometric analysis were adopted to discriminate coffees from different geographical origins and of different roasting degrees. Roasted coffee grounds were extracted using two methods: (1) solvent alone (dichloromethane, ethyl acetate, hexane, acetone, ethanol, or acetic acid) and (2) coextraction using a mixture of equal volume of the solvent and water. Experiment results showed that the coextraction method resulted in cleaner extract and provided a greater amount of spectral information, which was important for sample discrimination. Principal component analysis of infrared spectra of ethyl acetate extracts for dark and medium roast coffees showed separated clusters according to their geographical origins and roast degrees. Classification models based on soft independent modeling of class analogy analysis were used to classify different coffee samples. Coffees from four different countries, which were roasted to dark, were 100% correctly classified when ethyl acetate was used as a solvent. The FTIR-chemometric technique developed here may serve as a rapid tool for discriminating geographical origin of roasted coffees. Future studies involving green coffee beans and the use of larger sample size are needed to further validate the robustness of this technique.
在这项可行性研究中，采用傅里叶变换红外（FTIR）光谱和化学计量学分析来区分来自不同地理来源和不同烘焙程度的咖啡。使用两种方法提取烘焙咖啡粉：（1）仅使用溶剂（二氯甲烷、乙酸乙酯、正己烷、丙酮、乙醇或乙酸）和（2）使用溶剂和水等体积混合物的共提取。实验结果表明，共提取方法得到的提取物更干净，并提供了更多的光谱信息，这对于样品鉴别很重要。对深烘焙和中烘焙咖啡的乙酸乙酯提取物红外光谱进行主成分分析，根据其地理来源和烘焙程度显示出分离的聚类。基于类间类比分析的软独立建模的分类模型用于对不同的咖啡样品进行分类。当使用乙酸乙酯作为溶剂时，来自四个不同国家的深烘焙咖啡 100%被正确分类。这里开发的 FTIR-化学计量技术可作为一种快速工具，用于鉴别烘焙咖啡的地理来源。未来的研究需要涉及生咖啡豆，并使用更大的样本量，以进一步验证该技术的稳健性。
