Wang Jun, Jun Soojin, Bittenbender H C, Gautz Loren, Li Qing X
Univ. of Hawaii, Honolulu, USA.
J Food Sci. 2009 Jun;74(5):C385-91. doi: 10.1111/j.1750-3841.2009.01173.x.
Kona coffee, the variety of "Kona typica" grown in the north and south districts of Kona-Island, carries a unique stamp of the region of Big Island of Hawaii, U.S.A. The excellent quality of Kona coffee makes it among the best coffee products in the world. Fourier transform infrared (FTIR) spectroscopy integrated with an attenuated total reflectance (ATR) accessory and multivariate analysis was used for qualitative and quantitative analysis of ground and brewed Kona coffee and blends made with Kona coffee. The calibration set of Kona coffee consisted of 10 different blends of Kona-grown original coffee mixture from 14 different farms in Hawaii and a non-Kona-grown original coffee mixture from 3 different sampling sites in Hawaii. Derivative transformations (1st and 2nd), mathematical enhancements such as mean centering and variance scaling, multivariate regressions by partial least square (PLS), and principal components regression (PCR) were implemented to develop and enhance the calibration model. The calibration model was successfully validated using 9 synthetic blend sets of 100% Kona coffee mixture and its adulterant, 100% non-Kona coffee mixture. There were distinct peak variations of ground and brewed coffee blends in the spectral "fingerprint" region between 800 and 1900 cm(-1). The PLS-2nd derivative calibration model based on brewed Kona coffee with mean centering data processing showed the highest degree of accuracy with the lowest standard error of calibration value of 0.81 and the highest R(2) value of 0.999. The model was further validated by quantitative analysis of commercial Kona coffee blends. Results demonstrate that FTIR can be a rapid alternative to authenticate Kona coffee, which only needs very quick and simple sample preparations.
科纳咖啡，即种植于科纳岛南北地区的“科纳铁比卡”品种，带有美国夏威夷大岛该地区独特的印记。科纳咖啡的卓越品质使其跻身世界最佳咖啡产品之列。采用傅里叶变换红外（FTIR）光谱仪结合衰减全反射（ATR）附件及多变量分析，对研磨后的科纳咖啡、冲泡后的科纳咖啡以及用科纳咖啡制成的混合咖啡进行定性和定量分析。科纳咖啡校准集由来自夏威夷14个不同农场的10种不同的科纳种植原咖啡混合物以及来自夏威夷3个不同采样点的非科纳种植原咖啡混合物组成。实施了一阶和二阶导数变换、均值中心化和方差缩放等数学增强方法、偏最小二乘法（PLS）多变量回归以及主成分回归（PCR），以建立和增强校准模型。使用9组由100%科纳咖啡混合物及其掺假物100%非科纳咖啡混合物组成的合成混合集成功验证了校准模型。在800至1900 cm(-1) 的光谱“指纹”区域，研磨咖啡和冲泡咖啡混合物有明显的峰值变化。基于均值中心化数据处理的冲泡科纳咖啡的PLS二阶导数校准模型显示出最高的准确度，校准值的标准误差最低为0.81，R(2) 值最高为0.999。通过对市售科纳咖啡混合物的定量分析进一步验证了该模型。结果表明，FTIR可作为一种快速的方法来鉴定科纳咖啡，只需要非常快速和简单的样品制备。
