Abstract
We developed a mid-infrared (MIR) spectroscopic evaluation method of brewed coffee, whose quality and taste depend highly on properties such as the geographical origin and the roasting, grinding, blending, and extraction conditions, using an FT-IR spectrometer equipped with an attenuated total reflectance (ATR) accessory. In addition, the simultaneous content determination of the main components of coffee drink was performed by applying the FT-IR/ATR method. We studied the effects of different varieties of coffee and the degree of roasting on the MIR spectral characteristics of brewed coffee and determined the caffeine and chlorogenic acid content using the FT-IR/ATR method. Arabica (from Colombia, Brazil, and Guatemala) and Robusta (from Indonesia) coffee roasted to city was prepared as the sample. Indonesian coffee roasted to full city was also used. The differences between the second derivatives of the ATR spectra of the brewed Arabica and Robusta coffee were observed around the several absorption peaks, and the brewed coffee from Brazil had different spectral features from those of the other varieties of Arabica coffee. Additionally, the roasting conditions of the Indonesian beans were reflected in the spectral features of the brewed coffee. Moreover, the caffeine and chlorogenic acid content in brewed coffee was determined by spectroscopy. For the coffee drink that was composed of instant coffee, sugar, and coffee whitener, the content of each component was excellently determined using the FT-IR/ATR method by analyzing the spectroscopic interactions between the components.
