Influences of pH and temperature on infrared spectroscopic features of brewed coffee (original) (raw)

2011, Procedia food science

We developed an infrared spectroscopic evaluation method of brewed coffee, whose quality and taste highly depend on the chemical contents, the interactions between the components, the pH value and the temperature, using a Fourier transform infrared (FT-IR) spectrometer equipped with an attenuated total reflection (ATR) accessory. The objective of this study is to understand the influences of the pH values and temperature on the spectral features of brewed coffee and the main components, since the component balances of the organic acids originating from coffee beans and being produced during processes such as roasting and extraction could closely relate to the brewed coffee characteristics. The absorption peak sifts of the ATR spectra of brewed coffee were observed as the influences of the pH and temperatures. Therefore, by analyzing the spectra of the coffee components under the various pH and temperature conditions based on the ionic dissociation equilibrium theory, the spectral behavior of the brewed coffee model due to the pH and temperature changes could mainly result from those of the organic acids as the main components. Consequently, the infrared spectral information analysis would be acceptable as a new method to evaluate a profile of brewed coffee for the quality evaluation relating to the taste and the non-intensive on-line monitoring of the coffee process.

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