Coffee research using optical methods of physical and chemical analysis

The paper discusses aspects of application of optical methods of physical and chemical analysis to determine the identity of the functional groups of substances extraction at different ways of making coffee. Infrared spectroscopy, diffusion reflectance spectrophotometry and refractometry methods were used for the researches. A comparison of coffee preparation methods was conducted in cupping and aeropresse Aerobie Aeropress Coffee Maker. Temperature of the water used to brew, and the punching speed of liquid by aeropressa piston were selected as variable parameters. According to the research data the refractive index of all the samples is almost identical, but TDS is slightly different, and only TDS of samples prepared at a water temperature of 96 °C lies in the optimal range (1,15-1,35%). According to the infrared spectra of the samples the most complete recovery of caffeine, theobromine, theophylline, trigonelline and chlorogenic acid from the coffee beans is observed at a water temperature of 96 °C (at this temperature the absorption spectra of samples from cupping and aeropressa are almost identical). Typical for coffee peaks of caffeine, theobromine, theophylline and trigonelline (in the range of 270-275 nm) are observed in spectra of samples in the ultraviolet region, and they are most pronounced for the cupping. Sensory analysis of coffee samples showed that the samples prepared in cupping (96 °C) and aeropresse (96 °C, punching for 5 seconds) have optimal flavor, and their taste is practically identical, which is confirmed by the infrared spectroscopy data. The results show high prospects of using of optical methods of physical and chemical analysis to the quality and the identity of the coffee samples researches.