Caffeine extraction from coffee by supercritical fluid method

The influence of operating parameters on extraction of caffeine and nicotinic acid from green coffee beans was studied. Extraction was performed with supercritical carbon dioxide on a semi continuous flow apparatus at pressures 200 and 300 bar, and temperatures of 40, 60 and 80 °C. The constant flow rate of carbon dioxide in range from 0.06 to 0.1 kg/h was maintained during extraction. The raw material, residual material and the extracts were analysed on caffeine and nicotinic acid content using HPLC method. The highest total extraction yield was obtained at 300 bar and 80 °C and it was 13.8 %. The extraction efficiency of caffeine from green coffee beans was the highest at 200 bar and 60 °C where the extract contained 14.59 wt. % of caffeine and decreased with higher pressure. The results were compared with those obtained using conventional extraction with methanol where the efficiency of caffeine was 8.13 wt. % using the same grain size of raw material. The caffeine was concentrated in extract, while the nicotinic acid was concentrated in the residual material.Dynamic behaviour of extraction runs was analysed using mathematical model for describing the constant rate period. Based on the experimental data the mass transfer coefficients were calculated. Results showed good agreement between calculated and experimental data.

Keywords:

supercritical fluid extraction , extraction , caffeine , CO2