Efficient decaffeination of green coffee beans using pressure swing supercritical CO2 extraction

Supercritical CO 2 is a promising technology for caffeine extraction from green coffee beans owing to its safety, environmental friendliness, and caffeine selectivity. However, one of the drawbacks is its low efficiency and a large amount of CO 2 is required to achieve a high degree of decaffeination. Therefore, a pressure swing extraction method, in which the pressure was varied up and down during the operation, was used to achieve a high degree of decaffeination with less CO 2 supply. As a result, nearly 100 % decaffeination was achieved at 353 K and 30 MPa, with 80 % of the CO 2 supply, compared with the pressure constant operation (pressure was maintained at 30 MPa during the operation). Furthermore, it was demonstrated that the application of the pressure swing method enabled the maintenance of a comparable caffeine extraction efficiency without the water-soaking pretreatment process. Mass spectroscopy imaging was used to visualize the caffeine distribution, showing extraction from deeper bean parts under the pressure swing vs. the constant pressure extraction method. • Pressure swing CO2 extraction method was applied to decaffeination from coffee. • Pressure swing achieved 100 % decaffeination with low CO2 consumption. • Pressure swing maintained extraction efficiency without the water-soaking. • Mass spectrometry imaging revealed caffeine distribution differences.