Supercritical CO2 extraction of lipids from coffee silverskin: from laboratory optimization to industrial scale-up

Coffee is one of the most important food commodities worldwide. During the production of green coffee beans, the outer layers of coffee cherries are discarded generating wastes. Coffee silverskin (CS), the thin tegument covering green coffee beans, is the sole by-product of coffee roasting and is generated in importing countries. CS could be reused in other productive processes due to its interesting chemical composition. In particular, the lipidic fraction of CS presents potentialities in pharmaceutical, packaging, and cosmetic applications. In this work, the supercritical CO2 extraction of lipids from CS has been optimized at lab-scale using response surface methodology, for the first time. Design of experiment (DoE) and Principal Component Analysis were employed to investigate the effect of pressure and temperature on the extraction yield and on the composition of the extract in the range 100–500 bar and 40–80 °C. In particular, the different effect of temperature above and below the crossover pressure has been highlighted. Based on DoE results, the optimal extraction conditions were set at 400 bar in a temperature range between 50 and 60 °C, applied at industrial scale. As expected, the industrial scale extraction yields resulted higher compared to those obtained in laboratory (3.4 % ± 0.3 and 2.54 % ± 0.06, respectively), while the composition of the extracts did not show significant differences in term of fatty acids. These findings demonstrate the feasibility of scaling up supercritical CO2 extraction of lipids from coffee silverskin, offering a sustainable approach to valorise this by-product for high-value applications in various industries.