Valorisation of spent coffee through membrane processing

• Extracts from low-value spent coffee with biocompatible solvents were optimised.
• Fractionated extracts through membrane processing enriched in caffeine were studied.
• The overall bioactivity of fractionated extracts were higher than of crude extracts.
• The final extract obtained justifies a label ‘natural’.

This work optimised the sustainable process of producing a natural extract from spent coffee using membrane technology, with no organic solvents or adsorbents involved. The extract produced is enriched in caffeine with specific health benefits. Moreover, the extract has a “natural” label considering the use of biocompatible solvents and mild operating conditions, which is important for the target markets (cosmetics and energy food segments). Firstly, the optimisation of solvent extraction was performed, namely through adjusting its operating conditions, particularly extraction medium, weight ratio of extracting medium to spent coffee, extraction time and temperature of extraction. Then, the application of membranes was studied, evaluating whether the overall bioactivity of fractionated extracts through membrane processing (after removing undesirable larger molecules), was higher than the overall bioactivity of corresponding non fractionated extracts. An economic evaluation showed that the proposed process is viable, based on experimental data obtained at the pilot scale.