Circular valorization of green leafy side streams via pressurized liquid extraction techniques for recovery of...

Vegetable side streams are resulting non-edible by-products from vegetable processing. These side streams are a rich source of bioactive compounds and macromolecules. Despite their potential for high-value applications, these materials are frequently used in low-value applications or discarded, contributing to resource depletion and environmental concerns. This study investigates the valorization of vegetable side streams, specifically artichoke, broccoli, cauliflower, and spinach leaves, through pressurized liquid extraction (PLE) techniques aimed at recovering bioactive extracts. Two PLE methods were compared: low-pressure hot water extraction (LPHW) and sequential subcritical water extraction (s-SWE). The s-SWE method yielded higher cumulative extraction and demonstrated superior efficiency in recovering carbohydrates content, particularly pectins. It also produced extracts with enhanced bioactivity, notably great antioxidant activity due to increased phenolic compound content. Antimicrobial activity varied with the extraction method and it as biomass-dependent: LPHW extracts showed efficacy against Gram-positive for cauliflower leaf extracts, while s-SWE extracts were moderately active against both Gram-positive and negative bacteria strains for artichoke leaf extracts. These findings highlight the feasibility of pressurized liquid extraction as a non-conventional and sustainable technique for producing functional extracts from agro-food waste. Moreover, extract profiles can be tailored according to specific biorefinery goals, reinforcing the potential of vegetable side streams in circular economy strategies.