Optimisation of protein extraction from selenium-enriched Brassicaceae leaves

Vegetable side-streams have gained attention for their potential as sustainable and nutritious food sources for human consumption. This study focused on the optimisation of leaf protein extraction from selenium (Se)-enriched leaf meals (LMs) derived from the Brassicaceae family, including broccoli (Se-BrLM), cabbage (Se-CbLM), radish (Se-RaLM), and Cardamine violifolia (Se-CmLM) leaf meals. The primary focus of the extraction process revolved around two key protein fractions: albumin and glutelin, both highly abundant in the LMs. The results highlighted the significance of ionic strength, extractant pH, and solid-to-liquid (S/L) ratio in leaf protein extraction, with sonication time exerting a comparatively less pronounced influence. Within the Brassicaceae species investigated, the optimal conditions included an extractant pH of 9–10, sonication duration of 30–45 s, an S/L ratio of 1:40, and the inclusion of salt at concentrations of 60 and 300 mM. Under these conditions, Se-CmLM achieved a significantly higher mass yield of 4.80 % (dry basis, db) and protein recovery of 17.55 % (db), with RuBisCo as the major protein within the resulting protein concentrates. The protein–phenolic complex content was minimal, with in vitro protein digestibility of 76.71–80.36 %. This study emphasises the potential of Brassicaceae leaves as sustainable protein sources.