Valorization of cauliflower (Brassica oleracea L. var. botrytis) and beetroot (Beta vulgaris L.) leaves into leaf protein concentrates: techno-functional properties and effects on cell viability and glucose uptake

To meet the increasing demand for protein, search for alternative protein sources has increased, where upcycling waste leaves is a promising approach in terms of nutrition and sustainability. Leaf protein concentrates (LPCs) were extracted from beetroot and cauliflower leaves, and precipitated via heat treatment. Their potential as upcycled ingredients compared to commercial plant-based protein powders, soy and pea, was evaluated. LPCs exhibited significantly higher water and oil holding capacities than commercial proteins. Although pea protein had the highest foaming capacity, the foams formed by LPCs had higher stability over time. Protein solubility varied between 13 and 43% for beetroot LPC and 8–49% for cauliflower LPC. Despite variations in emulsion activity index, LPCs showed better emulsifying performance than commercial proteins, particularly above pH 4, according to droplet size data. In vitro bioaccessibility of LPCs was low, potentially due to impurities or phenolic compounds, and further analysis of antinutrients is needed. Cytotoxicity assay using Caco-2 cells showed low toxicity at all tested protein concentrations. The highest concentration (100 µg BSA/mL) resulted in 71% cell viability for beetroot and 86% for cauliflower LPC, with no significant differences at lower concentrations. Notably, cauliflower LPC selectively promoted proliferation in healthy HEK293T cells without stimulating HepG2 cancer cells. It did not influence glucose uptake in HEK293T cells, suggesting its effects are not linked to glucose metabolism. In contrast, beetroot LPC enhanced glucose uptake. Overall, LPCs show promising techno-functional properties, in some cases outperforming commercial proteins, and their selective bioactivity suggests potential use in plant-based or functional food applications.