Vegetable by-products, obtained from cauliflower (CA), broccoli (BRL), cabbage (CB) and beetroot (BR) can be a potentially good source of proteins. The proteins were obtained from leaves (LPs) of vegetables with alkaline extraction at pH 10, and their isoelectric precipitation at pH 4. Protein contents were in the range of 39.76 - 53.33%, and the molecular weights of fractions were mostly about 45, 25 and 14 kDa. Their solubility is higher in the alkaline environment, where they reach the highest solubility at pH 10 (9.7 mg/mL for CALP, 8.45 for BRLP, 5.35 mg/mL for CBLP, 5.5 mg/mL for BELP). Moreover, they showed favorable emulsifying abilities, water absorption capacities (0.62 to 1.61 g/g) and foaming capacity (86.3 to 92%) as well as stability (48.57 to 79.30%). Digestibility was studied using gastrointestinal proteases (pepsin and pancreatin), and all four LPs can easily be digested. The biologically active potential of the digests was evaluated measuring antioxidant capacity by two complementary methods - DPPH+ and ABTS+ radical cation scavenging activity. The values for DPPH+ and ABTS+ were in the range from 59 to 65.1% at 0.1 and 0.3 mg/ml to 0.22 mg/ml IC50 values, respectively. Therefore, it can be indicated from these results, that obtained LPs, owing to their good functional properties, may be considered as potential ingredients of health-promoting food and cosmetic products.
Keywords: Antioxidative capacity; Digestion; Functional properties; Leaf proteins; Vegetable by-products.