Ultrasound-Assisted Extraction of Mucilage: An Approach for the Full Utilization of Ora-Pro-Nóbis Leaves

Ora-pro-nóbis (OPN) leaves are remarkably high in mucilage content. Sustainable processing methods, such as ultrasound-assisted extraction (UAE), can enhance the yield and functionality of OPN mucilage (OPNM). The resulting residue (OPNR) can be utilized to support circular economy approaches. This study aimed to determine the optimal conditions for OPNM extraction and subsequently characterize OPNR. OPNM was extracted by UAE at different power levels (200, 400, 600, and 800 W) and by conventional methods (water bath extraction at 25°C and 80°C). After extraction, OPNR was separated by filtration. OPNM samples showed lower protein contents (10.68-16.01 g 100 g^-1) than OPNR samples (15.15-20.22 g 100 g^-1) but higher water solubility (79.45-89.64 g 100 g^-1), water absorption capacity (552.93-797.07 g 100 g^-1), and total phenolic content (64.1-122.1 mg 100 g^-1), resulting in higher antioxidant activity. Lightness values ranged from 35.97 to 41.72 (OPNM) and 38.55 to 44.79 (OPNR). OPNM samples had irregular and rough surfaces, high emulsifying capacity (600.68-621.31 mL oil g^-1), and adequate emulsion stability (80.12%-86.90%). OPNM samples exhibited pseudoplastic behavior; the best balance between viscosity and structural integrity was achieved with the 400 W UAE treatment. OPNM also contained bioactive compounds, such as rutin and malic acid, as well as a complete profile of essential and nonessential amino acids, particularly histidine, glutamine, and aspartic acid. These results demonstrate the feasibility of the full utilization of OPN leaves, with UAE recommended as the most effective method for obtaining mucilage with enhanced functionality.