Ultrasonic-Assisted Extraction and Antioxidant Potential of Valuable Protein from Ulva rigida Macroalgae.

green macroalgae or sea lettuce are rich sources of protein with nutritional benefits that promote health as a future plant-based functional ingredient in the food industry. Alkaline pretreatment improved ultrasonic-assisted protein extraction from biomass. Parameters affecting ultrasonic-assisted extraction of protein were type of solvent, biomass-solvent ratio, biomass preparation and extraction cycle. In vitro digestibility was evaluated from oven- and freeze-dried biomass. Results showed highest concentration and extraction yield of protein from using alkaline rather than acid and distilled water. A high biomass-solvent ratio at 1:10 or 0.1 g mL increased protein extraction. Higher alkaline concentration increased protein extraction. Highest protein extractability was 8.5% dry matter from freeze-dried biomass, with highest protein extraction and antioxidant activity from extraction of macroalgae at high alkaline concentrations. macroalgae oven-dried biomass presented suitable human digestibility. Efficient pretreatment of maximized protein hydrolysate and bioactive peptide production for wide-ranging applications.