Ultrasound-assisted alkaline extraction of spirulina proteins: Yields, technofunctional properties, and bioactive peptide analysis

The study investigated the use of ultrasound-assisted alkaline extraction (UAAE) to extract spirulina proteins from phycocyanin extraction residues. The objective was to optimize ultrasonication conditions and evaluate the technofunctional properties and potential health benefits of spirulina protein extracts (SPE). The technofunctional properties assessed included water-holding capacity, oil-holding capacity,  foaming properties, emulsifying properties, and protein solubility. The optimal ultrasonication condition was determined to be 450W for 15 minutes, resulting in a significantly improved production yield of 73%, a protein content of 71.5%, and a protein recovery of 80.1%. The highest protein solubility was observed at pH 9, with the isoelectric point at pH 4.5. The study also identified substantial bioactive peptides in the SPE,  with the top five bioactive peptides detected being dipeptidyl peptidase IV inhibitor (26%), Angiotensin-I-converting enzyme (ACE) inhibitor (25%), enzyme inhibitors (13%), taste peptides (9%), and neuropeptides  (3%). Non-redundant peptides were ranked from ACE inhibitor peptides (20%), enzyme inhibitor peptides (19%), neuropeptides (15%), stimulating peptides (13%), to antioxidative peptides (12%). Overall, the study highlighted the production of technofunctional spirulina proteins via UAAE, positioning  them as promising alternative protein ingredients for health food and nutritious feed applications.