Chemical structure and bio-functional properties of Arthrospira platensis peptides produced by ultrasonication-enzymolysis: Their emulsification capabilities

The present study aimed to use ultrasound-pretreatment (10-40 min) for the enzymatic hydrolysis (enzymolysis) of Arthrospira proteins (30-120 min) as well as evaluation of the techno-functional properties, amino acid composition, antioxidant properties, antibacterial activity, and chemical structure of the produced peptides. Also, the effect of enzymatic modification of proteins was evaluated on their role in the physical, oxidative, and morphological stability of oil in water emulsions. The results revealed that the techno-functional properties of Arthrospira proteins were significantly improved (especially in acidic conditions) after ultrasonicationenzymolysis treatment. Enzymolysis of sonicated-proteins resulted in the higher degree of hydrolysis (2.5-41.9 %), hydrophobic (2.4-34.8 %), and antioxidant (2.1-54.7 %) free amino acids, DPPH (21.6-67.8 %), ABTS (48.4-89.6 %), hydroxyl (35.3-79.1 %), nitric oxide (8.5-28.2 %) free radicals scavenging, reducing power (0.71-0.98), total antioxidant (0.7-1.43), chelating activity of iron (41.2-70.6 %), and copper ions (17.5-47.6 %) and also, inhibition of the growth of Escherichia coli and Bacillus cereus. Structural properties (especially amide A regions and secondary structures) were affected by enzymolysis and ultrasound treatment. Partially hydrolyzed proteins produced an emulsion with the highest physical and oxidative stability during storage. Also, SEM (scanning electron microscopy) images showed formation of particles with different morphological characteristics and the occurrence of agglomeration and aggregation phenomena during storage.