Ultrasound‐assisted alkaline extraction of proteins in several algae and their nutritional characteristics

Abstract

Summary Ultrasound‐assisted alkaline extraction (UAAE) and the nutritional quality of proteins from five algae ( Arthrospira platensis , Cladophora glomerata , Porphyra tenera , Laminaria japonica and Undaria pinnatifida ) were investigated. The UAAE of the A . platensis protein using a 60% amplitude level and 30 min extraction time provided the highest protein yield (81.86%) and altered the surface of A . platensis . Amino acid profiles revealed that lysine and branched‐chain amino acids (BCAAs) were dominant in most algal proteins. The C . glomerata protein had the highest digestibility (94.09%) and protein digestibility‐corrected amino acid scores for the BCAAs. The L . japonica protein demonstrated a rich source of aspartic and glutamic acids, giving an umami taste. The algal proteins contained low contents of carbohydrates (3.87–44.83 mg glucose equivalents g −1 ) and nucleic acids (0.60–8.57 mg g −1 ), while total phenolics were 6.13–70.13 mg gallic acid equivalents g −1 . Algal proteins could be a good ingredient in developing vegan and vegetarian foods.