Optimization of extraction conditions of proteins from Laurencia pyramidalis macroalgae response surface methodology: Investigation of bioactive and technofunctional potential and characterization studies

In this study, it was aimed to optimize the extraction conditions of ultrasound-assisted enzymatic extraction of proteins from a red macroalgae Laurencia pyramidalis using response surface methodology. The independent variables selected in the study were extraction time and enzyme/substrate ratio with 3 levels. The effects of independent variables on protein content (PC), total phenolic content (TPC) and antioxidant activity (AOA) of the extracts were investigated. Before extraction, chemical composition, protein solubility and zeta potential measurements of Laurencia pyramidalis were carried out within the scope of characterization studies of the algae. In addition, techno-functional properties such as water holding capacity (WHC), oil holding capacity (OHC), emulsion stability (ES), emulsion activity (EA), foaming capacity (FC) and foaming stability (FS) of the protein extracts obtained under optimum extraction conditions were investigated. Identification studies were carried out by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). According to the results, Laurencia pyramidalis macroalgae had a protein content of 13.09±0.24%, lipid content of 0.79±0.00%, ash content of 26.43±1.37% and crude fiber content of 15.22±0.09% in dry weight (dw). The protein extracts obtained under optimum extraction conditions (ultrasound application time of 6 min and enzyme/substrate of 2) were found to be PC 224.69 mg protein/g dw, TPC 341.10 mg gallic acid equivalent (GAE)/g dw and AOA 171.24 mg TE/g dw. The WAC, OAC, EA, ES, FC and FS of the protein extracts obtained under optimum extraction conditions were 97.85±0.29%, 189±0.24%, 43.89±0.06%, 5±0.00%, 5.42±0.05, and 1.44±0.01, respectively. According to the result of SDS-PAGE analysis, the protein extract had a few protein fractions between 11 kDa and 25 kDa. As a result, Laurencia pyramidalis macroalgae with high OAC and AOA can improve the structural and textural properties of foods.