Optimization of Protein Extraction from Halopteris scoparia Macroalgae by Ultrasonic-Assisted Enzymatic Extraction (UAEE): Bioactive, Chemical, and Technological Properties

Finding alternative food sources is now more crucial than ever because of the ever-growing global population, on the one hand, and the changing climate brought on by global warming, on the other. Macroalgae are currently a viable, novel, and alternative food source for the food industry. This research was centered on the optimization of extraction conditions of protein extracts from Halopteris scoparia by the response surface methodology based on the Box-Behnken design. According to the results, extraction yield (18.31-94.5%), total phenolic content (TPC) (11.70-19.07 mg GAE/g dw), and antioxidant activity (AOA_CUPRAC: 11.97-17.85 mg TE/g dw, AOA_ABTS: 45.45-78.02 mg TE/g dw), which were influenced by extraction parameters, were investigated. The optimum extraction conditions were ultrasound application time of 7.46 min, enzyme/substrate of 0.8, and extraction time of 2 h. The water (0.29 ± 0.07 g/g) and oil absorption capacity (1.37 ± 0.06 g/g), foaming capacity (8.50 ± 3.70%) and stability (8.50 ± 3.70%), and emulsion activity (37.5 ± 0.00%) and stability (62.22 ± 7.70%) of the protein extracts obtained under optimum conditions were investigated along with Fourier transform infrared spectroscopy, differential scanning calorimetry, and SDS-PAGE. Protein extracts obtained from H. scoparia showed high TPC and AOA, while the emulsion and foaming properties were found to be lower than those of the algal or plant proteins. The hydrolysis degree of protein hydrolysate from H. scoparia-obtained enzymatic hydrolysis was found to be 61.43%. Sixteen amino acids were identified from the H. scoparia protein hydrolysate. The total amino acid content in the protein hydrolysate was 10.44 mg/g protein. Tyrosine, one of the nonessential amino acids, and leucine and lysine, two of the essential amino acids, were determined as the main amino acids.