Characterization of protein extracted from the Omani seaweed- <i>Hypnea bryoides</i>

Hypnea bryoides ( H. bryoides ), a species of red seaweed (Rhodophyta), was previously found to contain a significant amount of protein. This study aimed to extract protein from H. bryoides and examine its functional and chemical properties, thereby facilitating its use. The protein was extracted in an alkaline solution (0.3 M NaOH, pH 12). The extraction yielded 31% from the original existing quantity, and the purity was 88.50 ± 0.71%. The protein demonstrated a higher oil-holding capacity (13.56 ± 0.26 g oil/g protein) compared to its water-holding capacity (9.61 ± 0.15 g water/g protein). The highest foaming capacity, solubility, emulsifying capacity, and stability were observed at pH 8 and 10 ( p ≤0.05), while the most outstanding foaming stability occurred at pH 4. The in vitro digestibility was 62.62 ± 3.29%. Furthermore, the molecular analysis revealed that β-sheet structures constitute the primary secondary structural component of H. bryoides proteins. A broad range of protein molecules with varying molecular weights (0.4-125.2 kDa) was identified. The amino acid profile indicated that essential amino acids accounted for 35.08% of the total, with methionine + cysteine as the limiting amino acid. Overall, this seaweed protein demonstrated good functional and chemical properties, making it suitable for many food applications.