Hydrolysis and characterization of bioactivity and functionality properties of protein fractions from Spirulina platensis and Sargassum illicifolium for active shrimp preservation

Marine algae are promising sources of bioactive proteins, but their functional potential remains underexplored. Developing natural preservatives for seafood (e.g., shrimp) is critical to replace synthetic additives and address spoilage during cold storage. This study aimed to (1) produce bioactive peptides from Spirulina platensis and Sargassum ilicifolium via enzymatic hydrolysis using Alcalase, Protamex, Pancreatin, Pepsin, and Bromelain, followed by fractionation through membrane ultrafiltration, (2) characterize their functional/antioxidant/antibacterial properties, and (3) evaluate their efficacy in chitosan-starch coatings for preserving shrimp (Litopenaeus vannamei). Pepsin and Pancreatin yielded the highest degrees of hydrolysis (DH) for S. platensis (24.85 %) and S. ilicifolium (25.25 %). These fractions exhibited excellent solubility (>80 % at pH 9), foaming (up to 46.22 %), emulsifying (EAI: 22.69 m²/g), and antioxidant properties (DPPH/ABTS scavenging and metal chelating activity). Sp- < 3 kDa inhibited L. monocytogenes (12.3 mm zone) and E. coli (9.1 mm), while Si- < 3 kDa was effective against S. typhimurium (6.2 mm). Coatings with Sp- < 3 kDa significantly reduced TVB-N (18.88 vs. 34.95 mg N/100 g in control), microbial counts (TVC: 7.07 vs. 8.51 log CFU/g), and lipid oxidation (PV: 1.86 vs. 2.97 mil eq. O₂/kg) after 9 days at 4 °C (P < 0.05). The <3 kDa fractions demonstrated dual antioxidant-antimicrobial effects, offering a natural alternative for active food packaging.