Phlorotannin-Alginate Extracts from <em>Nizimuddinia zanardinii</em>: Characterization and Application for Melanosis Inhibition and Quality Preservation of Pacific White Shrimp During Ice Storage

Phlorotannin-alginate extracts from brown seaweeds offer promising natural solutions for food preservation. This study investigated the extraction, characterization, and application of phlorotannins and alginate from Nizimuddinia zanardinii for inhibiting melanosis and preserving quality in Pacific white shrimp during ice storage. Methanol extraction yielded the highest phlorotannin content (19.14±0.65 mg PGH/g) with potent antioxidant (98.95±0.74% DPPH inhibition) and copper chelating (73.44±1.64%) activities. Alginate extraction efficiency was 4.73±0.38 g/100g seaweed, demonstrating moderate antioxidant properties. The extracts effectively inhibited shrimp polyphenol oxidase, with 2%phlorotannins+1% alginate showing 84.51% inhibition. When applied to shrimp, this combination significantly delayed melanosis development, suppressed microbial growth, and maintained lower pH, TVB-N, and lipid oxidation values during 16 days of ice storage compared to untreated controls. Sensory evaluation confirmed better retention of quality attributes in treated shrimp. These findings demonstrate the potential of N. zanardinii phlorotannin-alginate extracts as effective natural preservatives for maintaining shrimp quality during cold storage, offering a sustainable alternative to synthetic additives in seafood processing.