Review on seaweed derived sulfated and non-sulfated marine polysaccharides as multifunctional food ingredients: Structure–function relationships, bioactivities and applications in functional foods

Seaweed-derived hydrocolloids encompass both sulfated and non-sulfated polysaccharides that play a pivotal
role in food technology and human health. Sulfated polysaccharides such as carrageenan, fucoidan, ulvan, and
porphyran exhibit distinctive structural features that confer potent bioactive properties, including antioxidant,
immunomodulatory, antimicrobial, and prebiotic activities. Non-sulfated polysaccharides such as alginate and
agar (although primarily a galactan, contains sulfated agaropectin fractions) are equally important for their
remarkable gel-forming abilities, rheological modulation, and stabilization functions in diverse food matrices.
The functionality of these compounds is governed by their macromolecular architecture, degree of sulfation or
uronic acid content, and extraction methods, which collectively influence gelation behavior, viscosity, and
bioavailability. Recent advances in green extraction and chemical/physical modification strategies have further
enhanced both the techno-functional and bioactive performance of these hydrocolloids. This review critically
examines the structure–function relationships of major sulfated and non-sulfated seaweed polysaccharides,
highlighting their gel-forming capacity and multifunctional health benefits. By integrating insights from food
chemistry, marine biotechnology, and nutrition, the manuscript underscores the potential of seaweed polysaccharides
as next-generation functional food ingredients that combine technological versatility with bioactive
value.