Food‐Grade Polysaccharides From Sugar Kelp ( <i>Saccharina latissima</i> ): Green Biorefinery Strategies and Emerging Applications in Food Systems

Sugar kelp (Saccharina latissima) cultivation is rapidly expanding globally, creating an abundant and geographically diverse feedstock whose processing has not kept up with cultivation. This review addresses that gap with a carbohydrate-centric scope around alginate, fucoidan, laminarin, and cellulose, integrating the latest literature with practice-oriented assessments of green biorefinery routes, including ultrasound, microwave, super- and sub-critical fluids, and biocatalysis. In addition, we add comparative insights from our own laboratory work on selectivity, polymer integrity, contaminant control, and process robustness. Unlike broad algal overviews, this work establishes a process-structure-function framework that directly links extraction conditions to molecular attributes such as molecular weight, sulfate content, and M/G ratio, and their subsequent functional performance in food systems. We include a novel overview of biocatalysis in seaweed processing, moving beyond enzymatic hydrolysis to cover underexplored whole-cell fermentation for upgrading biomass toward synbiotic products. Finally, these technical insights are mapped to emerging food applications, including gut-promoting ingredients, encapsulation systems, edible films and coatings, fat and meat analogs, and clean-label ingredients. The result is a sugar-kelp-focused, implementation-minded guide for the sugar kelp industry around the globe to build scalable, food-grade biorefineries for high-value polysaccharide ingredients.