Acid extraction enzymatic method to measure laminaran in edible brown algae

Brown algae contain a β-glucan called laminaran that exhibits various biological activities, such as immune-enhancing, anti-cancer, and antioxidant properties. The laminaran content in brown algae varies depending on species, habitat, and season. When developing a laminaran-containing functional food using brown algae or its extract, accurate quantitative methods to determine laminaran content in a variety of brown algae and foodstuffs are required. In this study, we examined the applicability of the existing sodium hypochlorite extracting and enzymatic digesting (SEED) assay for the determination of the laminaran content of the brown alga Eisenia bicyclis . The laminaran content of E. bicyclis could be determined using the SEED assay. Furthermore, we developed a rapid and concise acid extraction enzymatic method. This method can specifically extract total water-soluble β-glucan (laminaran) and selectively convert it to glucose. The generated glucose content was determined using the glucose oxidase/peroxidase method. The validation test using brown algae E. bicyclis and Sargassum horneri revealed that the acid extraction-enzymatic method is accurate, precise, and applicable to the determination of the laminaran content in these brown algae. Furthermore, developed method was also applicable to laminaran-added processed foods.