Study Finds A Way To Extract Food Ingredient From Seaweed Swamping Gulf Beaches

Forget the Cleanup Crews: Researchers Want to Turn Sargassum Into a Food Industry Ingredient

Every summer, enormous rafts of brown seaweed wash ashore across the Caribbean, the Gulf of Mexico, and the coast of West Africa, smothering beaches, killing marine life, and costing communities millions in cleanup. Since 2011, these blooms of floating Sargassum have expanded into what scientists call the Great Atlantic Sargassum Belt. Researchers at Florida State University and partner institutions now see this ecological headache as an untapped resource. Their new study, published in Food Hydrocolloids, explores whether it could yield a purified alginate ingredient with potential food uses, one that could turn up in everything from salad dressings to dessert gels.

Alginate is a natural substance found in the cell walls of brown seaweed. When extracted and purified, it becomes a powder that dissolves in water and can thicken liquids, form gels, or help keep oil and water from separating. It already shows up in ice cream, dairy products, and salad dressings as a texture enhancer. Most commercial alginate currently comes from farmed or wild-harvested kelp. Sargassum, the free-floating kind responsible for those massive beach strandings, can contain up to 21 percent alginate by dry weight, making it a potentially large alternative source.

Raw Sargassum, though, is not safe to eat directly. It can accumulate toxic heavy metals from ocean water and carries high salt and fiber loads. So the researchers focused not on eating the seaweed itself but on extracting and purifying just the alginate, stripping away contaminants through acid washing, chemical separation, and other processing steps.

How the Processing Method Changed What Came Out

Corresponding author Qinchun Rao and colleagues at Florida State University collected Sargassum offshore in June 2024 for the main experiments, choosing ocean-harvested material over beach-gathered seaweed to reduce contamination from sand and debris. Before running any extractions, the team tested the raw seaweed for cadmium and lead. Cadmium came in at 0.49 milligrams per kilogram of dry weight, within the range previously reported for Sargassum across the Caribbean and Atlantic. Lead was below the instrument’s detection limit, meaning it was not detected at measurable levels in this sample.

For the extraction itself, the researchers first optimized the recipe by testing 15 different combinations of temperature, time, and the concentration of an alkaline solution. The sweet spot turned out to be 80 degrees Celsius for five hours, pulling out crude alginate at about 44 percent yield.

Before that extraction step, each batch went through one of three pretreatments, or none at all as a control. Autoclaving used high-heat, high-pressure steam at 121 degrees Celsius, the same technology used to sterilize surgical instruments. High-pressure processing, or HPP, squeezed the material under enormous pressure at room temperature, already used commercially to extend the shelf life of juices and deli meats. Sonication used high-frequency sound waves to create powerful bubbles in liquid that collapse and generate mechanical force, shaking the material apart without added heat.

Autoclaving Wrecked the Alginate. Sound Waves Did Not.

Autoclaving badly damaged the extracted alginate. It shattered the long molecular chains into fragments, reducing their size to roughly a tenth of what the untreated control produced. Gel strength fell from 175 grams in the control to just 77 grams. Oil-and-water stabilization dropped to between 5 and 6 percent. The heat wrecked the very properties that make alginate useful.

Sonication for 10 minutes preserved most of the molecular chain length and produced the highest gel strength among pretreated samples at 174 grams, nearly matching the untreated control. Extending to 30 minutes caused only minor reductions, suggesting short bursts of sound waves trim the chains just enough to improve workability without destroying the backbone needed for firm gels.

HPP told a different story for oil-and-water performance. At moderate pressure, it produced the best emulsification index among the pretreated samples at 17.2 percent. It did not beat the untreated control overall, but it showed that pressure treatment can tune alginate toward better performance in emulsion-style foods. The researchers suggest that partially shortening the molecular chains made them more mobile, allowing them to migrate faster to the boundary between oil and water droplets and lock the mixture in place.

Chemical analysis confirmed that none of the pretreatments changed the core chemistry of the alginate. Performance differences were driven by physical changes, including shorter chains and greater flexibility, rather than any alteration to the molecule itself.

No-Heat Methods Offer a Way to Tune Alginate for Different Jobs

Purified alginate yields across all pretreatments stayed in a narrow band of about 16 to 22 percent. What changed was the functional profile of what came out.

Sargassum strandings currently have few practical outlets beyond compost, soil amendments, or low-level animal feed. It is abundant, and in many places already being removed at public expense. Getting from these lab results to a reliable, contaminant-tested ingredient at commercial scale will require batch-to-batch verification of regulated metals in the purified alginate and testing in actual food systems, but the processing pathways already exist in the food industry.

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Disclaimer: The findings described in this article are based on a single peer-reviewed laboratory study and have not been evaluated by the FDA or any regulatory body for food safety purposes. Sargassum-derived alginate is not currently approved or commercially available as a food ingredient.

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