Alginat

Alginat, known in English as alginate, is a natural anionic polysaccharide obtained from the cell walls of brown seaweeds (Phaeophyceae), such as Laminaria and Macrocystis. It consists of blocks of two types of uronic acids, β-D-muronate (mannuronic acid) and α-L-guluronate, arranged in sequences that influence gel properties. Alginates are typically used in the form of salts, most commonly sodium alginate, or as the calcium salt.

In water, alginates form viscous solutions and, in the presence of divalent cations like calcium, they gel by ionotropic crosslinking. This gelation is often described by the egg-box model, where calcium ions bridge guluronate blocks to create stable hydrogels at ambient temperatures and physiological pH. The gel strength can be tuned by adjusting the ratio of mannuronate to guluronate blocks, ionic strength, and the type and concentration of crosslinking cations.

Applications of alginates are diverse. In the food industry, they act as thickeners, stabilizers, and texture modifiers and are used in dairy products, processed meats, confectionery, and as edible films. In medicine and dentistry, alginates are used in wound dressings to maintain a moist wound environment and in dental impression materials. In biotechnology, calcium alginate beads are used to immobilize cells and enzymes, and alginate gels serve as scaffolds for tissue engineering and controlled-release drug delivery.

Safety and regulation: alginates are widely recognized as safe as food additives in many jurisdictions (GRAS status in the United States), though high intake can cause gastrointestinal discomfort in some individuals, and improper handling of powdered forms poses a choking hazard. Proper processing reduces concerns about contaminants.