Mucilages

Mucilages are water-soluble polysaccharide substances produced by many plants. They are released when plant tissue is hydrated or damaged and, in aqueous environments, they swell to form viscous gels. They function as hydrated reservoirs and protective coatings in plants, helping retain water, lubricate tissues, and shield against desiccation and some pathogens. They are hydrocolloids; in contrast to plant gums, which are often exudates, mucilages are typically stored within tissues and released upon hydration.

Most mucilages are complex heteropolysaccharides, often containing uronic acids, neutral sugars such as galactose, arabinose, rhamnose, xylose, and others. They are stored in specialized cells or secreted from meristematic zones in seeds, roots, stems, or bark. Common plant sources include seeds of Plantago (psyllium), Linum (flax), Salvia hispanica (chia); okra (ladies' finger) fruit mucilage; slippery elm bark; aloe vera gel; and various cacti and mosses.

In addition to ecological roles, mucilages have wide applications. They act as natural thickening, gelling, and stabilizing agents due to their high water-binding capacity. In food production they improve texture and hydration and provide soluble dietary fiber. In pharmaceuticals and cosmetics they function as excipients and thickening agents. Psyllium mucilage is well known as a bulk laxative and dietary fiber; other mucilages are used similarly as inert thickeners or emulsifiers.

Extraction typically involves aqueous extraction of plant material, filtration to remove solids, and precipitation or drying to isolate the polysaccharide. Mucilages are generally considered safe for consumption and use, though high intake requires adequate fluid intake to avoid digestive discomfort.