Phycocolloids

Phycocolloids are polysaccharide-based hydrocolloids derived from marine algae (seaweed) that function as thickeners, gelling agents, and stabilizers in foods and other products. The term typically covers three major commercial families: agar, carrageenan, and alginates, each with distinct structures and gelling behaviors that enable a range of textures from gels to viscous solutions.

Agar is recovered from red seaweeds such as Gelidium and Gracilaria. Carrageenan comes from red algae, notably Kappaphycus and Eucheuma. Alginates are derived from brown seaweeds such as Laminaria, Ascophyllum, and Macrocystis. Extraction uses alkaline treatment and heat, followed by purification. Their polymers differ in sugar composition and linkages: agar forms strong gels; carrageenan comprises sulfated galactans with kappa, iota, or lambda types; alginates are guluronic/mannuronic acid blocks that gel with divalent cations.

In applications, phycocolloids provide texture and stability. Agar yields clear, firm gels that set at moderate temperatures. Carrageenan offers elastic or brittle gels and is common in dairy, meat, and beverage products. Alginates form ionically crosslinked gels with calcium and other cations, enabling molding, encapsulation, and controlled release in foods and pharmaceuticals.

Safety and regulation are region-specific; these materials are generally permitted as food additives when sourced from compliant suppliers. Potential concerns include contaminants such as heavy metals or iodine in seaweed, underscoring quality control and labeling. Sustainability emphasizes responsible harvesting and farming, with ongoing efforts to reduce environmental impact and reliance on wild stocks.