ABSTRACT
Alginates are a group of unbranched anionic copolymers composed of uronic acids. They are mainly derived from the cell walls of brown marine macroalgae (Phaeophyceae) and are composed of (1,4) linked β-d-mannuronic (M) and α-l-guluronic acids (G) arranged in homogeneous (MM or GG) and heterogeneous (MG or GM) blocks. The gelling properties of alginates are related to their GG blocks which have the ability to bind divalent cations leading to hydrogel formation by cross-linking processes called the “egg-box system”. These seaweed polysaccharides are authorized as a food additive by major regulatory agencies including the European Commission and U.S. Food and Drug Administration (FDA) and their market is driven by food applications notably for high G type alginate. The main species exploited for alginate production are Macrocystis pyrifera (South Africa), Fucus species (Australia, California, Chile and Mexico), Ascophyllum nodosum, Ecklonia and Durvillea (Europe) and Laminaria (Europe, Korea) and the annual production ranges from 30 to 40,000 t.yr−1. After their extraction using acid and alkaline treatments alginates are characterized using biochemical assays, chromatographic and spectroscopic analyses to obtain their fine structure identification and their potential physicochemical but also biological properties. This book chapter focuses on the extraction, characterization and applications of alginates from seaweeds.34
