*2.3.2.4 Alginate*

Alginate is a sodium salt of alginic acid which has the ability to form film [70]. Alginate polysaccharide is chiefly extracted from seaweed which is in brown colour [75]. Divalent cations such as Mg, Mn, Ca, Fe are used for making alginate coating material which possess gelling character [76]. d-mannuronic acid (M) and l-gulurinic acid (G) are present in alginate having different proportion, arrangement [77], and it affects its physical property [78]. If the ratio of M/G is less than 1, it is means alginate contained higher amount of guluronic acid and hence formed strong bond while, if the ration of M/G is more than 1, it shows less amount of guluronic acid in alginate which may result in flexible structure [79]. The alginic acid obtained from different species of brown algar may contain different polymers such as mannumaric acid unit as main or guluronic acid as a main or both/partial mannuronic and gulurinic acid [80]. Alginate has colloidal nature with stabilising, thickening

and suspending property which makes it suitable for film forming [81, 82]. Alginatebased edible film or coating has poor moisture barrier due to its hydrophilic nature [76], and also it has some desirable properties such as reduction in shrinkage and barrier for colour and odour [83]. Alginate forms coating/film by evaporation of solvent method which is done with or without gelation of it. For retarding dehydration and for protecting the oxidation of lipid in meat product, alginate coating/film is used [84]. For preparing the alginate, pieces of seaweed are dipped in sodium carbonate. After 2 h. slurry of sodium alginate was obtained which has glycellulose (undissolved part of seaweed). Obtained slurry was diluted with water and filtered through filter cloth, and then pressing is carried out. Then precipitation is done to obtain calcium alginate [81, 82].
