*2.3.1.4 Gluten*

Gluten has cohesiveness and elasticity which help to improve mechanical property of film [40]. Wheat gluten chiefly contains glutenins and gliadins, insoluble and soluble in aqueous alcohol, respectively [41]. Edible film made from wheat gluten has water barrier property [42], films are transparent, homogeneous and strong in nature [43]. By using high-pressure treatment to gluten film, the texture can be changed from smooth to rubber-like texture [44].

## *2.3.1.5 Zein*

Zein is a maize protein which is hydrophobic in nature. It is by-product of the oil industry and bio-ethanol [45]. It can be used in manufacturing of edible film, coating and pouches [22]. It is mostly used in confectionery industry as a coating material [46]. It consists of protein which is alcohol-soluble [47]. Zein film is insoluble in water due to more number of non-polar amino acids in it, and it also helps to enhance its water vapour barrier property [48]. Concentration of alcohol in alcoholic zein solution may changes its physico-chemical properties which affect the film properties. For producing functional film from zein, antioxidant and antimicrobial compounds are added to zein coating and films [49]. By treating the zein film forming solution with gamma irradiation helps to enhance its appearance, water barrier property and colour [50]. Zein also combines with polysaccharide and other protein-based film such as glucomannan to improve its property [51]. Zein has ability to assemble by itself due to its hydrophobic and hydrophilic nature [52].

### *2.3.2 Polysaccharides based films*

Polysaccharides such as starch, cellulose, chitin and chitosan, etc. are used for manufacturing of EF and EC. These ingredients are selected according to their suitability for mechanical strength, functional properties, etc. [19]. Polysaccharides are long chain of polymers which are made up of the repeating units of mono or disaccharides which are joined together by bonds called glycosidic bonds. In film characteristics and formation of it, H-bond has important role [15]. Polysaccharide films are made by coacervation process. During the coacervation process, the interaction of long-chain polymer gets changed, and this leads to forming new intermolecular hydrophilic and H-bonding after evaporating the solvent [2]. Polysaccharide coating has barrier properties such as O2, oil, and aroma, but it has poor moisture barrier property [19]. And it also has good structural and strength ability. Use of polysaccharide edible film helps to delay ripening of fruit and vegetables and hence, increases its shelf life too [53].

#### *2.3.2.1 Starch and derivatives*

Starch is chiefly present in tubers, roots and seed of plants. Maize, wheat, potato, etc. are mainly used in the industry as starch source [54]. Starch produces semicrystalline and amorphous layer due to formation of linear amylose and amylopectine (branched) by glucose polymerisation process [55]. Amylase is a polymer having linear structure which affects the amorphous nature of starch granules [54]. The concentration of amylase and amylopectine in starch is 20–30% and 70–80%, respectively [56]. Amylopectine and amylase are naturally present in granular form having size about 1–100 μm [54]. Mechanical property, barrier property of starch are dependent on it sources, concentration of amylase and amylopectine [57]. The application of starch-based films in food packaging is capable because of their environmental appeal, low cost, flexibility and transparency [58, 59]. Corn starch is a high amylose starch which is good source for formation of edible starch-based film. Film can be made from aqueous solution of starch and drying it for free-standing film [60]. Starch-based edible films help to prevent change in taste, appearance and flavour of contained food because film is tasteless, transparent and odourless in nature [57]. Starch film is highly hydrophilic in nature; due to this hydrophobicity, this film has poor barrier property for water. Main advantage of starch film is that it has excellent barrier property of CO2 and O2 [61].

#### *2.3.2.2 Cellulose and derivatives*

Cellulose is a common natural polymer present in nature. Repeating units of D-glucose linked by β-1,4, glycosidic bonds formed cellulose [62]. Cellulose has crystalline structure and tight packing of polymer chain which helps to resist salvation in aqueous media of edible film [60]. Due to the presence of intermolecular hydrogen

#### *Application of Edible Packaging in Dairy and Food Industry DOI: http://dx.doi.org/10.5772/intechopen.107850*

bond cellulose having insolubility in water to overcome it, cellulose treated with alkali helps to make it soluble in water [56]. Etherification of cellulose results in the formation of water-soluble ethers: methyl cellulose (MC), carboxy methyl cellulose (CMC), hydroxyl propyl methyl cellulose (HPMC) and hydroxyl propyl cellulose (HPC), these form good-quality edible film [63]. Edible film based on cellulose derivatives has various characteristics/properties such as resistant to CO2 and O2, transparent, odourless, flexible, water soluble, etc. The hydrophobic:hydrophilic ratio of these film components decided its WVP [31, 64]. Šuput et al. [61] stated that MC is less hydrophilic in nature, hence has water barrier property. Gas and barrier property of cellulose is mainly dependent on its molecular weight [3]. Cellulose-based film acts as anti-rancidic agent due to the presence of large surface area and bipolar in structure [65].
