*5.3.2 Water vapour permeability (WVP)/barrier property*

For preserving food and increasing the shelf life of food, water vapour barrier property is considered mostly and importantly too [176]. The edible film should have low WVP because those films have low WVP and are mainly ideal for food that contains more moisture; it helps to avoid moisture transmission between food and environment which results in a better quality of food [171]. WVP can be reduced by adding an antimicrobial agent to it. Chitosan films show higher water vapour permeability properties than gelatin-based films [170]. The chitosan-gelatin composite film possesses hydrophilic nature, and it forms a compact network; due to this, it has higher water vapour barrier properties [170]. Whey protein films effectively bound the water vapour condensation in fruit and vegetable packaging, thus restricting microbial spoilage. For same reasons, the RH and plasticiser type considerably affect the moisture permeability properties of protein films [177]. Combining linear and globular proteins results in a decrease in WVP [178]. WVP was lowered by gelatin and defatted soy proteins from 8.45 to 5.55 g mm kPa-1 h−1 m−2 [178]. Plastisisers have an impact on

WVP as well; it has been noted that utilising glycerol instead of PEG-400 and sorbitol results in greater WVP values. Sorbitol will provide the film with higher moisture barrier qualities because it is anticipated that edible films will have lower WVP [25].

### *5.3.3 Thermal property*

The thermal property of edible film is related the resistance of that film to temperature which helps to protect food when stored in different temperatures. Thermomechanical property of film can be determined by scanning the calorimetry and thermo-gravimetric method [179, 180].

#### *5.3.4 Antimicrobial property*

The antimicrobial property of edible film is improved by adding the antimicrobial compound to it. The edible film also has carrier property so it carries antimicrobial agents, which play their role upon food when comes in contact with it. Antimicrobial activity of edible film containing antimicrobial agent is very effective against fungi and bacteria [171]. In chitosan-based edible film, mainly curcumin, apple peel polyphenols, etc are present [181, 182]. The Agar disc diffusion method is used to measure the antimicrobial activity of antimicrobial agent added edible film. Previously microorganisms inoculated film cuts are placed on agar plate and incubated in suitable conditions, and then the inhibition zone is observed around the disc films [183].

#### *5.3.5 Moisture barrier properties*

Films with appropriate moisture barrier properties are required for a great number of applications. Many lipid compounds, such as animal and vegetable fats, aceto-glycerides, surfactants and waxes [184], have been used in the formation of edible films and coatings because of their excellent moisture barrier properties. Waxy coatings on fresh fruit and vegetables thus reduce weight loss due to dehydration during storage by 40–75% [185]. A multicomponent film was established by Guilbert in 1986 [186] and is made of casein or gelatin, carnauba wax, glycerol monopalmitate and monostearate. This film demonstrated good water vapour barrier qualities when applied as an emulsion and subsequently acidified with lactic acid after drying. Krochta et al. [184, 187] also reported that the composite films of casein and aceto-glycerides or wax placed as an emulsion.

### **5.4 Edibility and biodegradability**

The film is made from components that are totally edible, and if that is not eaten by consumers, also it has biodegradability property because it contains (environmentally safe) constituents or ingredients [15].

### **5.5 Carrier properties**

Antioxidants, antimicrobial, flavouring compounds, pigments and nutrients are added to the film during the blending process of raw material. In such cases, a functional group of the film is bonded with these additives and makes the film stronger and has good carrier property [168].
