*5.3.1 Gas barrier property*

Oxygen and carbon dioxide affect the respiration of postharvest fruit and vegetables and also speed up the oxidation of lipid containing food [170]. Gas permeation and WVP have same mass transfer principle [171]. Oxygen barrier property is efficiently measured by parameter, i.e. oxygen permeability or rate of oxygen transmission through it. These are inversely proportional to each other [172]. By comparing chitosan and gelatin film, the chitosan-based film has good oxygen property than the gelatin-based film [173]. Although the gelatin-based film has a poor oxygen barrier, chitosan-gelatin-based composite edible film has excellent oxygen barrier properties. One of the main benefits of whey protein films over polysaccharide films is lower gas permeability. Gas barrier properties of milk protein films are also better than those of several commonly used in edible, synthetic films. This feature can be used to form integrated packages of milk protein films and synthetic polymer films [174]. Hydrocolloid films provide good oxygen barrier properties in the absence of moisture. Gelatin films can be used to cover candy and dry foods, microencapsulate flavours, and keep frozen meats from rotting. Moisture improves oxygen permeability by greatly improving the transferability of the macromolecule chains. Composite films composed of carboxymethyl cellulose and fatty acid sucroesters have adequate oxygen barrier properties while yet being somewhat CO2 permeable [175]. On cooled bananas, this type of coating reduced CO2 exchange by only around half while reducing oxygen transfer by five times. This result is influenced by the kind, variety and temperature of the fruit.
