Food is a vital product for the survival of human beings and with passage of time quality concerns of consumers are rising. The Post Harvest loss of fruits and vegetables vary from 5 to 50% in India. Food packaging is best method for preservation off food material. Packaging is used as a mechanical protection and as a food preservation technology, retarding food product deterioration, extending shelf life, and maintaining the quality and safety of the packaged foods. Plastic is highly used food packaging material but plastics are polluting the environment, pose a danger to wildlife, do not degrade quickly and pose difficulties during recycling. The use of bio-based packaging materials for food depends on availability, quantities, prices, and properties of the materials. Biodegradable and edible food packaging material is replacement of plastic polythene.
Edible Film and Coating
Edible coatings and films are produced from edible biopolymers and food-grade additives. Edible films and coatings are thin layers applied on food products to protect them and improve their quality.. Polysaccharides (carbohydrates and gums), proteins, lipids, or a mixture of these food materials can be used for producing edible coating and films. Edible film as a solid sheet can be applied between food components or on the surface of the food system in order to inhibit migration moisture, CO2, oxygen, aromas and lipids. To improve the physical properties and other functionality of the edible films i.e. antimicrobial, antimicrobial and antioxidant properies plasticizers and other additives are combined with the film-forming biopolymers. Edible films and coatings enhance the quality of food products by protecting them from physical, chemical, and biological deterioration.
Edible coatings can potentially extend the shelf life and improve the quality of food by the control of mass transfer, gas permeability (O2, CO2), moisture and oil diffusion, and flavor and aroma losses by maintaining mechanical, rheological characteristics, color and appearance of foods. Edible coating also protects the food products from moisture migration, microbial growth on the surface, light-induced chemical changes, and oxidation of nutrients. Edible film and coating materials are biodegradable (Krochta, 2002). In fact, this biodegradability is one of the greatest benefits of edible films and coatings, along with their edibility.
The main film-forming materials are biopolymers, such as proteins, polysaccharides, lipids, and resins. They can be used alone or in combination. The physical and chemical characteristics of the biopolymers greatly influence the properties of the resulting films and coatings. Polysaccharide film-forming materials include starch, non-starch carbohydrates, gums, and fibers. The polysaccharides have simple monomers compared to proteins, which have 20 common amino acids. Due to the large numbers of hydroxyl groups or other hydrophilic moieties in the neutral carbohydrate structure, hydrogen bonds play the most significant role in film formation and characteristics.
Plasticizers are necessary ingredients for edible films and coatings, especially for polysaccharides and proteins. These film structures are often brittle and stiff due to extensive interactions between polymer molecules. Plasticizers are low-molecular-weight agents incorporated into the polymeric film-forming materials to increase the thermo plasticity of the polymers. The addition of plasticizers affects not only the elastic modulus and other mechanical properties, but also the resistance of edible films and coatings to permeation of vapors and gases.
Edible films and coatings can carry various active agents, such as emulsifiers, antioxidants, antimicrobials, nutraceuticals, flavors, and colorants, and can enhance food quality and safety, up to the level where the additives interfere with physical and mechanical properties of the films. Emulsifiers are surface-active agents of a amphiphilic nature that are capable of reducing the surface tension of the water lipid interface or the water air surface. They modify surface energy to control the adhesion and wettability of the film surface.
Besides emulsifiers, antioxidants and antimicrobial agents can also be incorporated into film-forming solutions to achieve active packaging or coating functions. They provide additional active functions to the edible film and coating system to protect food products from oxidation and microbial spoilage, resulting in quality improvement and enhanced safety
Functions and advantages of edible films/coatings
Edibility and biodegradability
The most beneficial characteristics of edible films and coatings are their edibility and inherent biodegradability. To maintain their edibility, all film components (i.e., biopolymers, plasticizers, and other additives) should be food-grade ingredients, all components should be biodegradable and environmentally safe.
Physical and mechanical protection
Edible films and coatings protect packaged or coated food products from physical damage caused by physical impact, pressure, vibrations, and other mechanical factors.
Migration, permeation, and barrier functions
The quality of most food products deteriorates via mass transfer phenomena, including moisture absorption, oil absorption, oxygen invasion, flavor loss, undesirable odor absorption, and the migration of packaging components into the food. These phenomena can occur between food and the atmospheric environment, food and packaging materials, or among heterogeneous ingredients in the food product itself. For example, atmospheric oxygen penetration into foods causes the oxidation of food ingredients, essential volatile flavors of beverages and confections may be absorbed into plastic packaging materials.
Convenience and quality preservation
Edible films and coatings provide many benefits in terms of handling convenience. The reinforced surface strength of fragile products makes handling easier. Coated fruits and vegetables have much higher resistance against bruising and tissue damage caused by physical impact and vibration