The principle aim of food packaging is to protect the food from the surrounding environmental conditions. Over the last few years, significant studies establish the concept to use edible coatings and films in food sector as alternative to packaging system.
The main reason of interest and research in edible packaging system is the rising preference of consumer for healthy food products and the awareness regarding the harmful causes of synthetic packaging system.
Edible packaging system can act as excellent carrier of antimicrobials antioxidants and provides several advantages against traditional coatings, such as good spreading, solubility and diffusivity. Edible coatings and films are thin layer of primary packaging of foods and consider edible in nature.
There is a small variation in the terms of coating and film on the basis of their technology. Edible coating is a thin layer of edible semi solid or liquid material coated on a food substance, while Edible film is a layer, made up of edible solid material, which can be coated on or placed between food substances.
Characteristics of edible film and coatings
Consist of non toxic and non allergic components
Give stability to food structure and avoid mechanical damage during handling, display and transportation.
Provide better adhesion to food surface when provide uniform coverage.
Control the migration of water to maintain optimum moisture level.
Give semi-permeability to control equilibrium of gases involved in anaerobic and aerobic respiration and retarding senescence.
Prevent loss of aroma, nutritional, flavor and sensory characteristics require for consumer acceptability while not altering the appearance or taste.
Provide microbial and biochemical stability while prevent contamination, infestation by pest, microbial proliferation, and other forms of deterioration.
Act as carrier for additives such as flavor, coloring agents and nutrients.
Easy to manufacture and inexpensive.
Materials used for edible films and coatings
The functionality of edible coatings and films depend on the material to be used and its main characteristics such as density, solubility, surface tension and viscosity. The main materials including lipids that decrease water transfer, polysaccharides to limit the transfer of oxygen and proteins to provide mechanical power to the coatings and films.
Polysacchaides
The most distinct character of polysaccharide and its derivatives is to provide structural stability and slow down the transfer of oxygen. They are low in cost and extensively used in the preparation of edible coatings and films. They also show ease in availability and better film forming characteristics. Starches and their derivatives like pectin, alginate, gums and chitosan help in the preparation of polysaccharide based films and coatings.
Protein
Protein films and coatings are hydrophilic in nature and prevent moisture uptake. Proteins coatings and films provide better barrier properties, mechanical strength, gases, aroma, lipid passage. The main plant based proteins are zein (corn protein), soy protein, wheat protein. The protein of animal origin include collagen, keratin, fish myofibril protein, gelatin, casein, egg white protein and whey proteins
Lipids
Lipids have good barriers properties against moisture, effective on coating of fruits and raw vegetables, resistant to vapor and gas transfer. The solvent and temperature are the main factors when using lipids as a coating material. The synthetic lipids like waxes and glycerines are also used as lipid coating.
Mixed formulations
Mixed combinations are heterogeneous coating materials in which hydrophobic constitutes are present in hydrophilic mixture. The main purpose is to obtain an aqueous coating with vapor barrier properties. The cellulose and ether are the common material for making mixed formulated films and coatings.
Solvent
Ethanol, acetone and water are the solvents for the preparation of edible coatings and films. Ethanol provides better tensile strength than films prepared from other solvents. Solvents provide better behavior in the environment of high humidity.
Plasticizer
Plasticizers help to improve mechanical properties of the coatings and films. Plasticizer provides both tensile strength, flexibility and permeability in coatings and films.
Other additives
These additives include antioxidants, anti browning agents, antimicrobials, emulsifiers, flavoring agents, colorants and other functional compounds. Probiotic bacteria are also incorporated into coatings and food films to provide active packaging for improving safety of food and providing health benefits.
Application:
- Fruits and vegetables
Edible films and coatings based on cellulose gums effectively slow down ripening process in fruits like mangoes, bananas and papayas. Various studies also showed that whey protein films and coatings can prevent oxidative degradation of fresh cut fruits and vegetables.
Edible films and coatings can be effective as moisture and oxygen barriers in a wide variety of fruits and vegetables In particular, antimicrobial containing films and coatings are recently gaining potential interest in reducing the deleterious effects caused by also minimal cut processing of fresh fruits and vegetables.
- Meat products
Meat and meat containing products are highly perishable food and special attention is required for these products. Three deterioration mechanisms are microbial spoilage, enzymatic autolysis and lipid oxidation.
Based on these facts, the utilization of coatings and films to preserve meat quality for longer periods while maintaining safety, has become necessary. Antimicrobial agents incorporated packaging can prove to be a significant way of preserving meat from microbes.
- Dairy products
This modern packaging system enables the stakeholders to preserve wide variety of cheeses. Bacteria, Yeasts, molds might occur on surface of cheese due to the environmental conditions, which considerably decreases the cheese quality and demands for the development of packaging systems to prevent spoilage.
As an alternative packaging system, edible films and coatings provide development in sensorial and nutritional attributes of cheese and extension of shelf stability of the product.
Conclusion
Edible films and coatings are very effective systems for the future prospective of food preservation and quality during storage. They can be applied where polymer packaging is not feasible, that is, Edible packaging is intelligent packaging because they are both active and selective and have infinite potential use.
The previous literature of edible materials and that of plastic polymers should be applied synergistically for the development of advanced techniques, biodegradable materials and new environmental approaches. Consequently, edible packaging potentiality appears to be a excellent key for future food packaging.
Authors:
1. Syed Shoaib Bukhari M.Sc (Hons.) Food Technology, UAF
2. Summar Fatima M.Sc (Hons.) Human Nutrition and Dietetics, UAF.
3. Muhammad Hassan M.Sc (Hons.) Food Technology, UAF
4. Muhammad Kamran Zahoor M.Sc (Hons.) Food Technology, UAF