“It’s so delicious that I want to eat the packaging as well!” This is turning into reality with edible films. With research being carried out in every field, edible packaging is also evolving and new materials are being used.
An edible film is a preformed thin layer of edible material placed on or between food components. It is different from edible coating which is a thin layer of edible material formed on a food. Edible films and coatings are natural polymers. These are usually obtained from agricultural products, such as animal and vegetable proteins, celluloses, gums, and lipids, and are biodegradable.
For a certain material to be used for making edible films, it should possess certain properties which make them functional. Let’s have a look on the most important ones.
Properties of edible films:
- They are, in general, good moisture barrier. Hence, they are able to inhibit moisture exchange between food product and atmosphere thus preventing microbial growth, texture changes, and undesirable chemical and enzymatic reactions.
- Edible films are also good oxygen barriers, hence able to preserve quality and extend the shelf life of oxygen-sensitive products.
- They are also effective barrier to non-polar aroma compounds, and hence preventing aroma loss and oxidation.
- Edible materials with high water vapor permeability can be used to minimize salt migration into food during brine-freezing processes in case of both edible films and coating. Also, materials with selective permeability can help limiting flavor and aroma loss during freeze-drying operations.
- The materials used are also effective carriers for antimicrobial and/or antioxidant compounds. These are also able to control the migration of molecules from the package to the product.
Materials under use:
Many materials have been used and the properties of the resulting edible films have been compared.
Edible films can be protein-based or polysaccharide-based when speaking in broad terms.
The various materials used so far are the following:
- Gelatin is widely used in the preparation of protein-based edible films. But, it is not a very good water vapor barrier.
- Zein is the most important protein in corn and it is also involved in preparing edible films. It is hydrophobic in nature due to high content of non-polar amino acids. It is a good water vapor barrier.
- Wheat gluten is also employed for this. Gluten films are very effective oxygen barriers but poor water vapor barriers.
- Soy protein is also a popular material due to it’s abundance and low cost.
- Casein, which comprises of 80% of the milk protein, is also used. The edible films prepared using casein are quite flexible but poor water vapor barriers.
- Mung bean protein has great potential for being used in making of edible films. The films prepared using the mung bean protein had superior mechanical properties and water vapor barrier properties.
- Collagen is also used to make commercially successful edible films.
- Starch, chitosan, cellulose derivatives, pectin, and galactomannans are also used to prepare polysaccharide-based edible films. Majorly, potato and tapioca starch is used.
- Quinoa protein-chitosan base films are also in study.
However, the use of edible packaging, both films and coatings, doesn’t always ensure good outcomes. Certain foods show adverse effects because of the application of edible films.
There are a few examples stated below:
Effect of the modified atmosphere
Modification of the internal atmosphere by the use of edible coatings can increase disorders associated with high carbon dioxide or low oxygen concentration. Waxing apples and pears inhibited normal ripening rate and if sufficient wax was applied, respiration was greatly inhibited and alcoholic flavors were developed by anaerobic fermentation. Apples coated with sucrose fatty acid ester had fewer detrimental changes in terms of fruit firmness, yellowing and weight loss but had increased incidence of core flush.
Tomatoes coated with 0.6 mm zein film produced alcohol and off flavors inside the tomatoes which were attributable to an internal gas composition that was too low in oxygen and too high in carbon dioxide.
Issues with the waxy films and coatings
Wax and safe mixtures are the most widely used edible coatings for fruits and vegetables. But, they are not equally effective for all produce. Another problem is that consumers tend to be wary of waxy coatings. Therefore, development of alternative edible coatings which do not impart a waxy taste are desirable. The effects of edible film coatings on internal gas composition and their interactions with quality parameters must be determined for coated fresh produce. For example, color change and firmness are very important quality parameters in fruits. Color change, loss of firmness, ethanol fermentation, decay ratio and weight loss of edible film coated fruits are all important qualities for various products.
Interested in learning more about such things? You can read our article on Edible Packaging to know all that you wish to know.