How edible packaging material for future sustainable growth?

Edible packaging film are stand-alone structures that have the appearance and protective functions similar to synthetic polymer films. However, they comprise edible proteins, polysaccharides, lipids and resins, and other components that render them edible. 

Thus, it can be consumed with a packaged product, resulting in less packaging that requires disposal. Also, since edible films are made from renewable resources, they contribute to packaging sustainability.

Usage of edible packaging material

Edible films by convention have thicknesses ≤of 10 mils ( ≤0.254 mm), above which they would be considered sheets. It can be used as food wraps, and some can be formed as food casings or can be heat-sealed into pouches for food products. 

Edible packaging on foods

Edible film packaging can also be included as coatings directly on the surfaces of food and pharmaceutical products, thus becoming a part of the product.

Present uses of edible films include:

Collagen casings on sausages inhibit moisture loss and oxygen transport and provide structural integrity.

Hydroxypropyl methylcellulose (HPMC) pouches for premeasured food and beverage ingredients.

Gelatine capsules for pharmaceuticals to improve product appearance, structural integrity, ingestibility, and stability.

Dissolvable breath strips are made from several different edible materials.

Edible packaging material- shellac and wax coatings

Present uses of edible films as coatings include shellac and wax coatings on fruits and vegetables to prevent moisture loss and improve the appearance; methylcellulose (MC) and HPMC coatings on fried foods to reduce fat update; shellac, wax, and zein coatings on confections and drug tablets to provide moisture resistance and improve the appearance; and MC and HPMC coatings on drug tablets to enhance product stability appearance and ingestibility.

Enhance the quality of the product with edible coating

Edible films and coatings are generally seen as having considerable potential for applications far beyond present uses for improving product quality and safety. 

In addition to controlling moisture, oxygen, aroma, and oil transport and protecting products from mechanical forces, edible films and coatings can act as carriers for edible antioxidants, antimicrobials, and other additives.

Furthermore, edible films can be positioned within food products as separate layers to reduce the migration of moisture, lipids, and solutes from one food component to another. In some instances, edible films and coatings can reduce the use of synthetic packaging films. 

However, they are not intended to eliminate the need for nonedible protective packaging. Instead, it is designed to work with conventional packaging to improve product quality and shelf life. 

Protecting layer by Edible Packaging

To the degree that an edible-film wrap, casing, pouch, capsule, or coating functions to protect the product from the environment, the amount and complexity of nonedible protective packaging can be reduced, leading to source reduction and improved recyclability. 

For example, an edible pouch for premeasured dry milk powders used in bakeries may only need a recyclable paperboard box as a secondary package. Or, an edible oxygen-barrier coating on roasted peanuts could eliminate the requirement for an oxygen-barrier layer in a flexible pouch, resulting in a single-layer moisture-barrier package that is more easily recycled. Also, after packaging is opened, an edible coating can continue to protect the product.

Edible Film Regulations

Components of edible films must meet the same rigorous standards applied to all food ingredients. Materials used in the formation of edible films must be generally recognized as safe (GRAS) for the intended use or sanctioned by the U.S. FDA Code of Federal Regulations or the U.S. Pharmacopoeia/ National Formulary (or equivalent). 

It is also necessary that all edible film components be included on the product label to provide information critical to consumers with allergies or intolerances to particular food components.

A. How is Edible Packaging Film Formed?

Film-forming materials available for edible films generally fall into polysaccharides, proteins, lipids, and resins derived from plants and animals.

Protein film formers include collagen, gelatine, casein, whey protein, corn zein, wheat gluten, and soy protein. Polysaccharide film-forming materials include cellulose derivatives, starch and starch derivatives, carrageenan, alginate, pectinate, and chitosan. Layering and blending of proteins and polysaccharides show potential for optimizing film properties.

Films can also be produced from purees of foods such as fruits and vegetables, containing combinations of ingredients. The polar hydrogen-bonding character of polysaccharides and proteins produces films that have

(a) high moisture permeability

(b) low oxygen and lipid permeabilities at lower relative humidity, and

c) compromised barrier and mechanical properties at higher relative humidity.

Edible lipids and resins include carnauba wax, candelilla wax, beeswax, triglycerides (e.g., milkfat fractions), acetylated monoglycerides, fatty acids, fatty alcohols, sucrose fatty acid esters, and shellac. 

Lipid and resin materials are not polymers and, therefore, do not generally form coherent stand-alone films. However, they can provide gloss and moisture-barrier coatings on food or drug surfaces or constitute a composite film’s moisture-barrier component.

Composite films can consist of either: –

(a) a lipid layer supported by a polysaccharide or protein layer or

(b) lipid material dispersed in a polysaccharide or protein matrix.

Materials used for edible films also can replace synthetic polymers in some nonedible Films, including replacing synthetic polymer coatings on paper or other synthetic plastics. Besides being derived from renewable resources, they are biodegradable. When used as coatings for paper or plastic, it can be more easily separated to make the paper or plastic more easily recyclable.

B) Plasticizers Nature of Edible Film Packaging

Like synthetic polymer films, edible films often require the incorporation of low-molecular-weight plasticizers to improve film flexibility and durability. Plasticizers generally interrupt polymer chain-to-chain interactions and lower the glass-transition temperature (Tg), resulting in greater flexibility and, unfortunately, increased film permeability.

Plasticizing materials acceptable for edible films include sucrose, glycerol, sorbitol, propylene glycol, polyethylene glycol, fatty acids, and monoglycerides. Depending on the composition, size, and shape of the plasticizer selected for a particular polysaccharide or protein film-former, barrier properties relative to mechanical properties’ improvement can be minimized. 

Water is also a plasticizer for polysaccharide and protein edible films. Thus, film moisture content affected by other plasticizers’ content and the surrounding relative humidity can dramatically affect edible-film properties. 

Other Additives Edible films can be considered active packaging because their edibility provides a function beyond the passive barrier. Edible films show promise for being functional by incorporating antioxidants, antimicrobials, nutrients, nutraceuticals, flavors, and colors to enhance food safety, nutrition, and quality. For some food-coating applications, the addition of surfactant to a film formulation may be necessary to ensure good surface wetting, spreading, and adhesion.

Edible Film Manufacture 

Methods for forming films include a wet (solvent) casting method and a dry (extrusion) method. Besides solvent casting, lipid films and coatings can also be formed from a melt.

Solvent Casting

This approach to forming edible films from aqueous, aqueous–ethanol, or ethanol solutions or dispersions is similar to producing certain synthetic films (e.g., polyvinyl chloride) by solvent casting. 

The solution or dispersion is spread on a smooth surface. After the solvent evaporates, a film can be stripped from the body. Except for collagen, corn zein, and wheat gluten, most polysaccharide and protein film-forming materials are soluble in water. 

This can be an advantage in terms of film manufacture and use but makes films whose properties are especially vulnerable to moisture.

Corn zein and wheat gluten films must be formed from aqueous– ethanol solution or an aqueous dispersion but provide a somewhat improved moisture barrier compared to other protein-based films formed from aqueous solution.

Wax films, layers, or coatings can be formed from ethanol solution. Edible-film production that requires ethanol necessitates appropriate safety measures and solvent recovery for commercialization.

Water-insoluble whey protein films result from heat-treated aqueous whey protein solutions due to denaturation and subsequent intermolecular crosslinking of individual whey protein molecules. 

Edible films from methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) are manufactured commercially by solvent casting on a continuous belt, with subsequent drying, removal winding the resulting film. 

Such films can be formed into edible, water-soluble pouches for food ingredients; HPMC capsule shells are highly used in Pharmaceutical packaging, especially where Moisture sensitivity is a concern.

Gelatin capsules cast from aqueous solutions find broad use in the pharmaceutical industry. Hard capsule halves are formed on steel pins by dipping into gelatin solution, followed by drying and removal from the pins. After a drug is filled into a challenging capsule half, two interlocking halves form the entire capsule.

Soft capsules containing a drug or vitamin are formed from two previously developed sheets of plasticized gelatine by injecting the drug when the two sheets are brought together between the rotating halves of roller dies. 

Polysaccharide–lipid bilayer films with excellent moisture-barrier properties have been produced from aqueous– ethanol solutions of cellulose derivatives with lipids. As the solvent evaporates, phase separation results in bilayer formation. 

Lipid layers or coatings can be formed directly from ethanol solution or aqueous emulsion. Stable emulsions of lipids in proteins or polysaccharides produce well-dispersed composite films with improved moisture barrier compared to protein or polysaccharide films alone but low moisture barrier compared to bilayer films. Research efforts continue to develop composite edible films with good moisture-barrier properties.

Molten Casting

A melt cooling can produce lipid films, layers, and coatings to have a solid structure. Challenges include the high temperatures required for some melts, film thickness control, adhesion, and brittleness of some 458 FILM, EDIBLE materials. Forming a lipid layer from a melt on a precast polysaccharide or protein film is an alternative approach for manufacturing an edible composite film with good moisture-barrier properties.

Extrusion

Water-insoluble, edible collagen film sausage casings and meat wraps are made by regenerating collagen extracted from animal hides. Collagen casings and wraps are produced by extruding a viscous, aqueous suspension of purified acidified collagen into a neutralizing coagulation bath, followed by washing, plasticizing, and drying. Some polysaccharides and proteins display thermoplastic behavior, and this property is being explored for edible-film production by thermoplastic extrusion. Successful, efficient production of edible films using conventional extrusion equipment would improve commercialization opportunities.

Usage for food and drug coatings

The formation of edible films as coatings on foods and drugs generally consists of solvent casting directly on the food or drug surface. Application of film-forming solution, suspension, or emulsion can be by dipping, spraying, dripping, or enrobing.

Edible packaging for food – Fruits and Vegetables

Edible coatings on the whole and minimally processed fruits and vegetables generally serve to reduce moisture loss, improve appearance, and, in some cases, control oxygen and carbon dioxide exchange and carry an antimicrobial. 

Materials commonly used include beeswax, carnauba wax, candelilla wax, shellac, and mineral oil. These materials cannot form stand-alone films but form continuous coatings on the fruit or vegetable surface. 

Film coatings based on polymeric materials such as cellulose derivatives, chitosan, and proteins have been developed to reduce oxygen and carbon dioxide exchange for respiration and ripening-rate reduction. 

Coating solution or emulsion is most typically sprayed or dripped onto the fruit or vegetable and onto a bed of brushes rotating either below or above the product, followed by drying. 

Thorough distribution of the coating over the whole fruit or vegetable is dependent on a clean, dry produce surface and suitable surface tension and viscosity of the coating formulation. 

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