Packaging of food

Packaging has become an integral part of the processing, preservation, marketing and even the cooking of foods.

Initially, packages served simply to contain products and to protect them from outside contamination. However, there has been tremendous growth in the development and design of new packages to fit specific needs.

While there has been adaptation of many of the traditional packaging materials, e.g paper, glass, and metals (tin, steel, and aluminium), much of the growth has been due to development of plastic or flexible packaging materials.

Packaging materials may be composed of single component (usually one chemical substance polymeric, building block form) or they may be composed of multiple components, consisting of the variety of materials, usually laminated in layers, offering many advantages not provided by single components.
Packaging of food 

Flexible container of retortable pouch

Retortable flexible containers are laminate structures that are thermally processed like a can.

It is flexible, heat sealable, flat container capable of withstanding the high temperature. The retort pouch is replacing the conventional metallic can to a great extent because of the ability of the pouch to withstand thermal processing and the convenience associated in handling the product.

The materials of the flexible containers provide superior barrier properties for a long shelf life, seal integrity, toughness and picture resistance and also withstand the rigors of thermal processing.

This container represents an alternative packaging system to conventional metal cans and glass jar.

The structure of the retortable pouch used today is made from a laminated of three materials:
*an outer layer of 12 um polyester film for strength
*an adhesive laminated to a middle layer 9-18 um aluminum film as a moisture, light and gas barrier, which is laminated to the inner layer of 76 um polypropylene film as the heat seal and food contact material.

The outer polyester layer gives the pouch strength, abrasion resistance and a surface for printing information about the contents.

The choice of barrier layers, sealant layers and food contact layers depends on the processing conditions, product application and desired shelf life.

Typical processing conditions involve temperatures of 121 ° C for times of up to 30 min.

The advent of the retort pouch processing technology has made availability of shelf stable ready-to-eat (RTE) foods a reality.
Flexible container of retortable pouch

Epoxy in food packaging

Epoxy resins are characterized by the presence of at least two epoxy (or oxirane) groups within their molecular structure.

The group is composed of a planar, three-membered ring comprising two carbon atoms and one oxygen atom.

Epoxy resins containing Bisphenol-A or BPA are used as the inside coating of almost all food and beverage cans. The function of epoxy resins are to provide a protective lining on the interior surface of food and beverage cans to prevent the cans’ contents from contacting and reacting with the metal walls, ensuring sterility.

Many types of internal enamel coatings are available for food containers including epoxy-phenolic, epoxy-amino, epoxy-acrylate, epoxy-anhydrite, vinyl organosol, thermoset polyester, thermoset polymer coated, phenolic, and oleoresinous.

The original can coatings were based on oleoresinous products that include all those materials made by fusing material gums and rosins and blending them with drying oils such as linseed or tung (Chinese wood oil).

Epoxy-phenolic are the commonly used lacquer. They are epoxy resins based on epichlorohydrin and bisphenol.

They are combined with phenolic resins, which re produced by the reaction of phenol with formaldehyde.

This combination gives a gold lacquer with good flexibility, adhesion and chemical resistance.
Epoxy in food packaging