The major categories of materials used for food packaging are glass, metals, paper and paperboard, and plastics. There are many multilayered packaging materials containing either layers of different plastics or combinations of plastics with paper/board, metal or glass.

TYPES OF PACKAGING MATERIALS ::

• PAPER: Paper and paperboard are sheet materials produced from an interlaced network of cellulose fibers derived from wood by using sulfate and sulfite. The fibers are then pulped, bleached, and treated with chemicals and strengthening agents to produce the paper product.


• PAPER BOARD: Paperboard is thicker than paper, with a higher weight per unit area, and is often made in multiple layers. It is commonly used to make containers for shipping, such as boxes, cartons and trays and is seldom used for direct food contact. There are several different types of paperboard, including white board, solid board, fiber board and chipboard.


• GLASS: The production of glass containers involves heating a mixture of silica (the glass former), sodium carbonate (the melting agent), limestone or calcium carbonate and alumina (stabilizers) to high temperatures until the materials melt into a thick liquid mass, which is then transferred to molds.
  
         ADVANTAGES: Glass possesses very good barrier properties, so it maintains product freshness for a long period of time without impairing the taste or flavor, visibility of product, the ability to withstand high processing temperatures.
  
         DISADVANTAGES: Brittle, heavy and non-degradable.


• PLASTIC: Plastics are synthesized by condensation, addition or crosslinking polymerization of monomer units. The thermal and mechanical properties can be partially modified in order to manufacture retortable packages with plastics that have a high melting point, or thermosealable packages making use of plastics with a low melting point and to develop very flexible structures (sachets and wrappings), semirigid structures (trays and tubs) and rigid structures (bottles, closures and tanks).


• METALS: Metal containers are vacuum-sealed and thermally sterilized under low oxygen pressure. The decomposition of nutrients is kept to a minimum in metal containers, since metals are a perfect barrier to oxygen, light and moisture. Aluminum and steel are the most predominantly used metals in food packaging.