LPT 311: Milk and Milk Products Technology (1+1)

PACKAGING MATERIALS FOR MILK AND DAIRY PRODUCTS

• The packaging materials include paper and paper based products (coated or lined), glass, tin plate, aluminium foil, timber (wood), plastics and laminates ( Tetra packs)
• Paper and paper based products
  • The paper and paper based products form an excellent packaging material for milk and milk products. They may be kraft paper, grease proof paper, vegetable parchment paper, glassine paper, wax coated paper, plastic coated paper, paper boards, solid fibre boards, liner boards, box boards etc.
  • The papers are used in the form of boxes, bags, wrappers, cartons, cups etc. The advantage of using paper is that it is weightless, capability for printing on the surface, low cost and easy disposability. The disadvantages include low wet and tear strength.
• Glass
  • The glass may be transparent or opaque. Glass is used in the form of bottles, tumblers, jars, jugs etc.
  • The advantages cited for glass as a packaging material include its strength, rigidity, ability to have a barrier for water and gas and inertness to chemical substances. The disadvantage is its heavy weight, and fragility.
• Tin plate
  • It may be made up of a thin sheet (0.025 mm thick) of mild steel coated on both sides with a layer of pure tin. It is desirable to have an internally lacquered can, which provides better resistance to corrosion.
  • The advantages cited for tin containers as a packaging material are their good strength and excellent barrier properties. The disadvantages are their high cost, heavy weight, difficulty in closing the lid of the container, and disposal. The containers are mostly used in the form of can.
• Aluminium foil
  • The common thickness of the foil used is 0.012 – 0.015 mm. To increase corrosion resistance, it may be lacquered (coated with lacquer) or a thin film of plastic can be applied for packing dairy products.
  • The advantages of these containers are good barrier properties, grease proof, non-absorption, shrink proof, odourless, tasteless, hygienic, non toxic, opaque to light, bright in appearance etc. The demerits are its low tear strength, susceptibility to strong acids and alkalis. It is mostly used in the form of wrapper, carton and box.
• Timber
  • The required qualities for the timber to act as a packaging material are it should be free from odour, have an attractive appearance, and required mechanical strength. It may be treated with casein formalin, or sprayed with paraffin wax or plastics or to make it more water resistant and to avoid the passage of timber taint to butter. It is generally used in the form of a box, tub, cask or barrel.
• Plastics
  • The use of plastics in packaging has made tremendous progress in recent years all over the world. A wide variety of plastics can be used as thermoformed, injection moulded or blow moulded containers, such as bottles, cartons, cups, boxes etc. The merits of rigid plastic containers are its low cost and ease of fabrication.
  • The demerits cited are lack of product compatibility, low barrier properties, plastic deterioration, lack of resistance to high heat and fragility at lower temperatures. Flexible plastic packaging films are used as wrappers or sachets or bags or pouches for packaging milk and dairy products. The flexible plastics can be classified in to two types.
• Low polymers
  • They include cellophane (coated with plain or nitrocellulose / saran / polyethylene), treated with cellulose etc.
• High polymers
  • Polyethylene, polypropylene, polystyrene, poly vinyl chloride, poly vinyledene chloride (cryovac), rubber hydrochloride (pliofilm), polyester, polyamide (nylon), saran (a mixed polymer), etc. form good packaging materials.
  • The merits cited for flexible packaging films are they can be easily applied and the packaging process can be readily mechanized; loss of moisture from the dairy product is practically nil; it confers protection to dairy products against attack by microorganisms, insects etc. The demerits are: not all technical problems in film packaging have been solved; failure to obtain a perfect seal and removal of all air before packaging may lead to spoilage; the most careful attention to detail is necessary, else faulty production will result; etc. Care has to be exercised in selecting food grade plastics for packaging of milk and dairy products; otherwise toxicity, if any, from the package will be transferred to the products.
• Laminates
  • They are formed by combining the complete surfaces of 2 or more webs of different films with the primary object of overcoming the defects of single films.
  • Usually laminations are made to strengthen the film material, to improve barrier properties, to improve grease resistance, to provide a surface that will heat seal, etc. Some of the typical laminates available for packaging are paper-polythene, cellophane-polythene, aluminium foil-polythene, paper aluminium foil-polythene, polyester-polythene, etc.
• Tera pack has Internal polyethylene layer seals in the liquid,
• Polyethylene layer needed for lamination process
• Aluminium foil provides a barrier to oxygen, flavours and light
• Polyethylene adhesion layer needed for lamination process
• Paperboard gives stability and strength
• Polyethylene layer protects food from external moisture