PACKAGING :


Introduction

The availability of flexible packaging material with wide range of permeability's to gases and vapours has sparked an interest in the use of these materials to extend the refrigerated shelf-life of highly perishable foods. By replacing the air surrounding the food with an optimum mixture of nitrogen, carbon dioxide, and oxygen prior to sealing at atmospheric or reduced pressure shelf-life can b extended from days to weeks.
Factors affecting cost-effective use of controlled atmosphere packaging include:

	Chemical and biological activity of foods
	Microbial contamination
	Product formulation
	Storage temperature
	Susceptibility of the product to chilling injury
	Consumer packaging preferences
	Product tolerance to high and low oxygen and carbondioxide concentrations.

The level of packaging and the chemical and biological activity of foods can be organised in a matrix to show how modified and controlled atmosphere can be used to help extend the shelf-life of perishable foods. Packages can be grouped as: impermeable, selectively permeable and highly permeable systems. Foods can be grouped as having minimal chemical activity, chemically active, and biological active foods.

MODIFIED ATMOSPHERE PACKAGING (MAP) :

The function of this packaging system is to extend the shelf-life of the product and, in some cases, allow it to be presented in more palatable manner. The shelf-life extension is achieved, as the name implies, by "modifying" the atmosphere inside the structure. Generally, this is done by injecting gas mixture inside the container-either carbondioxide, nitrogen, oxgyen or a combination before sealing.
The kind of film used in MAP also a roll in determining the shelf-life . In most MAP applications, conventional multilayer, high barrier films such as five-layer LDPE blown film with EVOH, Nylon or PVDC is used as the barrier layers.

There are certain features that controlled or modified atmosphere packaging will not accomplish. First, it will not replace refrigeration. It will inhibit microbial growth but it will not reduce the need for good manufacturing practices and sanitation. In fact, controlled and modified atmosphere packaging must be combined with good sanitation in order to achieve significant shelf-life extension.
A third major development involving modified atmosphere applications is with red meat and poultry. Experiments and commercial tests using gas mixtures of 50% carbon dioxide and oxygen have proven this mixture useful in extending the refrigerated shelf-life of prime cuts of beef. Colour which is dark on opening returns to normal red on exposure to air. Microbial growth is inhibited by the carbon dioxide, while the oxygen maintains the respiratory activity of the meat.
Poultry has been packed in multiple retail units with carbon dioxide flushed over the pack. The bulk package extends shelf-life during distribution prior to retail display. Fish portions could be prepacked and handled in a similar manner. In these cases, carbon dioxide inhabits microbial growth at refrigerated temperatures. It should be remembered that microbes are living plant cells. High concentrations of carbon dioxide inhabits the metabolic activity of many microbes. In summary, modification of the gas atmosphere surround foods combined with selectively permeable films can result in significant shelf-life extension, particularly at refrigerated temperatures. Applications include individual seal wrapping of produce, cuts of meat and bakery items. In the case of living foods, such as meat and produce, films or atmospheres must be selected to prevent the development of gas concentrations harmful to food quality. For products such as bread, pure carbon dioxide is useful in inhibiting mould growth. For products affected by oxygen, vacuum or nitrogen atmospheres, perhaps with hydrogen or oxygen scavenging systems, are desirable.

COMPOSITE PACKS :

In the packaging of many food product, composite packs can offer considerable advantages over alternative systems. A new process has recently been developed to overcome certain limitations felt earlier like low through put compared to, say cans or jars, and the fact that many containers are supplier pre-assembled making them difficult and expensive to store.

The new process allows the production of a wide variety of shapes and sizes.

The composites consists of four basic elements - body, base, membrane-lid and cap. The main body comprises a composite material consisting of a light weight high impact core of expanded polystyrene in the thickness range 0.6 to 1.2 mm. Externally, the core is coated with a plastic film. The inner face is coated with a plastic film or a combination of a film and aluminium foil, the function of these materials being to ensure optimum barrier properties against moisture, oxygen, etc. on contact with other elements which might adversely affect the pack contents. A wide choice of films is available, including, for example, PET, PVDC, or EVOH. The base, like the lid and Snap-On cap, are generally moulded from high impact polystyrene (HIPS) coated with a PET or other film to enhance barrier properties. The base is solid moulding, where the lid incorporates membrane, which is pierced to give access to the contents. Typically the membrane lid would comprise a heat-sealed paper / plastics film laminate. The cap is for Snap-On type with reclosability. For security, a tear tape can be provided between the Snap-On cap and body of the composite. Also, a hinge can be fitted to link the lid and end cap.

This is an overview of the Packaging Trends in the pipe-line.