Food packaging is something that we rarely think about unless the package is torn or damaged in some way. Yet packaging is an important component of the foods we buy. Not only does packaging protect food from external contamination; it also serves a whole host of other functions.

The role of packaging

Food packaging is an essential technique for preserving food quality, minimising food wastage and reducing the use of additives. The food package serves the important function of containing the food, protecting against chemical and physical damage and providing convenience in using the product information to the consumers.

Whether it's a can, glass bottle or jar or cardboard, packaging of our foods helps to protect it from contamination with microorganisms, pests and other contaminants. Packaging also helps to protect the form, shape and texture of the food inside, prevents the loss of flavours and odours, extends shelf life and regulates the water or moisture content of the food.In some cases, the choice of packaging material may affect the nutritional quality of a product. For example, opaque packaging such as cardboard cartons on milk products means that less of the light-sensitive vitamin riboflavin is lost from exposure to sunlight.

Packaging also provides an important medium whereby manufacturers can provide information on product features, nutritional contents and ingredient information.

Newer food packaging

Just as with other aspects of food technology, the area of packaging has undergone some innovative product developments to help ensure a safe and more nutritious food supply. One method of packaging that may be used for products such as coffee and spices is vacuum packaging where the product is placed in a plastic or aluminum foil pouch and most of the air is removed. The package around a food allows the internal atmosphere to be retained so the food stays fresh and safe.

Modified atmosphere packaging (MAP) relies on altering the composition of gases in contact with the food by replacing air with a single gas or a mixture of gases. This is then combined with low temperature storage of less than 3 °C. The aim of MAP is to exclude or greatly reduce oxygen levels, to retain the moisture content of the food and to inhibit aerobic microbial growth.

While this method of packaging works well to inhibit the growth of strict aerobic spoilage bacteria, many bacteria associated with foodborne illness, such as Clostridium spp., Campylobacter spp. and Listeria monocytogenes, are not affected to the same extent. Fortunately, there are other means to control these bacteria such as controlling the moisture levels and the pH of the food, as well as monitoring storage time and temperature.

The choice of packaging material depends on the recommended storage temperature for the food, the relative humidity of the package and the effect of light, if any, on the contents. Vacuum packaging and MAP are useful for high fat foods as they help prevent the fats becoming rancid by reducing the exposure to oxygen.

In "active packaging" materials are added to modify the composition of gases during storage. Oxygen adsorbers present in the food package help to reduce the level of oxygen in the package. This in turn reduces the growth of aerobic microorganisms and delays the deterioration of fats.

Packaging to suit busy lifestyles

In response to today's busy lifestyles, there is now a wide array of foods that are ready to be cooked - without even leaving the packaging!
"Sous-vide" is a technique in which food is vacuum packed then heated to extend the shelf life while still retaining the nutrients and the taste and texture of the food. Before eating, food is reheated in the packaging, which finalises the cooking of the food.

Some products are specifically packaged to be prepared in the microwave oven. These products generally use heat-resistant plastic materials for the containers such as crystallised polyethylene terephthalate (CPET) or polypropylene (PP).

Food safety

One aspect of packaging that is important in the area of food safety is the identification of a product that may have been tampered with or unintentionally damaged in some way during production or shipment. Some manufacturers use a variety of tamper-evident packaging such as vacuum-sealed pop-tops and special seals to indicate if a food package has been damaged or tampered with. Foods in dented cans or punctured wraps should not be eaten as the food may have become contaminated with harmful microorganisms.

More on Packaging

Research into the best and safest ways to package foods has progressed considerably in recent years. In particular, a lot of research has been undertaken into the best choice of packaging materials for different foods, especially the interaction between foods and packaging and the environmental impact of different packaging materials. A future issue of Food Today will look at advances made in these areas.

Tips on food safety

Packaging helps to ensure the safety and quality of foods. Here are some further tips on keeping foods safe.

• Read and follow the storage conditions on the food package.
• Don't buy cans or packages that are torn, damaged or disfigured in some way.
• It's a good idea to wash the tops of drink cans and bottles before drinking from them or use a straw as dust may settle on the products during transportation and storage.
• Don't wrap foods directly in newspaper as the ink from the print may contaminate the food.

References

• Briggs DR and Lennard LB. Recent Developments in Food Technologies in "Food and Nutrition, Wahlqvist (Ed) 1997
• Food Technology and Public Health. World Health Organization of the United Nations

FOOD TODAY 06/2002