Packaging trends: the past ten years

Food packaging is traditionally required to have many functions: to contain and protect the food, to provide a surface for information labels, to add a distinct brand identity and to present the food attractively so that consumers will purchase it.

The packaging area is probably the fastest developing part of the food industry, and one where innovations are constantly being developed. The two biggest changes over the past ten years have come from two different fronts. For example, various ‘green’ measures have been introduced, in response to an increasing concern with the impact that food packaging can have on the environment. Alternatively, using technology to tell us more about food and its condition, or using technology to enhance the quality and safety of food.

Green Packaging

Although food packaging has a small environmental impact, comprising less than three per cent of food waste on average, consumers feel that they would like to see products packaged with less material. This is sometimes referred to as sustainable packaging. Collectively, packaging that is of minimal impact is efficient, renewable and recyclable. In response to this the packaging industry has developed a range of solutions:

• Packaging light weighting means thinning down the packaging that is used in a product, or using an alternative packaging for the product that delivers a weight saving. For example, improvements in barrier technology mean that the packaging film can be a few microns thick. The walls of beverage cans have thinned considerably, such that they no longer provide support when stacked. The solution is to inject a small amount of liquid nitrogen into cans as they are filled; this expends to gaseous nitrogen and keeps can walls rigid under load. Light weighting has also been developed for glass, and for PET drinks bottles.
• Flexible pouch technology instead of metal cans has been used for retorted products. Some packaging suppliers have developed vertical and horizontal form fill alternatives to thermoformed lidded trays for fresh vegetables, greatly reducing the quantity of packaging.

Better film design has meant that instead of two or three different film types used as a multilayer barrier, the same type of film can be used in a multilayer film, allowing for recycling.

Often, biodegradable and renewable go hand in hand; for example, polylactic acid (PLA) is a biodegradable polymer that is being used in bag and tray applications. It is developed from corn starch and other feed stocks. It is produced by bacterial fermentation of starch to lactic acid, which is then made into the polymer. The development of renewable plastics depends upon availability of feed stock and conversion technology.

Smart packaging

This is sometimes split into packaging that can sense the environment and convey information – ‘intelligent packaging’, and the ability to change the internal packaging environment in response to internal and external changes – ‘active packaging’. Examples of the former include food freshness indicators, time/ temperature indicators, and RFID devices. Examples of the latter include self-venting films, self-heating or cooling packs, gas scavengers and emitters. Packaging can be termed ‘active’ when it performs some desired role in food preservation.

Modified Atmosphere Packaging (MAP)

The use of MAP has grown considerably over the past ten years. New developments include the use of argon used instead of nitrogen for some applications, as it has a beneficial effect on reducing food spoilage. Other changes have included the use of MAP in new applications, or expansion into new products in existing areas; for example, fresh produce, fresh meat, poultry and fin fish, ready meals and bakery products.

Oxygen Scavengers

Oxygen is a major cause of food deterioration causing oxidation of fats and oils, enzymic discolouration and the growth of aerobic micro-organisms such as moulds, many yeasts and bacteria. Oxygen scavengers have been the subject of considerable research and are the most commercially important type of active packaging.

The commonest method is to place iron powder in a small, highly oxygen permeable sachet, which is then often placed under the label in the pack. These scavengers are able to reduce oxygen levels to less than 0.01 per cent, which is less than the residual levels of 0.3-3.0 per cent achievable by MAP.

New developments have used polymeric scavengers requiring UV activation. These systems can be subjected to conventional extrusion processes, providing the potential to incorporate scavengers within the body of films and mouldings.

Some barriers that have been developed are microwaveable; they are used in soup containers, for example. Some are activated by water, and are incorporated into the wall of a container, to minimise oxygen uptake and flavour change in beer, for example.

Carbon dioxide emitters

Carbon dioxide extends shelf life by preventing or slowing microbial growth. As well as the addition of carbon dioxide to the pack in MAP, some oxygen absorbers have been developed which emit an equal amount of carbon dioxide to the oxygen absorbed, in order to prevent pack collapse. Other carbon dioxide emitters act to replace the carbon dioxide which can permeate through the packaging material.

The majority of carbon dioxide emitters on the market are available in sachet form, with the active agents being ascorbic acid, sodium hydrogen carbonate and ferrous carbonate.

Ethylene scavengers

Ethylene is given off by fruit and vegetables as they ripen and age. It accelerates the respiration rate and ripening process; control of ethylene helps to extend the shelf life. The most effective ethylene scavenger systems have used potassium permanganate immobilised on inert minerals such as zeolites or silica gel. Activated carbon and titanium dioxide offer possible alternatives and avoid the objections to using potassium permanganate which is toxic and hence cannot come into food contact.

In recent years a number of produce packaging films and bags have contained finely ground minerals. The films are usually coloured green to prevent UV entering the pack.

Active releasing concepts – anti-microbial

The growth of micro-organisms is a major cause of food deterioration for several foodstuffs, and as a result, considerable research has been carried out in this area to study the effect of the release of anti-microbial substances from packaging materials.

Ethanol emitters

Ethanol has anti-microbial properties and a number of applications using sachets have been patented. The effectiveness of ethanol as an anti-microbial agent depends on a number of factors, in particular the quantity of ethanol emitted. Too low a level and the ethanol is not effective; too high a level can result in taint.

Moisture absorbers

Excess moisture is a major cause of food spoilage and many examples of moisture absorbers exist. Several companies manufacture moisture absorbers in the form of sachets, pads or sheets. In dried foodstuffs, desiccants such as silica gel, calcium oxide or activated clays are contained within a tear resistant permeable plastic sachet. Drip absorbent pads are made from two layers of sheet, often of cellulose fibre and an inner layer of high absorbent polymer granules such as polyacrylate salts, or super-absorbent polymer coated fibres.

Flavour/odour absorbers

In general these take the form of films impregnated with composites used in rigid/semi-rigid containers and flexible packaging. Possible applications are for fruit juices to reduce bitterness, whole fish, for the removal of amines and a range of foods containing oil for the removal of aldehydes.

Edible films and coatings

Edible films and coatings are produced from edible biopolymers and food- grade additives. Films are a separate structure, usually thin; if thicker they are called sheets. Coatings are films applied directly to the product. Polymers can be proteins, carbohydrates, gums, or lipids, singly or in combination. Plasticisers and other additives are combined with the film forming polymers to modify the functional properties of the film. Uptake is dependant upon consumer acceptance and regulatory issues; they must be made of food-grade, non-toxic materials.

They have been used for some time in various applications, from wax coatings on fruits and confectionery, sausage casings made from collagen, and coatings for delicate products, such as nuts, or bakery products to protect from oxidation and/or physical damage.

New applications include the use of edible films and coatings to deliver an active concept, for example an antimicrobial, or to reduce water vapour, oxygen, carbon dioxide or ethylene transfer into or out of the product.

Market value of active packaging

A survey conducted in the US showed that desiccants and oxygen scavengers were the most commonly used types of active packaging, with about 1000-1500 million units of the former, and 1500-200 million units of the latter, per annum. Annual growth was about 12-15 per cent, from 2003-2006. The next most popular were drip control pads, with 700-750 million units per annum, and a growth of 38 per cent over 2003-2006.

Future trends

Sustainable or green packaging is going to remain the major item on the packaging agenda for the foreseeable future, with the increase in environmental concerns at the local, national and global level. Light weighting, alternative technologies, biodegradable and products made from renewable resources will form the core of this movement.

Amendments to the food contact regulations within the EU permitting active and intelligent packaging should allow for an increase in the use of this technology for this market. Active packaging will continue to increase its market share in the new technologies, as it can deliver cost effective spoilage and safety control for minimal environmental impact.