Active and intelligent packaging
Food packaging has many functions and in its most basic form it is used to prevent food from coming into contact with contaminants, whilst also making items easier to handle as they pass through the supply chain. As packing technology has become more advanced, active packaging has been developed which is capable of performing additional functions such as:
• Decreasing microbial growth
• Extending shelf life, and
• Retaining food quality by preventing undesirable flavours or colour changes from developing, or nutrients from being lost.
Intelligent packaging, on the other hand, monitors the state of the food within the packaging or surrounding environment and relays this information to the food processor, retailer or consumer. Because the materials used in active and intelligent packaging come into direct contact with food items, there are EU regulations that specify how this packaging should be used and what it can be made of. Materials can only be added to an approved list once their safety has been assessed. However, due to the high costs associated with some of these packaging technologies they are not always widely used.
Active packaging is designed either as an active layer incorporated onto traditional packaging material or as sachets containing active compounds, that are included inside the packaging. These are the main ways it is used:
• Releasing beneficial compounds into the packaging, for example preservatives or flavours.
• Removing or absorbing undesirable compounds, for example the plant hormone ethylene.
• Controlling the temperature of the product using self-heating and self-cooling components.
• Preventing microbial growth by treating the inner surface of the packaging.
Ethylene is a colourless and odourless gas that acts as a plant hormone and plays a key role in initiating fruit ripening. When fruits produce or are exposed to ethylene they begin to ripen and their tissues start to soften. If this ripening begins too early during transport or storage phases, prior the fruit being purchased by the consumer, it can lead to increased food waste. Active packaging that incorporates ethylene absorbers therefore reduces spoilage and increases shelf life.
Modified atmosphere packaging
Modified atmosphere packaging is a form of active packaging where the composition of the air surrounding the food product is altered to extend its shelf life and retain its texture and colour. This technique is applied to perishable food products such as fresh fruit, vegetables, meat and fish. The most commonly used gases are oxygen, carbon dioxide and nitrogen.
Consider a bagged salad. When salad leaves are harvested, they don’t enter a dormant state but continue to respire which uses up starches, sugars and organic acids in the leaves and oxygen from the surrounding atmosphere, producing carbon dioxide and water. This process of respiration can ultimately reduce the quality of the product as the breakdown of proteins, carbohydrates (especially sugars) and fats leads to a loss of colour, nutrition and flavour. The production of water also causes moisture to build up inside the packaging (if it’s not permeable), which creates an environment suitable for bacteria and mold to grow in.
Respiration cannot be completely stopped but the use of modified atmosphere packing can slow it down and therefore enhance the shelf life of fruits and vegetables. This is achieved by reducing the concentration of oxygen inside the packaging and increasing the levels of carbon dioxide. The earth’s atmosphere is composed of approximately 21% oxygen but in modified atmosphere packaging, it is typically reduced to between 2-14%.
Meat products have different modified atmosphere requirements. Consumers typically prefer to purchase red meat products that have a bright red appearance, as they associate this with freshness. One way of achieving this colour throughout the shelf life is to package red meat in a high oxygen (80%) and carbon dioxide (20%) atmosphere. The high concentration of oxygen helps the bright red colouration, whilst the high carbon dioxide concentration inhibits the growth of spoilage bacteria.
Intelligent packaging is capable of informing the consumer, or others within the food supply chain, about the state of the food (freshness) or the environment that the food has been kept in. For example, some forms of intelligent packing incorporate a sticker that changes colour if the product is kept above or below critical temperatures, as this could indicate it might be unsafe for consumption. Researchers are also investigating indicators that detect different aspects of food quality as these could potentially replace use-by dates. Having more dynamic use-by dates could help improve food safety and reduce food waste.
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