Active packaging may be defined as an approach to packaging that involves the intentional addition of subsidiary constituents to the packaging material or the headspace to preserve and enhance the quality of packed foods. Several active packaging solutions are available that help manufacturers mitigate against food spoilage at various stages of the supply chain. Examples of active packaging solutions include oxygen scavengers, moisture absorbers, and odour absorbers, among others, all designed to extend the shelf life of packaged food products. In this article, we will explore some of the common active packaging solutions available on the market.
Oxygen Scavengers in Food Packaging
The term “oxygen scavengers” is applied to substances that chemically combine with and effectively remove oxygen from the headspace of the packaging environment. Oxygen scavengers may be incorporated directly in the packaging structure, or they may be contained in sachets that are packaged along with the food product. By absorbing oxygen from a food or beverage container, these scavengers retard the proliferation of aerobic spoilage agents and interfere with oxidative degradation reactions. Oxygen scavengers are used in packaging systems for baked goods, snacks, spices, dried fruits, cured meats, dairy products, pasta, coffee, and tea, among others.
Microbiological spoilage is one of the leading causes of food deterioration, and it mostly occurs in the presence of oxygen. This can be attributed to the fact that oxygen provides an ideal environment for the growth of aerobic or oxygen-loving microorganisms. When packaged with oxygen scavengers, foods are maintained in a low oxygen state that discourages the growth and proliferation of aerobic bacteria and moulds that may lead to spoilage. Oxygen scavengers not only minimise the risk of spoilage but also protect consumers from potential exposure to some of these microorganisms.
Oxygen scavengers also play a significant role in slowing down some biologically catalysed oxidative reactions that may occur in certain packaged foodstuffs. As these enzymatic reactions require the presence of oxygen, limiting the availability of this critical reaction component affords packaged foods significantly longer shelf life. With oxygen scavengers, polyunsaturated fats do not develop rancidity rapidly, nor do vitamins A, C and E degrade as they typically would when exposed to elevated levels of oxygen. Oxygen scavengers may also reduce or eliminate the use of chemical preservatives such as BHA, BHT, sorbates, and benzoates, thus preserving the flavour, aroma, and texture of the packaged foodstuffs.
Controlling Moisture Levels in Packaged Foods
Moisture regulation is necessary to protect packaged foods from the accumulation of excess moisture, which may result in a lowering of the quality of the packaged food product as well as deterioration of the packaging. The correct application of moisture control measures mitigates against these adverse outcomes while balancing this with the need to preserve just the right amount of moisture to keep the product quality excellent. As the main purpose of moisture control is to lower water activity (aw), this suppresses the growth of mould, yeast, and spoilage bacteria on foods with high aw, such as ready-to-eat meals.
Normal respiration accounts for evaporative moisture loss from fresh produce, fresh meat, fish, poultry, or other minimally processed foods. Moisture may also accumulate in packaged goods because of condensation or “sweating.” This is a frequent problem among packaged foods, especially fresh produce. This phenomenon occurs when some parts of the package become cooler than others, resulting in condensation in the form of moisture droplets. While this may be desirable in certain products, the appearance of these droplets may decrease consumer appeal and reduce the shelf life of the product.
Additionally, the metabolism of fat, carbohydrates and other biomolecules produces water, and since moist foods tend to have a high vapour pressure, the breakdown of these biological molecules leads to a build-up of humidity in the headspace of a food package. Without adequate moisture control, the accumulation of humidity in the packaging tends to moisten the surface of packaged food products. Soluble nutrients may seep into the water encouraging the rapid growth of mould or other spoilage microbes. This creates a food safety hazard for consumers and potential losses at several points along the supply chain.
Desiccants for Control of Moisture in Food Packaging
Several desiccants and humidity-controlling agents may be employed in food packaging to maintain a constant relative humidity surrounding dry foods and non-food products such as pharmaceuticals. Examples of these moisture control agents include silica gel, activated clays, and molecular sieve. Desiccants may be successfully applied to a wide range of foods, such as nuts, dried fruits, popcorn, and spices. Silica gel is widely used because of its non-toxic nature and high relative humidity tolerance. Molecular sieve is commonly applied to products that require quick protection from moisture-induced degradation as it tends to be aggressive in nature and adsorbs fastest at low relative humidity.
For packaged dried food applications, desiccants such as silica gel, activated clays and minerals are typically contained within tear-resistant, moisture-permeable packets. The amount of desiccant used depends on its moisture-absorbing rate as well as the water-vapour transmission rate of the packaging film and the intrinsic properties of the packaged food, so it is important to choose the best desiccant for each dry packaged food product. The correct choice of desiccant ensures the best product longevity and quality.
As for fresh foods and high aw products, the amount of desiccant applied should balance the need to remove excess moisture while preventing any quality losses on the product. A good example of such an application would be the transportation of fresh tomatoes and avocados at room temperature. If chilled, these foods suffer chill injury, resulting in losses of colour and flavour. If stored at room temperature, this loss is prevented; however, moisture accumulation owing to the high metabolic rates of these food items may lead to rotting. As such, applying a non-aggressive desiccant helps improve the shelf-life without lowering the product quality.
Odour Control and Scavenging Technology in Food Packaging
The world is full of odours that colour our olfactory senses with hues that range from pleasant to obnoxious. In humans, as the olfactory sense is so intricately connected with the sense of taste, the smell of a food or beverage may affect consumer appeal. As the human nose is incredibly sensitive, odour concentrations in the parts per trillion can be detected. Odour controlling technologies allow manufacturers to ward off unwanted odours from packaged products, keeping these products in their best condition for broad consumer acceptance. This section addresses the technologies available for scavenging odour from packaged food through the application of active packaging.
Odour Scavengers Based on Activated Carbon
Activated carbon/charcoal is a treated form of carbon that has the capacity to adsorb and remove several odours. As all smells come from specific molecules or combinations of molecules, odour control depends on agents with a high adsorption capacity for the effective removal of these molecules. Activated carbon serves as an excellent odour and gas adsorbent due to its highly porous nature and large surface area for adsorption.
Activated Carbon-based odour scavengers are popular because of their high efficiency, low cost of production and moisture absorption properties. However, because of their black colour, it may be necessary to contain odour scavengers in sachets or pouches to prevent from mixing with the product and detracting from good consumer appeal. It is also important to use these odour scavengers in a controlled environment as activated carbon can surrender some or all the adsorbed odours when heated or saturated with odour.
Oxygen scavengers along with moisture and odour controlling agents provide great opportunities for manufacturers in the food industry to deploy effective active packaging solutions that guarantee products with predictably long shelf lives. As each product is unique, selecting an appropriate active packaging strategy may be challenging for those without experience in this area. The perfect strategy depends on an in-depth understanding of the origin of the problem and designing an appropriate packaging structure for the specific food application.
By partnering with an active packaging manufacturer with a demonstrable record of accomplishment in the manufacture and supply of active packaging solutions, packaging technologists can develop and deploy the best systems for their unique products. Cilicant helps manufacturers and food packagers develop fully customised end-to-end solutions for their packaged foods.
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