Waste not, want not

Good packaging reduces food spoilage and increases the shelf life of products. Induction heat sealing is used extensively on PET packaging for foods that contain high levels of oils and fats, although this method can be challenging in glass containers Peter Tindale

According to the Food and Agriculture Organization of the United Nations (UN), 1.6bn tonnes of food worth about US$1.2 trillion is lost or goes to waste each year. That is approximately one-third of the total amount of food produced globally.

There are many reasons for this misuse of resources but the UN says the five key drivers are “lack of awareness of the issue and of possible solutions, inadequate supply chain infrastructure, supply chain efficiency efforts that do not focus sufficiently on food loss and waste, weak collaboration across the value chain and insufficient regulations”.

One factor to consider is how the food is packaged, as this can be part of the problem but also part of the solution. Peter Maddox, director of WRAP, a not-for-profit organisation working to encourage sustainable sourcing and use of the world’s resources, says: “The way food and drink is packaged, labelled and priced can influence household food waste, and retailers and brands are uniquely placed to help minimise food waste in the home.”

If a product is not sealed appropriately, its shelf life can be reduced. The humble induction seal has played a part in increasing shelf life as it creates a hermetic seal on the neck of the packaging container and also reduces leakages and spoilage.

Its adoption by the dairy industry is a good example. With 99% of the UK’s dairy industry turning to induction heat sealing on milk packaging, leakage rates are now at <0.001%. One Australian milk brand experienced a growth in sales and a shelf life improvement for its milk from 12 to 14 days following its introduction on its products.

However, the process of applying the liner to the container, to achieve the desired hermetic, tamper-evident and easily removable seal, is critical to its success. Several key process conditions must be met and maintained throughout the filling operation to guarantee successful container sealing on a fastmoving filling line.

Induction heat sealing is a non-contact method involving close control of three key parameters: pressure, heat and time.

Pressure is needed for the liner to have an even seal to the lip of the container opening and is achieved by the torque heads of the capper when placing the closure onto the filled container. Heat is then applied via electromagnetic induction coils that raise the temperature of the aluminium foil liner sufficiently to melt a thin polymer layer between the foil and the neck of the closure. Finally, the amount of time that the closure passes beneath the induction coil and the following cooling period determines the success of the sealing bond.

Packaging challenges

Research shows that glass and polyethylene terephthalate (PET) bottles are suitable for food contact materials in the edible oil sector and provide adequate protection during oil shelf life.

The PET bottles are usually sealed using plastic press-on hinge closures, or screw lid caps with plastic inners. For foods that contain high levels of oils and fats, such as nut butters and other sauces and condiments, induction heat sealing has been extensively used on PET packaging to achieve a strong seal and promote extended shelf life.

However, the sealing of high oil or fat content products in glass containers is a challenge due to the same process of induction heat sealing being problematic on glass. This makes it difficult for packaging companies to guarantee a fully hermetic seal around the rim of glass containers using induction heated liners particularly when there is a risk of oil, wax or cream from the product being filled contaminating the neck of the container.

Steam-applied metal caps are sometimes used to try to overcome this problem but they are expensive, timeconsuming and not always effective. They are also impossible to remove by hand if the consumer’s grip strength is limited. Selig’s GlassFuze solution, for example, combines increased adhesion to glass with a good resistance to oil penetration.

Perfect peanut butter

For one UK food producer, the oiliness of peanut butter meant its glass jars were not maintaining a 100% hermetic seal and leakage was becoming a source of customer dissatisfaction. Switching to plastic packaging was not an option.

To resolve the issue, Selig replaced the original seal with its DELTASEAL liner, combined with GlassFuze heat sealing technology. The DELTASEAL liner incorporates a polymer lamination between the foil and board of the seal so that when opened, the foil remains on the container, showing tamper evidence.  Peter Tindale is sales director at Selig, a global manufacturer of tamper evident cap and closure lining materials for a range of sectors including food and beverage, pharmaceutical, cosmetics and healthcare