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Packaging technology doubles shelf life

20 June, 2013

The latest European innovation for chilled ready meals is manufactured on a continuous production line and claims it can extend shelf life up to 45 days. If this seems a little hard to believe then read on…

In the supermarket ready meals section the consumer has the choice between a fully frozen product or a chilled product. Presently, the chilled meal  generally commands a premium consumer perception over the frozen range for several reasons.

For example the freezing process can damage the product quality, rendering crisp vegetables into a mush when reheated. The factory freezing process will also dehydrate the meal, and storage in a domestic freezer will continue to dehydrate it. This affects the final quality and eating experience.

The chilled product also has greater visual appeal on the supermarket shelf than a frozen meal as its display appearance is identical to the reheated meal, and the packaging is generally designed to show this off.

And of course the chilled meal is perceived as fresh and healthy, whereas the frozen dinner could be up to 12 months old.

As a result the chilled product also commands a premium market price, and so its popularity amongst manufacturers is increasing.

However, the primary challenge for chilled ready meals manufacturers is the limited shelf life of the product, requiring a flexible production process and slick logistics to optimise the time the product is present on supermarket shelves.

There are two main methods used extensively to extend chilled meal shelf life and still retain that "just made" appeal.

Pasteurisation involves heating the product up post-production to ensure sterility and provide a shelf life of up to 14 days. Modified atmosphere packaging (MAP) displaces air in the package with either CO2, nitrogen or a mixture of both, and can extend shelf life by up to 10 days.

For retailers, wastage rates and discounts are high due to the pressure to sell within the products limited shelf life and the inevitable loss of any product that remains unsold once it has passed its use-by date.

Innovation

There is now a process on the market which claims to extend the shelf life of these meals by 30-45 days (under industry standard chilled storage conditions) while maintianing the quality of their pasteurised equivalents.

The technology was invented in Sweden by a company called Micvac. A range of ready meals products using this process is already being manufactured and sold in one of Australia’s leading supermarket chains.

Firstly, the Micvac process is designed to fully cook the product in the plant, by the use of a continuous industrial microwave tunnel, instead of alternatives such as a spiral oven. This renders segregated high risk/low risk divisions within the plant as unnecessary, as the raw ingredients can be assembled into the tray.

The tray is then sealed and the contents fully cooked within the microwave tunnel. All product leaving the plant has therefore been fully cooked in a sealed tray, and is sterile. The microwave oven provides a very rapid and thorough cook within a small footprint, the cooking performance of which cannot be matched by a spiral oven.

It should be noted that some hydrated products such as rice and pasta require partial cooking prior to assembly due to the differing cooking characteristics of the components of the meal.

This is more than just another microwave cooking technology. The clever part of the  process is the patented one-way valve which is attached to the film that seals the top of every meal. This valve allows the cooking steam to escape from the pack during the rapid microwave cooking process and therefore prevents the pack from exploding.

Once the meal is cooked the valve closes during cooling to ensure the pack remains fully purged and no outside air is allowed back in.

The novel, muti-purpose nature of this valve allows it to serve firstly as described above in the initial cooking process, then as a cooking tool for the consumer when they reheat the meal in their microwave oven.

Once heated, the valve emits a loud whistling noise to indicate that the meal is ready. This is due to the passage of hot steam through the valve exactly as it occurred during the factory cooking process.

Build it and they will come

Mirvac’s innovation is smart in more ways than just how it cooks and re-heats food. The company makes and supplies a number of the unique elements of this new technology, all of which can be implemented into any standard ready meal manufacturing process.

These features will be of interest to the rest of the ready meal industry.

The film that covers the meals and the valves are each supplied in roll form by Micvac. A purpose-built module called a MVU (Micvac Valve Unit) is integrated into your existing tray sealer and applies the valve and the seal whilst the sealer is running. Micvac manufacture the valves themselves to ensure they all meet the required quality standards.

The microwave tunnels are supplied and supported by Micvac from their Swedish base.

The special microwaveable "Flextray" trays are manufactured under licence at various sites but can be obtained through Micvac directly.

Outside of these process particulars any standard ready meals plant would already have the necessary equipment in use to manufacture this product.

Conclusion

The appeal of chilled ready meals is their quality, and authenticity to restaurant quality food. There are other life extending methodologies which will take the product life well beyond 6 months, such as deep freezing or retorting, but products preserved by these methods cannot match the fresh appeal of the chilled product and are proving hard to market to the consumer.

The growth area in the supermarket aisles is in fresh and chilled foods. This sector is predicted to grow significantly over the next 5 years and will outperform the overall growth in supermarket sales displacing tinned and boxed foods from the shelves.

Retailers will be looking for ways to maximise their displays of chilled foods and reduce wastage in this high margin sector. Extending shelf life while maintaining quality is the surefire way of assuring a product ends up on enough shopping lists.

*Martin Bevis is one of Wiley's senior process engineers and has worked on a diverse range of food manufacturing projects in the UK, Europe and Australia.

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