Metal gets the green light

VR Food Packaging 2008
September 2008

Preparations for the market launch of microwave-friendly metal packaging.

"We're expecting the first microwave meals in metal packaging to be launched at the beginning of next year at the latest", said Jorg Höppner, Managing Director of the German Verband Metallverpackungen (Metal Packaging Manufacturers Association, VMV).

This development has been made possible by the Fraunhofer Institute for Process Engineering and Packaging in Freising/Germany, which has proven in a survey that metal packaging is suitable for use in microwave ovens.

The packaging industry has known for some time now that shallow metal containers with a large surface diameter are microwave oven-safe.

The widespread opinion that metal containers will damage microwave ovens is based on past experiences using outdated technology. When a new generation of magnetrons was introduced in the 1980s, it made microwave ovens robust enough to heat up food in metal packaging without any problems. "The packaging industry has taken the important step of backing up this knowledge with scientific findings. Although advance tests delivered very positive results, a credible study by an independent a credible study by an independent institute was essential to convince consumers and food manufacturers. We even had to educate microwave oven makers", explained Höppner.

The Fraunhofer lnstitute was commissioned by the 'Metal in Microwave Industry Group' - an international initiative - to investigate the safety of tinplate and aluminium packaging far use in microwave ovens. The Metal in Microwave Industry Group is composed of Alcan Rhenalu, Crown Food Europe, lmpress, Novelis, the Association of European Producers of Steel for Packaging (Apeal) and Fördergesellschaft Metallverpack ungen (FGM).

The researchers used five different metal containers of different dimensions and shapes - both round and rectangular - and containers with between 200 g and 450 g content. A 700 watt, 800 watt, 900 watt and 1000 watt house hold microwave oven was used to eliminate potential sources of error. Typical ready meals such as chilli con carne and a children's meal (pasta with vegetables and meat balls in sauce) were microwaved.

One of the containers had tap water in it so that the researchers could test heating efficiency. Egg batter was used to obtain information about heat distribution because it turns from semi-liquid to solid very quickly in areas where heat fields are created in the microwaving process.

During around 1000 microwave heating experiments, which also incorporated the results of a survey in 2006, the institute tested temperature distribution and cooking times in various containers. Under norm al handling conditions and respecting the basic rules of microwave operation (see information box), no sparks were observed and no functional oven damage was found.

The study concluded that the shallow and wide open containers made of aluminium or tinplate are most suitable for use in microwave ovens. AIthough microwave heating times for food in metal containers were longer than in similar plastic containers, there was better heating uniformity in the tested metal containers.

Initial applications prior to market maturity

It is already general knowledge that consumers are using more and more ready meals in their daily eating routines. A recent survey by Datamonitor has also revealed that microwave oven usage is on the increase in Europe and the USA. Modern-day requirements of mobility and fIexibility leave many people with very little time to prepare meals the "traditional" way.
Food manufacturers have responded to these changes by introducing a wider range of convenience products that cook quickly and satisfy modern nutrition requirements.
These ready meals have to satisfy high consumer expectations, otherwise the term "convenience food" would just be a buzzword, and the packaging also has to reflect consumer preferences.
It is important for packaging to be transport-stable, have a long shelf life and to be easy to open.
Environmental considerations are also coming to play an increasingly important role in product choices.
Metal packaging that is "microwave-friendly" is said to satisfy a great many requirements. For example, it offers complete protection against light and air, which means a long shelf life without the need to use preservatives, and it doesn't consume energy because it doesn't have to be stored in the refrigerator.
Metal packaging  is perfect for easily perishable foods and foods that contain valuable vitamins, both of which are sensitive to oxygen and UV light.

The recycling rate for tinplate was 89 percent in 2006, which is considerably higher than the 70 percent rate prescribed by the German Packaging Ordinance.
Unlike other packaging materials, tinplate is not "down-cycled". Both steel or tinplate and aluminium can be recycled an unlimited number of times without any impairment of quality.
"Products in metal packaging have attributes that offer many different advantages. Substantiated proof that metal containers are microwave-friendly will drive progress in the development of new products with the benefit that consumers will have more choice - irrespective of whether their buying decision is influenced by packaging design, convenience aspects or environmental considerations", said Höppner.

Important rules when using metal containers in the microwave

1. The container lid has to be fully removed.
2. Only heat up one container at a time in the microwave.
3. Lace the container at the centre of the turntable and make sure that there is a gap between the container and the oven walls of at least two-and a-hall centimetres.
4. If the oven doesn't have a glass turntable, place the container on a plate.
5. Only microwave full containers.


 

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