By Greg Hooper - 10 June 2011

Selecting the correct packaging and providing good heating or reheating instructions is as important to the quality and safety of heated product as is the effort spent creating the product. I have seen many a potentially good product spoilt by poor packaging shape and materials and inadequately developed cooking or reheating instructions.

I spend my working life advising clients on the development of microwave and conventional heating instructions that will bring the best out of their product. Whether for conventionally or microwave heated foods, there are sophisticated technologies for assessing heating regimes to get an in-depth understanding of heating effects on product safety and overall quality.

Instructions for the reheating or cooking of foods should be developed to ensure that all areas attain a safe heat process and prevent a reduction in the organoleptic quality caused by overheating of edges or certain components.

Techniques used for instruction development

The trials performed and instrumentation used depend on the nature of the product under investigation and the heating method. In all instruction development projects the time-temperature history of the product is monitored and recorded, using either thermocouple or fibre-optic temperature measurement data logging techniques.

The use of calibrated or performance assessed appliances is crucial. Did you know that two correctly rated microwave ovens (e.g. 850W/ E category) can heat a particular food at different rates and give rise to different hot and cold spot temperatures and locations? This is why it is so important to use a wide range of microwave ovens for developing instructions. Reliance on a single microwave has caused many problems and will continue to do so!

Knowledge of the heating profile is important to ensure that the process permits a sufficient reduction in food poisoning organisms, should they be present. The time-temperature data generated from the instruction development trials can be used to determine the exact lethality of the heating process. Monitoring the temperature of the food during heating can also indicate if and where problems may occur with overheating. Steps can then be taken in the instruction design to reduce these effects.

Packaging considerations

The selection of the appropriate package shape and material is imperative to the safety of microwave heated products. Unlike conventional hot air ovens, the maximum temperature of microwave heated foods is not governed by the oven air temperature. Microwave heated food temperatures can increase until a particular food component (e.g. water, fats, sugars) either boils or starts to smoulder. This can lead to problems with packages melting and the associated risks of possible ignition of the plastic and the migration of plastic components into the food.

It is essential to enable the consumer to adequately reheat or cook the product in question - for both safety and quality reasons. For microwave foods, knowledge and understanding are needed of the unusual way they are heated, in order for reliable instructions to be calculated.

But ultimately, whether the product is designed for microwave or conventional heating by the consumer, investing the effort into getting the heating instructions correct is an essential part of delivering the quality of product you want the consumer to experience.

About Greg Hooper

Greg has worked here at Campden BRI since 1990, after studying Applied Science (Physics and Chemistry). As part of his extensive knowledge and experience in thermal processing and microwave cooking, he was instrumental in setting up the microwave heating category rating system used in the UK, and has travelled internationally assisting and advising on the safe development of microwave products and rating systems.

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