Reformulated microwave meals could pose risk

Many manufacturers have failed to review the effects of microwaves on products that have been reformulated to reduce salt, sugar and fat, and this could put consumers at risk and waste huge amounts of energy, according to one expert.

Gordon Andrews, technical officer of the Microwave Technologies Association and md of GAMA Microwave Technology, says that the issue is of concern to the entire microwave industry. He claims that even some big UK ready meal manufacturers have omitted to test their products again - often because they no longer have in-house expertise to identify that problems might exist.“We work with probably most of the major microwave food companies in the country: we are calibrating their ovens; we are training them; we are doing all sorts of activities,” said Andrews. “There are two problems: one is the level of knowledge of microwave food engineering, which varies depending on the organisation. But equally in the food industry, you have got such a mobility of staff these days that whatever is known is lost.”

According to Andrews, salt, sugar and fat are three of the most microwave-reactive ingredients likely to be used in a microwaveable food product. He advised that reformulated products should be fully tested and their performance in microwaves re-evaluated so that back-of-pack heating guidelines might be adjusted as required.

“There are ingredients in foods which react - sometimes violently, sometimes not so violently - to microwave energy,” said Andrews. “And if you play around with them you affect the balance of that microwave meal. And if you don’t thoroughly test the product then it leads to all sorts of problems.”

Salt significantly reduces microwave penetration and salt reduction therefore potentially increases energy penetration depth. Sugar is a very good absorber of microwave energy. For example, high sugar jam or fruit-filled pie fillings can easily reach temperatures sufficient to burn a person’s mouth, he said. And fats and oils are poor absorbers of microwave energy, even though their specific heat capacity is relatively low, and with some having ‘thermal runaway’ characteristics as they heat up.

“Many of the food manufacturers removed salt and some of them didn’t test and we had lots of situations where there were ‘volcanoes’ occurring in food simply because the energy was penetrating further,” said Andrews. “In the case of sugar … by all means remove the sugar but in some instances the sugar is there to act as a means of generating heat in desserts, sweets and puddings so that you get more even heating.”

Andrews added: “In the case of fats, most of them are almost transparent to microwave energy, not completely, but of course they only need a small amount of energy to raise their temperature.”

But it is not just for health and safety reasons that the micowaveability of foods needs to be re-evaluated and their cooking instructions adjusted, claimed Andrews. There are also good energy conservation reasons. “You imagine 20M pieces of equipment and saving one Watt of energy, that suddenly starts to become a significant number,” he said.

“Take that through to a microwave meal and everyone assumes a microwave meal is fast,” he added. “But the food research associations and my own organisation are working on systems whereby if the food is correctly cooked and correctly formulated and dealt with in a proper way, you can probably lop a minute to a minute and a half off most microwave-ready meals.”