How to use your microwave safely

It helps get food to the table fast, but there are some essential things you need to know before pressing that 'start' button Behold the West's favourite appliance: the microwave, an effective, no-fuss way to get dinner on the table - fast. Microwave ovens emit radio waves that cause water molecules to quickly flip back and forth. 'That flipping causes friction which generates a lot of heat,' says Dr Catherine Donnelly, professor of nutrition and food science at the University of Vermont. 'The food cooks based on how the water molecules move around in the product.' So, foods with higher water content like soups, sauces and coffee or tea heat up more quickly. But with the controversy over electromagnetic waves, the safety of plastic wraps and containers, and the potential release of harmful carcinogens, many Americans are re-thinking their beloved convenience. Here's what you need to know before pressing 'start': The fine art of defrosting While microwaving is the quickest way to defrost food, it's hardly an exact science. If you've ever tried to thaw a large roast in the microwave, you may have watched part of the meat defrost - and even cook - while the rest remained frozen. The problem: Ice keeps water molecules locked in place so they don't absorb microwave energy. 'Some models have defrost settings which power on for a few seconds and then cycle off,' explains microwave expert Anuradha Prakash with the Institute of Food Technologists and associate professor of food science and nutrition at Chapman University in Orange, California. While the power is off, heat disperses throughout the food, which melts the ice. So when the appliance cycles back on, the food absorbs more energy and thaws more evenly. Healthier heating 'Microwaving cooks food faster than a conventional oven which helps maintain texture, colour, and nutrients,' says Dr Prakash. For example, when you cook vegetables on the stove, water-soluble vitamins like vitamin C and some of the B vitamins dissolve in the water. But microwaving retains these nutrients and keeps vegetables crisp as long as you don't add a lot of liquid or overcook the food. When it comes to cooking meat, place large cuts in the microwave on low power for longer periods of time. This heats the centre of meat without overcooking the edges. Better yet, cut the meat in portions so there's a uniform thickness, suggests Professor Sara Risch of the school of packaging at Michigan State University. Re-heating When re-heating food, use low power, add some water (or other liquid) and keep the product covered to maintain steam and prevent it from drying out. 'Microwave heating isn't uniform, so you're likely to get cold spots in prepared meals,' says DrDonnelly. That's why instructions on microwavable meals recommend stirring the product midway through cooking. Under wraps In general, it's safe to use wax paper, cooking bags, parchment paper, paper plates, plastic wrap and white paper towels (the dyes in non-white towels aren't approved for use in the microwave). Since chemicals from plastic wraps and other coverings may leach into food during microwave heating, experts recommend pulling plastic wrap taut so it doesn't touch food - especially if the food is high in fat. As for aluminium, it doesn't reflect the microwaves, so if it's covering a product, the food won't heat. Containers: The good, the bad Anything that's labelled 'microwave safe' is approved for up to 240 hours in the microwave, so you can feel free to re-use these containers several times. Other containers may be equally safe, but if they aren't labelled, their components haven't been tested and approved. Soft or flexible containers like margarine tubs are more likely to break down quickly and potentially leach chemicals into your food. Better to use the plastic lids that come with the microwave or rigid plastic containers. WHAT ISN'T SAFE: Yogurt, margarine or other plastic tubs. They may warp or melt in the microwave releasing harmful chemicals into food. 'Styrofoam is the worst,' says Mr Prakash. 'I've seen people re-heat leftovers from a restaurant in the same polystyrene container. The compounds that make up polystyrene are not things you should be eating.' Also be wary of imported dishware with glazes since some of these goods are not microwave-compatible. Use the wrong one and you may see sparks or burn your hands. - FEATUREWELL