A New Technology That’s Now Old Hat - The Microwave Oven

03 July 1999

Which kitchen does not possess a microwave oven today? It heats that cup of milk, cooks a tasty snack or thaws out the chicken earmarked for Sunday lunch. A relatively recent development, the microwave oven is widespread in European households.

In an environment of social change, where working women spend less time preparing meals, the microwave oven is a welcome solution. As well as conventionally made meals, it cooks the plethora of ready-to-eat foods now available on the market. Although a fairly modern invention, the microwave is now a familiar appliance.

How does it work?

Microwaves form part of the electromagnetic spectrum, and their frequency is situated between infrared waves and radio and television waves. Scientists during World War II realised that these microwaves then used in communication systems had other uses. Since then, the early technology has been transformed into the modern, sophisticated kitchen appliance. In an oven cavity, a magnetron transforms electrical energy at low frequency into high frequency microwaves and sends this concentrated energy down a waveguide, which enters the food. The energy makes the water molecules in the food vibrate at 2.5 billion times a second and heating occurs due to rotation of the water molecules.

Don't forget...

As with all food preparation, whether conventional or microwaved, consumers should follow heating instructions on the food packaging and ensure that the food is thoroughly cooked. The depth to which microwaves penetrate a food differs depending on its density. For example, foods like minced beef or pureed potatoes cook faster than denser foods such as steak or whole potatoes. Sometimes microwaved food has hot and cold spots; this is because energy distribution is uneven. Mode stirrers or turn tables in the oven help improve the energy distribution in the food. Microwaves cook food from the outside to the centre. Small food items cook faster than large ones. For this reason, thicker or denser portions of food should be placed to the outside of the cooking dish with thinner less dense ones placed on the inside. One item cooks faster than several. The explanation is that when the energy is divided among several foods the cooking time is longer.

What about vitamins and minerals?

Vitamin retention in some cases of microwaved foods can be even better than in conventionally cooked foods. This improvement is due to the higher energy levels and thus shorter cooking time required in a microwave oven. Minerals cannot be destroyed during food treatment, they can however, be lost in cooking water or meat juices. Studies of a variety of vegetables cooked conventionally, and in a microwave oven, for various lengths of time, revealed a negligible change in mineral content regardless of cooking method.1 Cooking in microwave ovens is safe; it saves on energy and time. A high tech. research result is now a common household technology!


  1. ILSI Concise Monograph, Microwave Ovens, 1998