| A magnetron in a microwave oven generates | | | | (unless a convection/microwave oven is used). If |
| electromagnetic waves of very high frequency and | | | | browning is desired, it must usually be achieved by |
| very short wavelength, hence the name microwave. | | | | other methods of cookery. |
| When food and similar substances are subjected to | | | | 3. Frozen food placed in a microwave will thaw and |
| microwaves, they absorb energy and heat very | | | | heat unevenly because the ice crystals reflect the |
| quickly. | | | | waves. With raw food there is a danger that thawed |
| The actual heating takes place by molecular friction | | | | patches will start to cook before other parts are |
| within the food itself. This is why the surrounding | | | | completely thawed. |
| area does not get hot. Because different foods | | | | For this reason food should be almost thawed before |
| absorb microwaves at different rates, the heating | | | | being heated. Alternatively, the food may be |
| time varies. Large loads can increase the heating | | | | subjected to short bursts of microwaves with |
| times due to the fact that the available energy in the | | | | periods of rest in between. The higher the starting |
| microwave is fixed. For these reasons the size, shape | | | | temperature, the faster the food will be heated. |
| and thickness of the food must be standardized to | | | | 4. Accurate timing is essential. An error of 30-60 |
| even up the heating time as much as possible. | | | | seconds overexposure can cause overheating and |
| Microwave energy can pass through china and plastic | | | | spoiling. |
| dishes, but is reflected by metal containers or foil, so | | | | 5. Dense (thick) food (such as boiled potatoes) takes |
| they should not be used. It can penetrate food to | | | | longer to heat than lighter food such as zucchini. The |
| about 4cm. Complete heating relies on the transfer | | | | food must be matched for size and density to |
| of heat by conduction from the heated parts to the | | | | achieve even heating. |
| cooler areas. Hence the parts of a plate in contact | | | | 6. Microwave ovens are not suitable for cooking red |
| with the food get hot before the rim does. | | | | meats, but good results can be obtained with poultry, |
| Advantages | | | | fish and foods with an open porous texture. |
| 1. Food can be heated in small quantities very quickly. | | | | 7. The pastry of pies and tarts containing moist fillings |
| It is particularly suitable for heating pre-plated or | | | | becomes soft and loses its texture because of the |
| ready-to-eat food. If it is used correctly, there is no | | | | steam generated from the filling. |
| loss of flavour. | | | | If these goods are exposed to radiant heat such as |
| 2. Hot food can be boosted to correct serving | | | | an infrared light the crispness of the pastry can be |
| temperatures. | | | | restored, but long exposure will lead to dryness. |
| 3. Food can be kept cold and single portions can be | | | | Other pastries can be heated successfully but they |
| heated to order, thus keeping the food fresher. | | | | tend to dry out if kept for any length of time. |
| 4. Waste can be avoided by heating food only when | | | | Summary |
| required. | | | | Microwave ovens are useful for heating food where |
| 5. By combining a microwave oven with conventional | | | | suitably prepared items are required to be served in |
| cooking appliances, cooking times can be shortened. | | | | small quantities over a long time. They are ideal for |
| 6. Microwave ovens are very compact and do not | | | | heating one or two portions of food that has been |
| require extraction canopies. | | | | kept cold until it is ordered. They should be used to |
| Limitations | | | | reconstitute food held at chilled, not frozen, |
| 1. Only one or two portions can be heated at a time. | | | | temperatures. |
| 2. Food will not colour or brown in a microwave oven | | | | |