Microwave ovens are used daily, in restaurants, cafeterias, snack bars, and almost every household. This is despite the fact, that the full effect of microwaves on food is not fully understood. A recent food agency enquiry summary, confirms the absence of a full risk assessment and knowledge.
A microwave oven cooks food by exposing it to microwave radiation, (electromagnetic energy). On contact with food, this energy causes rotation in the water molecules. This movement produces friction between the water molecules, causing them to heat rapidly, and thus heat the food.
In comparison to traditional methods of reheating food, microwaving is notorious for the lack of crust formation, and the severe toughening of flour and starch based products. The low surface temperature is responsible for the lack of crust formation. The worst toughening is caused by the internal boiling of the water molecules. Beside water loss, the internally generated steam causes two main textural effects when it is vented out. The first being the replacement of non-condensable gases, (air), in the product voids, with a condensable gas, (steam). When the steam cools and condenses, a vacuum may be created in the voids, causing their collapse. The result of this is the formation of a more compact and tougher structure. The second mechanism is mainly relevant to products in which starch is an important structural element. This textural effect involves the extraction of amylase from starch granules, which is redistributed, to eventually form a heavy layer on the walls of the structural foam cells of the baked food.
The use of a microwave oven to heat food can destroy much of its nutritional value. What started as nutritious food may be rendered nutritionally valueless. This is caused by the dielectric heating utilised by microwave ovens. Studies have shown that food exposed to microwaves loses 30 to 40 percent of its Vitamin B12 content.
When microwave heating foods contained in plastic, carcinogenic contaminants pass from the plastic into the food. This is exacerbated if single use containers are reused. Due to 2.4 GHz radiation emitted by microwave ovens, the body can be instantly affected. A common cause of this is leaky door seals. How many people routinely get their microwave serviced?
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