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Since different foods heat at different rates of speed, there are several infl uencing factors that should
be taken into consideration when heating foods with microwave energy.
1. The lower the initial temperature of a food, the longer it will take to heat in a microwave oven.
2. Since with a microwave oven you are heating with time rather than temperature, it is helpful to
know the starting temperatures of the foods. Foods held at room temperature will heat more
quickly than refrigerated foods.
3. The different chemical makeups of foods affect the heating times. Highly salted foods heat faster
than non-cured items. Animal fats heat more quickly than lean parts of meat. Fats in a colloidal
state heat faster than protein (egg yolk cooks before the white).
4. The density of a food is determined by how compact the molecules are arranged within the
food. A pound of roast beef is denser than a pound of bread. Even though they weigh the same,
the bread contains more air and is therefore less dense. Denser foods require longer heating
times.
5. The thicker the food, the longer the heating time. If two foods have the same density, the thinner
food will heat before the thicker one.
6. The shape of the food also affects the heating time. Low round foods that are depressed in the
center heat faster than highly mounded scooped foods. This has to do again with the density.
The denser the mass to be heated, the longer the heating time.
7. The more food placed in the oven cavity at one time, the longer the heating time. This is because
there is a constant level of energy coming out of the magnetron tube during the heating pro-
cess. If there are several food items in the oven, they will each absorb some of the energy thus
making the total heating time longer. The time required for heating is not directly proportional
to the increased amount of food. The heating time should be increased by about 80% for each
additional like food item.
Timing guide
