Does Water Boiled in Microwave Tastes Different？

For years, people with the habit of drinking tea insist that water heated in the microwave tastes different.

Typically, when heating the liquid, the heating source (e.g. furnace) heats the container from below. Through the circulation known as convection, the liquid at the bottom of the container becomes hotter and less dense, and then rises to the top, making the cooler liquid at the top pushed to the bottom and heated. Ultimately, there would be an even liquid temperature.

However, in a microwave oven, there are heating source everywhere. Therefore, the entire container would be heated, and no convection occurs. Also, the liquid at the top of the container would finally be much hotter than that at the bottom.

The team at the University of Electronic Science and Technology of China studied this uneven heating and proposed a solution to this common problem.

The team found that silvering the edges of glass container can eliminate the effects of microwaves to the surface of the liquid. As the guide of the wave, silver can reduce the electric field at the top and effectively stop warming. This leads to a process similar to conventional convection, thus making the temperature more evenly distributed.

Putting silver in a microwave oven may seems like a dangerous idea, but a fine-tuning to the geometry prevents the metal from being ignited in the microwave. Similar metal structure was made safe to be used inside microwaves and rice cookers.

Zeng Baoqing, co-author of the paper and professor of electronic science and engineering at the University of Electronic Science and Technology, said: “After a careful design, the inflammable metal edges are under weak magnetic field, so that it can be prevented from ignition and remains safety.” 

Solids don’t convect. So, how to heat food evenly is a totally different challenge.

Zeng said: “As for solids, there is no simple way to design a bowl or plate to achieve better heating. We can change the magnetic field distribution, but the effect would be little.”

The group is considering other ways to make solid food more evenly heated, but currently, they are too expensive to be applied. Now, they are concentrating on the cooperation with microwave oven manufacturers to commercialize their microwave attachments.