Tea Blog

The problem with boiling water for tea in a microwave, something that many tea aficionados abhor, is mainly the problem of “super heating.” But what is this and does it impact the flavor of the tea steeped using it?

According to an episode of “Good Eats,” which hubby and I used to watch a lot, the host Alton Brown talked about this phenomenon and how to prevent it. The first thing to note is that water will form a film where the top layer of molecules in a cup or other container, or even in a drop or puddle where there is no motion, will cling together rather strongly, needing a bit of extra effort to break through. When heating water in the microwave, the molecules are heated within their center under that film. The molecules can reach boiling temperature (212° F or 100° C at lower elevations) without breaking the film and roiling (where bubbles burst up through the film in rapid succession). The best prevention, according to Brown, is a stick set in the cup. It breaks the film and allows the roiling to take place when it should, that is, when the water has reached boiling temperature, not much later when it has super-heated to a higher temperature.

Does This Affect Tea Flavor?

Here is that million-dollar question, as they say on the quiz shows. Does this super-heating matter? It does in that some of your water can boil away (turn into steam inside the microwave) and you can get scalded when trying to pour this super-heated water since it will bubble up rather violently when hitting a cooler surface. (You can prevent that by stirring the water a little after removing it from the microwave or letting it sit for about 10-20 seconds.) But affecting taste is a tougher thing to determine.

All I can give you here is anecdotal evidence and some statements by various tea aficionados who seem to be on both sides of this issue (some saying it does affect the tea flavor, and others saying it does not). Hubby and I tend to super-heat the water more often than we care to admit (we heat in the microwave when fixing small amounts of a black tea), even when using that stick. We stir the water to release pent-up bubbles and then pour into the pot. The flavor seems pretty normal to us. To truly tell, though, we’d need to set up a very controlled experiment. The same amount of water heated in the microwave and in a kettle on the stove. The same amount of tea in identical teapots. The same steeping time. And yes, we’ve done this a couple of times. Still no difference.

There is a claim that super-heated and re-heated water has less oxygen, but since the process of boiling does not split the water molecule and merely loosens its bond with its neighboring molecule so that it can float into the air as steam, I do not see how this could be so. The folks who claim that super-heated water is not good for steeping tea and thus decry the use of a microwave for heating water since such super heating is more possible seem to be thinking this lack of oxygen does occur.

Either way, it is probably better to avoid such over heating as much as possible, but not because of any degrading of the flavor of the tea steeped in that super-heated water.

See more of A.C. Cargill’s articles here.

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