Tuesday, January 7, 2014
A (not so) Nice Cup of Tea
Wolke is a former chemistry professor at the University of Pittsburgh, and his cookbook is a mix of recipes, short articles and FAQs, all clustered around the literal science of food and cooking. Here's what he has to say about this post's topic:
When I make tea with microwave-heated water, why doesn't it taste as good as when I make it with teakettle water?
Microwave heated water isn't as hot as kettle-heated water, even though it may look like it's boiling.
Water for tea must be boiling hot in order to extract all the color and flavor. Caffeine, for example, won't dissolve in water that's much cooler than 175 degrees. That's why the teapot--or if you're a bag-at-a-time brewer, the cup--should be preheated, to prevent the water from cooling too much during brewing.
When you've got a full, vigorous boil going in a tea kettle you know that all of the water is boiling hot--around 212 degrees. That's because the heated water at the bottom of the kettle rises, to be replaced by cooler water, which then becomes heated and rises, and so on. So the entire kettleful reaches boiling temperatures at pretty much the same time. The bubbling further mixes it to a uniform temperature.
But microwaves heat only the outer inch or so of the water all around the cup, because that's as far as they can penetrate. The water in the middle of the cup gets hot more slowly, through contact with the outer portions. When the outer portions of the water have reached boiling temperature and start to bubble, you can be tricked into thinking all of the water in the cup is that hot. But the average temperature may be much lower, and your tea will be short-changed of good flavor.
Another reason that kettle-heated water is better is that heating a cup of water to boiling in a microwave oven can be tricky.
Happy cookbook review!