Experimenting with microwaving water for tea

I posted a possible explanation for why microwaving water for tea might not work well, and this follows up on that.

I've microwaved water in the past and experienced that fizzing effect mentioned there.  There's nothing as solid for evidence as experiencing something for yourself.  But since I never heat water in a microwave now I don't have any recent experience of any kind to draw on.  And I've never comparison tasted tea made with water heated in two different ways, so I try that for this.

not how my tea infusion process typically goes

Backing up a bit; why else not to use a microwave for heating water for tea

I never did flesh out the hearsay account of why to not use a microwave in the first place.  That earlier post centered on the one guess for why it might be a bad idea, only related to dissolved air content throwing off texture.  The one World of Tea article I had cited was more about debunking a claim that it's healthier, which could only work so well since that original claim was supposedly coming from research findings, from testing.  It would take counter-example testing with varying conclusions to conclusively reject that, and they didn't do that.

Here are some typical reasons cited in a popular tea blog post, in the Tea For Me Please blog:

Lack of Control

...Although you could certainly use a thermometer to check the water afterwards I would would much rather use a variable temperature electric kettle.

Superheated Water

...I've seen some websites claim that this is not true however I've seen it happen myself. Snopes also agrees with me. Placing something non-metallic like a wooden chopstick into the cup can help avoid this happening but I'd rather be safe than sorry.

It Just Doesn't Taste the Same

It could very well all be in my head but I just don't enjoy tea that was made with microwaved water as much as stove-top or kettle heated water... Some theories suggest that the amount of dissolved oxygen is reduced, creating a flatter tasting cup.

It Makes That Weird Froth On Top

Since microwaved water lacks a nucleation point for air bubbles, it tends to make a weird froth on the surface of your cup once a tea bag or sugar is added to the cup. You all know what I'm talking about. I just can't bring myself to enjoy a frothy cuppa unless the tea in question is matcha.

Temperature control, the first point, is a main factor in making tea, one that comes up a good bit in this post related to testing results.

Lately I've been running across more people claiming they like almost all tea brewed at boiling point or near boiling point, and moderate aspect results by adjusting infusion time instead of temperature.  One person even claimed that can work for green tea.  Personal preference would seem to be a factor in this, that extraction of different compounds would vary by these factors.  It wouldn't seem to work to cite one approach and outcome as objectively best for everyone.  It would seem that any conclusion drawn would relate to a case of a process being best per a preference instead, although some degree of informed consensus agreement about that would also be possible.

On the second point, superheating is possible.  Snopes wouldn't lie about confirming that.  But in general it doesn't seem a high risk, or a big problem.  I guess that's up until you get burned.

That third point about taste is a little non-specific, in the more general first part.  Related to the theory mentioned--"hypothesis," per terminology correction input on my own post, but in standard loose English use "theory" works there--according to the solubility curves of oxygen and nitrogen in water at different temperatures there is next to no dissolved gas in water near boiling point; it just won't hold it.  The real problem seems to be that the air could be leaving the water less effectively based on heating method, even though less really is soluble at that temperature, which seems to be the cause of the fourth and last point.  

I'm not sure what else could cause a tea to be frothy.  I'll move on to trying to recreate that experience myself.

The first experiment

The initial idea was to compare tea made with microwaved water with water heated in the typical Thai version of a kettle, a larger device designed to heat water and keep a store of it hot throughout the day.  It's definitely not the same thing as the better variable-temperature versions more serious enthusiasts might use, but it is what I make tea with while I'm at work.  The water source for both will be the same, bottled water, the type that comes in a dispenser.  This version is from Chang, a beer company that also sells water.  It's a bit off the subject but "chang" means elephant in Thai.

I wanted to use tea bags, which I don't typically use, or actually own any of, since that seems to be the standard set-up discussed in related articles.  My wife did some interpreter work recently and snagged some from a local hotel hosting it, made by Dilmah (Ceylon; Sri Lankan CTC black tea).


Some of their loose teas actually aren't that bad but I don't have high hopes for this version.  Tea-bag tea does tend to be bad, due to using dust or finely ground leaves in order to maximize flavor per quantity and reduce cost, and to brew faster.

Simple enough, right?  I should clarify that I'm not trying to "do science" here, just trying something out, checking on a general range of results.  I'm not tasting it in a double-blind process, and there are lots variables I'm not exploring, and levels of potential test controls I'm not applying.  The idea was that I could just run it again if things seemed inconclusive, and that's how it worked out, as a series of three comparisons.


In the first attempt I initially microwaved the water for two minutes, and it didn't seem at full-boil temperature, so I gave it 30 more seconds--not tightly controlled methodology.  I let both samples brew around three minutes, but didn't time it.

First round results

The microwaved water boiled after the extra 30 seconds; it was boiling when I took it out.  It occurred to me that this might throw off the experience of fizzing water, since it wouldn't take many seconds of agitation from the water being at a full rolling boil to help dissolved air outgass.  That's assuming that my prior interpretation of that potential problem was even accurate.

The cups were really small--just what they had on hand in the office, since I don't have two identical versions of the cup I usually use there--and in the end it was on the strong side, not at all ideally brewed.  I'm really out of practice making tea using tea bags.


The microwaved water version brewed slightly darker.  Upon tasting both I realized there was a temperature difference, that the kettle hadn't been maintaining a full boiling point temperature.  It would've been easy to hit a "reboil" button to adjust for that.  Most likely that alone would throw off any results, using two different temperatures, but I'll still run through my impressions.




That microwaved water didn't seem fizzy, and didn't feel different at all.  The main differences seemed to relate to using slightly hotter water.  That tea version was brewed slightly stronger, which didn't work quite as well.  It's possible that beyond the infusion strength difference the proportion of extracted compounds varying accounted for the cooler kettle-heated water tea being a bit softer.  Altogether the kettle-water version was better, softer, with less harsh astringency and earthy edge, but I'd expect that related most to temperature difference.

not recommended, even for testing purposes

The tea did seem ok as tea bag teas go.  I don't drink lots of those, maybe not quite once a year it comes up.  But I did try a Lipton version recently when traveling, their "international" variation.  It was flat-out awful.  I wouldn't want to drink much of this Dilmah tea-bag tea either but it was at least drinkable plain, without sugar and milk.  It tasted like CTC Ceylon typically does, with a bit of malt, just not as much as in CTC Assam, and a pronounced mineral undertone.  From there somewhat earthy flavor range could be described in lots of different ways (woody, like leather, "tastes like tea").


It wasn't really a success as experiments go.  Giving it that extra 30 seconds probably threw off a chance to experience any fizzing and made for a water temperature parameter split.  I guess at a minimum it confirmed that under those conditions the water heating method results really didn't seem to have been a factor, positive or negative, beyond what I interpreted as temperature difference related.

A second try

I tried it again at work another day, trying to recreate the "fizzy" tea effect and see the difference.  That was based on using the exact same tea (a Dilmah tea-bag Ceylon) and the same conditions.  Results weren't so different.

It didn't work to try and back off the microwave time to achieve the super-saturated air condition.  For whatever reason that water was at full rolling boil at two minutes this time (in the same 900 watt microwave), versus not being that hot in the first trial after that length of time.  Maybe that's somehow related to using a slightly larger cup with slightly more liquid in it (?), made of glass instead of ceramic.  It's hard to guess how those factors would relate to the water heating faster the second time.

The tea kettle had just went through a re-boil cycle so it should have been at full boiling point but it was still very slightly cooler--strange.  There seemed to be a correspondence to cooler water working better, again, for the astringency in the tea-bag CTC tea being moderated by backing off full boiling point temperature.  Using a larger cup and more water made for less concentrated tea, which was better.  Again I was disappointed to not get the "fizzing" to occur, and again didn't notice any texture difference in the water.

It was interesting noting how large a difference that slightly different water temperatures made in the tea aspects, which was more minimal in this test version.  Just a little below boiling point--that water in the kettle had just boiled; I saw the indicator and heard it--was nicer, less harsh and astringent.  Of course I'm not accustomed to drinking much CTC tea, and people who do might often add either milk or sugar to offset that, or both.  It seemed like a better test was going to relate to using a tea I actually like, an orthodox version versus a CTC tea-bag tea, so I tried that the third time.

A third trial, orthodox Assam, brewed at home

I tried the same type of experiment at home using an orthodox Assam I reviewed not too long ago (that Assam Teahaus version).  Again the problem was going to be using water at exactly the same temperature.  I do have a thermometer around the house somewhere, just for that purpose, but I'm out of the habit of testing water temperatures, and didn't turn it up for the test.  I typically use a hot water dispenser that's part of the filtration system for brewing at home, which doesn't provide full boiling point temperature water, but it's not so far off it.  I don't remember results from measuring it from back when I was into checking on that, with that final brewing temperature version varying a lot if based on whether you preheat teaware or not.

The idea was to get the water to that point of supersaturation of dissolved air, just below boiling point, but in three tries microwaving water it didn't really work.

maybe just a little froth, but I was really looking for fizz

That water source I used at home is filtered Bangkok tap water.  It's safe to drink unfiltered, or so they say (and I just happened to read a research paper on that here).  There's also an online water quality monitoring system of remote sensor results seeming to support that claim, but we drink it after it has passed through a three-stage filtration system.

It's probably not an ideal water source for brewing tea, but then people vary on what is.  The best approach is probably to test different waters with different teas to find an optimum.  Per online discussion that might relate to a matrix mapping of bests-per-type versus one best bottled water solution across all types (with a bit on that in this experiment).  I've tried out different forms of water in the past but nothing even as rigidly controlled as this loose microwave-heating testing methodology.  I'm an engineer, not a scientist.  Engineers tend to build as limited models as needed to get things to work and then use functional output testing to make adjustments, versus tightly controlled experimental trials.

Related to the one concern I was curious if this water source (filtered tap water) would contain the same degree of dissolved air as water-cooler large-jar stored water.  I'm not sure; I'm really raising it as a question versus speculating about that.


In the first test the microwaved water was slightly too cool, due to backing off temperature to stop it from going to a full rolling boil, and it wasn't a fair comparison.  I was using a hybrid approach between Western and Gong Fu preparations so getting another two or more comparable infusions wouldn't be a problem, but results could vary slightly based on having the tea more or less "brewed out."


There might have been a little bit of minor bubbling initially but it didn't seem to affect the texture of the tea.  It happened with both heat-source varied water versions during the initial infusion (to both samples), and seemed to relate to the tea getting wet initially, maybe not due to that "outgassing saturated air" effect.  At any rate the texture in tasting the teas didn't seem to vary, or seem off.


On the second try the water temperature seemed more comparable, both slightly off full boiling point by a nearly identical amount (per noticing it, not measurement).  The texture was essentially the same and the taste didn't vary either.  Without pronounced astringency in that tea type to begin with that aspect wasn't a factor, as it had been for the CTC tea.


I tried it again for a third infusion, since producing multiple infusions was the theme, based on using those parameters.  Still no fizzing, and still not really much in the way of difference for results, in any aspect range, for flavor or feel.  It's not really what I expected.

Conclusions

I couldn't reconstruct that fizzing effect in microwaving the water for brewing.  I didn't notice any difference in outcome that probably wasn't tied to slight variation in temperature, and later when that was better sorted out there was no apparent difference.  I'm not saying that microwaved water is as suitable as kettle-heated water, just that in trying direct comparison three times over six different infusions I couldn't get any significant limitation or difference to show up, besides variations related to a lack of temperature control in the trials.

It's not easy to microwave water to get it just short of boiling point.  That stands out more in comparison with a kettle that can perform a temperature control function, since jar-style kettles that sort of maintain a heated water supply do vary in temperature output.  In retrospect I could've just heated the water over and over, to try a half dozen or more cycles instead of just using the water however it turned out.  External factors came into play related to that: sometimes my weekend mornings are well structured for spending two or three hours on a tea tasting process and sometimes they're not.

Maybe microwaving water isn't so bad.  Maybe it is much worse, and I missed noticing that in these experiments.  I suppose that the one time you eventually experience your tea fizzing with that "weird froth on top" could be a deal-breaker.

my three kids at the vet; easy to spot which was adopted