Scientific experiments with bread: steam

I’m not actually going to report on any experiment, simply describe one I’d like to see done and see actual results. On other topics I rant about “experts” making all sorts of wild claims without any actual science (or very sketchy, often cherry-picked) to back them up. Since bread has little controversial aspect, certainly not political, presumably science can be objectively done and reported.

[btw: If anyone actually reads this, please adds some links in comments for any experiments you know]

I have a ton of bread books and have tried to both do the method and understand the principles behind each method. Some books do provide scientific explanations for what they recommend, but few actually provide any links to actual journal articles. A few Net searches reveal there are some journals and some organizations that do research, but the information I can find is fairly limited.

In particular what I’m after is understanding (and then using properly) steam. Usually in the “hearth” baking approach steam is applied. If I could afford, plus have a code-legal place to put it, I’d get myself one of the actual professional bakery ovens with builtin steam injectors. But in home baking in an ordinary oven the choices are fairly limited:

  1. spray a water mist, with variations on how and when
  2. steam pan, with a few variations on that, both quantity and initial temperature
  3. ice cubes, with a couple of variations

The authors of my cookbooks (or online sources) all have their favorite way to generate steam, but nowhere have I seen any experimental data to indicate which is really best.

My most recent book acquisition, Amy’s Bread, actually uses all three (really necessary? can’t they decide which really works?). This is a book by professional bakers who, presumably, at their bakery use professional ovens, so they don’t really provide any data as to why they do all three approaches for a home oven.

Now various books explain, to my satisfaction (but still with no data) the point of steam. When the raw dough hits the heat of the oven immediately the outside is going to get hot and also begin to lose moisture. Bread dough is a fairly good insulator so heat will only migrate slowly to the interior of the loaf. For a brief time the elevated temperature senjds the yeast into high-gear just before it kills them. And while the bread is still very elastic any existing gas bubbles will expand as they warm up until the bread matrix becomes rigid enough to prevent any further expansion. This is the well-known oven spring and critical to a really good crumb.

The point of the steam (or directly misting the outside of the bread) is to either reduce temperature to a level where the developing crust is still very elastic and/or increase moisture and thus elasticity of the crust. This “soft”/elastic outer skin can thus expand and not (at least excessively) confine the oven spring. Of course, slashing the bread gives the developing crust yet another way to expand and thus allow more internal expansion.

OK, fine, makes sense, but it would be interesting to actually have some science about this.

Now what do I mean by ‘science’. Start at first principles/theory, like the Standard Model and attempt for work up from elementary particles to a complex composite. Well, maybe, but that’s probably silly. OTOH, experimental science can help a lot (Sheldon Cooper would roll his eyes). To do a ‘scientific’ experiment really means just being very careful to control and measure all relevant conditions, to anticipate variability in measured outcomes and thus use statistical methods, both simple measurements and then more standardized tests to determine statistical significance (hey there, Nate Silver, any ideas for this project).

At home I think there will be a big problem – simply not enough volume in a home oven to do enough loaves to get results. But I’d assume, with a large baker’s oven (assuming the steam injection is controllable, say in quantity and time, all the way to no steam) we could do the experiment, i.e. toss in a few loaves (using one batch of dough) and bake with steam and without steam and measure results.

But even this simple approach has a couple of issues: a) while the first batch is baking (either with or w/o steam) the dough for the next batch is sitting around and it’s alive and changing, so whatever we measure might be due to that, b) the shape is a relevant parameter, so we’d really need to probably do three shapes: very long baguette, short batard, and boule. If we find a recipe that can make all three shapes that would be nice but that too has some problems, c) the dough recipe, let’s ignore flour type and/or other ingredients, but hydration is clearly an issue, as well as method of rise, d) to deal with the first issue, maybe we’d use two ovens (so dough for all loaves is the same), but then we have to deal with variability of ovens, and, e) finally, I’ll assume results will not be so obvious and therefore we need to repeat the experiment (each variation) sufficient number of times (10?, 50?, 1000?) that we can deduce statistically significant results. Oh yeah, also remembered, f) to slash or not and maybe also how to slash (many cookbooks describe different cuts, of course, claiming theirs are the best).

In short, whew, that’s a lot of baking and a lot of measuring before we have any clear cut idea (meaning evidence, not guesswork) about exactly what steam does. If I had a lot of money, a couple of assistants, and a few weeks, (sorta what America’s Test Kitchen does) maybe we’d get some results.

[I’d love to see results from an experiment like this, does anyone know of any?]

But so much for my gedanken experiment which would merely be a baseline for now considering how to do this experiment in a home kitchen. IOW, I think we’d need to narrow the test conditions, based on the first results, to the circumstances where steam had the greatest effect in the more controllable conditions (steam injectors) before we start messing with ice cubes vs misting.

[Time out, speaking of all this, my oven is up to temperature, time to do my experiment with sample size of 1. Oh terrific, off to a terrible start. The recipe calls for a 1.5 rise on the peel. I normally use semolina (instead of cornmeal) to get loaf to slide off peel, but this is such a wet dough it was totally stuck to peel so getting it off both destroyed the nice boule shape as well as deflated the dough. Wonder what I’ll get (will report in next post). In general I’ve had a lot of trouble getting dough off peel and onto baking stone – so another experiment to try (easier than steam) – how to get that to work. I’m sure bakers with years of experience have no trouble with this, but for an amateur, even with considerable experience this is still problematic for me.]

[Note to new bakers: Be very careful adding water to the already hot pan in your oven. Despite adding boiling water when the water hits the 450F pan it splatters like crazy. This can: a) burn you (I used a long silcone mitt), and, b) break the glass in your oven. Even if you use a water container with long spout (a good idea) this is still a tricky and potentially hazardous step]

Now continuing:

For a home baker without huge time to experiment, I think we’d have to do crude experiments, which I’ll suggest and maybe try. While repetition is required to get statistically significant results, perhaps the effect of steam is large enough that even a single test would reveal some outcome.

So I’d try these experiments:

  1. a cup of boiling water in steam pan seems likely to have the largest result, so try this first: So, simple, make a dough where an extra 30 minutes of rise wouldn’t seem to make much difference and make two boules. Bake the first without adding any water, bake the second with the recipe’s recommended amount of water. Then with a new dough (made a couple hours later than first, but with same recipe), repeat, but in the opposite order. Make sure you remember which loaves are which, cut each exactly in half, measure the height and the width, also making subjective evaluation of crumb and crust. Any difference? Who knows (TBD).
  2. the idea behind ice cubes is that they turn to steam slowly (vs misting which may evaporate very quickly), so this would probably be the next experiment. Repeat the process in #1, with and without the ice cubes. Any difference?
  3. And finally just do misting, say directly on the loaf (or not) and then after a couple of minutes mist the oven (or not). Any difference?
  4. Do Amy’s approach, i.e. all three or none. This probably is the most extreme test of steam (also the most trouble doing the baking), so if this has little effect it’s unlikely the first three will either.

Now without actually doing the experiment I would bet there will be very little difference, but who knows. If there is any difference, then repeat the experiment enough times, measure the data carefully, plot it and do some statistical analysis. And of course, taste the bread. How is the crust? How is the crumb? (probably taste won’t be affected, but who knows, that’s the point of experiments, to find out rather than assume).

If any difference can be detected, then maybe vary the dough hydration (probably more important variable than shape), but maybe also do some different shapes. And if there are any differences, then try some different recipes, esp. varying flour (both protein content in white flour, but also ratios of whole to white flours).

Whew, how long would all this take. I imagine if I did nothing else I could probably do three experiments per day (six loaves). So it would take at least a week to just get results for one shape and one recipe. So probably it would take a month for all the variations (that make sense to try, given there are huge numbers of variations within reach of home bakers). And maybe all that work (and who’s going to eat all that bread!) might yield a result.

So as a final comment I’d like to suggest one more level on this – the so-called power of crowds, aka, group-sourcing. To get any results takes a lot of time, effort, money, plus probably has some ambiguous results. So we need VOLUME of experiments. Now I know there are some good websites and blogs devoted to bread, but if I could get about 50 volunteers as a result of this post (who am I kidding) I’ll volunteer to set up a protocol and mechanism for processing the results – any takers? And if this works, just imagine the other experiments we could do. Maybe in a few years with a few thousand volunteers we could actually write a bread baking book based on science instead of age-old (and possibly wrong) wisdom.



About dmill96

old fat (but now getting trim and fit) guy, who used to create software in Silicon Valley (almost before it was called that), who used to go backpacking and bicycling and cross-country skiing and now geodashes, drives AWD in Wyoming, takes pictures, and writes long blog posts and does xizquvjyk.
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6 Responses to Scientific experiments with bread: steam

  1. dmill96 says:

    btw: I did just find this article which sorta covers the first test I proposed.

  2. dmill96 says:

    And here is a nice experimental setup that also provides some results about steam.

  3. dmill96 says:

    Ah, another method to inject steam I’d never seen before. Soak three dish towels and put these in your steam pan, sounds like a good idea. Other ideas in this post, using various Rube Goldberg setups at home sound too hard to try.

  4. battegays says:

    Dear dailydouq, I just saw your visit to my blog and out of curiosity I visited yours. I am fascinated by your article. I discovered by chance that combining traditional baking with steaming you have much better results. It was actually the oven that insisted in baking this way (no other baking option under chapter bread). It’s quite a new oven, only 2-3 years old, and it will alternate hot air to steaming time.
    I would think that if you find a recipient with a cover that has tiny holes, only a certain amount of steam can come out… so the release would be slower… maybe combined with the idea of filling it with ice instead of water….
    Wish you good luck with your research!

  5. Linda says:

    Try making the bread in a Dutch oven. I didn’t believe it myself until I tried it! Best was that I didn’t even the bread dough neither! :).

    • dmill96 says:

      Thanks for your comment. I’ve used both a Dutch oven and a clay baker to get good results using the Lahey no-knead approach and some variations. I think this is one of the easier approaches to get a very good result. But while it is easy and good it still doesn’t quite approach the results of artisanal bakers with their steam ovens and, so far, I haven’t had as good results with the various “hearth” baking approaches in a kitchen oven. So I still haven’t found the best approach yet but that makes it fun to keep trying.

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