It’s no secret how much a fan I am of the tangzhong method when it comes to making plush, longer-keeping breads, since I use it in so many of my recipes, and I go on incessantly about it here and elsewhere.
For the vanishingly small number of you who don’t know what the tangzong method is yet, it involves adding a precooked flour paste to a bread dough, in order to increase the amount of water it can hold. Flour is about 75% starch, and starches are really, really good at holding onto water once the two are heated together (or “gelatinized”). By adding a precooked starch to a dough, you add what amounts to “stealth” water—it’s in there, but it doesn’t make the dough wetter, because the it is tightly bound up within the starches. But it does make the finished bread softer and slower to stale (the more water in a bread overall, the softer its starches are and the slower they are to crystallize).
Strictly speaking, “tangzhong” refers to the use of a flour-and-water paste, but since the process really involves the gelatinization of starches, there are several other techniques that produce the exact same effect, like porridge breads (where a cooked grain porridge is added to a dough), or potato bread (where cooked, mashed potato is used). While the starch concentration and the type of starch varies from one add-in to the next, the end result is more or less identical, at least in terms of the moisture-retaining effects on the finished bread. (There are other differences, obviously—while potato breads don’t usually taste like potatoes, porridge breads, since they involve the use of whole grains, generally carry the character of the grain within them.)
Because I use the tangzhong method so often, I’m constantly playing around with how it is done. There are a few things about it that I often bump up against and have been working to improve/avoid if possible:
You have to heat the flour and water mixture, which means it needs to cool down before you can add it to a dough, or it’ll muck with fermentation. This is a minor thing, since you can either just wait for it to cool, or use more-cold-than-normal ingredients in the remainder of the dough to bring it down to the proper temperature. Usually the latter approach means adding very cold water or milk, though doing that is not necessarily possible, especially when a high percentage of the water in a dough comes from things other than water, like the eggs in a brioche.
You typically make the paste by heating the flour and water on the stovetop, whisking it constantly while it heats up to avoid lumps. This is generally fine, except for two things: it dirties a couple of extra dishes, and, more importantly, it’s easy to overcook the paste, driving off some of the water it contains, which can muck with the bread’s final hydration. You can get around this by making the paste over a hot water bath (itself sort of a pain), or by doing it in the microwave, in short bursts (which doesn’t always avoid lumpiness, since you cannot stir it constantly).
Three: When—as in the aforementioned high-egg brioche—most of the water comes from an ingredient other than water or milk, there’s sometimes not enough water in the dough to make the paste, or at least not enough water to make the paste in a non-lumpy, easy-to-incorporate-into-a-dough consistency. This problem is compounded when you add a sourdough starter or another preferment, which can tie up all the remaining water. (It’s not possible to feed your starter with eggs instead of water to get around this—trust me, I’ve tried it.)
I’ve yet to land on a consistent, one-size-fits-all approach to tangzhong paste creation, but I recently have started working with something I think gets close.
Enter instant mashed potato flakes. The ones I’ve been using (Whole Foods or Bob’s Red Mill brand) are nothing more than cooked, shredded, and dehydrated potatoes. Thanks to some magic I don't yet understand, the starches they contain remain gelatinized, despite being dehydrated. Which means you can pretty much add them straight into a dough and they will suck up moisture and act as a precooked starch. This also means a) no need to heat up the gel, b) no risk of overheating the gel, and c) no issues with running out of water for other aspects of the recipe (you can even rehydrate the potato flakes with egg if need be).
There is one minor thing to work around: the flakes are flakes and not a powder, so if you want to have them blend invisibly into a dough, you have one of two options. You can grind them in a spice mill or blender to a fine powder (which you can then store for future use and add directly to the dry ingredients in a dough), or place them in your stand mixer with the paddle attached, add a small amount of liquid, and beat the mixture to a smooth paste before adding the remaining liquids (gradually, to avoid lumpiness).
Have I done a proper side-by-side comparing instant mashed potatoes to a flour-based tangzhong in a dough? No, I have not yet (it’s on my long to-do list). But I have made a bunch of nice breads using instant mashed potatoes and they have all the hallmarks of a great tangzhong bread, including the series of recipes for hamburger and hot dog buns that I am working up for the summer 2021 edition of Edible Boston (and to share here eventually, of course). And using instant mashed potatoes in bread recipes is nothing new (even Nigella mentions using them in her latest cookbook).