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What is Dough Stretching?

Reader Jane happened to mention dough stretching in the comment fields of the below post on sourdough starters. The comment elicited several follow-up questions about dough stretching and yeast in general, which I thought I’d answer here on the main page instead of in the comment fields.

So let’s get down to business: what is dough stretching? It’s pretty much as it sounds — a process by which you gently tug bread dough into an elongated shape as it rises, and then fold it or roll it back up into a lump and let it rise some more. You generally start the stretching at about the mid-point of the initial rise (after mixing your bread dough, but before you shape the loaf).


Baking Powder

Baking powder is a leavening reaction in a can. It’s a combination of baking soda (sodium bicarbonate) and at least one other acid, usually two, and then a little cornstarch to absorb any moisture and prevent the reaction from happening prematurely. As you might expect it’s the combination of acids that determine the way the baking powder performs, since different acids react with the soda in different ways depending on the conditions.


Baking Soda

Sodium bicarbonate (baking soda) is the baking world’s go-to chemical bubbling agent. It’s a crystalline alkaline powder which, once it’s combined with water, dissolves into sodium ions and bicarbonate ions, the latter of which react with acid to create carbon dioxide gas.

That’s all very straightforward, no? However the interesting thing about baking soda is that you can get reactions of different speeds depending on what sorts of acids you pair it with. Common kitchen acids


Baker’s Ammonia a.k.a. Hartshorn

You don’t have to be a chemist to spot a certain pattern in the names of chemical leavening agents. Potassium carbonate. Potassium bicarbonate. Sodium carbonate. Sodium Bicarbonate. All are compounds that release CO2 when they’re either reacted with acids and/or degraded by heat. The logical question at this point is: are there any other carbonate salts out there that do the same job and that you can also safely eat?



Around the year 1775 industrial age chemists discovered that if you expose pearlash (potassium carbonate) to carbon dioxide gas the result was potassium bicarbonate, a compound that’s about twice as potent as regular old pearlash. The creation was dubbed “saleratus”, a Latin word meaning “aerated salt.” The discovery prompted an American entrepreneur by the name of Nathan Read to try making the stuff, which he did by suspending pearlash over vats of fermenting rum which produce — you guessed it — CO2. Very clever indeed. Read’s saleratus came on the market in 1788. But the stuff never really caught on as a leavener, mostly because it wasn’t terribly pure and hence not very reliable.



If you or someone you know is into old (actually very old) recipes, odds are you’ve seen this listed as an ingredient here and there. Pearlash is refined potassium carbonate, an alkaline salt found in wood ashes that also goes by the name potash. Potash was used for a lot of things back in the 1700s and 1800s, especially glassmaking. These days we mostly know it as a fertilizer, but once upon a time it was used to leaven things like corn cakes since it makes bubbles when it gets wet. Given that potash was made from wood ash, its effect on the flavor of corn cakes was as you might expect, but hey, at least the texture was lighter.


Osmotolerant Yeast

I don’t have a picture of this because I don’t have any and you have to special order it in bulk. What, you think I’m made of money? This is a highly specialized form of instant yeast, actually a different yeast species called Pichia sorbitophila. It was discovered in 1980 infecting a container full of 70% sorbitol, a sugar alcohol. That’s a heck of an unfriendly environment for any small critter, and when it was discovered that sorbitophila produced as much CO2 as other fermenting yeast species (Saccharomyces cerevisiae, Zygosaccharomyces rouxii, Debaryomyces hansenii) a product was born.


Pizza Yeast

This is a new, you might say “novelty”, yeast the was introduced to the American market in 2010. It’s a form of rapid-rise yeast which as the name implies is specifically intended for pizza makers, more specifically inexperienced pizza makers who want a quick dough that they can mix, shape and bake in 30 minutes. It’s an interesting idea…I don’t know how well it’s selling but it’s received a lot of positive reviews.


Why use packaged yeast at all?

Several readers have written in to ask this question, and it’s a good one. Now that home bakers are so widely using bread starters and preferments, why bother with the packaged stuff since it delivers inferior flavor even if the rise is faster? I can think of a few reasons.

Concentrated yeast cultures — brewer’s yeast or packaged yeast — work faster and so create lighter, fluffier breads. Bakers, especially those living in cities, have known this for centuries. These urban dwellers are people who’ve historically had access to brewery leftovers as well as more finely-milled flours. That’s why in general their breads tended to be more toothsome (at least when they weren’t full of sawdust and mice) if not the most flavorful.


Rapid Rise Yeast

As the name implies this is the fastest-rising of all the various packaged yeasts. A version of instant yeast, it’s made via similar methods but the granules are even narrower and thinner…almost rod-like if you can see them. That means they absorb moisture and dissolve even faster, so they start working, reproducing and making CO2 almost immediately.