My kids and I are big fans of the TV show MythBusters, where the hosts use science to prove or disprove myths such as: Can a can of cookie dough in the refrigerator explode in a hot car ? And what actually happens when you mix Pop Rocks and soda?
Following in their footsteps, I'm here to answer a common baking question: Does salt kill yeast?
Photography by Rick Holbrook; food styling by Kaitlin Wayne
If you've made some bread, you've probably come across a warning about how you should never let salt and yeast come into direct contact because “salt kills the yeast.” But is it true?
Salt is hygroscopic, meaning it readily absorbs water from its surroundings. If a large amount of salt (or sugar, which is also hygroscopic) were combined with a small amount of yeast and left for a long time, it could theoretically rob the yeast of water to the extent that the yeast cells . it would start to die. Research and Development Director Sue Gray explains: “If you add a large amount of salt, say a tablespoon, to 1/4 teaspoon of yeast and let it sit for a while, it may have a negative effect, but not in concentrations. we use in baking.” In most recipes, salt represents 2% of the total mixture (based on the weight of the flour), a percentage low enough that it would never kill the yeast present in the dough. Plus, they won't be in direct contact for long; usually, it's only a few minutes between combining the ingredients and mixing your dough.
So while it is theoretically it is possible that the salt kills the yeast, it is practically not a concern; you can let them touch with no ill effects.
Photography by Mark Weinberg; food styling by Liz Neily
This is not to say that salt has no effect on yeast at all; of course yes. Salt acts as a yeast inhibitor, slowing the growth and reproduction of yeast in the bread dough. This may sound harmful, but it is actually desirable, helping to control yeast growth so that your dough ferments at a controlled rate. (The presence of salt also contributes positively to yeast dough by strengthening its gluten network and helping to brown the crust – read more about this on our blog, Why is salt important in sourdough bread?)
Additionally, adding hygroscopic salt (or sugar) to yeast doughs causes the yeast cells to release some of their water through their cell walls, causing them to dehydrate and shrink. This osmotic shock to the yeast cells results in a short “lag phase” where the yeast doesn't do much of anything. But the yeast can withstand this blow, quickly recovering and entering the “expansion phase” where it begins to produce carbon dioxide that causes the dough to rise.
After all, if you've waited a while and your dough isn't rising and you think your yeast has died, don't blame the salt: Yeast can lose its effectiveness if stored improperly, or if combined with very hot water (above 139°F).
But the main point here: In any normal, practical scenario where a baker would combine yeast and salt, there's no chance that letting the two touch—or mixing them together—would cause the yeast to die. This myth? Destroyed.
Ready to do some yeast baking? Stock now.
Cover picture (Light rye bread) by Rick Holbrook; food styling by Kaitlin Wayne.
