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The Impact of Too-Hot Water on Yeast

By Cook's Illustrated Published March 2014

There's a real risk of using water that’s above 120 degrees in yeasted doughs—no matter what manufacturer instructions say.

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We recently noticed that the instructions on some instant and rapid-rise yeast products recommend using 120- to 130-degree water for making bread doughs—curious, since those temperatures are dangerously close to the range at which yeast rapidly dies: 130 to 140 degrees.

According to the manufacturers, their reasoning is to “guarantee yeast activity.” However, we suspect that the true intent is to guarantee yeast activity that is both rapid and visible. We know that yeast is perfectly active when combined with water at far colder temperatures (we use ice water when proofing doughs for days to develop flavor)—the yeast just “wakes up” very slowly. Using hotter water would appeal to bakers for whom seeing dough bubble and rise (and seeing this happen quickly) is believing.

We advise patience, not only because such hot water can kill the yeast, which means that your dough won’t rise, but also because at the very least it can negatively affect the structure and flavor of the finished bread by encouraging overproofing or overheating during mixing. Both result in overactive yeast, which creates sour flavors and loss of dough structure (i.e., less rise) through overproduction of acids and carbon dioxide.

To see the impact of too-hot water on dough for ourselves, we made dinner rolls, pizza bianca, and cinnamon swirl bread using 130-degree water and compared these baked goods with control batches made with water at the temperatures called for in our recipes (none of which went higher than 110 degrees). The higher-temperature water affected the rolls the least: These rolls were pretty close in appearance to the control batch, although several tasters picked up on a sour flavor. The pizza bianca and cinnamon swirl bread made with 130-degree water suffered significantly. Both were more dense and squat than their controls and tasted slightly sour. But perhaps most notably, while initially the proofing for all three recipes happened more quickly using 130-degree water, by the second hour or so, these hot doughs had cooled down, the proofing had slowed, and all the control versions had caught up. In other words, there’s no real timesaver in using water that’s above 120 degrees in yeasted doughs—and there’s a real risk of ruining them.

OVERHEATED: 130-degree water stunts rise.

SAFE AND SURE: Room-temperature water lets yeast do its job.