My post this week comes from a friend who asked:
How warm does the water have to be for the yeast to proof right? (Is, in fact, the temperature of the water related to the proofing of the yeast?) I was always taught to do lukewarm water (it’s possible my water is generally more than lukewarm—does that kill the yeast?) and then add some kind of sugar/honey for the yeast to eat, and then it will all work out right. But it never seems to bubble up quite like I want it to. How to change this?
This question made me automatically think back to the classes I took, and a formula we had to use whenever we made yeast breads. To get very technical for a moment, the recipes we used in our ‘professional’ book listed a temperature for the dough, usually anywhere from 78°F to 86°F. This is the temperature at which the dough should be for the best fermentation/proofing results (yeast has its best growth from 70°F-90°F). To figure out the right temperature for the water we had to multiply the desired dough temperature by three, then subtract the room temperature, the flour temperature and the machine friction temperature.
For example, a recipe for brioche in my book says that the dough temperature should be 84°F. Multiply that by three to get 252. The room temperature was 64°F, the flour was 58°F, and we always used an average temperature of 20°F for the machine friction. Take 252 and subtract 64, 58 and 20, and we get 110, so the temperature of the water should be 110°F. I can remember holding my thermometer under the water until it reached the right temperature, filling the measuring cup, and taking the temperature of the water again in the cup just to be sure. We also used fresh yeast for our recipes, so it didn’t need the initial proofing. However, the book instructs that if you are using active dry yeast, it should be “rehydrated in four times its weight of warm water (about 110°F).”* If the water is too warm it can definitely slow down the yeast’s growth, and warmer still will kill the yeast (140°F).
If you don’t have a digital thermometer, don’t worry. It would give you a more exact temperature, but it’s certainly not mandatory in order to get good bread. You can measure the temperature of the water like you would for a baby’s bottle. If the water feels hot on the inside of your arm, it’s probably too hot for the yeast; if it feels lukewarm on the inside of your arm, it’s probably okay; and if it feels cool on your arm, it’s probably too cold.
There are several other factors that can affect how your dough proofs.
- Adding sugar or honey will definitely help speed up yeast’s growth. Yeast consumes the sugar and turns it into carbon dioxide and alcohol – the gas contributes to the leavening, and the alcohol is evaporated while baking. Extra sugar is not absolutely necessary, in fact many of the recipes I have don’t even call for sugar when you’re initially softening the yeast. As you make the dough the yeast feeds on sugars in the flour, but added sugar (as long as it’s in the recipe) can speed things along. If you have too much, it may make it go too fast, which can cause it to over-ferment and not come out very well.
- Dough proofs best from 78°F to 86°F, so if you have the dough in a cool room it may not rise as well; conversely, if it is too warm it can slow growth, or kill the yeast (so don’t proof it on the vent of the oven as it preheats like I used to). I’ve heard several people say they use the top of their fridge, as it is generally warm to being with, and it is higher up in the room (warm air rises).
- The length of time needed can vary. It is important to follow the recipe’s guidelines, but if your proofing temperature is higher than normal it will likely take less time than what the recipe calls for. It’s best to just pay close attention to the dough and watch for when it has actually doubled in bulk.
The most important thing is to keep trying. If it didn’t work well, adjust something for the next time and see if it makes a difference: add a little more (or less) sugar; try letting the dough rest in different places; try different temperatures of water; try different types of yeast if you have them available (active dry, instant, or fresh). Just make sure you keep track of what you did so you remember what works well. Happy Baking!
*Gisslen, Wayne (2005). Professional Baking (4th edition). Hoboken, New Jersey: John Wiley & Sons, Inc. p. 51.