When baking with yeast, remember that it is a living thing, and living things can be killed. So treat it right and then get out of its way.
That’s not to say that it’s volatile and will blow up in your face. But, if you abuse your yeast while attempting to whip up a sweet baguette; you will be disappointed because the yeast will quietly retreat and leave you with unleavened bread.
The way yeast makes your bread or rolls rise is by fermenting the carbohydrates in the dough and “chang[ing] it into carbon dioxide gas and alcohol.” The gas that is released is what makes the dough rise and what gets released in puffs of yeasty air when you punch the risen dough down.
Yeast is a tiny plant and can be hurt or killed if its circumstances aren’t conducive. One way it can be killed is if it’s surrounding temperature is wrong. Being a bacteria yeast likes to be kept in the temperature that most other food should be kept out of to prevent harmful bacteria from growing and multiplying. Therefore, when you cover your dough and set it in a warm moist place, the place should ideally be 70 to 90 degrees. Keep the area below 70 and you’ll find that the bread doesn’t rise as well and at 45 degrees or lower the yeast will freeze up and shut down. However, if your room gets above 100 degrees the fermentation will also slow down and above 140 degrees will kill it dead.
Working with yeast has a great deal to do with timing as well; and perhaps more importantly, patience. Breadmaking is not a quick endeavor and one might be tempted to skip a couple of yeast crucial steps to save time, but please don’t. First of all to pre-activate the active dry yeast that most people bake with, it has to be warmly moistened. Soak it in four times it’s weight in warm water, and mind the temperature guidelines written above, don’t put it in water warmer than 90 or you risk its death.
The most important part of turning a yeast dough into a soft bread product (well, besides baking it) is letting the adequately dough rise. Cover the dough and give it the necessary hour to rise to twice it’s size. Don’t rush this step or think that you can skip it entirely and rely on the heat of the oven to let the yeast work, because the above 400 degrees required to bake the dough will kill the yeast.
Punching the dough down is important as well. Don’t punch it too hard, just enough to let all that air out. Follow these strong suggestions and your yeast will be the helpful part of your dough that it should be.
Gisslen, Wayne. “Professional Cooking”.