From Storage to Room Temp

• Yeast, whose Latin name means “sugar fungus,” remains dormant when stored in a refrigerator or freezer. To begin working with it in a recipe, manufacturers advise resting it for 45 minutes at room temperature. But the wry experts at King Arthur Flour, admitting impatience, take it straight from freezer to dough without problems. Yeast begins to wake up when it's mixed with liquids warmed to 70 F in bread machines, note Anne Gardiner and Sue Wilson, authors of “The Inquisitive Cook.” Your water needs to be even warmer for certain applications -- 105 F if you mix the yeast with sugar, and up to 120 to 130 F when you mix the liquids and yeast with dry ingredients.

The ‘Death Zone’

• Yeast survives for a while after the shaped loaf goes into the heat. But at 130 to 140 degrees Fahrenheit, the yeast cells hit their death zone. They’ve done their job of releasing small amounts of alcohol for flavor and the gas bubbles that allow your loaf to rise. Yeast also dies instantly if water 140 F or hotter touches it.

What Happens in the Oven

• Before the yeast cells die, there’s a lot of action and intrigue in the hot oven. Yeast produces gas rapidly when the loaf first encounters the heat source, writes Wayne Gisslen in “Professional Baking.” This comes to a halt when the interior temperature of the loaf reaches the 130 to 140 F mark. Production of steam continues before and after this point. A loaf can eventually reach 400 to 425 degrees before you pull it out of the oven, or even 500 degrees for pita breads flash baked on a pizza stone.

Wild Things

• As long as you aren’t blasting your yeast with furnace-like heat, it’s a tough little member of the fungus family that can survive rather well, even without special help. If you bake bread a lot, your kitchen is, in fact, full of wild yeast cells wafting about, which help the purchased yeast in your dough work more vigorously. Yeast also stores indefinitely in the freezer, transferred from vacuum-packed bricks into zippered bags.