1.2. Yeast in breads
Baker’s yeast comes in three varieties: instant, active dry, and fresh. All three
types are the same strain: Saccharomyces cerevisiae. The instant
and active dry versions have been dried so as to form a protective shell of dead yeast
cells surrounding some still-living cells. Fresh yeast—also called cake
yeast because it is sold in a compressed cake form—is essentially a block
of the yeast without any protective shell, giving it a much shorter shelf life (well,
fridge life): cake yeast is good for about two weeks in the fridge, whereas instant
yeast is good for about a year and active dry yeast is good for about two years in the
cupboard.
Instant and active dry yeast are essentially identical, with two differences. First,
active dry yeast has a thicker protective shell around it. This gives it a longer shelf
life, but it also means it must be soaked in water before use to soften up the
protective shell. The second difference is that the quantity of active yeast cells in
active dry yeast is lower than in instant yeast, because the thicker protective shell
takes up more space: when a recipe calls for 1 teaspoon (2.9g) of active dry yeast, you
can substitute in ¾ teaspoon (2.3g) of instant yeast.
Instant yeast is
the easiest to work with: add it directly into the dry ingredients and mix. Unless you
have reason to work with active dry or cake yeast, use instant yeast. Remember to store
it in the fridge!
Note:
If you have active dry yeast instead, you will need to proof it first.
Proofing—soaking in lukewarm water—softens the hard shell around the active dry yeast
granules. Use lukewarm water (105°F / 40°C). If the water is below 100°F / 38°C, an
amino acid called glutathione will leak out from the cell walls and make your dough
sticky; if it’s above 120°F / 49°C, the yeast will show very little activity.
Don’t be worried about too-hot tap water killing your yeast. Yeast actually dies
somewhere above 131°F / 55°C, so too-hot water from the tap shouldn’t be able to kill
the yeast; it just slows down reproduction. You can confirm this by filling a glass
with your hottest tap water, dumping in some yeast, waiting a few minutes to give the
yeast time to come up to temperature, and then adding some flour and watching the
yeast still do its thing.
You can skip all this proofing and temperature stuff by just using instant
yeast.
Yeast Waffles
Baker’s yeast contains a number of enzymes,
one of which, zymase, converts simple sugars (dextrose and fructose) into carbon
dioxide and alcohol. It’s this enzyme that gives yeast its rising capabilities.
Zymase doesn’t break down lactose sugars, though, so doughs and batters made with
milk will end up tasting sweeter. This is why some bread recipes call for milk and
why foods like yeast waffles come out with a rich, sweet flavor.
At least two hours in advance, but preferably the night before, measure out and
whisk together:
1¾ cups (450g) milk (whole,
preferably)½ cup (115g) melted butter
2 teaspoons (10g) sugar or honey
1 teaspoon (6g) salt (table salt—not the kosher or
flaky type)2 ½ cups (300g) flour (all-purpose)
1 tablespoon (15g) instant yeast
(not
active dry yeast)2 large (120g) eggs
Cover and store at room temperature. Make sure to use a large bowl or container
with enough headspace to allow the batter to rise.
Briefly stir the batter and then bake in your waffle iron per instructions of your
waffle iron manufacturer.
Notes
-
In baking, use table salt, not kosher or flake salt, because the
finer-grained salt will mix more uniformly into the batter. -
Try using honey, maple syrup, or agave nectar instead of sugar, and
try substituting whole wheat flour or oat flour for half of the all-purpose
flour. -
If your waffles come out not as crispy as you like, toss them in an
oven preheated to 250°F / 120°C—hot enough to quickly evaporate out water, cold
enough to avoid caramelization and Maillard reactions.
