The pressure was high during Bread Week as the bakers vied for a Paul Hollywood handshake after making a variety of, well, bread. The signature challenge asked bakers to make a batch of monkey bread, a sticky pull-apart bread made from balls of dough layered and baked in a Bundt pan. The technical challenge then requested bakers make a dozen “ring doughnuts” and the showstopper challenged them to assemble tiered sweet breads.
Some bakers struggled with presentation, giving judges misshapen, funky-looking bakes. Others failed to cook their bread entirely. But the greatest difficulty proved to be activating yeast — a tricky yet crucial step when making leavened bread and similar baked goods.
Working with yeast can be daunting, but it doesn’t have to be with the right guidance. Here to answer all our yeast-related concerns is Trung Vu, chef-instructor of Pastry & Baking Arts at the Institute of Culinary Education’s New York City campus.
What kinds of baking yeast are widely available?
“There are three main types of commercially available yeast. You can get yeast either in active dry form, which is probably the most common. You can also find instant yeast in most supermarkets as well. It’s very similar to active dry yeast and even looks almost identical to active dry yeast. The third type of yeast is fresh yeast, which also goes by compressed yeast or cake yeast. It will look completely different from the other two types of yeast because it will already have a water content inside of it, so it usually comes wrapped in plastic. And it’s not as easily found in a lot of supermarkets, but it can be bought at specialty stores.
Active dry yeast has to be activated in water or a liquid containing water. Instant yeast can also be activated by whisking it together with water. Some chefs don’t do that, though. They will add instant yeast directly into things like flour, because even though it looks very similar to active dry yeast, the granules are a lot smaller. When the yeast granules touch any type of moisture in the dough, they become activated.”
How is yeast activated?
Yeast is activated in water or through moisture. It needs to survive, because yeast is an organism just like you and I, and we need the same things. We need water and we need food, which the yeast gets from the simple sugars found in most flours. So for instance, if you’re using all-purpose flour or bread flour to bake your bread, the yeast can eat the simple sugars inside of those flours and then break them down into carbon dioxide gas, which leavens the dough, and lactic acid. The lactic acid, after some time, will cause the dough to smell like beer.
What’s the ideal temperature range for activating yeast?
When you’re activating the yeast in water, a lot of recipes will tell you to use slightly warm water — between 100 and 110 degrees Fahrenheit or so. If the water is too hot, then it could potentially kill the yeast.
What other liquids can be used to activate yeast?
I’d say to not be fooled by other liquids. For instance, oil is a liquid, but it doesn’t contain any water inside of it, so you can’t activate yeast inside of oil. And if there is oil in the recipe (just like milk), I would activate it in a water-based liquid first before I start adding things that contain fats that could get in the way of the water absorption. Challah, for example, calls for vegetable oil. I would activate the yeast with just water first before I add oil, eggs or other liquids to that mixture.
How can you tell your yeast has been activated?
You want to make sure that your yeast is completely dissolved. If I was making a recipe that called for both water and milk and I was using active dry yeast, I would probably activate the yeast in just the water before I add the milk. Even though you can activate active dry yeast in milk, certain milk enzymes and proteins can inhibit the individual yeast granules, which contain almost a skin or coating.
If I’m using milk to dissolve my active dry yeast, I’d take an extra step to whisk it really well and check it thoroughly before I start adding other ingredients to the mix — like flour — to make sure that it’s fully dissolved.
Aside from high heat, what are some other yeast killers?
Salt, if you put it directly into the yeast culture, could damage a portion of that culture. When I’m mixing breads, I always make sure to add flour on top of all of those yeasty liquids. And then, I’ll even push the flour around if I see that any of the yeasty liquids are still exposed, so that the salt doesn’t hit it directly. The flour basically acts like a little buffer between the salt and the yeast. Eventually, the salt and yeast will meet each other. But in such low concentrations of salt, we don’t consider it killing the yeast.
If you make a bread with no salt whatsoever, that’s not good for the yeast either, because that will actually lead to fermentation happening too quickly.
Bleach or chlorine could also definitely inhibit yeast development. Most cake flour that’s sold in the U.S. is bleached, which gives it that very white appearance. Chemical leaveners, like baking powder and baking soda, however, can actually help the process there. But cake flour isn’t a great choice if you’re trying to make things with more natural yeast. When I say natural yeast, I mean yeast that’s found in sourdoughs. I prefer unbleached flour when dealing with those types of yeasts.
Bleach can also be found in water. Depending on the region, your water could contain a higher level of chlorine that could also inhibit yeast development.
What about granulated sugar?
The thing about sugar is that it’s hygroscopic, which means that it’s always going to draw moisture from its surroundings. In fact, salt is hygroscopic too. If you have too high of a concentration of salt or sugar in your recipe, it could basically steal that water molecule and prevent the yeast from doing its job.
How should you properly store yeast?
Fresh yeast already contains water, so that has to stay refrigerated. It usually has a shelf life of about a month. As for active dry and instant yeast, the best place to store them is in a cool, dark and dry environment — like a pantry. Some people even wrap their yeast really well using a vacuum seal and store it in the freezer. The freezer is kind of like a desert. If you keep your yeast really tightly wrapped, it should stay dry — and your yeast should last for years.
