You can buy bread just about anywhere, but that's not nearly as satisfying as making your own. You get to have control over the ingredients, you decide what kind of bread you'll end up with, and it's just plain enjoyable. One of the key ingredients in baking your own bread is yeast, and the baking shelf at your supermarket has lots of different kinds. The most common choice is active dry yeast, which has a few specific advantages and disadvantages compared to others. You might find a different yeast is best for a specific recipe, but active dry yeast is a good, versatile choice for most baking.
Why It's Dry
The most basic form of yeast is fresh yeast, the kind that's sold in cakes out of the refrigerator section. Fresh yeast is already active – you could think of it as "awake" – so when you crumble it into your mixing bowl, the yeast is ready to get right to work on your dough.
The problem with fresh yeast is that it needs refrigeration, and if it's not used within a week or two, it'll die. Yeast makers got around this limitation decades ago by drying the yeast, which makes it dormant, and then forming it into granules with a protective shell of dried yeast particles. When it's manufactured this way, dry yeast keeps on the shelf for months. That makes it a lot more convenient, both for you as the baker and for the retailer who has to keep yeast in stock. When you're ready to bake, just wet the yeast so it can bounce back to life.
The Quick-Rise Yeasts
Active dry yeast isn't the only kind that's made by the above process. You'll also see dry yeast labeled under several different names, including instant, quick-rise and bread machine yeast. They're all pretty similar, though some small differences exist between manufacturers. These types are basically the same thing as active dry yeast, but milled into smaller particles that absorb water and come back to life more quickly. You can stir them right into your other dry ingredients, and they'll take in all the moisture they need as you mix the dough. That's a big convenience, especially in bread machine baking. Some brands of active dry yeast can be used the same way, but usually it's safest to wet it first.
Active Dry Versus Fresh Yeast
Professional bakers and serious amateurs love fresh yeast, because nothing raises a batch of bread quite as well. The disadvantage is that it's hard to find. It's so perishable that retailers have a hard time making money on it, and it's not really well suited for online ordering and delivery.
With active dry yeast, you can keep a jar in your fridge or individual pouches in your pantry for months and use it whenever you need it. You'll just need to activate your yeast first, or "prove" it, by stirring it into liquid and waiting for it to foam up vigorously. At that point. it's pretty much the same thing as fresh yeast, and ready to use in your recipe. You'll also know that your yeast is healthy and ready to work, because you've watched it wake up – that's where the "proving part" comes in – while fresh yeast looks exactly the same whether it's alive or dead.
Active Dry Versus Quick-Rise Yeasts
You can make excellent bread with active dry yeast or quick-rise yeast, whichever you've got on hand, but they're used a bit differently. Manufacturers carefully cultivate individual strains of yeast for the characteristics they want – just like farmers do with corn, or dog breeders with their dogs – and quick-rise yeasts are selected for their ability to raise a loaf in a hurry. That's an advantage when you're looking for a quick loaf, either by hand or in a bread machine.
Artisan bread is a whole different story, because it's all about a long, slow rise. Active dry yeast is better for that job, because its yeasts aren't as specialized. That's what you'd want for the popular no-knead breads that call for you to keep your dough in the fridge and bring it out when you're ready to bake. You can still use active dry yeast in a faster-rising recipe by proving it and adding it to the wet ingredients, rather than to the dry ingredients. Your bread won't happen quite as quickly as with a quick-rise yeast, but the end result will be pretty similar. A loaf made with quick-rising yeast might be slightly lighter and airier, because the yeast usually includes dough enhancers like ascorbic acid that help simulate the good effects of a longer, slower rise.