Yeast — a beneficial fungus — is a key ingredient in many risen breads, such as pitas, dinner roles, and sandwich bread. Making these at home can save you money, but in order to do so, you’ll need to purchase yeast. Many recipes call for active dry yeast, and knowing how to pick the best can help you produce delicious baked goods. The best active dry yeast is labeled as "active", has a specific appearance, is packaged in a manner that fits your baking style, and has not been sitting on the shelf too long.
The best active dry yeast is labeled a specific way. Packaging should say simply "active dry yeast." Yeasts sold as "instant yeast" or "rapid-rise yeast" contain more active yeast cells than active dry yeast. That may sound like an advantage, but if you use "instant yeast" or "rapid rise" yeast in a recipe that calls for active dry yeast, your baked good will rise too quickly. This means it may taste boozy from over-fermentation, or even collapse in the oven.
This type of yeast should also have a specific appearance. Yeast should have the consistency of table sugar and pour as easily as sugar does, with no clumping. It should show no signs of moisture, foreign matter, or any other form of contamination. Good-quality yeast should also smell lightly of beer or fresh bread, with no sour, sulfuric, or "off" smells. Foul odors indicate rot.
Thirdly, the best active dry yeast for you will be packaged in a manner that fits your baking style. It generally comes in jars and individually sealed packets. If you bake often, or need to adjust the amount of yeast you use to compensate for altitude, jarred yeast may be best for you. Conversely, if you bake infrequently or use recipes exactly as written, yeast sold in packets will keep longer and is probably your best bet.
Finally, the best active dry yeast will also be young yeast. Like all living things, yeast has a lifespan. Old yeast will not work as well as young yeast, since more of its cells will have died. When shopping for yeast, always check the expiration date and do not buy yeast that is close to expiring. It also helps to buy from a busy, well-traveled market, as the yeast sold there is less likely to have been sitting on the shelf a long time.