Yeast: The Basics
By:
Sydny Carter
Yeast is a living thing, a unicellular organism found wild in air and water, with cultivated strains used for beer brewing, winemaking and baking.
Yeast creates carbon dioxide gas, alcohol, and other organic compounds during growth. The gas is the rising agent in bread, and other "waste" products create the subtle flavors that make a good loaf. Wild yeast can be used to make starters, mixtures used as natural leavening for breads. Many bakers use a combination of a starter plus packaged yeast, which is more reliable and whose growth rate can be controlled.
Types of yeast
Active Dry Yeast
is the most commonly available form for home bakers. It is available in ¼-oz packets or jars. The yeast is dormant, and is best used after proofing and rehydrating. Sprinkle the yeast over warm water (105-115 degrees F) and a pinch of sugar, and let it stand for 10 minutes until creamy and bubbly. It can be stored in a cool dry place and in unopened packages for up to 15 months, but do not use it after the expiration date. Store open containers in the refrigerator.
Instant Yeast is a dry yeast developed in the past thirty years. It comes in smaller granules than active dry yeast, absorbs liquid rapidly, and doesn't need to be hydrated or "proofed" before being mixed into flour. Bread Machine Yeast and Rapid Rise Yeast is instant yeast that may include ascorbic acid, a dough conditioner. Less rising time is required, allowing home bakers to bake a loaf of bread fairly quickly. To develop more flavor--such as for artisan-style breads--a long, slow fermentation is best: store the shaped loaves overnight in the refrigerator before bringing to room temperature and to a full rise. Store instant yeast in a cool dry place, or in the refrigerator once the package has been opened. Do not use yeast after the expiration date.
Fresh Yeast, also known as compressed or cake yeast, is active yeast. It has good rising qualities and produces excellent-tasting bread, croissants and Danish pastries. It is sold in tiny cakes in the refrigerated section of many supermarkets. Fresh yeast does not keep well; it will last about two weeks if refrigerated. The yeast should be pale gray-brown, fragrant, soft and crumbly, not hard, dark brown and crusty. Any mold growing on the surface is an indication that the yeast should be discarded. Fresh yeast should be proofed in tepid water (80-90 degrees F) without contact with salt or sugar. This yeast type is a good choice for breads requiring a long cool rise, or for breads made using the sponge method.
Wild Yeast and Starters
Before yeast was available in grocery stores, bakers kept colonies of yeast for making bread. These colonies were known as starters, and were sometimes passed on from generation to generation. You can make your own starter using commercial yeast, by using potato water (from boiled potatoes) to attract and feed wild yeasts present in the air around us, or by using the yeast found on the skins of organic grapes or organic raisins. Keep the starter in a one-quart crock, jar, or airtight container.
Feeding your starter
Feed your starter by taking one cup of the starter and discarding any left in the jar. In a mixing bowl, combine the reserved starter, one cup flour, and one cup tepid water (measurements need not be exact). Use a whisk, spatula or even your hands to mix it well. Add more water if necessary; it should resemble pancake batter. Cover and let stand at room temperature for 24 hours. If your kitchen is cold, the starter may need more time to show some activity--bubbles and visible growth; be patient. Feed as above. After a starter has been growing for 5 or 6 days, it can be stored in the refrigerator to slow its growth and to free you from the daily feeding schedule. Feed refrigerated starters once a week, allowing them to grow at room temperature before returning them to the fridge.
Baking with your starter
About two to three days before you plan to bake, remove the starter from the refrigerator. Let it warm to room temperature to get active. Feed it twice the first day and every 4 to 6 hours on the second: the repeated introduction of fresh food should make the yeast very active. If you plan to make multiple loaves of bread, you can increase the feeding amounts: use two cups of reserved starter, two cups flour and two cups water. When adding the starter to your recipe, always reserve a cup of your starter to continue the yeast strain! Over time, the yeast's natural fermentation process will develop wonderful flavors, giving you a one-of-a-kind family heirloom.
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