What's the Difference Between Active Dry, Instant, and Fresh Yeast?
There's a lot of choice when it comes to baker's yeast — active dry yeast, instant yeast, fresh yeast, not to mention wild yeast. It can be tricky to know which is the right one to use for what recipe. Here's what you need to know about different types of yeast for baking.
What is Yeast?
Yeast is a single-cell living organism that acts as a leavening agent to make dough rise. It does this by consuming and converting sugars into carbon dioxide, which produces the bubbles in the dough that make it expand — or rise — as it "proofs" in a warm, moist environment, and again as it bakes in a hot oven.
No matter what form your yeast comes in — active dry yeast, instant (or rapid-rise), or fresh yeast — it needs to multiply and grow in a sympathetic environment. The correct environment includes moisture, food (in the form of sugar or starch), and a warm, nurturing temperature.
Active Dry Yeast
Active dry yeast is the most commonly available form for home bakers and is available in ¼-oz packets or jars. The yeast is dormant; it needs to be re-hydrated and proofed before using. Dry yeast should be stored in a cool dry place; but do not use it after the expiration date on the package. Store open containers in the refrigerator.
Instant yeast is a dry yeast that comes in smaller granules than active dry yeast, absorbs liquid rapidly, and does not need to be rehydrated or proofed before being mixed into flour. Bread machine yeast and rapid-rise yeast are instant yeasts that may include ascorbic acid, a dough conditioner. Bread machine yeast is an instant yeast especially formulated for use in a bread machine. Again, store the yeast in a cool dry place, or in the refrigerator once the package has been opened. Do not use yeast after the expiration date.
Related: How to Make Bread in a Bread Machine
Fresh yeast, also known as compressed or cake yeast, is active yeast. It's 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, or 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 to 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, such as this Italian Biga recipe.
Wild Yeast and Starters
Before yeast was available in grocery stores, bakers kept colonies of live yeast for making bread (think sourdough 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.
Related: How to Make Sourdough Bread
VIDEO: Sourdough Starter
Get the recipe for Sourdough Starter II
How to Substitute Different Types of Yeast
In commercial baking, precise measurements are key. Home bakers generally don't need to reduce or increase liquid amounts to compensate for the type of yeast used since the quantities are so small.
- Each little .25-ounce packet of active dry yeast contains about 2 ½ teaspoons of yeast.
- To substitute instant or bread machine yeast for active dry yeast, use 25% less instant yeast than active dry.
- A 6-oz cube of cake yeast is roughly equivalent to 1½ to 2 teaspoons instant yeast or 2 to 2¼ teaspoons active dry yeast.