Everything you need to know to know about baking leavenings (plus how to substitute one for the other)!
Baking Soda
What is it?
Baking soda, or Sodium Bicarbonate, is a chemical compound that is slightly salty and alkaline. Baking soda reacts with acid to create carbon dioxide - in baking applications, the release of carbon dioxide in a batter or dough is what causes the product to rise. Heat can also be used with baking soda to release carbon dioxide because of thermal decomposition, however without the addition of something acidic (think lemon juice, buttermilk, cream of tartar, cocoa or vinegar), only half of the available carbon dioxide is released and the food can end up with a bitter or almost soapy taste. Baking soda is about three to four times as strong as baking powder and should not be substituted one for one.
What is it used for?
1. Baking: baking soda is great in recipes where an additional acidic component is also used. You'll often find baking soda as the leavening agent in recipes that contain cocoa, buttermilk or a small amount of vinegar (a tablespoon or less), such as in chocolate cakes. You'll also find baking soda used in conjunction with baking powder, as baking powder contains an acidic element - such as in chocolate chip cookies.
2. Laundry: to de-odorize, add a 1/2 cup or so of baking soda to your next load to get rid of stubborn odors such as mildew in towels or workout gear. Baking soda is also great for keeping white towels/sheets/clothing bright white over time.
3. Disinfectant: baking soda has mild disinfectant properties and can be used as a fungicide, especially in bathroom grout. It's great at absorbing odors and can be used to help freshen up the refrigerator or musty cabinets (just add a cup of baking soda to a bowl or cup and place where needed).
Equivalent: if you are out of baking soda, replace with 3x the amount of baking powder - if the recipe calls for 1 teaspoon baking soda, it can be replaced with 3 teaspoons baking powder. There may be minor flavor or texture differences.
Baking Powder
What is it?
Baking powder is a chemical leavening agent that contains 1) about 30% sodium bicarbonate, 2) a weak acid and 3) a buffering agent (such as cornstarch) to help absorb any moisture and keep the sodium bicarbonate and the acid from reacting before it's intended use.
There are two types of baking powder: single acting and double acting. Single-Acting Baking Powder contains a fast-acting acid that reacts with sodium bicarbonate in a wet mixture at room temperature. Double-Acting Baking Powder contains a fast-acting and a slow-acting acid - the slow-acting acid does not react until heated. Most baking powders sold at grocery stores today are double-acting, meaning they react first when mixed with liquid (in a batter or dough) and second when heated in the oven or on the stovetop.
What is it used for?
Baking powder is better in recipes that don't have an acidic component because the acid is already included in the baking powder mixture. Quick breads, biscuits, cookies, pancakes, etc. that don't include buttermilk, lemon juice, vinegar or cocoa are great candidates for baking powder. For extra oomph, a small amount of baking soda (1/4 - 1/2 teaspoon) can be added along side the baking powder in these types of recipes because baking powder contains the necessary acid for it to react.
Baking powder and baking soda are best used in recipes where the flavor of fermentation (like in yeast breads) is not desired, such as in cakes, cookies or biscuits. Recipes using baking powder and baking soda are also much faster to make as they react quickly with liquid and heat to leaven baked goods.
Equivalent: if you are out of baking powder, replace with a mixture of baking soda, cream of tartar and cornstarch. 1 teaspoon baking powder = 1/4 teaspoon baking soda + 1/2 teaspoon cream of tartar (or vinegar, lemon juice) + 1/4 teaspoon cornstarch.
Yeast
What is it? Yeast are single-celled microorganisms that are members of the fungus kingdom. They've been around hundreds of millions of years and are found in a wide variety of environments - from the skins of fruits & berries, flowers, soils, and the deep sea. Yeast are used in many different applications, most famously breads, beer, kombucha teas and supplements like nutritional yeast.
We'll focus on baking yeasts which are divided into 4 categories:
1. Active Dry yeast: This type of dry yeast is one of the most common varieties sold in grocery stores. The granulated yeast is dormant until mixed with water. It's a good idea to "proof" this type of yeast before using: add the yeast to lukewarm water (as called for in the recipe) and allow it to sit 10-15 minutes until it begins to foam. It is then ready to be added to the recipe. This type of yeast is shelf stable and does not need to be refrigerated. To substitute active dry yeast for instant yeast, use 25% more - for every 1 teaspoon of instant yeast, you'll need 1 1/4 teaspoons active dry yeast.
2. Instant Yeast: Instant yeast was introduced in the 1970's and is a finer milled dry yeast that dissolves & activates faster. This variety of yeast does not need to be proofed and can be mixed directly into the dough. Some brands, including RapidRise Yeast and some bread machine yeasts include ascorbic acid and other dough stabilizers to help strengthen the dough. Instant yeast is also shelf stable and does not need to be refrigerated. To substitute instant yeast for active dry yeast, use 25% less - for every 1 teaspoon of active dry yeast, you'll need 3/4 teaspoon instant yeast.
3. Fresh yeast: Fresh yeast is sold in blocks labeled as "cake yeast" or "compressed yeast" which contain fresh yeast cells and about 70% moisture. They have a soft and crumbly texture and strong yeast smell. Fresh yeast cakes are perishable (2 week life span) and must be refrigerated - it can usually be found in the refrigerated section near the butter if your store carries it. To use fresh yeast, crumble the cake or block and either add to your recipe or soak in warm water before adding. Some say breads are more flavorful using fresh yeast and others believe the flavor is about the same as dried or instant yeast. To substitute, for every 1/4 oz packet of active dry yeast, replace with 2/3 oz fresh yeast cake.
4. Homemade Yeast (aka cultivating wild yeast to make your own starter): This method takes advantage of naturally occurring yeast & bacteria cells in the air or surface of flour particles to create a fermented starter that can be used to raise breads. To cultivate your own yeast (aka starter:
Mix together equal parts flour and water (1/4 cup of each will work to start) and stir to combine well - during this process the starch is broken down into simple sugars that the yeast and bacteria can feed on. Cover loosely with a lid or tea towel. Keep at room temperature 3-5 days.
Each day, morning and night, add one tablespoon each flour and water - this feeds the yeast. In 3-5 days, the mixture will begin to bubble. At about day 5, your yeast mixture should have risen and doubled in volume and is ready to use.
Use homemade yeast starter in recipes that call for a starter or sourdough starter instead of yeast, as it is not easy to substitute in recipes that call for dried yeast. To store, you can either continue to feed it twice a day at room temperature, or store in the fridge and feed once a week.