Baking soda
Baking soda is an alkaline compound that produces carbon dioxide only when it comes into contact with an acidic ingredient. Acids the most often used to react with baking soda are buttermilk (or milk soured with the addition of vinegar or lemon juice), yogurt, sour cream, honey, molasses or fruit purées (bananas, apples). Given that not all recipes include an acidic ingredient, another option is needed: baking powder.
Baking powder
Baking powder (in other words, a chemical leavening agent) contains both baking soda and an acidic compound. When baking powder is combined with liquid ingredients in a recipe, it dissolves and allows the two compounds to interact, releasing carbon dioxide.
Baking powder also contains cornstarch, which serves to keep the two active ingredients separate. Two kinds of baking powder exist on the market: regular and double-acting baking powder. Unfortunately, labels don’t often clearly indicate the type, which means you need to look at the ingredients list to distinguish between the two.
1. Regular baking powder
This type of baking powder contains baking soda and only one acidic compound, such as monocalcium phosphate. It’s the formula of the popular Magic Baking Powder brand. Regular baking powder releases CO2 the moment it’s mixed with a liquid. Dough and batters made with it begin to rise when the dry and liquid ingredients are mixed together. That’s why you’re best off getting the dish into the oven as quickly as possible.
2. Double-acting baking powder
This chemical leavening agent contains one extra ingredient than regular baking powder. It’s usually sodium aluminum sulphate (SAS), a compound that only reacts when its temperature surpasses 120°F (50°C), for it to also produce CO2. This is why the baking powder is called double acting: it reacts the first time as soon as it gets wet (like single-acting baking powder) and a second time in the oven. This means that doughs and batters can rest before baking and rise continuously.
Why do we sometimes use both?
Often in a single recipe you’ll notice both baking soda and baking powder in the ingredients list. Why both? Cakes, muffins and quick breads require a certain ratio of chemical leavening agent per cup of flour to ensure the production of a good dose of CO2. If a recipe doesn’t contain enough acidic ingredients to react with the baking soda and release the amount of CO2 required, you must compensate for what’s lacking by also adding baking powder.
Muffins and dessert breads
Pumpkin Bread
The perfect dose
While it may seem counterintuitive, using too much leavening agent is the same as not using enough. When there’s an oversupply of CO2, the gas bubbles that form in the batter become so big that they fuse, rise to the surface and burst, leaving an insufficient amount of gas to raise the dough or batter.
But there are other good reasons for using a light hand, especially with baking soda. A baking soda that doesn’t react with an acid is transformed by the heat into an unpleasant, soapy-tasting compound. Too much baking soda also makes pastries darker (browning, also known as the Maillard reaction, occurs more easily when dough is alkaline). And it can change the colour of fruits and nuts: cherries, blueberries and raspberries may turn blue while sunflower seeds may become green.
How much is enough?
Generally speaking, you can rely on the quantities of leavening agents given in recipes. They may sometimes, however, contain too much. How can you tell?
Here are a few guidelines to help you:
➢ Allow 1 to 2 teaspoons (5 to 10 ml) of baking powder or ¼ teaspoon (1 ml) of baking soda (used in combination with an acidic ingredient) for each 1 cup (250 ml) of flour.
➢ Know that ½ teaspoon (2.5 ml) of baking soda used in combination with 1 cup (250 ml) of buttermilk or soured milk produces as much carbon dioxide as 2 teaspoons (10 ml) of baking powder. To sour milk, combine 1 tablespoon (15 ml) of vinegar or lemon juice with 1 cup (250 ml) of milk and let rest for 5 minutes.
Testing whether your baking powder is still active
Baking soda can pretty much keep indefinitely. Baking powder, however, can lose its effectiveness over time, especially if it’s been exposed to humid conditions. Brands recommend using their product within a year of opening the container. To test whether your baking powder is still active, combine a spoonful with about ½ cup (125 ml) of hot water. If it bubbles and fizzes, it’s still good to use.
In a pinch…
Fresh out of baking powder? You can easily make your own by mixing ½ teaspoon (2.5 ml) of cream of tartar with ¼ teaspoon (1 ml) of baking soda. This amount will replace 1 teaspoon (5 ml) of commercial baking powder.
What is ammonium carbonate?
This lesser-known leavening agent (also known as baking ammonia) was often used to make traditional cookies like Lebkuchen (gingerbread cookies), Springerle and ammonia cookies. Unlike baking powder and baking soda, ammonium carbonate doesn’t need to react with an acidic ingredient to produce carbon dioxide.
In the presence of heat and humidity, it simply breaks down into ammonia (which you can definitely smell during baking), carbon dioxide and water. Baking ammonia can be found in bulk grocery stores and some ethnic grocery stores.
An explosive experiment
Here’s a simple experiment that lets you compare the effects of baking soda and baking powder. Put a spoonful of baking soda in a tall glass and a spoonful of baking powder in another. Add a little water to the glass with the baking powder; after a few seconds the mixture will begin to fizz and form bubbles. These bubbles are carbon dioxide. Then add some water to the glass that contains the baking soda. What happens? Nothing!
That’s because the baking soda needs to react with an acid in order to produce CO2. Now add a little vinegar to the baking soda glass: bubbles will appear quickly and in an impressive amount. That’s why in baking, baking soda is used in conjunction with an acidic ingredient such as buttermilk, lemon juice, yogurt or puréed fruit. Try this experiment with your kids; they’ll love it!
