Air: Baking’s Key Variable - Chemical Leaveners (part 5) - Baking Powder - Pumpkin Cake

2. Baking Powder

Baking powder solves the “balancing act” problem encountered when using baking soda by including acids alongside the bicarbonates. And since the acids are specifically mixed into baking powder, they can be optimized for baking; you don’t have to rely on whatever acids happen to be present in the food being made.

Baking powder, at its simplest, can be made with just one type of bicarbonate and one type of acid. This is why, in a pinch, you can make your own baking powder: 2 parts cream of tartar to 1 part baking soda. Cream of tartar—potassium hydrogen tartrate—will dissolve in water, freeing tartaric acid (C₄H₆O₆) to react with the sodium bicarbonate.

Commercial baking powders are a bit fancier than this, though. Different acids have different rates of reaction and reaction temperatures, so using multiple types of acid allows for the creation of a baking powder that’s essentially time-released. This isn’t just clever marketing: in baked goods, if the CO₂-generating reaction occurs too slowly, you’ll end up with a dense, fallen product. And if those reactions happen too quickly, the food won’t have time to properly set so as to be able to hold on to the gas, resulting in things like collapsed cakes.

Note:

Some people find that baking powder made with sodium aluminum sulfate tastes more bitter than that made with other acids, such as monocalcium phosphate.

Double-acting baking powder—this is the stuff you’ll find at the grocery store—uses both slow- and fast-acting acids to help prevent these types of problems. Fast-acting acids, such as tartaric acid (in cream of tartar) and monocalcium phosphate monohydrate, can work at room temperature; slow-acting acids, such as sodium aluminum sulfate, need heat and time to release CO₂. As long as the ratio of ingredients in your baked products is roughly correct and you’re baking within an acceptable temperature range, baking powder is unlikely to be the culprit in failed baking experiments.

Still, if you’re getting unexpected results with a commercial baking powder, check whether your ingredients are highly acidic. Acidity impacts baking powder; more acidic ingredients in a recipe will require less baking power. If that doesn’t turn up any suspects, check how long it has been since the baking powder was opened. Even though commercial baking powders contain cornstarch, which absorbs moisture to extend the shelf life, the chemicals in baking powder will eventually react with each other. Standard shelf life is about six months after being opened.

Pumpkin Cake

There are two broad types of cake batters: high-ratio cakes—those that have more sugar and water than flour (or by some definitions, just a lot of sugar)—and low-ratio cakes—which tend to have coarser crumbs. For high-ratio cakes, there should be more sugar than flour (by weight) and more eggs than fats (again, by weight), and the liquid mass (eggs, milk, water) should be heavier than the sugar.

Consider this pumpkin cake, which is a high-ratio cake (245g of pumpkin contains 220g of water—you can look these sorts of things up in the USDA National Nutrient Database, available online at http://www.nal.usda.gov/fnic/foodcomp/search/).

In a mixing bowl, measure out and then mix with an electric mixer to thoroughly combine:

1 cup (245g) pumpkin (canned, or roast and puree your own)

1 cup (200g) sugar

¾ cup (160g) canola oil

2 large (120g) eggs

1 ½ cups (180g) flour

¼ cup (40g) raisins

2 teaspoons (5g) cinnamon

1 teaspoon (5g) baking powder

½ teaspoon (5g) baking soda

½ teaspoon (3g) salt

½ teaspoon (2g) vanilla extract

Transfer to a greased cake pan or spring form and bake in an oven preheated to 350°F / 175°C until a toothpick comes out dry, about 20 minutes.

Notes

• Try adding dried pears soaked in brandy. You can also hold back some of the raisins and sprinkle them on top.

• One nice thing about high-ratio cakes is that they don’t have much gluten, so they won’t turn out like bread, even with excessive beating. With a total weight of 920 grams, of which only roughly 20 grams is gluten, there just isn’t enough gluten present in this cake to give it a bread-like texture. There’s also a fair amount of both sugar and fats to interfere with gluten development.

If you’re making a quick cake like this pumpkin cake as the finale to an informal dinner party, try serving it directly on a single plate or even a cutting board. Besides lending a pleasant casual feel, this’ll mean fewer dishes to wash!