Kitchen Mysteries is a weekly exploration of oddities surrounding cooking and food. They could be recipes that fail when they shouldn't, conflicting advice from different sources, or just plain weirdness. If it happens in a kitchen, and you're not sure why, send a tweet to The Food Geek to find out what's happening.
Keri asks via twitter:
The purpose behind baking powder and baking soda is to react with the ingredients in your batter and release carbon dioxide gas. Ideally, these gases will meet up with bubbles that you've made in your batter by whisking or beating, make them larger, and provide some lift in your baked goods.
Baking soda is alkaline, and it reacts with any acidic ingredients in your batter (such as buttermilk or lemon juice). The baking soda neutralizes some or all of the acid, and in the process releases the carbon dioxide we mentioned before.
Baking powder is a little more clever: it contains a powdered acid along with the baking soda (it's the balanced Yin and Yang of the leavening world). No reaction can happen without water, so it's fine in its package, but once the water is added, bubbles happen.
A baked good is a delicate dance of flavor, appearance, and body. Some acid gives a nice flavor to a dough, but too much might overwhelm, and it will certainly keep the baked good from browning as much as it can. Still, the batter might not have enough acid to lift the entire quick bread enough just using baking soda—thus, some recipes call for both ingredients. This way, you don't have to dial the baking soda up to 11, which can give a soapy taste to your muffins. And nobody likes a soapy muffin.
Like masked heroes from comic books and movies, some baking powders lead double lives. These "double-acting" baking powders use their special, mutant properties to not only add bubbles when you add the liquid, but also to create more bubbles when they get to a higher temperature. The endless war of double-acting baking powders against poorly-leavened quick breads makes the world a better place.
Here's the situation: you mix together some batter. Bubbles are made. You finish combining the batter, and bubbles escape. You pour the batter into pan, bubbles escape. You realize that the oven hasn't preheated, and bubbles escape. What's to be done? It's no problem if you've used double-acting baking powder, which will add more bubbles once heat is applied. Ta da!
So in summary:
- Needs an acidic ingredient in the batter to react with
- Allows baked goods to be browner after baking
- Can taste soapy
- Only creates bubbles when it first reacts with the acid
- Contains both an acid and a base
- The double-acting variety will continue to produce bubbles in the oven
I hope this helps to understand the recipes, and how to know when to follow their lead and when to ignore it.