A leavening agent is baking soda, yeast or baking powder. It's that magical ingredient that makes your cakes rise. Do you know that cakes rise twice? Yes, it's true. The batter rises first in the mixing bowl as you are putting everything together and then it rises for the final time when the heat from the oven activates the leavening agent in your recipe. The leavening agent doesn't work alone though, in most cases (unless baking soda and baking powder are both included in a recipe) there's an acidic ingredient that ACTIVATES the leavening agent causing it to release carbon dioxide. In the world of baking this means AIR BUBBLES. These lovely air bubbles get trapped in the cake structure and cause the cake to rise.
THE MAGIC COMBO
I use baking soda as a leavening agent almost exclusively because I'm not keen on baking powder, it can often have aluminum in it and there is NO WAY I want that in my cakes. Also, I'm just not crazy about the flavor of baking powder.Baking soda is highly REACTIVE with acidic ingredients and this is where the CHEMISTRY of cake science gets fun.
Baking soda reacts with acids like sour cream, buttermilk, yogurt, etc., and the reaction causes carbon dioxide to be released. The release of carbon dioxide creates those lovely AIR BUBBLES that cause the cake to rise. If you want to see a BIGGER reaction add some cider vinegar to the recipe. It heightens the reaction and the end affect is often true bliss or it can be a real DISASTER if the balance isn't right between the ingredient levels. The balance between all of these ingredients is critical as too much of one thing can cause the cake to fail completely or cause is it to be a big, huge mess!
The carbon dioxide is what causes the cake to rise and this is great as long as you have a batter STRUCTURE that traps the gas bubbles.
A WINNING STRUCTURE
Great cake requires a structure that HOLDS those gas bubbles and this is where wheat flour reigns supreme. Wheat flour has gluten and gluten is a PROTEIN bond that results in a tight dough or batter structure, these protein bonds hold the bubbles in the batter and the cake rises high. However, the strength of gluten protein bonds is a double-edged sword because the more you work the dough the tighter the bonds become and before you know it you are fighting with dough or batter that feels like RUBBER. The way to avoid this is to not over beat the batter. SAVE YOUR PRECIOUS BAKED GOODS from being tough and rubbery by barely working the dough or batter.
GF BAKING IS DEEP SCIENCE
Now let's think about gluten-free baked goods. There's no gluten protein bonds to hold the carbon-dioxide-air-bubbles in the batter once the leavening agent is activated so the cake doesn't rise- all of those little bubbles just depart the scene and don't do their job UNLESS we've come up with a way to build a GF cake structure that will hold those bubbles. YES there is a way but this discussion is for another day when our brains aren't already overworked from cake chemistry :)))
LASTLY- HERE ARE SOME THOUGHTS ABOUT THE NEED TO PREHEAT THE OVEN
Your baked goods will be so happy if they enter an oven that is hot and ready to work. This means it's necessary to preheat the oven for at least 15 minutes. Forget about that little bell that goes off when the oven has reached the desired temp. That little ding sound is reporting that the AIR temp in the oven has reached the desired temperature but we want the walls, racks, everything in the oven to be the necessary temperature. Here's why- when you open the oven door ALL of the hot air comes rushing out. However, if the walls of the oven are hot then the radiant temperature of the oven stays high. Because of this preheat your oven for AT LEAST 15 minutes and your cakes will be oh so happy. They will start rising immediately upon entering the oven.
Important: Never, EVER open the oven door the first 25 minutes of baking your cake. Here's the reason- the cake starts rising fast so the top of the cake may appear to be done but internally it's still an uncooked batter. Opening the oven door causes the temperature in the oven to immediately drop at least 25 degrees and then your cake drops because of the change in temperature.
Warning: Family members may pass by the kitchen and see your gorgeous cake baking and want to take a closer look by opening the oven door. Save relationships by letting people know to not even think about opening the oven door.
ABOUT YOUR OVEN TEMP SETTING
The digital temperature reading on your oven is a GUIDELINE. Think of this reading on your oven as a starting point. The only way to know the true temp in your oven is to keep an OVEN THERMOMETER in there all of the time. All that matters is the temperature reading on the oven thermometer, not what the oven dashboard is telling you. There is often a big discrepancy between these two readings.
Most cakes bake at 350 degrees Fahrenheit. If you use a convection oven you may drop the temp by 25 degrees. Halfway through the cooking time, even if you have a convection oven, rotate your pans because even with convection ovens there can be hot spots causing your cakes to bake unevenly.
USE 2' DEEP PANS
The longer it takes to get the center of the cake done the DRYER the cake edges will be. Avoid this issue by using 2" deep pans. You can use a baking core with deeper pans, and even insulating strips to protect the edges, but I advise to forget all this and go with 2" deep pans. This is especially true if you are not a professional baker or pastry chef.
Happy Baking friends!! I love chatting about baking and sugar artistry.