Skinning the Sodium Bicarbonate Cat

Reader Ted writes in with a fascinating question:

So, I’ve been tinkering with recipes for bran muffins, and hoping to come up with something other than hockey pucks (the grocery store can do them; why can’t I?) and I started thinking about baking soda vs baking powder. I was looking on the net about the two, and came across [an] article, and something in it puzzled me. [Joy the Baker] writes:

When sodium bicarbonate [baking soda] meets with heat, carbon dioxide gas is formed. It’s this gas that gives rise to our favorite cakes, cookies and biscuits. There is one drawback to the production of this gas. When heated, sodium bicarbonate also produces sodium carbonate, which doesn’t taste very good. If you’ve ever eaten any metallic tasting cakes or biscuits, you know what I’m talking about. Thankfully, the metallic taste of sodium carbonate can be neutralized by acid. Lemon, yogurt, buttermilk, and unsweetened natural cocoa powder can neutralize the taste of sodium carbonate and keep our baked goods risen and lifted.

I thought that sodium bicarb fizzed when exposed to acid, not heat. You haven’t done a series on chemical leaveners, and it would be an excellent addition to the website, I think. (And how about a bran muffin recipe?)

Love that question! The answer, Ted, is that Joy is very right when she says that you can get CO2 by applying heat to baking soda. Actually there are several ways you can react sodium bicarbonate to produce CO2 bubbles, and heat is one of them (actually it’s not a reaction per se, but rather thermal decomposition). Of course baking soda reacts with acid as every baker knows. The third way to get CO2 from sodium bicarbonate is by combining it with certain bases. That seems counterintuitive — and indeed we don’t do it in the kitchen — but it works. Indeed natural living types sometimes combine baking soda with a little hydrogen peroxide to make a fizzy “natural” toothpaste.

Where I myself get a little confused with the quote is the implied idea that somehow the soda won’t react with any acid in the mix until after the batter goes in the oven. It absolutely will — as soon as the soda and the acid ingredient are combined in the mixing step, heat or no heat. And that’s really the idea.

If, after that initial reaction, there still is some soda left unreacted, you’re going to have problems. True the oven heat will thermally decompose it, but as Joy points out one of the products of the decomposition is sodium carbonate, which doesn’t taste good. It does indeed have a metallic taste and worse still, if there’s much fat in the batter it will combine with it to produce soap, which is never welcome in a muffin. So I think that in truth Joy has things a little backward here. The lesson is to always have enough acid in a soda-only recipe to react all of it.

Hope that helps, Ted. As for the bran muffins…that’s a good idea. For now try adding a little more AP flour to the mix to bump up the gluten content. If that’s not an option a seed gum goo like flax to help capture some bubbles. I’ll see what I can do about a chemical leavened series!