Everyday Kitchen Chemistry – How Baking Soda and Powder Work

Even if you loved cooking but hated science in school, I can guarantee that you’ll find this article to be interesting! And maybe we can all learn something useful for our “from scratch” baking and cleaning. But before you get too engrossed in the scientific details, I have a question for you. Have you ever eaten someones cookies or biscuits and found to your dismay that they had a soapy aftertaste? I can explain why that happens so you never do that to someone else – so keep reading!

“Chemistry” – the very word conjures up images of people hidden behind masks, goggles, and white coats doesn’t it? For me it certainly does make things sound complicated and intimidating, but really it’s just a way of describing how things work or react together. But wait… don’t stop reading now! Before you put down your computer and go make a nice whole wheat sandwich with fresh preserves, let’s discuss that bread. What on earth does bread have to do with chemistry you may ask? Quite a bit, actually. Bread comes in many forms from flat tortillas to fluffy white bread that feels like eating a cloud, quick bread to sourdough, and hundreds of variations in between. Have you ever made your own bread? It’s actually pretty easy and unless you mess up the portions of salt I’d say that even a flop is still edible (if it’s really bad, try using it for croutons in a salad or on top of French Onion soup).

We all know that yeast produces little bubbles of gas as it rapidly multiplies – hence the bubbles in the bread that lighten it, and that’s chemistry. This is a chemical reaction caused by one thing acting on another, converting sugar found in the dough or in the flour itself to alcohol and carbon dioxide as waste products of yeast reproduction. I’m not making this sound very appetizing am I? However, without the bubbles, most of the bread we eat would be heavy and dense, and much harder to eat and digest. Wild yeast is found all around us and it’s what’s found in most sourdough starters. But there’s also gluten to talk about. No-knead breads work on the principle that you can build up the gluten which gives strength and elasticity to the bread not through the vigorous 10 minute kneading of our grandmothers, but simply through a little mixing and time. When I make bread for the market I obviously make larger batches of 4-8 loaves so I can be efficient and still knead that much dough at once. My goal is to knead it smooth, at which point it becomes quite stiff and I let it rest. I do this a few times. Each time it’s been rested it feels softer again as the gluten strands relax a little, then all it takes is a quick knead of 3 or 4 turns to lengthen and strengthen them again before another rise and rest. Kneading does quicken the process as opposed to waiting, but I still like to combine both methods in my bread making – it works for my recipe and for the type of flour I use. If you’re making gluten free bread then this is obviously a moot point.

How about in quick bread? There’s no yeast so we use different things to make quick bread fluff up. Quick breads include biscuits, cookies, baked goods like banana bread and zucchini loaf and muffins. They all rely on a simple chemical reaction to rise the mix before and during baking. Yes, the eggs do play a part in many recipes for providing strength to the finished product and some moisture to steam when cooking, but for the initial bubbles and rising it’s purely chemical.

The Simple Chemistry Behind Baking Soda

If you look at your list of ingredients you’ll find baking powder and/or baking soda listed. Have you ever wondered what the difference is? Don’t they work the same? Well, baking soda is simply sodium bicarbonate, or NaHCO3 to its friends. It’s a white crystalline powder found in many fridges as a deodorizer, and it has tons of uses around the homestead for cleaning, in toothpaste and of course for baking. It’s an alkali (the opposite of an acid) and tastes a bit like salty washing soda but really, who wants to taste that? Yuck! Only someone with a terrible case of heartburn and no antacids in sight.

Baking soda works by reacting with an acid to produce gas bubbles and is enjoyed by bakers and children alike for this property. If you combine baking soda (alkaline) and vinegar (acid) in a closed space such as a plastic bag it will produce enough gas to pop or explode the bag which is great fun and has made many a science fair volcano erupt. Bakers use this property to rise their goodies which is why recipes using baking soda alone have an acidic ingredient for the soda to react with. This can be buttermilk, lemon juice, vinegar, etc. And this is why sometimes when you make your Grandma’s biscuits yours come out flat and taste soapy. Either you’ve used too much soda causing the soapy taste, or you haven’t used an acid to promote the bubbling reaction. Grandma used buttermilk or sour milk which is acidic and in these modern times we often substitute regular milk for it thinking it’ll taste the same. But we’re leaving out the crucial reaction needed to properly neutralize the soda and raise the biscuits. You really must have something acidic, so if you’re using plain milk I recommend you add some vinegar to it to make it sour first. Or lemon juice. Or check out my recipe below. There’s still something about real buttermilk though that makes the best biscuits. Grandma sure knew what she was doing! There’s even a glowing reference in Laura Ingalls Wilder’s Little House on the Prairie books about how great her mother’s biscuits were and how fluffy, so we know they’ve been a kitchen delight for generations. Am I making you hungry yet? Here’s the recipe we use here at the farm for delicious soft biscuits, it makes 12-15, enough to cover a pan. You’ll notice that it’s made with baking powder instead of baking soda and I’ll explain why in a moment. These biscuits are good with jam, gravy, or on top of a casserole, and they’re a great way to teach kids about baking and give them some confidence in the kitchen.

Humblebee Farms Biscuits Recipe

• 3 cups all purpose flour
• 1/4 cup sugar
• 4 tsp. baking powder
• 1/2 tsp. cream of tartar
• 3/4 tsp. Salt
• 1/2 cup shortening, butter or lard
• 1 egg, beaten
• 1 1/8 cup milk (a little more if the weather and flour are very dry)

Directions: Turn your oven to hot or about 475 degrees and let it thoroughly preheat. In a large bowl combine the sugar, flour, baking powder, cream of tartar, and salt. Mix. Cut the fat in (whichever fat you used) until it resembles coarse crumbs. You can use a pastry blender for this, or a knife, but it’s best to not melt the fat by using your hands. Mix together the egg and milk in another small bowl and the pour the wet mixture over the crumbs. Mix together until it starts to come away from the sides of the bowl. Turn it out onto a floured surface and knead it a dozen times. Too much kneading and you’ll get tough biscuits. I roll mine out to about 3/4 inch thick then cut with a biscuit cutter (best), glass (it works), or for less waste just cut it up into 12 pieces. Put on a parchment-lined baking sheet with a little space between the biscuits and bake in the middle of the oven for 12-15 minutes until they’re light golden brown. Keep an eye on them the first time you make them to see how quickly your oven cooks them. Cool on a rack and enjoy! If you’re using them as a topping on top of a casserole, place them on top and keep the dish covered for the first 30 minutes of cooking, and then remove the cover for the last few minutes of cooking to brown the tops of the biscuits. If you’re making biscuits to go with a roast dinner I recommend taking your meat out of the oven when it’s done and covering it with foil, then leaving it to rest for 20 minutes before carving it. During that 20 minutes you can make biscuits and gravy.

The Simple Chemistry Behind Baking Powder

Okay back to baking powder. This is also sodium bicarbonate but it includes an acidifying agent as well (cream of tartar) and often a starch to act as a drying agent. It’s available as single action and double action and the difference is that single action is activated by moisture and needs to be cooked right away, whereas the double action will bubble a little at room temperature but will increase the bubbling at oven temperatures so loaves made with double action baking powder can wait a few minutes to be baked. Most baking powder these days is double action, in fact I went to several stores this weekend looking at the baking powder and only found double action in my area. The biscuit recipe above uses both cream of tartar and baking powder.

When we’re making new recipes, the goal is always the same – produce something tasty. And the ingredients we use contribute to both the flavor and the texture of the finished products. But what if you run out of one ingredient? Can you substitute without ruining your recipe? You can substitute baking powder in the place of baking soda (you’ll need 1.5 times as much and it can affect the taste) but you cannot substitute baking soda for the baking powder. Don’t panic though, what you can do is make your own baking powder. Remember I told you it was made from baking soda and cream of tartar? All you need to do to is mix two parts cream of tartar and one part baking soda and there you go, you’ll never run out of baking powder again. Homemade baking powder doesn’t have a drying agent in it so it won’t keep very long. The moisture in the air is enough to cause the two chemicals to react, so if you make your own make it up in very small batches.

Baking powder and baking soda will both last about 18 months if kept in a well sealed container, possibly longer in dry conditions. But there will come a day when you’ve got to wonder if it’s still good for baking. How do you know without wasting a whole batch of cookies?

To test baking soda for effectiveness I take a small amount (half a teaspoon) and place it in a little pile in a bowl. Then I drip vinegar on it and see if it bubbles. Pretty simple. Vigorous bubbling indicates that your baking soda is still good. If very few or no bubbles form, then I’d recommend that you use it to scrub down your bathtub. It’s still a good gentle abrasive even when it’s not good for cooking. Baking powder is a little different but still easy to test. Boil a kettle or run the hot tap for a little bit to get about a half cup of water. Mix in a tablespoon of baking powder and observe. If it bubbles a lot then it’s still good. If not, I’m afraid you’ll have to throw it out. But you can keep the plastic container for future use or to use while making your own baking powder. This test doesn’t work if the water is cold, by the way.

I hope you’ve found this information to be helpful. Do you have a favorite recipe that uses basic ingredients that you’d like to share? Learning to make meals with the food you grow and adding in biscuits and other homemade fillers just makes life that much more delicious! Here in Nova Scotia, September is “Eat 50% Local” month. It’s a fairly new idea that encourages people to shop at local farms and farmers markets during our harvest time to eat healthy local produce and meats. It’s also a great way to meet your local farmers and make new friendships. My tip for the month is to learn to make great biscuits and enjoy them with some good fresh homemade jam. They keep from one meal to the next and can be eaten with both sweet and savory foods.