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Mar. 25, 2011

Science Dad on Baking

by Vince Harriman

Click to enlarge images

Beckett viewing yeast

One of the great things about spring break at the beach is all the extra time. So much extra time that one morning I decided to make pancakes from scratch. Now, I haven't made pancakes from scratch in decades, but I thought I could handle it. What could go wrong, right?

We had all the ingredients, I found a basic recipe on the internet... Wait, stop right there. An untested recipe from the internet. I shouldn't have asked what could go wrong. The recipe seemed ok. I hesitated when it called for two full tablespoons of baking powder -- seemed like an awful lot -- but Beckett and Rowan were sitting on their breakfast stools patiently watching, so I dutifully added two full tablespoons and started cooking. They were without a doubt the tallest pancakes I've ever seen. Beckett took one bite and said they were disgusting -- they tasted like pretzels with syrup. But it wasn't a total loss. We had a nice talk about science and cooking after I made a second batch using only a single teaspoon of baking powder.

I decided we'd do some baking back home and talk about the different ingredients needed and what each ingredient did. Every recipe is different, but most share common and obvious ingredients. Blueberry pancakes need blueberries, pumpkin pies need pumpkin, scones need chocolate (trust me, the best scones have chocolate!). What they all also have is a hidden, essential ingredient. I asked Beckett to tell me what made the beach pancakes so tall, and since we've baked many things together, he knew right away -- a chemical reaction.

The air pockets in bread

We started with something different -- yeast. One of the great things about doing science with Beckett every week is how much I learn. I knew that yeast was a simple, single-celled organism. What I did not know is that yeast is a fungus. Baking yeast (scientific name: Saccharomyces cerevisiae, which means 'sugar eating fungus of beer') is related to mushrooms and slimes!

We filled a small bowl with warm water, then added some sugar and some powder yeast. It didn't take too long to see the yeast change and grow. At first Beckett didn't like the smell, but after a couple of minutes he realized it was the smell of bread. We whiffed the bowl to smell the gases the yeast released as it ate the sugar. I pulled out a slice of bread (baking bread will be a project this weekend) and we inspected the holes formed by the gases. We pulled out our microscope (thanks, Grandma!) and prepared a slide of yeast cells and had a look. They don't honestly look like much, but if you are patient and have a decent microscope, you can see them multiply.

A pinch of this, a spoon of that...

Next we mixed some baking powder and water -- and watched a nice chemical reaction. Baking powder (chemical formula NaHCO3 -- a mixture of sodium, hydrogen and oxygen) reacts with water, acids, and the acids in many foods such as yogurts or citrus fruits. Breads made with baking powder instead of yeast are typically called batter breads or quick breads because the baking powder provides a quick chemical reaction and the recipe does not depend on the live growth of yeast. A pinch of this, a spoon of that...But enough of this science talk! It was time to conduct an experiment, and even Rowan joined in. We decided to bake some chocolate chip cookies using the correct amount of baking powder and watch them rise.

Another successful science project!

Science Dad's Chocolate Chip Cookie Recipe
Start with a stick of softened butter (ph 6.1-6.4, slightly acidic). Add 3/8 cup brown sugar and 3/8 cup white sugar (ph neutral) and blend together. Add a large egg (ph 7.6-8, slightly basic) and whisk together. Add a half teaspoon of both salt and baking soda and mix well. Add half a teaspoon of vanilla extract (unknown ph) and mix well. Add just over a cup of unbleached flour (ph 5.5-6.5) and mix well. Then add as many chocolate chips as you see fit. Spoon onto a greased sheet and bake at 375 degrees for 10-12 minutes. (Why bake at 375? Find out in this cool TalkingScience link here.) When you take the cookies out of the oven, let them cool and rest for a minute or two, then very gently move them while still warm to keep them from sticking. Then share and enjoy!

And consider that humans have been leavening baked goods for over 6,000 years and yeast is considered one of the oldest 'domesticated' life forms.

About Vince Harriman

Science Dad, AKA Vince Harriman, is a freelance writer living in Annapolis. His two sons, Beckett-6 and Rowan-2 1/2 ask him 'why' approximately 6,542 times a day.

The views expressed are those of the author and are not necessarily those of Science Friday.

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