In light of Friday's horrific mass-shooting tragedyin Colorado, I've decided to postpone my planned piece on the horrors of poison gas. It's coming your way eventually. Right after the rather troubling history of death penalty chemistry.
But for today, let's give ourselves a break, and talk about lighter subjects, easier aspects of life. In fact, nothing more serious than chocolate chip cookies. For one thing, chocolate is famously about comfort. And there's science to back that up. I've always likedthis report, by blogger Dave Munger, on a study that found chocolate associated with both pleasure and guilt. Not to mention the many scientific pronouncementsassuring us that the chemistry of chocolate really does make us feel better.
And, fortunately, I have a recipe for excellent chocolate chip cookies, derived -- I assure you -- from the best of chemistry experiments.
Last summer, I ran a home chemistry experiment in search of the perfect cookie. I was inspired by biochemist, food scientist, and cookbook author Shirley Corriher.I'd heard her speak at an international chemistry symposium; the resulting cookie post, which I've created in part today, is here. And you can listen to Corriher here, in an earlier NPR interview where you'll catch the fizz of enthusiasm that sent me home, inspired to bake.
I'd been thinking about the mystery of the cookie for a while anyway. My late Kentucky grandmother made the best chocolate chip cookies known to humankind (yes, even better than your grandmother's) and I'd never been able to recreate them. She *claimed *she just followed the recipe on the Toll House bag but I just knew there was some grandmotherly magic that she hadn't shared.
And Corriher raised three points that I thought it would be fun to explore as a kitchen chemist:
The chemistry of butter gives it a lower melting point than shortening. That means that cookies made with butter spread out more rapidly. They're flatter and crisper. "If you want soft, fluffy cookies," she said, "then you want to try shortening."
The amount of protein in flour affects the texture of the cookie. All wheat flours contain protein. When exposed to moisture and heat, the proteins break down to form a protein-composite called gluten. The more gluten the more elasticity and strength you'll find in the dough. So if you want a chewier cookie, you want a higher protein flour. For delicate and crumbly, a lower protein flour. As a general rule, cake flours contain about 8 percent protein and all-purpose flours between 10 and 12 percent. I went with a middle-range bread flour.
A chocolate chip cookie recipe has very little liquid in it. What's there comes from the eggs, the water in butter or shortening, and the vanilla. So the longer the dough is left to sit, the more of those precious liquids absorb into flour and sugar.
The dough that sits longer, thus, is drier as the liquid soaks up, less sticky, easier to handle. And, both chemists and professional bakers tell us,the flavors absorb more richly as well. In that earlier NPR interview, Corriher recommended up to 36 hours after mixing the dough before baking. Talking to me -- and I suspect recognizing that I wasn't nearly patient enough to wait that long -- she suggested 24 hours instead.
I set up my experiment as follows:
Every Saturday morning for three weekends in a row, I made two batches of chocolate chip cookies. One was made with butter, one with butter-flavored shortening. I split each batch in two. I baked half of the dough immediately, saved the other half in the refrigerator, baked it the next day.
And here's where I discovered the natural limits of the home experiment. I needed a polished test kitchen surrounded by impartial chemists bearing measuring cups. Instead, I had a 17-year-old son who hated dark chocolate (milk chocolate chips, Mom!) and a husband who couldn't believe I'd consider anything but dark chocolate. ("Don't you think they're better with that contrast to bitter chocolate?") And back to the son. ("Mom! Don't listen to Dad!")
My son hates nuts. My husband prefers them in his cookies. They're in my test kitchen discussing the merits of the additives. I burn a batch. Just a little. My husband likes his cookies extra crispy. My son likes them on the doughy side. I agree to leave out the nuts since I've ruined this batch of cookies for the teenage control group.
But here's the other problem with home test kitchen. The cook has a hidden agenda, that of recreating her grandmother's cookies. And about 100 or so cookies into the experiment, she realizes that these are too sweet. The over-nighting of the dough does create more uniformly golden batches, but they're too sweet, too white sugary, too lacking in the faint tinge of caramel that colors my memory.
So eventually I switch to brown sugar entirely. And in the butter version of these cookies that last one comes pretty damn close of what I remember, which mostly proves to me that memory is an unreliable measure. Because I know darn well that my grandmother was a Crisco devotee and dedicated believer in the magic of white sugar.
But it doesn't really matter if I've recreated the cookie chemistry of my childhood. I've made a memory for my own child and standing by a hot oven, breathing the buttery chocolate air of my own making, that feels exactly right to me.
Final Recipe
- 1 cup butter
- 1 1/2 cups brown sugar
- 2 eggs
- 2 teaspoons vanilla extract
- 2 1/4 cups all-purpose flour
- 1 teaspoon baking soda
- 1 teaspoon salt
- 2 cups milk chocolate chips
- Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
- In a large bowl, cream together the butter and brown sugar. Add the eggs one at a time, beating with each addition, then stir in the vanilla. Combine flour, baking soda and salt; gradually stir into the creamed mixture. Finally, fold in the chocolate chips. Drop by spoonfuls onto cookie sheets.
- Bake for 8 to 10 minutes in the preheated oven. Remove cookies from hot sheets and allow to cool on a rack or board.
Image: Jamison_Judd/Flickr
