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New Year, New Resolutions (and research on chocolate chip cookies!)

January 10, 2013

I’ve been silent on this blog and on Twitter for over a month now, mostly because I’ve been preoccupied with other things. Applying for postdocs and a fellowship, writing papers, even performing in the Nutcracker(*) – you name it, I was probably doing it.

But, while I’ve still got some work to do on my postdoc applications, and there are always more papers to be written, I’m determined to get back to this blog in the new year. My goal last year was to average a post every two weeks, which I didn’t quite manage (I wrote 16 science-related posts and 5 articles for the Daily Cardinal over the 11 months since starting this blog), so I’m going to try for that again this year, and hopefully I’ll make it this time.

I have plenty of ideas – and several half-written posts – floating around on my Google Docs account, so it’s mostly just a matter of making myself sit down and write. Prod me if I start to fall behind, okay?

In the spirit of “catching up”, I spent half an hour yesterday reading through all of the items in my RSS feeds that I neglected over the holidays. In particular, I have a feed that sends me the titles of every single science- and medicine-related paper published by UW-Madison researchers each week. This feed averages 90 to 150 items a week(+), and when I logged in to Google Reader this week I found 345 unread items.

There are a couple of pretty cool topics in there, ranging from using nanowires to make high-capacity cathodes for lithium ion batteries to studying whether giving birth to twins affects cows’ future reproductive success.

But my favorite, by far, is a paper from food science in which the authors studied chocolate chip cookies. I couldn’t resist writing a short research highlight on this one just for fun… because really, how cool is it to bake chocolate chip cookies for research?!

So what did these authors do, and why on earth were they studying chocolate chip cookies?

If you’ve ever heated chocolate up too much and let it cool, or even if you’ve ever kept a chocolate bar sitting around in a cabinet for too long, you might have noticed it develop grayish spots, caused by fat molecules in the chocolate rearranging into a different crystalline form. This is called “bloom,” and while it doesn’t really affect the taste, it doesn’t look very appetizing, either.

The authors of this paper noticed that chocolate chips in chocolate chip cookies usually don’t exhibit bloom, even though they get heated way past the point where chocolate loses temper. They theorized that this might be because oil in the cookies migrates into the chocolate, changes the way the cocoa butter crystallizes, and prevents bloom.

So, they tested this out by baking cookies with different amounts of fat in the dough, stored them for 10 days at room temperature, and looked to see which cookies developed bloom. They found that putting more oil in the cookie dough led to less bloom on the chocolate chips. They also used an analytical technique (gas chromatography) to measure how much fat actually migrated between the chocolate chips and the surrounding dough, and found that more fat migration led to less bloom.

Being good scientists, they had to make sure other ingredients in the cookies weren’t affecting the results, so they also made “cookies” using just sand, fat, and chocolate chips.

In the sand cookies, they found roughly the same dependence on the fat content as they did in the actual cookies, though it generally took slightly less fat in the sand mixture to prevent bloom than it did in the cookie dough. Curiously, though, they found that it took more fat actually migrating into the chocolate chips to achieve this effect. They speculated that the extra ingredients in cookie dough (like water) and the microstructure of the dough make it harder for fat to migrate in real cookies, which might explain some of these differences.

My one question about this research is that I think chocolate chips have a lot of additives in them that help them hold their shape while cookies bake, and that changes their behavior if you try to temper them for other stuff. I’d love to see whether these results are any different if you use chunks of regular baking chocolate.

As a scientist and an avid baker, this article was a lot of fun. I particularly enjoyed Figure 2, which shows chocolate chip cookies with three chocolate chips precisely embedded in the top for analysis, and “standard recipe” given in Table 1 (with all ingredients listed by weight!).

But perhaps the best line of this article was at the very end of the conclusions: “Further work in the area is warranted.”

Why yes, yes it is.

Original article:

Bloom on chocolate chips baked in cookies
A. Frazier & R. W. Hartel, Food Research International 48:2 (2012), pages 380–386
doi/link: 10.1016/j.foodres.2012.05.011

(*) This is what I look like in ballerina mode. Surprise?

(+) The research volume coming out of this university astonishes me. This works out to roughly 5000 science-related papers by UW-Madison authors each year!


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