MadSci Network: Chemistry
Query:

Re: what makes cookies soft?

Date: Mon Feb 28 08:43:33 2000
Posted By: Jill Irvin, Staff, Food and Nutrition, Ohio State University
Area of science: Chemistry
ID: 951447929.Ch
Message:

Well, Leah, there are 2 major things that make cookies soft - one is how much fat is in the cookie and the other is how long you bake them.

First, let's talk about the fat. When flour and water are combined and mixed together, they form a substance called gluten. This is a strong, elastic substance that gives baked products their structure. Without gluten, you would have to drink your cookie, instead of chewing it. The more you mix these two together (flour and water), the stronger the gluten becomes, so that eventually your cookie could end up like a brick - too hard to eat. Now, what does fat have to do with it? Well, fat coats the flour and doesn't allow the water to mix with it. If the flour doesn't get wet, it can't form the gluten. So, if cookies are really soft, they probably have a lot of fat in them or they were not mixed very much so that very little gluten was formed. (And, by the way, all kinds of liquids count as water - milk, juice - because the major thing in these is water). So, that is one way to get a soft cookie.

The other way is how much you bake them. As you bake cookies, the water that is in them evaporates. The longer you bake them, the more water evaporates, which makes the cookies harder and harder. Now, of course, you have to bake them some or else you would be eating cookie batter instead of cookies. However, at some point, the cookies have been cooked enough to be soft and chewy and not hard. A really good example of this is a sorta new kind of cookie called a biscotti. They are very hard because they are baked twice.

You can get more information about baked items by looking in food science books and some cookbooks. The ones I use are:

Food Science by Helen Charley, published by John Wiley & Sons
Introductory Foods by Marion Bennion, published by Merrill Prentice Hall

These are probably a little too difficult for you to fully understand, but your teacher should be able to help you understand the information. Food is a great way to learn science and math.

Thanks very much for the question.

Jill Irvin
Ohio State University


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