Wednesday, 3 December 2014

Cookie Chemistry: Using Science to Bribe Santa

As Santa can attest to, nothing quite beats the mouth-watering aroma, delightful texture, and scrumptious taste of a plate of perfectly baked cookies. Since the early 1930's Santa has been munching down on plates of cookies left out by children, desperate to make up for a year of sub-par behaviour. If the man in red merely took a nibble of one cookie from every plate left out for him each year, he would eat over 336 million cookies in one night. Unfortunately for Santa, those cookies probably aren’t  always the picture of cookie perfection.

It is notoriously difficult to bake a perfect cookie. First of all, not everyone’s definition of "perfect" is the same. Some prefer a more light and cakey consistency. For others, the perfect cookie is flat and crisp around the edges with a gooey centre. Still others find that perfect means the treat is chewy throughout. Second, most people have no idea why one recipe will result in a chocolate chip cookie that is crisp and flat while another, seemingly identical, recipe will result in cookies that are dense and chewy. It should come as no surprise that science is to blame for your failures in baking.There are a myriad of variations on the traditional chocolate chip recipe, but for time’s sake, we’ve narrowed it down into three main cookie types: flat, cakey, and chewy.

Flat Cookies:

These cookies are flat with crisp edges and a soft, gooey centre. Surprisingly, they are a result of increasing the amount of leavening agents in the dough. Using a mixture of leavening agents, usually baking soda and baking powder, will increase the spread of the cookies. Baking soda encourages browning by neutralizing the acidity in the brown sugar, vanilla, and butter, leading to crispy edges. Baking powder, which is a mix of baking soda and an acid, reacts when introduced to a liquid (i.e. melting butter) giving off carbon dioxide and producing little pockets of air throughout the dough, causing it to rise in the oven. The overload of the two leavening agents causes larger and less stable air pockets in the dough which will collapse as the cookies cool, leaving you with a delectably soft and gooey centre.

Cakey Cookies:

These cookies are puffy and soft. This texture is achieved by using only baking powder as the leavening agent in the dough.  While baking soda relies on the acidity of other ingredients in the cookie to form its reaction, baking powder already contains the acid (usually calcium phosphate) and reacts when introduced to a liquid (you can see this reaction by adding a drop of water to baking soda). Melting butter and sugar in the baking cookie activate the baking powder, releasing carbon dioxide. The result is a mess of small air pockets in the cookie that push upward and cool into a stable dome.

Chewy Cookies:

These cookies are… well… chewy. The texture is a result of two changes to your traditional chocolate chip cookie recipe: melted butter and bread flour. Normally, recipes call for softened butter (solid butter at room temperature). Melting the butter instead causes the milk fats and water to separate. This will be useful when you combine the wet ingredients with the bread flour. The protein content of bread flour is higher than that of regular, all purpose flour and that leads to a tougher end product. That is why bread flour is used to bake chewy baguettes. Those extra proteins in the bread flour combine with the water in the melted butter to form gluten, which is chewy! The bread flour will also absorb more moisture, resulting in moister cookies.

Believe it or not, there are even more variations to be had on the traditional chocolate chip cookie. Check out this blog to see how other ingredients and baking techniques affect cookies.