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The science behind your favourite Christmas baking

By Pamela Freeman, December 23 2021—

There’s nothing better to do in December than bake cookies. In case you need a reason other than they are delicious, baking is the way to show people you love them over the holidays. This tradition dates back centuries when sugar and spices were harder to come by and a genuine gift. Baking is also the way to relieve stress during finals and what better way to get through that last chapter than a fresh chocolate crinkle straight out of the oven. 

Baking is a science. There is a combination of certain ingredients, mixed in a specific way, to produce the intended rise, texture and flavour. The ingredients — typically butter, sugar, eggs, vanilla, salt, a leavener and flour — all play an important part. Knowing these roles can help you experiment, improvise and improve your baking. This article will explore each ingredient to help you create a dream holiday cookie plate and if you don’t know where to start, recipes will be provided for inspiration.

Butter, the main fat incorporated into cookies, helps cookies spread, prevents gluten formation and also provides flavour. Butter and sugar are creamed together as a crucial step in determining the structure and texture of your cookie. Sugar incorporates air into the butter, a form of mechanical leavening, to provide rise without the use of a chemical reaction. The sugar is also dissolved in the moisture of the butter and it can create more holes in the fat. 

Butter is an emulsion of water and fat, which do not mix as fat does not have a charge to bind to the polar water molecules and dairy solids to hold it together. At 92 degrees Fahrenheit butter will melt — the dough will start to spread out and water is released. Water within the dough will expand into steam. This is the start of the numerous stages of dough baking.

Many cookie recipes call for “room temperature” butter, such as this whipped version of shortbread that has a high butter content and will live up to its melt-in-your-mouth title. In practice, room temperature means slightly cooler than ambient, at about 65-68 degrees Fahrenheit or 18-20 degrees Celsius. Butter, out of the fridge for about an hour, will be cool to the touch and only have a slight indent when you press into it.

This is perfect and what most bakers recommend as it mixes easily and smoothly. Cold butter has more of a chance to mix unevenly unless beaten well. Other recipes call for melted butter, which will spread more when cooking and have less structure. It will lead to a chewier cookie as more, smaller air holes are produced when the water evaporates.

Margarine, shortening, or plant-based butter are often used as vegan substitutes. These will change the flavor more than the consistency of cookies. For another dairy-free option, notice how biscotti uses a low oil to flour ratio, making it dry and crunchy in a good way.

Sugar is not only the star sweetener, it helps determine the density, flavour and structure of a cookie. Granulated sugar browns the cookies through caramelization, crisps the cookies by absorbing moisture in the dough and produces more air bubbles as it is less dense.

Brown sugar makes for chewier cookies as it contains molasses — 10-20 per cent depending on the type — which adds moisture and is slightly acidic. Other sweeteners, such as maple syrup, agave syrup or honey add extra moisture to cookies, and can be added or substituted with care to remove other liquid from the recipe.

Sugar, due to the sheer amount added, will partially dissolve during mixing and continue dissolving as it melts in the heat of the oven. This helps the dough soften and spread. There are two important processes that sugar undergoes — Maillard reactions and caramelization.

 At 310 degrees Fahrenheit, Maillard reactions start to happen in which proteins and sugars react and rearrange into ring-like structures. This reactive process produces a distinct browning and develops complex flavours and smells not only in cookies but in bread, burgers and coffee among many other foods. Brown sugar is ideal for these reactions as it contains both glucose and fructose, lending to better development of flavours than white sugar, which contains mostly fructose.

Around 320 degrees Fahrenheit the caramelization process begins. Under the heat, sugar disintegrates into its components which react with one another to form bitter, sour, nutty or sweet compounds. At 355 degrees Fahrenheit, around the typical oven temperature for cookies, the caramelization is moderate to produce those flavours and a medium brown colour. White sugar is ideal here, as brown sugar can burn. For a demonstration on how using only white sugar can provide a specific effect, try these sugar cookies.

Eggs provide moisture, protein and fat to cookies. The egg white’s moisture provides structure by bonding with starch as well as steam when heated, while its protein helps make it chewy by helping trap air. The egg yolk provides fat, inhibiting gluten development.

The use of only egg whites or yolks is situational — each one can provide a cakey or a dense, tender cookie depending on the other ingredients and mixing technique. These small batch one-yolk cookies are an amazing classic, a chewy cookie from only using the yolk. Note, they also only use brown sugar. There is a complementary double chocolate chunk cookie recipe to use the leftover egg white.

In a given recipe, it may call for room temperature eggs as well as butter. Beating in warm eggs, with a looser protein structure, helps incorporate more air into the dough. This air, as mentioned, helps with expansion while baking. At 144 degrees Fahrenheit, the numerous proteins in eggs unfold and intertwine, solidifying and giving substance to the dough. This is also a good temperature as salmonella is killed.

Vanilla is used in modest amounts but is vital to bring out the flavours within the other ingredients. Artificial vanilla extract contains vanillin, the flavourful compound found in vanilla beans. Pure vanilla extract is made from extracting flavour from vanilla beans by soaking them in alcohol and water. Arguably, the artificial version is better when baking cookies, as it is developed to survive the high oven temperature, whereas the pure extract will boil off and lose the desired vanilla essence. 

Leaveners, namely baking soda and baking powder, are used to give rise to the cookies and make them soft and fluffy. Other ways help leaven your cookies, such as incorporating air in when creaming butter and sugar but the leavener, with its chemical reactions, does most of the heavy lifting.

Baking soda or sodium bicarbonate, is an alkaline, or basic, powder. It is paired, and reacts with an acidic ingredient in the dough such as brown sugar, molasses, cream of tartar or cocoa. An acid-base reaction neutralizes the effects of the reactants. The specific ingredients in baking are purposely crafted to produce carbon dioxide in the neutralization reaction and this aerates the dough. 

Baking powder is a combination of baking soda and an acid, meaning that it is self-contained as a leavener and these ingredients will neutralize each other in reaction. Typical grocery store baking powder is double-acting, meaning it is activated in the dough when exposed to liquid and also activated when heated. Cornstarch is also added to baking powder as a buffer, preventing reactions before use.

Some recipes use both soda and powder to find the right ratio between basic and acidic ingredients. At 212 degrees Fahrenheit, the water within the dough will steam and evaporate. The cookie dries out and is left soft, with air pockets throughout. The carbon dioxide gas produced by the chemical leavening also aids this airiness.

Cream of tartar is the key for snickerdoodles’ signature taste, and these ones have added flair thanks to maple syrup. Cocoa and molasses work well with baking soda in chocolate molasses cookies for a bittersweet and chewy result.

Salt has a straightforward but vital role. It acts as a flavour enhancer, balancing the sweetness. It also strengthens the networks of proteins, providing a little extra boost for the structure of the cookie. Salt is used sparingly, so most recipes recommend using unsalted butter and adding salt yourself to control the amount used. Salt sprinkled on top of a cookie provides a little extra contrast to the sweet flavours, for example in Allison Roman’s salted butter chocolate chunk shortbread that went viral a couple of years ago.

Flour is crucial in determining the texture of your cookie. The flour-to-butter ratio, if high, lends to dry dough and a tender or crumbly cookie. If low, baked goods will be cakey or chewy. In cookie recipes, the ratio can change greatly depending on the specific type, however, most will be in the middle. 

Typically, recipes call for all-purpose white flour. White flour contains only the endosperm of wheat — the part which is full of starch and protein. It is a mixture of hard wheat, one high in proteins, and soft wheat, one lower in protein and higher in starch. Depending on the protein and gluten proportion in the flour, the strength of your dough and how it will mix with the moist ingredients will change.

For example, bread flour is higher in protein, and thus gluten, bringing structure and chew to the dough, while cake flour is low in protein, leading to soft and light baked goods. A step in the wheat processing, bleaching, leads to less gluten formation by chemically affecting the protein content. Sometimes this is useful, as in cake flour but sometimes is purely for aesthetic purposes. Levain bakery in New York is famous for giant, gooey cookies and this copycat chocolate chip cookie recipe uses cake flour to make it soft and tender. It also uses high heat and a short baking time for this result. 

Whole wheat flour, on the other hand, contains the entire wheat kernel — the endosperm, as well as the bran, the outer coating and germ, where new wheat is produced. These components contain fibre and nutrients. Using whole wheat flour will make cookies denser, heartier and less chewy. Gluten-free flour mixes typically mimic all-purpose white flour.

The mix adds back in the springiness of the network of proteins by adding in other chemicals — specifically, ones with long chains of sugars or starches that provide structure and help keep moisture in the dough. However, this is not always needed, as in these chewy, gluten-free oat flour cookies, which also use egg yolks and brown sugar to help with the texture.

As discussed, gluten is an important factor in the overall texture. Gluten is a network of proteins that help make cookies springy, but if too developed can make them tough instead. It is made of glutenin, a protein in a long chain, and gliadin, a round protein, that combine with water. This strong structure helps give substance to baked goods. It can help hold the cookie together when the dough melts and spreads.

Mixing the dough helps bring together the differently shaped proteins, creating a matrix, however, be careful not to overmix the flour. A simple mantra for most baking is “mix all day before you add the flour.” Since water is necessary for gluten formation, a couple of ways to hinder it are fat, which could coat and help make the flour water-resistant and sugar, which helps absorb moisture. Salt, on the other hand, strengthens this network of proteins. Gluten development in cookies is a fine balance between chewy and tough.

With this base knowledge of cookie dough ingredients, you’ll have a head start on any recipe you try. There are many factors that can affect how a cookie turns out aside from the ingredients, namely the oven temperature, pan type, pan lining and storage method. If those things are intimidating, feel free to stop here and eat the dough. The FDA may warn that raw eggs could have salmonella and raw flour could have E. coli but a little risk makes it taste even better.

There are many other cookie recipes to enjoy over the holidays — rugelach is a flaky dessert whose four-ingredient dough contains cream cheese, pfeffernuesse is a soft, spiced gingerbread cookie, maple pecan cookies are an easy classic that contains neither an egg nor a leavener and alfajores are a buttery sandwich cookie filled with smooth dulce de leche. No matter which way you choose to bake this season, I think you’ll find that science is quite sweet.

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