Are your cookies in the oven (or just came out)? And you're wondering what turns raw raw dough into crunchy or chewy cookies? Of course, heat causes these changes, but what is the chemistry behind the changes? We're delving into what exactly happens in the oven, a little entertainment for you to read while waiting for the cookies to come out!
what happens in the oven
The biggest difference between inside and outside the oven: the temperature. Once this cookie is in the oven, the ambient temperature rises to over 140°C (250°F). The outside of the cookie will heat up very quickly, but the inside will take a while to heat up, depending on the size of the cookie (we've discussed this phenomenon before, usingcake as an example). However, as soon as the heat hits your cookie, even if it's just the outside, the baking begins!
A cookie dough…
There are many different cookies with many different ingredients. What exactly happens to a cookie depends on what is contained in that cookie. In general, however, most cookies contain most, if not all, of these ingredients:
- Fett: This can come from oils, butter, margarine, chocolate, tahini, nut flours, etc.
- propellant: Most often it is baking soda or baking soda
- protein: Eggs and milk are rich in protein, but wheat flour also contains them (Gluten), as well as walnuts and aquafaba (aprotein substitute)
- Strength: often comes from flour (wheat is perhaps the most common, but can also come from a variety of other sources such as rice or tapioca)
- Water: Eggs, milk (whether vegetable or dairy), fruits all contain water
- Zucker: can be “regular” granulated sugar, lactose (found in milk), or sugar syrup like corn, maple, or rice syrup
...begins to transform
Once the cookie dough is in the oven, each of these ingredients will begin to transform in one way or another. Also, they will most likely interact with each other as well. some will be easyphase change(e.g. melting or evaporation), others participate in a chemical reaction or permanently transform. Let's delve into each of the mechanisms below, trying to figure out how they will affect the final texture and taste of the cookie!:
- Fett: If your shortening is solid before it goes into the oven (eg coconut oil, butter, margarine), it will melt in the oven. This starts at very low temperatures, starting at 50°C most of it becomes liquid.
- propellant: are activated by heat, causing theformation of carbon dioxide, take the cookie
- protein: Each protein behaves differently, but most will denature, some will help the cookie bake, some won't affect the texture as much
- Strength: Starch boils, similar to whenboiled potatoes
- Water: evaporates once above boiling point (100°C / 212°F), if it evaporates inside the biscuit but can't escape, it might help to rise a little
- Zucker: brown the biscuit duecaramelization&Maillard reactions(The second also requires proteins to pass)
fusion of fats
If your cookie contains solid fats, think butter (not melted), margarine or coconut oil, melting these fats is one of the first things that happens in the oven. Since solid shortening gives cookie dough firmness (which is why you may be asked to refrigerate your shortbread dough before slicing or rolling), melting shortening does the opposite. The biscuit will soften.
If your biscuit contains a lot of previously solid fat, it can be so soft that the dough spreads. Whether this happens depends on the proportion of its ingredients, as we found in testscrumbly dry cake. For example, flour helps a cookie stick together. If your cookie uses less compared to the amount of fat, it will likely spread more (good example: thesebrown butter cookies, which should spread out a lot).
Melted fats can also make your biscuit shiny. This is due to liquid fats, which reflect light differently than solid ones.
Melting of most fats used in baking is generally complete at 50°C (122°F). As such, it's one of the first big changes you'll see to your cookie.
The thrusters come into play
If you're looking for a more airy cookie with a slight lift, chances are you've added a little baking powder or baking soda to your cookie. Baking soda and sodium bicarbonate work in very similar ways. Both contain sodium carbonate. When baking soda comes into contact with acid, it reacts to form carbon dioxide gases. This will expand your cookie dough. Although these reactions occur at lower temperatures (especially with sodium bicarbonate), they occur much faster and to a greater extent when they occur at elevated temperatures.
This is where the oven comes into play. Once the dough is heated, thepropellantwill begin to expand your cookie dough. This reaction starts at very low temperatures, well below the actual oven temperature. This is a good thing. All biscuit expansion must be done before the biscuit sets (how much this happens in the oven depends on the biscuit). For example, once proteins start to solidify, they become less inflexible.
Both the melting of the fats and the expansion caused by the leavening agents begin at very moderate temperatures, just above room temperature. The rest of the processes will start later, as soon as the biscuit continues to heat up. Also, processes will become more chaotic and most of them will happen simultaneously while also interacting with each other.
Protein denaturation is one such process.Proteinare complex folded structures composed of long chains of amino acids. These three-dimensional structures are important for their functionality, but most proteins cannot tolerate high temperatures. Elevated temperatures (about 60-70°C and up, but this depends a lot on the specific protein) cause proteins to unfold in a process called denaturation. This process causes changes in the behavior of proteins.
How denaturation affects the behavior of proteins depends on the protein. If you've seen an egg boil, seen it harden and change color, there's a big change going on. In general, a large percentage of egg protein "sets up" due to denaturation. This helps your cookie to be more solid, especially if it's based on aprotein foam structure.
Other proteins, on the other hand, have less of an impact. Milk proteins, for example, do not configure in a similar way, nor do gluten proteins. However, its denaturation affects the texture and structure of the biscuit.
cook the starch
So far, most of the changes we've discussed haven't "baked" the cookie, meaning the cookie has been irreversibly changed. But, as we all know, there is no way to turn a cookie, after baking, into the original dough.
Even the melting of fat and the effects of leavening agents do not permanently alter the biscuit. If the biscuit dough is unable to retain the gas formed, it will simply dissipate over time. Protein denaturation is irreversible and particularly important for egg-based biscuits. The other major permanent transformation is the cooking of the starch.
Starch is one of the main ingredients in most flours (eg wheat, rice or cassava flour).StrengthIt's a big and complexcarbohydrate. When in contact with water, starch absorbs water. If you heat this mixture, the starch will swell to absorb even more water. Eventually, the starch granules break apart and release individual molecules. This process is called gelatinization. If you have already made a roux-based sauce (ex.bechamel), you will have seen it before your eyes.
This gelatinization process, cooking the starch, helps to harden the biscuit. If you don't have enough flour (or egg, which plays a similar role) in your biscuit, it can break down later due to the inability to keep all these components in place.
As long as the surrounding air is dry enough, the water evaporates. At room temperature, this happens slowly. But if you leave a bowl of water outside long enough, it will dry out over the course of several days. As you can intuitively know, this process is much faster at higher temperatures. When water boils at 100°C at sea level (212°F), the water continuously evaporates.
A hot oven will also evaporate the water from the cookie dough. In some cases, water can escape easily. In other cases, the water evaporates but is trapped in the biscuit. This can help a cookie expand a bit (although it's less powerful than the effects of baking soda and baking soda).
If enough water evaporates, your food can be crunchy and crunchy (see our example atcrispy chicken skin). Crunchy foods therefore have very little, for example chips or biscuits.
Therefore, controlling water evaporation is important to obtain the ideal biscuit texture. If you want your biscuit to be chewy, don't evaporate too much water. However, if you are looking for a crispy biscuit, you can leave it there for a few more minutes to allow more water to evaporate. Chewy/crunchy is affected by the recipe itself, but a few minutes more (or less) in the oven can certainly make a big difference.
Finally, once the cookie gets nice and hot, many chemical reactions happen at the same time, giving the cookies flavor and color. Most of these reactions involve some type of sugar.
Depending on the type of cookie, the sugar can caramelize. Caramelization only occurs at temperatures well above 100°C (212°F). The exact temperature depends on the type of sugar in your cookie, sucrose (the chemical name for sugar in granulated sugar) caramelizes at a different temperature than, for example, glucose and fructose (found in invert sugar).
As caramelization takes place at relatively high temperatures, this will not happen to everyone. For this, you need to have very little water and plenty of sugar (preferably in the dry part on the outside).
A more common chemical reaction that occurs in almost all cookies is the Maillard reaction. OMaillard reactionit is a reaction between reducing sugars (eg glucose) and proteins (eg those in butter). Even though he describes it as just one reaction, it's actually a series of complex reactions, all happening at the same time. Along the way, many different flavor molecules are formed, as well as a brown color.
The Maillard reaction takes place at room temperature, but very, very slowly. It may take months before you see a color change. However, it accelerates significantly at higher temperatures, especially if the amount of moisture is not too high (which is often the case with cookies).
To go out
When you're satisfied with how all these processes are going, it's time to take your cookies out of the oven. You can judge this by the color of the cookies, their shape, or just experience based on the required baking time.
However, don't be surprised if your cookie doesn't turn out the way you envisioned. It's probably still a lot softer in texture, for example. Remember, the cookie is still warm, so all the fat is still oozing out. Furthermore, starch structures are softer and thicker as they cool. It's not until your cookie is completely legal that you can tell if it's what you expect it to be. And even as it cools down, you still have some control over what happens. We have another post for you that covers everything you need to know.cool your cookies:-).