Bread essentially consists of four simple ingredients, yet how do they combine to form such a timeless and hearty food? Learn all the intricate details of breadmaking on the molecular level right here, so you can recreate your own mouthwatering bread with the perfect texture.
Background
Bread is one of the oldest foods in the world, yet it is still commonly eaten today by people all over the world. Archaeologists have correlated the development of human civilization with the evolution of bread wheat. In Neolithic times, when the first bread was made, lumps of unleavened dough were simply placed on hot stones in the embers of wood fires. Making bread was probably one of the first chemistry experiments!
Bread can also be found in so many different forms, from savory flatbread and baguettes, to sweet cornbread and banana bread. It's extremely versatile and can be paired with many other toppings and foods, but it's also still delicious and flavorful on its own. I love bread and I think it's perfect for any meal or occasion! While chewing on a thick slice of warm, crusty white bread slathered with butter, I contemplated how these ingredients could come together and make such different varieties of bread. I decided to try to make my own loaf, and see the chemical reactions and processes first hand. Knowing how the ingredients interacted would allow me to recreate those delicious breads without fail!
Procedure
The most basic type of bread usually just has four ingredients: water, flour, yeast and salt. I decided to *spice* up my recipe by adding some extra flavors of rosemary, black pepper, and olive oil, but the essential chemistry would still be the same. For my specific recipe with servings and measurements click here.
First, I mixed the flour, active dry yeast, salt, ground black pepper, olive oil, and rosemary together. As I poured the water in and combined all the ingredients, the water began disappearing and a sticky dough formed. I made sure not to overmix the dough before covering it with plastic and leaving it to rest for 15 hours.
I let my Dutch Oven heat up as I formed my dough into a ball shape and let it rest. I placed the dough into the pot and covered it, baking for 30 minutes before removing the lid and baking for another 15 minutes.
The first time I tried this recipe, the crust wasn't very brown. However, the next time I tried, the crust was brown and crunchy while the insides were cloud-like and chewy. I wanted to see the hidden, behind-the-scenes processes in making bread that caused such differences between the first and second time I made bread. Let's get to the exciting part - the science!
Science!
As mentioned earlier, the four main ingredients of flour, yeast, water, and salt and how they interact are basis for the chemical reactions that form the final bread product. From the previous procedure section, we can break down the breadmaking process into four steps: mixing the ingredients, kneading the dough, fermenting, and baking. I will explore each ingredient and their combinations in this process, starting with flour.
The proteins in flour generally make up 10-15% and are essential to the properties of bread. These proteins include glutenins and gliadins, which are huge molecules made of many amino acids. These proteins are collectively referred to as gluten, a more familiar name you have probably heard before.
In the flour itself, these proteins are inert, but as soon as water is added, they are able to line up with each other and interact. They form hydrogen bonds and disulfide cross-links between their chains, creating a giant gluten network throughout the dough. When we knead the dough, these proteins uncoil and interact with each other more strongly, strengthening the network.
Another ingredient that can affect the dough’s gluten network is salt, which is mostly for taste but also affects the gluten network. Salt strengthens the network, making the dough more elastic. This gluten network is vital for the bread to be able to rise, as it traps the gas bubbles in bread, making it fluffy rather than dense. This is especially important for no-knead bread recipes, like the ones I used.
However, the bread also needs another ingredient to rise - the yeast. Here's where all the interactions start to happen. Water by itself doesn't do much either, but starch from the flour absorbs the water. Yeast are single-celled organisms containing enzymes that lie dormant until they come in contact with warm water. They can then break down the starch in flour into sugars, first using amylase to break down the starch to maltose, and then using maltase to break down maltose into glucose. The yeast metabolizes the glucose sugar for energy and produces carbon dioxide and ethanol (an alcohol byproduct) - just like in the fermentation of beer. The alcohol burns off during the baking, so no need to worry! This reaction looks like: C6H12O6 → 2C2H5OH + 2 CO2
One molecule of glucose sugar yields two of alcohol and two of carbon dioxide gas. The carbon dioxide gas bubbles move around slowly throughout the dough as it ferments, which rearranges the proteins in the bread dough into a network without kneading. Later on, as the dough rises and proofs, its volume increases due to the carbon dioxide produced in fermentation. The carbon dioxide expands as the bread dough warms and bakes in the oven, and is essential for the pockets of air in the bread. The more carbon dioxide produced during fermentation, the softer the bread will be when baked.
The other product, alcohol, also helps leaven the bread. While at room temperature, the alcohol is liquid, but in the oven, the alcohol evaporates into gas bubbles that contribute to the rise of your bread. The water also evaporates and helps the bread rise in this way. Thus, yeast is not only essential in strengthening the gluten network, but also in reacting and creating byproducts that help leaven bread.
The bread stops rising when the crust becomes stiff enough to resist expansion. At 70-80 degrees Celsius, the gluten proteins form strong cross-links and the water-filled starch granules swell and set. The yeast has already died at this point. Now that the bread's walls can no longer stretch, the gas pressure in the holes builds. This causes the walls to pop ad create the open networks of holes you see when you slice a loaf.
Finally, the sugar produced by fermentation isn’t all metabolized by the yeast. Instead, it participates in the Maillard reaction, a series of reactions between sugars and amino acids that occur rapidly above 140˚C, so while the bread bakes. These reactions produce a whole range of products, which can add flavor to the bread, and also help to form the hearty brown crust.The Maillard reaction is also found in cookies. If you like bread with a deep brown crust with more flavor, it's a good idea to cook the loaf a little longer to allow the high temperatures to caramelize the sugars in the crust.
You might wonder how this whole process works for gluten-free bread. in this case, gluten-free flours such as rice flour must be used, and xanthan gum is commonly added. This is a polysaccharide produced by a bacterium which can help provide a similarly elasticity to gluten.
After your bread is cooked, it will of course start to go stale due to the starch crystallizing and hardening over time. Though this can be temporarily reversed by reheating the bread. Fun fact: storing bread in the fridge actually accelerates the staling process, so it's best to eat it soon after it's baked!
Conclusion
It's amazing how basic bread with only four ingredients can have so many different reactions occurring in the background! Now I know that to get a browned crust, I just need to make sure my oven temperature is high enough and to bake it for longer! Additionally, fermenting it for longer allows for more carbon dioxide bubbles and a softer, chewier dough. More importantly, now we know we can't get tipsy from bread. Next time you have time, skip buying underbaked supermarket bread loafs, and bake your own delicious bread!
Link to my rosemary dutch oven bread recipe.
Link to my post on the history & culture of bread.
Want to Learn More? (always cite your sources, kids)
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