The Science of Breadmaking

People have been making bread for approximately 30,000 years—almost since we were still cavemen! Even though we might not have understood what was happening when we first started making bread, there’s actually a ton of science behind how it works.

In this home experiment, we’ll bake a very simple (but crazy delicious!) loaf of bread using just four ingredients: water, flour, yeast, and salt. Breadmaking involves a lot of irreversible chemistry, so make sure you read through the recipe first to get an idea of what you’ll be doing at each step. Then, at the end, we’ll talk about the science of what happened along the way.

Materials

• Plastic wrap
• Thermometer
• Metric scale
• Cooking spray
• Large spoon (the stiffer, the better)
• Large bowl
• A clean counter top
• 1-2 cookie sheets
• Shallow metal baking pan (at least 1″ deep)
• 1-2 pieces of parchment, one per cookie sheet
• Olive oil
• 567 g bread flour
• 11 g salt
• 3.5 g instant yeast
• 385 g water (room temperature), plus an extra cup or so of hot water.

Procedure

1. Add all the dry ingredients (flour, salt, and yeast) in the large bowl and stir to combine.
2. Pour 385 g of room-temperature water in and mix until everything is well-combined. The dough will be a bit sticky. If it’s too dry, add in a small amount of room-temperature water; if it’s too wet, add in some more flour.
3. Pour a couple tablespoons of olive oil directly on the clean counter top and spread it around with your hands. It’ll keep the wet dough from sticking to your fingers and the countertop. Dump the dough out onto the oiled counter, and spoon out any remaining dough from the bowl.
4. Take a small piece of dough between your fingers and try to stretch it out. What do you notice about the dough? Is it stretchy, or is it chunky and easily pulled apart?
5. Place the dough bit back with the main dough pile. Loosely grab the side closest to you, pull and stretch it towards you, and fold it back onto itself—kind of like folding a towel in half. Repeat with the opposite side. Do this about 10-15 times. To see a video of how the stretch-and-fold method works, click here.
6. Spray the large bowl liberally with cooking spray, and place it upside-down over the dough pile. This will keep the dough from drying out. Let the dough sit for 20 minutes.
7. Do three more rounds of stretch-and-folds, waiting 20 minutes in between each round.
8. After the last stretch-and-fold, place the dough back in the bowl and cover with a sheet of plastic wrap sprayed with cooking spray. Let the dough sit until it’s doubled in size. This should take around an hour to 90 minutes, depending on how warm it is in your home.
9. Take another small piece of dough between your fingers and stretch it out again. What do you notice this time? Is it still chunky, or is it stretchier this time?
10. Shape the loaves: dust a clean section of countertop with flour this time, and divide the dough into two or three even pieces. Gently shape each piece into a rough rectangle shape (it doesn’t have to be perfect), and fold the edges into the middle, just as if you’re about to make a paper airplane. Gently tamp down the edges in the middle of the dough with your fingers. Fold the dough in half again, and tamp down the edges. To see how a video of how the shaping works, click here.
11. Pan the loaves: place the dough seam-side down on a sheet of parchment paper sprayed with cooking oil. It should resemble a log shape. Repeat with the remaining pieces of dough and place on the parchment sheet. Give each loaf plenty of room to rise—don’t put more than two loaves on one parchment sheet.
12. Let the loaves rise: cover each loaf with another sheet of plastic wrap sprayed with cooking spray. Let the loaves rise until one and a half times their size. It should take around an hour, again depending on how warm your home is. Watch them carefully–you don’t want them to get too big or they will deflate in the oven!
13. When the loaves have almost reached their final size, put the empty metal baking pan in your oven and preheat it to 500 degrees Fahrenheit. Let the pan heat up with the oven.
14. Score the loaves: take your sharpest knife, and gently slice two diagonal shallow lines across the top of the loaf.
15. Place the loaves – parchment paper and all – on cookie sheets (don’t worry – the parchment won’t burn). Get a cup or so of hot water ready.
16. Open the oven door. Very carefully, pour the hot water into the empty metal baking pan. This will create a lot of sizzling and steam; don’t be alarmed—that’s why you’re doing it. Slide in the cookie sheet with the loaves of bread, and close the door. If you have two cookie sheets with bread on them, you may have to bake one at a time depending on how many racks are in your oven.
17. After five minutes, reduce the temperature of the oven to 450 degrees Fahrenheit.
18. After ten minutes, rotate the loaves around so they bake evenly.
19. After twenty minutes, check the loaves again. Remove from oven when they’ve reached a deep golden brown color.
20. If you have any more loaves to bake, turn the heat back up to 500 degrees Fahrenheit and repeat the baking process from step 16 for these loaves as well. Remember to add in fresh water to the metal baking pan; you can pour it on top of any remaining water if there is still some left.
21. Let loaves sit for ten minutes to cool down before you slice them.
22. Enjoy!

What happens when you mix the ingredients together?

Although there are only four ingredients that you use in the mix, there are actually a ton of unseen chemicals that you’re working with. Flour is more than just a white powder: it contains many proteins, mainly in the form of glutenin and gliadin. It also contains a lot of carbohydrates, in the form of simple sugars like glucose, or in the form of longer chains of sugars, called starches.

Normally, the chemicals stay in a non-reactive form as long as they’re dry. But when you add water, something changes: suddenly, they start combining and reacting to form thousands of entirely new chemicals as well! The water reactivates the yeast so they start chewing away at starches like little Pac-men and spitting out other sugars, carbon dioxide, and alcohols. Water also allows the glutenin and gliadin to combine to form a network of stretchy super-protein: gluten (here’s a cool video actually showing how gluten is formed).

How does the bread rise?

When you did the stretch-and-folds, you were actually organizing the gluten molecules so that they created a sort of molecular net. Then, when they yeast started producing carbon dioxide, it actually inflated the “net.” It works the exact same way as when you blow up a pool toy or inflate a hot-air balloon!

What does baking do?

Baking serves multiple purposes. The first stages of baking allow the bread to rise even further in the oven—something that bakers call “oven spring.” What’s actually happening is that the yeast is heating up, metabolizing faster, and increasing their production of carbon dioxide, so the loaf rises higher. By the time the loaf has reached 140 degrees Fahrenheit, though, the yeast cells are all dead, but the loaf continues to rise: this time, from simple heat expansion of carbon dioxide gases, plus water vapor and evaporating alcohols left over from the yeast’s glory days.

Finally, when the loaf reaches about 200 degrees Fahrenheit, enough water is drawn out of the loaf and the final poofed-up structure of the bread hardens into its final shape. If the bread is heated much beyond this point, it begins to burn.

Why do we bake with steam?

When you made the oven steamy, it actually allowed for even more physical changes to happen. The steam kept the crust of the bread soft and pliable, so that it could rise even further and create an airier bread. Otherwise, the crust would have dried out too soon, and it would have stopped rising.

Additionally, the steam allowed for more chemical changes to happen. Water transmits heat better than air alone, and so it allowed the bread to bake more evenly. Because of the better heat transfer, it also allowed a unique phenomenon in cooking to occur: Maillard reactions. These are special bonds that form between proteins and sugars, and they create hundreds of super-flavorful new molecules. It’s the same thing that gives a seared steak its great flavor and the bread crust its nice golden-brown color.

There you have it! Even though there are a lot of complex scientific processes going on, the end result is one thing: a delicious piece of chemistry we call bread. If you’re interested in learning even more about some of the processes going on behind the scenes of breadmaking, check out Serious Eat’s Breadmaking 101 guide. Bon appetit!