Baking bread does involve science, but as the saying goes, it's not rocket science.
If you're a beginning bread baker, you don't really need to read this. Just pick a recipe, follow it exactly, and don't make any substitutions.
But if you've baked a few loaves and they've come out all right, you might be starting to think about experimenting. What if you used milk instead of water? Or tried a different type of flour? And what's the deal with gluten?
We obviously can't cover every variable here. Bread baking is complex and there are a lot of things that can go wrong—or right! Still, if there's anything more gratifying than baking a perfect loaf from a recipe, it's coming up with a recipe of your own.
So if that's where you're at, or at least where you're headed, this is the article for you.
Yeast is the ingredient that causes bread to rise and it's also a source of flavor and aroma. Yeast is a biological organism that consumes sugar and produces alcohol and CO2 gas. It's this gas that leavens baked goods.
There are various forms of yeast, including active dry yeast, which comes in packets and needs to be rehydrated before using; instant yeast, which you can add directly to your dry ingredients; and fresh yeast (sometimes called cake yeast), which comes in the form of a paste.
Fresh yeast has the shortest shelf life, but it imparts a much stronger yeast flavor and aroma than the other two kinds.
Wheat flour is the main ingredient in bread, and like yeast, it, too, is available in a wide variety of types. The main variations have to do with the amount of a protein called gluten that a given flour contains.
Hard flour is high in gluten, between 12 and 15 percent by weight, and produces a chewier, heartier, crunchier loaf. Soft flour is lower in protein, around 7 to 9 percent, and produces a softer, more delicate bread. All-purpose flour is a blend of both and comes in right in the middle, usually 10 to 11 percent gluten.
Bread flour is a high-gluten blend of flour and it's what you'll usually use for making bread and pizza doughs. But different brands will feature different percentages and will be made from different types of wheat.
Whole wheat flour is made by grinding the entire wheat kernel, including the bran and the germ, whereas white flour is only the endosperm—the inside part of the grain, with the germ and bran removed. Whole wheat flour contains more fiber and protein than white flour, but it also has a shorter shelf life. In general, higher-protein flours will spoil more quickly.
Fat, Sugar, and Salt
Most hard-crusted breads, sandwich breads, and whole-grain breads are made from lean dough, meaning they are low in fat and sugar. Exceptions to this include rich breads like brioche, focaccia, and croissants, as well as sweet pastries like cinnamon rolls. This is necessarily so, since both fat and sugar interfere with gluten development, producing shorter protein strands and thus a more crumbly, less chewy consistency.
Salt, on the other hand, hastens gluten development, making it an essential ingredient in any bread dough. Experimenting with the addition of fats and sugars can yield interesting results. For instance, a small amount of oil or melted butter will produce a softer, richer bread. Even substituting milk for some of the water in the dough will produce a noticeably softer loaf.
Likewise, sugar interferes with gluten development, but it's also the food for the yeast. Even a small amount of extra sugar can, therefore, trigger higher CO2 release and thus produce a lighter, airier loaf.
Mixing and Fermentation
Mixing, including kneading, is what causes the gluten molecules in the dough to develop. The longer you knead the dough, the more the glutens develop and the chewier and harder your bread will be. If you don't knead your dough enough, it may not hold its shape.
On the other hand, some breads call for no kneading at all. What they require instead is an extra-long fermentation time. Fermentation is what happens to a ball of unbaked dough that sits in a warm place for a certain amount of time. During that time, the yeast continues to consume sugar and produce gas, while the glutens relax and become more elastic.
Since it happens invisibly, and without any intervention on the part of the baker, fermentation is the part of bread baking that most closely resembles magic. But experimenting with longer and shorter fermentation times is definitely a good way to understand how fermentation relates to the finished bread.
What happens when the dough hits the oven is that the yeast produces one last sudden rush of gas, which ceases once the dough reaches 140 F since this is the temperature at which the yeast dies. As the bread bakes, the glutens become firm and the starches absorb water, while the top of the loaf turns brown. Steam can promote the browning of the crust, as does brushing the top of the unbaked loaf with milk or egg wash. Many bakers will use a sharp knife to slash the top of the dough, which allows it to expand more fully without bursting.