For a long time I have been scared to attempt bread because it seemed like such an involved process where so many things could go wrong. A lot of that was driven by how scientific it seemed. In reality, it’s so similar to the science of so many other baked goods, you now are just able to see it first-hand! Much of the science of bread stars the fungus yeast. When we buy yeast in grocery stores it’s usually called either active dry yeast or instant yeast. The difference between these two packages, and yes there is a difference, is active dry yeast should be dissolved in warm water before use (105 degrees fahrenheit is the ideal temperature, too hot may kill the yeast but too cold will not activate the yeast), while instant yeast can be mixed in directly with dry ingredients like flour. So, if you want the perfect loaf (or pizza, or roll, etc), make sure to pay attention to what kind of yeast the recipe calls for, and how you might be able to substitute it for yours.

Yeast can seem like the mysterious force behind bread, without which bread would never be bread. In fact, yeast does the same thing as many more recognizable ingredients like baking soda and baking powder. The difference is that baking soda and acid, called chemical leaveners, achieve their rise through chemical reactions triggered either through water or heat. Yeast is a natural leavener. It’s a living organism! Yeast helps bread rise through a biological reaction. Yeast feeds off starches, the glucose in the flour, and produces ethanol and CO2. This process, like making pickles, is called fermentation. But how does this gas not just escape the mixture? That’s another way the flour comes in handy. When combined with water, two proteins within flour, glutenin and gliadin, form things called gluten networks, which strengthen the dough and trap gas within it. That’s how dough goes from loose clumps to one large mass. Different flours will end in different cooked textures. Bread flour has more protein, more gliadin and glutenin, which means more gluten strands will be formed throughout the process, ending in a chewier result, important for pizza and bread. Cake flour and pastry flour both have much lower amounts of protein, meaning the end result is soft and crumbly. Kneading the dough is important because it strengthens the gluten networks by stretching and compressing them. The result is an elastic dough that springs back when you press into it.

But what about the other ingredients in bread? Fats like butter and oil make the dough’s gluten network softer, producing a softer bread. They also prevent water from escaping the dough during the baking process, increasing the final bread’s moisture. Sugar, you may assume, would be used for taste and feeding the yeast further. In fact, sugar serves an even greater invisible role. In heat, sugar undergoes a chemical reaction called the Maillard reaction. More specifics in this graphic, but essentially it browns and hardens the sugar, like during caramelization.

This helps form the hard, golden-brown crust of the bread. Salt helps with taste, but also helps to strengthen the gluten networks and slow down the fermentation process.

One of the breads I made this week, challah, included eggs, an uncommon ingredient for breads. Egg has multiple effects on a dough. The high water content of an egg helps maintain the moisture necessary for gluten development. The fats in the egg act similar to other fats like butter, weakening the structure for a softer inside after baking. Eggs are also high in protein, but egg proteins are softer than gluten protein. These also affect the texture of the bread by making the dough softer and more crumbly.