The Science of Making Bread

Reading Time: 3 minutes

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By Yaqi Zeng

The messy kitchen is covered with white powdery flour, and the heat glows from the oven as the bread starts to rise. This is a familiar sight for many of us following arduous hours poured into baking the perfect loaf of bread.

Many people have taken up a new activity—baking bread—during the COVID-19 pandemic. Two of the most popular treats include banana bread and sourdough bread. Instagram and TikTok have been flooded with bread-making videos, which make the process look much easier than it actually is. The common clip of a TikToker opening the oven to reveal a fresh loaf of bread takes more than mixing a list of ingredients. In reality, many scientific elements are at play.

Making sourdough bread is an art that requires patience, practice, water, and flour. The sour flavor and chewy texture are what make sourdough so unique. To make sourdough, there must be a self-sustaining fermentation of flour, water, wild yeasts, and bacteria, which results in lactic and acetic acids. First, flour and water must be used as starters to achieve fermentation, the process of extracting energy from carbohydrates without oxygen. Combining equal quantities of water and flour and letting it sit for five days is ideal to facilitate fermentation.

After establishing this starter, one must add even more flour and water. Then, knead the bread. This adds oxygen to the dough, increases the development of gluten, and results in a relatively quick baking time of three to four hours. Interestingly, sourdough contains several different species of lactic acid bacteria, primarily Lactobacillus sanfranciscensis, which produces a characteristically sour flavor. Though the microbes in starters are largely dependent on the flour used when making the bread, they are also reflective of those found on the baker’s hand.

When attempting to achieve a very open crumb for the internal structure, one should use good flour with high protein while slowly adding in water. The more water added, the softer the dough and the bigger the bubbles. Then, sugars and amino acids, which are on the loaf’s surface, will start to react with steam in the oven at 150 degrees Celsius. This causes the amino acids and sugars to condense on the surface and become flexible for a longer period of time. Finally, this condensation ends in a burst of fermentation, which creates gas bubbles and allows for existing bubbles to expand.

The many possible combinations of enzymes in sourdough can create unique flavors and crusts. Sugars and amino acids on the loaf's surface start to react at 150 degrees Celsius in the Maillard reaction, giving it a distinctive taste and coloring. There are more than 300 different flavor compounds based on the proteases and amino acids, which all depend on the combination of ingredients used in the dough and the duration of the fermentation process. A longer fermentation process creates richer flavors. Experienced bakers often let the dough ferment for three to four hours before cooking to achieve a more flavorful loaf.

Unlike sourdough bread, banana bread does not require any yeast in order to rise. The key to making a good loaf of banana bread lies not in the bacteria, but in the bananas. In order to make banana bread sweet, one must use overripe bananas that are completely brown or black. Overripe bananas are essential for banana bread because as bananas ripen, their starch is converted to sugar. The starch is broken down by the enzyme amylase, which converts the starch to the sugars maltose and glucose. As bananas ripen, their sugar content can increase by three percent, with an unripe banana having a sugar concentration of 16.2 percent and a ripe banana having one of 19.3 percent. Of course, if you don’t have any overripe bananas at home, you can still make them soft, brown, and sweet by putting them in the oven at 150 degrees Celsius for 15 to 20 minutes. The heat from the oven will oxidize the amino acid tyrosine, which will produce the pigment melanin and change the color of the bananas. Though this does not naturally ripen the bananas by breaking down starch, it’s a quick alternative to make the bananas ideal for your loaf of banana bread.

The next time you’re inspired to make your own bread by a video on social media, think of the science behind your wonderful creation. There are a multitude of factors that contribute to bread-making—from the bacteria present to the cooking temperatures. Producing a loaf