6th Grade · Science · Reading Passage · shared by Luke Morgan
This free 6th Grade Science reading passage explains how yeast makes bread rise, covering metabolism, fermentation, carbon dioxide, and gluten.
The Tiny Baker: How Yeast Makes Bread Rise
When you bite into a warm piece of fluffy bread, you are enjoying the work of a tiny fungus. This microscopic organism is known as Saccharomyces cerevisiae , but most people call it baker's yeast. Although it looks like a dry powder, yeast is a living creature that needs food to survive. When mixed into warm water, the organism wakes up and begins searching for energy. This process is why bread dough grows into a light loaf.
The primary goal of yeast is to find energy, which it gets by consuming simple sugars found in the flour. Once the yeast is active, it begins a biological journey called metabolism to break down these sugars for fuel. This is not just a snack; it is a chemical reaction that changes the dough. As the yeast eats, it releases energy that allows it to grow and multiply. Without this activity, the dough would remain a flat, heavy brick.
During this phase, the yeast performs a special type of chemical breakdown known as fermentation to survive. As the yeast processes the sugar, it creates two main byproducts: a tiny amount of alcohol and a gas called carbon dioxide. Carbon dioxide is the most important part because it creates millions of tiny bubbles. These bubbles push against the stretchy dough, causing it to expand and rise slowly. This gas production transforms the dense mixture into a soft sponge.
The structure of the bread is just as important as the gas because the bubbles must be trapped inside. Flour contains proteins that form a stretchy web called gluten, which acts like a balloon around the gas. As the yeast continues its work, the gluten stretches further to hold the gas. When the dough is placed in a hot oven, the heat causes the gas to expand. Eventually, the yeast dies, but the airy structure remains…