How does fermentation turn corn starch into alcohol?

To convert corn starch into alcohol, the starch must first be transformed into fermentable sugars, which are then processed by yeast. This process generally follows these steps:

• Mashing: The corn grain is ground and heated to break down the protective starch cells, allowing the starch to be wetted and liquefied.1
• Conversion to Sugar: Enzymes—typically provided by adding malted grain—are introduced to the mash. These enzymes break down the complex starch molecules into fermentable sugars, such as dextrose and maltose.21
• Fermentation: Once the sugars are available, yeast is added to the mixture. The yeast cells feed on these sugars, producing ethanol (alcohol) and carbon dioxide as byproducts.314

This process is a fundamental method for producing both distilled spirits and biofuel from corn. While corn-based ethanol is used as a fuel additive, it is important to note that its production has sparked significant ethical debate regarding the "food versus fuel" conflict, as it diverts arable land and crops away from the human food chain and can negatively impact biodiversity.35