Fermentation Explained

By Cook's Illustrated Published September 2016

When we realized how many ingredients we call for in recipes are fermented, we decided that a closer look at fermentation was in order.

Fermentation is a process in which bacteria and/or yeasts consume carbohydrates and proteins often naturally present in food, producing alcohols, lactic acid, acetic acid, and/or carbon dioxide as byproducts. Water and salt are often added to the mix because both create a fermentation-friendly environment. (Salt can also keep bad bacteria at bay.) Fermentation helps preserve food and alters its texture, scent, and flavor. When we compared fresh lemon to store-bought preserved lemons, the fresh lemons were bright, sharp, and citrusy, while the preserved lemons were floral, briny, and pungent, with a slight chemical-like flavor.

Fermented foods are also easy to digest, and their bacteria are thought to offer health benefits (which helps explain their recent uptick in popularity).


Foods like pickles, vinegar, and yogurt have the tang that we often associate with fermentation. And of course beer and wine are fermented. But all these everyday foods also get deep flavor from fermentation.

  • Chocolate
  • Coffee
  • Olives
  • Bread
  • Vanilla
  • Hot sauce
  • Cheese