Fermentation is a food science process in which microbes change sugars and other food molecules into new substances. It matters because it helps make foods such as yogurt, kimchi, sauerkraut, sourdough bread, kombucha, and cheese. Fermentation can improve flavor, texture, shelf life, and sometimes nutrition.
It also shows how biology and chemistry work together in everyday foods.
Key Facts
- Fermentation is often anaerobic, meaning it happens with little or no oxygen.
- Lactic acid fermentation: glucose -> lactic acid + energy.
- Alcoholic fermentation: C6H12O6 -> 2 C2H5OH + 2 CO2 + energy.
- Microbes such as bacteria and yeast use enzymes to break down food molecules.
- Acid production lowers pH, which can slow the growth of many harmful microbes.
- Fermentation can increase some B vitamins, create probiotics, and make certain nutrients easier to absorb.
Vocabulary
- Fermentation
- Fermentation is a process in which microorganisms break down sugars and release products such as acids, alcohol, or carbon dioxide.
- Microorganism
- A microorganism is a living thing too small to see clearly without a microscope, such as a bacterium or yeast cell.
- Lactic acid
- Lactic acid is a sour-tasting acid made by certain bacteria during fermentation.
- Anaerobic
- Anaerobic means occurring without oxygen or with very little oxygen present.
- Probiotic
- A probiotic is a live microorganism that may support health when consumed in the right amount.
Common Mistakes to Avoid
- Thinking all fermented foods contain alcohol is wrong because many fermentations, such as yogurt and sauerkraut, mainly produce lactic acid instead of ethanol.
- Assuming fermentation and rotting are the same is wrong because controlled fermentation uses helpful microbes and safe conditions, while rotting is uncontrolled decomposition that may include harmful organisms.
- Forgetting that temperature affects fermentation is wrong because microbes and enzymes work faster or slower depending on temperature, and very high heat can kill them.
- Believing probiotics survive every cooking process is wrong because high heat can kill many live microbes, so cooked fermented foods may not contain active probiotics.
Practice Questions
- 1 A jar of cabbage begins at pH 6.2 and drops to pH 3.8 during fermentation. By how many pH units did the acidity change?
- 2 Yeast ferments 3 molecules of glucose using the equation C6H12O6 -> 2 C2H5OH + 2 CO2. How many molecules of carbon dioxide are produced?
- 3 A student seals a jar of vegetables with salt water and notices bubbles after several days. Explain what the bubbles likely are, what microbes are doing, and why the food becomes more acidic.