Anaerobic Fermentation, Science In The Kitchen

Anaerobic Fermentation, Science In The Kitchen

Anaerobic Fermentation, Science In The Kitchen

Fermentation is a process that happens when bacteria and yeast break down sugars to make energy without using oxygen. Aerobic fermentation uses oxygen, while anaerobic fermentation happens without oxygen. Understanding the science behind anaerobic fermentation can help explain how we preserve and flavour foods through controlled rotting. Read on to learn how you can harness this process to deliver delightful fermented products from sourdough to sauerkraut and fermented veggies.

What Causes Anaerobic Fermentation?

Anaerobic fermentation happens when bacteria or yeast are in an environment without oxygen. This could be an enclosed jar or underwater environment. The lack of oxygen forces the bacteria or yeast to get energy in a different way, other than aerobic respiration.

Instead of using oxygen, anaerobic bacteria (most often lactobacillus) get energy from glycolysis. This is when glucose is broken down and energy is released. Lactic acid fermentation and alcohol fermentation are two types of anaerobic processes.

How Do You Get Anaerobic Bacteria?

Anaerobic bacteria are found naturally in certain environments like marshes, hot springs, and the digestive systems of animals. Foods like spicy kimchi, sauerkraut, and yogurt contain live anaerobic bacteria.

to make fermented vegetables like this courgette, you need anaerobic fermentation

To grow anaerobic bacteria at home, you can create an oxygen-free environment. This is done by fermenting in an airlocked jar and combining with salt to create an environment that favours these bacteria and preventing the bad bacteria from dominating. The bacteria already present on the food will thrive and grow without oxygen.

The Four Types of Fermentation

There are four main types of fermentation:

1. Lactic Acid Fermentation

This fermentation happens in foods like sauerkraut, kimchi, and pickles. Lactic acid bacteria convert sugars into lactic acid. The acidity helps preserve foods and adds tangy flavour.

2. Alcoholic Fermentation

Yeast perform alcoholic fermentation on sugars. This makes ethanol alcohol and carbon dioxide. Examples are beer, wine, cider, and bread.

3. Acetic Acid Fermentation

Acetic acid bacteria convert alcohol into acetic acid or vinegar. This adds sour flavour. Foods include vinegar, kombucha, and fermented foods exposed to oxygen.

4. Propionic Acid Fermentation

Propionibacteria convert lactate into propionic acid, acetic acid, and carbon dioxide. This fermentation helps ripen cheeses like Swiss cheese.

swiss cheese does not require anaerobic fermentation

What Causes Anaerobic Bacteria to Grow?

Anaerobic bacteria grow through the process of fermentation. When there is no oxygen present, the bacteria switch to getting energy through glycolysis instead of aerobic respiration.

Anaerobic bacteria feed on sugars and starches present in the food. As they eat and digest these carbs, the bacteria multiply and spread. Factors like temperature, acidity, and salinity impact how fast the bacteria grow.

The Difference Between Aerobic and Anaerobic Fermentation

The main difference is that aerobic fermentation uses oxygen, while anaerobic happens without oxygen present.

In aerobic fermentation, bacteria convert sugars into carbon dioxide and water. Examples are the process of composting food scraps or retting fibres like hemp stalks.

Anaerobic fermentation creates different end products like alcohol, acids, and gases. The lack of oxygen forces the bacteria to get energy through glycolysis instead of aerobic respiration.

Products of Anaerobic Fermentation

The products made by anaerobic fermentation depend on the type.

  • Lactic acid fermentation produces lactic acid, carbon dioxide, and sometimes small amounts of alcohol like in sauerkraut.
  • Alcoholic fermentation makes ethanol alcohol and carbon dioxide like in wine and beer.
  • Acetic acid fermentation creates acetic acid or vinegar.
  • Propionic acid fermentation produces propionic acid, acetic acid, and carbon dioxide which helps ripen cheeses.

These acids, alcohols, and gases all help preserve food and add distinct flavours. The carbon dioxide released can also create the bubbly texture in foods like bread and kombucha.

What is Lactic Acid?

Lactic acid is a type of acid made by lactic acid bacteria through anaerobic fermentation. It gives foods like sauerkraut, yogurt, and sourdough bread a tart, tangy taste.

Lactic acid also helps preserve foods. The acidity prevents the growth of harmful bacteria. This allows fermented foods to be shelf-stable for months.

Foods Preserved by Anaerobic Fermentation

Many foods rely on anaerobic fermentation by lactic acid bacteria to preserve and flavour them. Common examples include:

The lactic acid and other products create an environment that discourages spoilage while adding flavor.

Foods Requiring Aerobic Fermentation

While many foods rely on anaerobic fermentation, some fermented foods require oxygen:

  • Vinegar (acetic acid fermentation)
  • Compost
  • Tea
  • Retted fibers like hemp stalks
  • Cacao beans

Exposure to oxygen allows different bacteria and fungi to thrive compared to anaerobic environments. This results in different flavours and textures.

Risks of Anaerobic Fermentation

Anaerobic fermentation is generally safe but there are some risks:

Follow proper procedures by keeping vegetables submerged, monitoring fermentation, and releasing pressure buildup. Only eat properly fermented foods that show no signs of spoilage.

Conclusion

Anaerobic fermentation relies on bacteria that can thrive without oxygen present. The lack of oxygen leads to unique metabolic processes that create lactic acid, alcohols, carbon dioxide, and other compounds. These products help preserve and add distinct sour, tangy flavors to fermented foods. Understanding the science behind anaerobic fermentation allows us to better control the rotting process for safely flavored and preserved foods.

Frequently Asked Questions About Anaerobic Fermentation

What are some signs of successful anaerobic fermentation?

Signs your food has fermented properly under anaerobic conditions include the development of bubbles, a sour aroma, increased acidity, and a tangy flavour. The food should not have any signs of mould or rotten odours.

How do I know if my ferment has gone bad?

Fermented foods that have spoiled due to improper fermentation may smell rancid, rotten, or cheesy. You may see mould growing. The food may also be very slimy. Discard any ferments that show these signs of spoilage.

What temperature is best for anaerobic fermentation?

The ideal temperature is generally between 15°F to 21°F. Cooler temperatures slow fermentation while warmer speeds it up. Avoid letting fermenting foods get above 26°F as this can encourage mould growth.

Can I ferment foods anaerobically without special equipment?

You can ferment foods like sauerkraut, pickles, and kimchi anaerobically without any special equipment. Just closely pack the food into a cleaned glass jar and ensure it stays fully submerged under its liquid to prevent mold growth.

How do I know when my anaerobic ferment is done?

Taste the food regularly after about 1 week. It’s ready when the flavour is acidic and tangy but still pleasant. The vegetables should also be slightly softened but still crunchy.