There are so many different styles of fermentation that it’s difficult to explore all of them. However, fermentation processes typically fall under two very broad categories: wild fermentation and inoculation. Both processes require manipulating the environment and giving microbes the ideal environment to metabolize a substrate to create a byproduct. Wild fermentation is utilizing microbes already present in our environment, while inoculation is creating the environment then adding microbes to the environment with intention. 

Here’s a look at a few of the most common types of fermentation.

Lactic Acid Fermentation

Lacto-Fermentation is arguably one of the most common types found in food. How it works is that foods are submerged in a salty brine in a fermentation crock. Salt kills bacteria that cause food spoilage, but doesn’t harm lactobacillus bacteria, which are present pretty much everywhere. So, after a while of soaking in this salty brine, the lactobacillus go to work converting the carbohydrates in the vegetables into lactic acid, which in turn aids in preservation while also imparting a tangy flavor. 

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Ethyl Alcohol Fermentation

Ethyl alcohol fermentation is what gives us beer, wine, and sprits as well as bread. Note that sourdough bread uses a combination of ethyl alcohol and lactic acid fermentation. The yeast gives the bread its rise while the lactobacillus gives it its sour flavor. 

Beer and wine typically undergo two stages of fermentation, known as primary and secondary fermentation. The primary stage triggers a rapid production of alcohol, while the secondary stage is slower and helps to develop more complex flavors.

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Acetic Acid Fermentation

Some people regard acetic acid fermentation as a third type of fermentation, although it is arguably a version of ethyl alcohol fermentation. It’s the process that turns wine to vinegar, so if you were wanting to make wine, it’s not good, but if your goal is vinegar, then it’s great.

How it works is that certain bacteria, known as acetic acid bacteria, oxidize alcohol and sugar to form acetic acid, which, when highly diluted, is simply ordinary vinegar. In addition to vinegar, this process is also a secondary fermentation stage in making kombucha, following the initial stage of ethyl alcohol fermentation.

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Beyond the three core types of fermentation, there are also several emerging fermentation techniques including: 

Alkaline Fermentation

Alkaline-fermented foods constitute a group of lesser-known food products that are widely consumed in Southeast Asian and African countries. In alkaline-fermented foods, the protein of the raw materials is broken down into amino acids and peptides; ammonia is released during the fermentation, raising the pH of the final products and giving the food a strong ammoniacal smell.

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Precision Fermentation

With precision fermentation, bioengineering techniques are used to program microorganisms by giving them a specific genetic code to produce a compound of interest when fermented under precise conditions. The genetic code is the exact copy of the DNA sequence found in a digitized database on animal or plant DNA sequence; however, it requires no animal or plant involvement. The result is a molecularly identical ingredient produced by microorganisms. Precision fermentation provides more opportunities for plant-based meat and dairy manufacturers to deliver a meat/dairy-like experience. Seizing the opportunities that the progress of digitalization is offering would boost the production of high-value ingredients such as enzymes, fats, proteins, and vitamins.

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Butyric Acid Fermentation

This type of fermentation is characteristic of obligate anaerobic bacteria of genus clostridium. This occurs in retting of jute fiber, rancid butter, tobacco processing, and tanning of leather. Butyric acid is produced in the human colon as a product of dietary fiber fermentation. It is an important source of energy for colorectal epithelium. Sugar is first oxidized to pyruvate by the process of glycolysis and then pyruvate is further oxidized to form acetyl-CoA by the oxidoreductase enzyme system with the production of H2 and CO2. Acetyl-CoA is further reduced to form butyric acid. This type of fermentation leads to a relatively higher yield of energy. Three molecules of ATP are formed.

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Biomass fermentation 

A new technique used to turn mycelium, the root structure of mushrooms, into a bacon substitute.  

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Propionic Acid Fermentation

This process, carried out by propionibacteria, converts lactic acid into propionic acid, acetic acid, carbon dioxide, and water. It is important in the production of Swiss cheese, where it contributes to the development of the characteristic holes and flavor.

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Information on this spread courtesy of the following sources: