Science of fermentation | History, types, and stages

Alcohol, yogurt, kimchi, soy sauce, and other fermented foods are now a significant part of our diet. They are also becoming more popular due to their alleged health benefits. Have you ever wondered what happens during fermentation and what role microorganisms play? Continue reading to learn about science of fermentation.

What is fermentation?

Fermentation is any metabolic process in which the activity of microorganisms causes a desirable change in food and beverages, whether it’s increasing flavor, preserving foods, providing health benefits, or something else.

‘Ferment’ comes from the Latin verb ‘fervere,’ which means ‘to boil.’ Fermentation is, ironically, possible without the use of heat.

History of fermentation science

Wine fermentation was first recorded in 7000 BC. Traditionally, winemakers crushed fruits with their feet before leaving them to sit in containers. Earlier, people thought the transfer of microorganisms from winemakers’ feet to crushed fruits caused fermentation.

The hypothesis was validated in the 17th century when the invention of high-quality optical lenses allowed the visualization of single-celled microorganisms for the first time. Louis Pasteur, a French microbiologist, demonstrated through experiments that the cause of wine fermentation is due to a type of fungi known as yeast.

An accident at a sugar beet distillery in 1856 resulted in a groundbreaking discovery critical to the production of cheese and yogurt. Pasteur’s task was to investigate the ‘spoiled’ beetroot mixture and discover lactic acid, which caused a sour taste. Many objects smaller than yeasts were also present in the sour beetroot mixture. This coincidental event contributed to our understanding of how fungi and bacteria ferment differently.

Contrary to what Pasteur proposed, it was not until the early 1900s that Nobel Laureate Eduard Buechner discovered that fermentation could occur with cell-free yeast extracts consisting only of enzymes. Since then, we’ve created various fermented foods, including the well-known Kombucha.

 Although we have a good understanding of how to control fermentation, there are still many ways to improve industrial fermentation. Modern gene sequencing, genetic engineering, microfluidics, and electronic ‘nose’ technologies, for example, can make our favorite fermented foods even more delicious.

Three forms of fermentation

Below are the three forms of fermentation

Lactic acid fermentation

Starches or sugars are broken down during this anaerobic process to produce lactic acid and other waste products. Lactic acid bacteria keep foods safe from microbial spoilage and the body from microbial disease. There is the use of lactic acid fermentation to manufacture foods such as yogurt, pickles, and sauerkraut.

Ethanol (or alcohol) fermentation

In this type of fermentation, yeasts convert pyruvate molecules in sugars into alcohol and carbon dioxide molecules, producing wine, beer, and bread.

Acetic acid fermentation 

It is an oxidation process that turns sugars from grains or fruit into sour vinegar and condiments. As a result, there is a distinction between apple cider and apple cider vinegar used in cooking.

Stages of fermentation

Here are the two stages of fermentation-

Primary-level

Microbes begin rapidly working on raw ingredients such as fruit, vegetables, or dairy during this brief phase. The microbes in the food or the liquid around it (like the brine used for fermented vegetables) stop putrefying bacteria from colonizing the food instead. Yeasts and other microbes convert carbohydrates (sugars) into other substances such as alcohol and acids.

Secondary-level

Alcohol levels rise during this more prolonged stage of fermentation, which can last several days or even weeks, as yeasts and microbes die off, and their available food source (carbohydrates) becomes scarcer. Winemakers and brewers use secondary fermentation to create alcoholic beverages.

The pH of the ferment can vary significantly from when it began, affecting the chemical reactions between the microbes and their environment. Once the alcohol content reaches 12-15% and kills the yeast, preventing further fermentation, distillation is required to remove water while condensing the alcohol content to produce a higher percentage of alcohol.

DNA sequencing 

The ratio of microbial populations can change with slight temperature and pH changes during different stages of fermentation. Consider the traditional Korean dish kimchi. Traditionally, you make kimchi by fermenting cabbage with lactic acid bacteria. However, different lactic acid bacteria strains thrive at different pH levels.

DNA sequencing technologies are beneficial for identifying microbial population fluctuations. Each microorganism has a distinct DNA structure. Researchers have used DNA sequencing tools to map the genomes of many different life forms, including microorganisms essential for fermentation. 

Recent technological advancements have also accelerated the speed of DNA sequencing and reduced costs, making DNA sequencing more affordable in the food industry.

Genetic engineering

The term ‘genetic engineering’ (or ‘modification’) broadly refers to cutting and pasting the DNA genome to produce cells with specific traits. With advanced gene editing techniques such as CRISPR, the efficiency of genetic engineering has increased.

Microorganisms with more desirable characteristics than their wild-type cousins have been created thanks to genetic engineering.

One can genetically engineer microorganisms to produce a single high-purity end product. It makes them more advantageous than their wild-type counterparts, who typically produce a mixed bag of end products.

Droplet and microfluidic bioreactors

Traditional industrial-scale fermentation is carried out in large bioreactors with a few thousand liters of capacity. This method is costly and incompatible with the rapid testing of the following fermentation recipes. On the other hand, droplet bioreactors allow for faster fermentation by enclosing raw ingredients and microorganisms in tiny droplets of a few microliters.

Key takeaways

• Fermentation is a chemical process that breaks down molecules such as glucose anaerobically. In a broader sense, fermentation is the foaming that occurs during the production of wine and beer, a process that has been around for at least 10,000 years.
• Alcohol, yogurt, kimchi, and soy sauce are all fermented food that is part of our daily diet.
• Lactic acid fermentation, Ethanol fermentation, and Acetic acid fermentation are the three types.

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FAQs

Q1. What is the science of fermentation called?

Answer- The science of fermentation is known as zymology.

Q2. Does fermentation require oxygen?

Answer- Fermentation does not require oxygen and is thus anaerobic. Fermentation will replenish NAD+ from the NADH + H+ produced by glycolysis.

Q3. What is needed for the fermentation to occur?

Answer- Both types of fermentation require two primary components: a sugar source and a bacterial culture; alcohol fermentations typically use yeast, whereas lactic acid fermentations typically use lactic acid bacteria.