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Fermentation is an intricate biochemical process with a profound history of enhancing human diets. It involves the breakdown of organic substances by microorganisms such as bacteria, yeast, and fungi, leading to the production of various fermented foods like yogurt, kimchi, and kombucha. These foods are not only valued for their unique flavors and textures but also for their significant contributions to nutrition and health. This blog delves into the scientific underpinnings of fermentation, examining its diverse processes, the types of foods it produces, and the extensive benefits it offers.
Fermentation is a microbiological reaction; it is the decomposition of organic substances, produced by the action of living organisms, namely bacteria, yeast, or fungi1.
A general definition describes fermentation as “a biochemical process through which most microorganisms decompose carbohydrates to produce energy under anaerobic conditions2,” while Louis Pasteur considered that “fermentation is life in the absence of oxygen3.”
There are many types of fermentation: yeast fermentation, lactic acid fermentation, butyric acid fermentation, propionic acid fermentation, and acetic acid fermentation2. It is this diversity of possible processes that leads to a variety of end products, which include carbon dioxide, ethanol, organic acids, and other organic molecules2. As the authors of a 2020 article titled “Fermentative Foods: Microbiology, Biochemistry, Potential Human Health Benefits and Public Health Issues” put it “it is many of these products that make fermentation so useful and interesting both to science and industry2.”
In sum, fermentation is the process by which microorganisms – bacteria, yeast, and fungi – break down complex molecules, such as proteins, fats, and carbohydrates, into simpler compounds in the absence of oxygen (anaerobic conditions). More simply, the process by which a substance breaks down into a simpler substance1.
There are different definitions of fermented foods:
To simplify and find a consensus in the use of the term, a panel of experts defined fermented foods as “foods made through desired microbial growth and enzymatic conversions of food components6”.
Initially, the production of fermented foods such as yogurt and cultured milk products, wine, and beer, sauerkraut, and kimchi, was important because it helped increase the shelf life of fresh products and preserve foods from spoiling, it made consumption of certain foods safer, and improved palatability and sensory properties (organoleptic properties) of food when compared to the raw foods4,7,8.
However, with increased research into the properties of these foods, we now know that fermented foods can have high nutritional and functional value, due to the transformation of the initial substrates (the raw food material) and the formation of bioactive or bioavailable products in the final product (the fermented food). Fermentation contributes to an increase in the bioavailability of desired compounds and alters nutritional constituents8. As mentioned in a 2024 article “Controlled growth of specific microbial strains during fermentation leads to desirable biochemical changes, the release of bioactive molecules, increased food digestibility, and enhanced nutrient bioavailability7.”
Many fermented foods also contain living microorganisms of which some are genetically similar to strains used as probiotics. Although only a limited number of clinical studies on fermented foods have been performed, there is evidence that these foods provide health benefits well beyond the starting food materials4.
Fermentation is a natural process that results from microbial metabolism and can also lead to food spoilage. The microorganism that is used to make a fermented food can be the same microorganism that causes food to spoil1. The expert definition of fermented food highlights “desired microbial growth6” to undoubtedly distinguish fermentation from food spoilage, adding that “spoilage is clearly unintentional and fermentation is deliberate and controlled to generate the desirable attributes6.” Hence, the main difference between food fermentation and food spoilage is whether the process is desired or not; “if the process results in desirable food it is termed fermentation; when it results in decomposition, it will be called spoilage6.” The beauty of food fermentation is that “the growth of spoilage and pathogenic organisms is inhibited by the metabolites generated by the fermenting organism9” and food fermentation may prevent food from spoiling.
Some of the microorganisms used in the process of food fermentation may also become harmful under certain undesirable conditions. As with any food, “there are safety concerns associated with live pathogenic microorganisms as well as toxins or metabolic products that can produce harmful effects6.” However, most lactic acid bacteria (LAB), yeasts and fungi used for food fermentation are “non-pathogenic and do not produce toxins or harmful end-products6.”
There are a few exceptions, nonetheless. It is the case with some mycotoxins (fungal toxins) which may be produced when fermentation conditions are compromised, and/ or there is poor hygiene of the raw food materials used during fermentation10. Food contamination may also happen after fermentation. This is not common in the US, but it still happens in many African countries and can pose a considerable health hazard. To prevent mycotoxin contamination, which happens mostly in developing nations, experts highlight the importance of using “mycotoxin-free raw material and to prepare it in good sanitary and hygiene conditions10.”
On the bright side, when made with proper conditions, “fermented foods and the bacteria and fungi responsible for their manufacture have a long history of safe use6.”
Fermentation stands as a remarkable intersection of science and tradition, offering a deeper understanding of how microorganisms can transform simple ingredients into complex, nutrient-rich foods. This process not only extends the shelf life and enhances the safety of foods but also boosts their nutritional value and introduces beneficial bioactive compounds. As we continue to explore and refine our knowledge of fermentation, we uncover its potential to improve dietary health and well-being. By appreciating and harnessing the power of fermentation, we continue to benefit from its longstanding contributions to culinary practices and scientific advancements.
To further your understanding, check out our other blogs on related topics: History and Introduction of Fermentation, Fermented Foods, Probiotics and Prebiotics, and The Power of Fermented Food. Each article provides additional insights into the fascinating world of fermentation and its impact on our health.
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