Fermentation is a natural process in which microorganisms—yeasts, bacteria, or fungi—convert carbohydrates into alcohols, carbon dioxide, and organic acids in the absence of oxygen. The purpose is to obtain metabolic energy.
Microbial cells possess enzymes (such as amylases, cellulases, proteases, etc.) that allow the breakdown of complex organic molecules into simpler products that can be readily utilized.
This biotechnology, used since ancient times, enhances food preservation, enriches foods with functional properties—such as probiotic, antimicrobial, immunomodulatory, and antioxidant effects—improves digestibility, and reduces antinutrients contained in foods.
Today, fermentation is widely used by industry in the following sectors:
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Food
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Cosmetics
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Nutraceuticals
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Veterinary
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Environmental
The Importance of Fermented Foods for Our Health
Fermented foods in our diet represent a rich source of compounds beneficial for the health of the gut microbiota and the digestive system, and they can also strengthen the immune system.
Scientific and nutritional studies have shown that probiotic microorganisms can produce peptides with antimicrobial activity, increase antioxidant molecule content, produce polyamines and short-chain organic acids capable of reducing inflammation, and help prevent cardiovascular diseases, diabetes, and obesity (Nevin Sanlier et al., 2017; Limon et al., 2015; Parker et al., 2020; Filosa et al., 2018).
In dairy-based food matrices, fermentation also leads to increased levels of conjugated linoleic acid (CLA). This compound exerts beneficial effects on lipid profiles, immune system activity, and anticancer properties (M. A. McGuire and M. K. McGuire, 2000; H-J Song et al., 2005).
Fermentation is also important for the production of certain B vitamins (folic acid, riboflavin, and vitamin B12), further enriching foods with bioactive compounds valuable to the body.
Types of Fermentation
The most well-known and widely used types of fermentation in the food industry are:
Lactic Fermentation
Lactic fermentation involves the transformation of glucose or another fermentable sugar into lactic acid and is extensively used for producing many foods. A typical example is the transformation of milk into yogurt or cheese, using bacterial species such as Streptococcus, Lactobacillus, and Lactococcus.
The lactic acid produced lowers the pH, causing the precipitation of milk proteins (caseins), which gives yogurt its characteristic texture and sour taste. For cheese, lactic cultures acidify the milk and curd, which is essential for converting milk into cheese and for its maturation.
Acetic Fermentation
Acetic acid is produced through the oxidation of ethanol to acetaldehyde and finally to acetic acid by specific bacteria such as Acetobacter or Gluconobacter, which are commonly found in the environment. This type of fermentation is typically used for vinegar production.
Alcoholic Fermentation
Alcoholic fermentation is a biological process that converts sugars—glucose, fructose, and sucrose—into ethanol and carbon dioxide, producing cellular energy.
Alcoholic fermentation has many uses, including the production of alcoholic beverages, biofuels, and the leavening of dough and bread. It is also used in producing kefir, a fermented milk similar to yogurt, which contains small amounts of alcohol and carbon dioxide due to the alcoholic fermentation activity of yeasts present.
Conclusions
Fermentation is thus an important process for the functionalization of various foods that, thanks to the presence of probiotic bacterial species and/or the production of bioactive molecules, exhibit multiple and significant beneficial properties. They improve intestinal health by promoting the proper balance of gut flora, strengthen the immune system, and support the proper functioning of the cardiovascular system.
Fermentation also enriches foods with vitamins, minerals, and compounds with high antioxidant activity. It sometimes improves digestibility by reducing antinutrients and ensuring the availability of the typical nutrients characterizing these products.
References
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Sanlier, N., Gokcen, B. B., & Sezgin, A. C. (2017). Health benefits of fermented foods. Critical Reviews in Food Science and Nutrition, 0(0), 1–22. https://doi.org/10.1080/10408398.2017.1383355
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Limón, R. I., Peñas, E., Torino, M. I., Martínez-Villaluenga, C., Dueñas, M., & Frias, J. (2015). Fermentation enhances the content of bioactive compounds in kidney bean extracts. Food Chemistry, 172, 343-352. https://doi.org/10.1016/j.foodchem.2014.09.08
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Filosa, S., Di Meo, F., & Crispi, S. (2018). Polyphenols-gut microbiota interplay and brain neuromodulation. Neural Regeneration Research, 13(12), 2055-2059. https://doi.org/10.4103/1673-5374.241429
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Parker, A., Fonseca, S., & Carding, S. R. (2020). Gut microbes and metabolites as modulators of blood-brain barrier integrity and brain health. Gut Microbes, 11(2), 135-157. https://doi.org/10.1080/19490976.2019.1638722
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McGuire, M. A., & McGuire, M. K. (2000). Conjugated linoleic acid (CLA): A ruminant fatty acid with beneficial effects on human health. Journal of Animal Science, 77, 1-8.
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Song, H.-J., Grant, I., Rotondo, D., Mohede, I., Sattar, N., Heys, S. D., & Wahle, K. W. J. (2005). Effect of CLA supplementation on immune function in young healthy volunteers. European Journal of Clinical Nutrition, 59, 508–517. https://doi.org/10.1038/sj.ejcn.1602102
