Fermentation in food processing
Microbial conversion of carbohydrates to alcohol or acids without oxidizing agents.
Fermentation in food processing is a method where microorganisms like yeasts or bacteria convert carbohydrates into alcohol or organic acids, without an oxidizing agent being involved. This process is typically intentional, and its scientific study is called zymology or zymurgy. While the term can specifically refer to turning sugars into ethanol for alcoholic beverages such as wine, beer, and cider, similar microbial activity also leavens bread by producing carbon dioxide and preserves sour foods like sauerkraut and yogurt through lactic acid. Other common fermented products include vinegar, olives, and cheese, while more localized versions may use beans, grains, vegetables, fruit, honey, dairy, or fish.
Humans have exploited fermentation since ancient times, likely after accidentally discovering it when forgotten containers of food allowed yeast and bacteria to grow. The earliest known archaeological evidence is 13,000-year-old beer residue, with a gruel-like consistency, found in a cave near Haifa, Israel. Another early alcoholic drink, made from fruit, rice, and honey, dates to 7000–6600 BC in the Neolithic Chinese village of Jiahu. Winemaking appears around 6000 BC in Georgia, and 7,000-year-old wine jars from Iran’s Zagros Mountains are now at the University of Pennsylvania. Strong evidence also shows fermented drinks in Babylon (circa 3000 BC), ancient Egypt (circa 3150 BC), pre-Hispanic Mexico (circa 2000 BC), and Sudan (circa 1500 BC).
The science of zymology was founded in 1856 by French chemist Louis Pasteur, who linked yeast to fermentation. Studying how yeast converts sugar to alcohol, Pasteur concluded that a “vital force” called ferments, active only within living yeast cells, catalyzed the reaction. He wrote that alcoholic fermentation is tied to the life of yeast cells, not their death or decay. However, in 1897, German chemist Eduard Buchner showed that fermentation could occur without living yeast, using an enzyme complex he named zymase, secreted by yeast. This discovery of “cell-free fermentation” earned him the 1907 Nobel Prize in Chemistry. A year earlier, in 1906, studies of ethanol fermentation led to the early identification of oxidized nicotinamide adenine dinucleotide (NAD+).
The byproducts of food fermentation—alcohol, preservative organic acids, and carbon dioxide—all serve human purposes.
- Earliest archaeological evidence
- 13,000-year-old residue of beer found in a cave near Haifa, Israel
- Early alcoholic drink date
- 7000 to 6600 BC in Jiahu, China
- Winemaking date
- circa 6000 BC in Georgia
- Founder of zymology
- Louis Pasteur in 1856
- Discovery of cell free fermentation
- Eduard Buchner in 1897
- Nobel prize year
- 1907
Lore & Background
Natural fermentation predates human history, with humans likely having unintentionally discovered the process by storing excess foods in containers that were later forgotten, allowing yeast and bacteria to grow. The earliest archaeological evidence is a 13,000-year-old beer residue found in a cave near Haifa, Israel. Another early alcoholic drink, made from fruit, rice, and honey, dates from 7000 to 6600 BC in the Neolithic Chinese village of Jiahu, and winemaking dates from circa 6000 BC in Georgia. There is strong evidence of fermented alcoholic drinks in Babylon (ca. 3000 BC), ancient Egypt (ca. 3150 BC), pre-Hispanic Mexico (ca. 2000 BC), and Sudan (ca. 1500 BC).
The French chemist Louis Pasteur founded zymology in 1856 when he connected yeast to fermentation, concluding that fermentation was catalyzed by a vital force within living yeast cells. However, in 1897 Eduard Buchner found that sugar was fermented even without living yeast cells, by an enzyme complex he termed zymase, leading to the discovery of 'cell-free fermentation.' One year earlier in 1906, ethanol fermentation studies led to the early discovery of oxidized nicotinamide adenine dinucleotide (NAD+).
Reader's Guide
Fermentation serves five main purposes in food processing: enriching the diet through diverse flavors, aromas, and textures; preserving substantial amounts of food via lactic acid, alcohol, acetic acid, and alkaline fermentations; enriching food substrates with protein, essential amino acids, and vitamins; eliminating antinutrients; and reducing cooking time and fuel use. The byproducts—alcohol, preservative organic acids, and carbon dioxide—have found human uses, such as turning fruit juices into wine, grains into beer, and starchy foods into spirits, while carbon dioxide leavens bread and organic acids preserve vegetables and dairy products. Beverages produced through fermentation have likely been universally associated with ceremonies and festivals, as inferred from drinkware and residues. Risks include potential foodborne illnesses like botulism if sterilization is inadequate, with Alaska experiencing a steady increase of botulism cases since 1985 due to traditional fermentation practices using plastic containers. Additionally, fermented food contains a carcinogenic by-product, ethyl carbamate, and a 2009 review across Asia concluded that regularly eating pickled vegetables roughly doubles the risk for esophageal squamous cell carcinoma.
Did You Know?
- Louis Pasteur founded zymology in 1856 by connecting yeast to fermentation.
- Eduard Buchner discovered cell-free fermentation in 1897, winning the Nobel Prize in Chemistry in 1907.
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