fermentation

noun

fer·​men·​ta·​tion ˌfər-mən-ˈtā-shən 

-ˌmen-

plural fermentations

1

a

: the enzyme-catalyzed anaerobic breakdown of an energy-rich compound (such as a carbohydrate to carbon dioxide and alcohol or to an organic acid) by the action of microorganisms (such as bacteria or yeast) that occurs naturally and is commonly used in the production of various products (such as food, alcoholic beverages, and pharmaceuticals) especially by controlling microbial enzymatic activity

The wine then undergoes a long fermentation that results in a high alcohol content (15 to 17 percent) and a dry wine.

—Kim Marcus

The panda is quite unlike most other herbivores, however, whose digestive tracts contain bacteria and protozoans that break down hard-to-digest plant materials through fermentation.

—Miriam Levine Helbok

During a starter's fermentation, yeast produces alcohol, carbon dioxide, and sulfur compounds, all of which contribute to good bread's unique flavor.

—J. Kenji Alt

Cultured butter is made from cream in which fermentation—the conversion of milk sugars into lactic acid—has begun to take place.

—Ben Mims

broadly : any of various enzyme-catalyzed aerobic or anaerobic processes (such as oxidation) involving transformation of organic compounds

Most of the catechins are oxidized during the natural fermentation process that converts fresh green tea leaves to black tea.

—Food & Fitness Advisor

Tobacco fermentation is basically highly controlled composting, and releases many chemicals and impurities that would otherwise ruin the tobacco's flavor.

—Tad Gage

b

: an instance or occurrence of fermentation

The process is simplicity itself—a couple of fermentations, a gradual tilting of the bottle to remove the sediment and a final addition of sugar to make it brut or doux.

—Miles Kington

The ancient Chinese also stored vegetables in a pickling brine with a vinegar base. Various vinegars, made from fermentations of rice, wheat, grapes, or even peaches, were used.

—Nina Simonds

2

: ferment sense 2

Music concerts, poetry readings, and other progressive campus activities can produce intellectual fermentation and thought provoking ideas.

—Robert Hoffman

Synonyms

• turmoil
• ferment
• unrest

Examples of fermentation in a Sentence

a wave of change followed by a period of social fermentation

Recent Examples on the Web

After a fermentation process that once relied on the warmth of a salt block and sunlight, now replicated by a light bulb in a cabinet, the mixture is combined with yeast and flour, left to rise again. —Gabi De La Rosa, Southern Living, 17 Aug. 2025

Aged cheeses undergo fermentation and drying processes that intensify flavor and extend shelf life, while cottage cheese has a higher moisture content and must be refrigerated to prevent spoilage. —Daryl Austin, USA Today, 29 July 2025

After primary fermentation, 80 percent of the wine undergoes malolactic fermentation in oak barrels, and the wine is then aged in 80 percent new oak and the remainder in one year old oak for 16 months. —Mike Desimone, Robb Report, 13 July 2025

Hand harvested, the grapes undergo fermentation and then age 77% in French oak barrels for 9 months and 23% in cement tanks. —John Mariani, Forbes.com, 11 July 2025

Word History

First Known Use

1601, in the meaning defined at sense 1a

Rhymes for fermentation

• abdication
• aberration
• abjuration
• abnegation
• abrogation
• acceptation
• acclamation
• acclimation
• accusation
• activation
• actuation
• acylation

Kids Definition

fermentation

noun

fer·​men·​ta·​tion ˌfər-mən-ˈtā-shən 

-ˌmen-

: chemical breaking down of a substance (as in the souring of milk or the formation of alcohol from sugar) produced by an enzyme and often accompanied by the formation of a gas

fermentative

(ˌ)fər-ˈment-ət-iv

adjective

Medical Definition

fermentation

noun

fer·​men·​ta·​tion ˌfər-mən-ˈtā-shən, -ˌmen- 

: the enzyme-catalyzed anaerobic breakdown of an energy-rich compound (as a carbohydrate to carbon dioxide and alcohol or to an organic acid) by the action of microorganisms (as bacteria or yeast) that occurs naturally and is commonly used in the production of various products (as food, alcoholic beverages, and pharmaceuticals) especially by controlling microbial enzymatic activity

… Pasteur proved that microorganisms cause fermentation, the process that turns grape juice into wine.

—Ken Reese, Today's Chemist

broadly : any of various enzyme-catalyzed aerobic or anaerobic processes (such as oxidation) involving transformation of organic compounds

Most of the catechins are oxidized during the natural fermentation process that converts fresh green tea leaves to black tea.

—Food & Fitness Advisor