Fermentability

Fermentability is the extent to which a substrate, typically a carbohydrate, can be fermented by microorganisms under specified conditions. It is a property that influences how much of the material can be converted into fermentation end products such as ethanol, organic acids, and gases, and it helps describe the potential outcomes of fermentation processes.

In brewing and related fermentation science, fermentability refers to the portion of fermentable sugars in wort or mash that yeast can convert into ethanol and carbon dioxide. It affects apparent attenuation, final gravity, body, sweetness, and dryness of the finished product. Fermentability is influenced by substrate composition (types of sugars and dextrins), mash temperature and pH, enzyme activity, and the presence of nonfermentable carbohydrates. Higher mash temperatures tend to produce less fermentable wort, resulting in fuller-bodied, sweeter beers, while lower temperatures generally yield more fermentable sugars and a drier beer.

In nutrition and gut microbiology, fermentability describes how readily dietary carbohydrates are fermented by the gut microbiota. Fermentable fibers, such as inulin, fructooligosaccharides, pectin, and resistant starch, are broken down to short-chain fatty acids by colonic bacteria, with implications for energy balance, gut health, and colonic environment. Factors include fiber chemistry, solubility, microbiome composition, transit time, and pH.

Measurement and relevance: brewing uses apparent attenuation and final gravity to gauge fermentability and guide recipe formulation; nutritional science employs in vitro fermentation assays or in vivo studies to assess fermentability and its physiological effects.

See also: attenuation, fermentation, dietary fiber, resistant starch.