Fructooligosaccharide

Fructooligosaccharides (FOS) are a class of short-chain fructans consisting of beta-(2→1) linked fructose units, typically with a terminal glucose moiety. The chains usually have a degree of polymerization (DP) from about 3 to 10; common members include kestose (DP3), nystose (DP4) and fructofuranosyl-nystose (DP5).

FOS occur naturally in many plants, especially inulin-rich species such as chicory root and Jerusalem artichoke, as well as onions, garlic, leeks and bananas. Commercial FOS are produced by partial hydrolysis or enzymatic synthesis of longer inulin-type fructans or by transformation of sucrose.

Biologically, FOS are prebiotics: they resist human digestion and are fermented by colonic bacteria, preferentially promoting the growth of Bifidobacteria and, to a lesser extent, Lactobacilli. Fermentation yields short-chain fatty acids that contribute to gut health and may modestly affect mineral absorption and stool characteristics. They provide about 1.5–2 kcal per gram.

Applications include use as a dietary fiber supplement, a low-calorie bulking agent, and a sugar replacer in foods such as yogurts, cereals and beverages. They have a mild, pleasant sweetness (roughly one-third to one-half that of sucrose) and can improve texture. High intake can cause gastrointestinal symptoms such as gas and bloating in some individuals.