Fruktane

Fruktane, known in English as fructans, are a class of storage polysaccharides composed mainly of fructose units, sometimes with a terminal glucose. They vary in the type of linkage and the degree of polymerization. The main subtypes are inulin-type fructans, which have β(2→1) linkages between fructose units (often ending with a glucose residue), and levan-type fructans, which use β(2→6) linkages. Some fructans can have mixed linkages or branched structures.

Fructans occur in a wide range of plants and serve as storage carbohydrates. They are particularly abundant in chicory root, Jerusalem artichoke, onions, garlic, wheat, and barley. In industry, inulin and oligofructose are produced from sucrose by microbial or enzymatic fructosyltransferases and are commonly used as dietary fibers and prebiotics, as well as functional ingredients to modify texture or replace sugars in foods.

Humans lack the enzymes to digest most fructans, so they pass intact into the colon where they are fermented by gut bacteria. This fermentation produces short-chain fatty acids and gases and can stimulate the growth of beneficial bacteria, such as Bifidobacteria, giving fructans a prebiotic effect. Potential health effects include improved mineral absorption and stool regularity, though responses vary and fructans are also categorized as FODMAPs, which can trigger symptoms in some individuals, particularly those with irritable bowel syndrome.

As nutrients and food ingredients, fructans contribute dietary fiber with relatively low energy density, typically around 1.5–2 kcal per gram due to partial fermentation.