Fructooligosaccharides (FOS) also sometimes calledoligofructose oroligofructan, areoligosaccharidefructans, used as an alternativesweetener. FOS exhibits sweetness levels between 30 and 50 percent ofsugar in commercially preparedsyrups.[unreliable source?][1] It occurs naturally, and its commercial use emerged in the 1980s in response to demand for healthier andcalorie-reduced foods.
Two different classes of fructooligosaccharide (FOS) mixtures are produced commercially, based oninulin degradation ortransfructosylation processes.
FOS can be produced by degradation of inulin, or polyfructose, a polymer ofD-fructoseresidues linked by β(2→1) bonds with a terminal α(1→2) linkedD-glucose. The degree of polymerization of inulin ranges from 10 to 60. Inulin can be degraded enzymatically or chemically to a mixture of oligosaccharides with the general structure Glu–Frun (abbrev. GFn) and Frum (Fm), with n and m ranging from 1 to 7. This process also occurs to some extent in nature, and these oligosaccharides may be found in a large number of plants, especially inJerusalem artichoke,chicory and theblue agave plant. The main components of commercial products arekestose (GF2),nystose (GF3),fructosylnystose (GF4),bifurcose (GF3),inulobiose (F2),inulotriose (F3), andinulotetraose (F4).
The second class of FOS is prepared by the transfructosylation action of a β-fructosidase ofAspergillus niger orAspergillus[2] onsucrose. The resulting mixture has the general formula of GFn, with n ranging from 1 to 5. Contrary to the inulin-derived FOS, not only is there β(1→2) binding but other linkages do occur, however, in limited numbers.[3]
Because of the configuration of theirglycosidic bonds, fructooligosaccharides resisthydrolysis bysalivary and intestinaldigestive enzymes. In thecolon they are fermented byanaerobic bacteria. In other words, they have a lowercaloric value, while contributing to thedietary fiber fraction of the diet. Fructooligosaccharides are moresoluble than inulins and are, therefore, sometimes used as an additive toyogurt and other (dairy) products. Fructooligosaccharides are used specially in combination with high-intensity artificial sweeteners, whose sweetness profile and aftertaste it improves.
FOS is extracted from theblue agave plant as well as fruits and vegetables such asbananas,onions,chicory root,garlic,asparagus,jícama, andleeks. Some grains and cereals, such aswheat andbarley, also contain FOS.[4] TheJerusalem artichoke and its relativeyacón together with the blue agave plant have been found to have the highest concentrations of FOS of cultured plants.[5]
FOS has been a popular sweetener inJapan andKorea for many years,[6] even before 1990, when the Japanese government installed a "Functionalized Food Study Committee" of 22 experts to start to regulate "special nutrition foods orfunctional foods" that contain the categories of fortified foods (e.g.,vitamin-fortified wheat flour),[7][unreliable source?] and is now becoming increasingly popular in Western cultures for itsprebiotic effects. FOS serves as a substrate for microflora in the large intestine, increasing the overallgastrointestinal tract health. It has also been proposed as a supplement for treatingyeast infections.[8]
Several studies have found that FOS and inulin promotecalcium absorption in both the animal and the human gut.[9][10] The intestinal microflora in the lower gut can ferment FOS, which results in a reduced pH. Calcium is more soluble in acid, and, therefore, more of it comes out of food and is available to move from the gut into the bloodstream.
In arandomized controlled trial involving 36 twin pairs aged 60 and above, participants were given either a prebiotic (3375 mginulin and 3488 mg FOS) or aplacebo daily for 12 weeks along withresistance exercise andbranched-chain amino acid (BCAA) supplementation. The trial, conducted remotely, showed that the prebiotic supplement led to changes in thegut microbiome, specifically increasingBifidobacterium abundance. While there was no significant difference in chair rise time between the prebiotic and placebo groups, the prebiotic did improvecognition. The study suggests that simple gut microbiome interventions could enhancecognitive function in the elderly.[11][12]
FOS can be considered a smalldietary fibre with (like all types of fibre) low caloric value. The fermentation of FOS results in the production of gases and short chain fatty acids. The latter provide some energy to the body.
All inulin-type prebiotics, including FOS, are generally thought to stimulate the growth ofBifidobacteria species.Bifidobacteria are considered beneficial bacteria. This effect has not been uniformly found in all studies, either forBifidobacteria or for other gut organisms.[13][unreliable source?] FOS are also fermented by numerous bacterial species in the intestine, includingKlebsiella,E. coli[14] and manyClostridium species, which can be pathogenic in the gut. These species are responsible mainly for the gas formation (hydrogen, carbon dioxide and methane), which results after ingestion of FOS[citation needed]. Studies have shown that up to 20 grams/day is well tolerated.[15]FOS are not well tolerated in individuals withIrritable Bowel Syndrome (IBS) or withFODMAP sensitivity.[16]
FOS is classified asgenerally recognized as safe (GRAS).[17]
TheFood Safety Authority warned parents of babies that a major European baby-formula brand made in New Zealand does not comply with local regulations (because it contains fructo-oligosaccharides (FOS)), and urged them to stop using it.[18]
FOS use has been approved in the European Union; allowing addition of FOS inrestricted amounts to baby formula (for babies up to 6 months) and follow-on formula (for babies between 6 and 12 months). Infant and follow-on formula products containing FOS have been sold in the EU since 1999.[18]
FOS is currently not approved for use in baby formula.[19]
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