Fructooligosaccharides (FOS) also sometimes called oligofructose or oligofructan, are

oligosaccharide An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sug ...

fructans, used as an alternative

sweetener {{Wiktionary, sweetener A sweetener is a substance added to food or drink to impart the flavor of sweetness, either because it contains a type of sugar, or because it contains a sweet-tasting sugar substitute. Many artificial sweeteners have been ...

. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially prepared

syrup In cooking, a syrup (less commonly sirup; from ar, شراب; , beverage, wine and la, sirupus) is a condiment that is a thick, viscous liquid consisting primarily of a solution of sugar in water, containing a large amount of dissolved sugars ...

s. It occurs naturally, and its commercial use emerged in the 1980s in response to consumer demand for healthier and calorie-reduced foods.

Chemistry

Two different classes of fructooligosaccharide (FOS) mixtures are produced commercially, based on

inulin Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a m ...

degradation or transfructosylation processes. FOS can be produced by degradation of inulin, or polyfructose, a polymer of D-fructose

residue Residue may refer to: Chemistry and biology * An amino acid, within a peptide chain * Crop residue, materials left after agricultural processes * Pesticide residue, refers to the pesticides that may remain on or in food after they are applied ...

s linked by β(2→1) bonds with a terminal α(1→2) linked D-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–Fru_n (abbrev. GF_n) and Fru_m (F_m), with n and m ranging from 1 to 7. This process also occurs to some extent in nature, and these oligosaccharides can be found in a large number of plants, especially in

Jerusalem artichoke The Jerusalem artichoke (''Helianthus tuberosus''), also called sunroot, sunchoke, wild sunflower, topinambur, or earth apple, is a species of sunflower native to central North America. It is cultivated widely across the temperate zone for its ...

chicory Common chicory (''Cichorium intybus'') is a somewhat woody, perennial herbaceous plant of the family Asteraceae, usually with bright blue flowers, rarely white or pink. Native to the Old World, it has been introduced to North America and Austra ...

and the

blue agave ''Agave tequilana'', commonly called blue agave () or tequila agave, is an agave plant that is an important economic product of Jalisco, Mexico, due to its role as the base ingredient of tequila, a popular distilled beverage. The high production ...

plant. The main components of commercial products are kestose (GF₂), nystose (GF₃), fructosylnystose (GF₄), bifurcose (GF₃), inulobiose (F₂), inulotriose (F₃), and inulotetraose (F₄). The second class of FOS is prepared by the transfructosylation action of a β-fructosidase of ''

Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the ''Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on de ...

'' or '' Aspergillus '' on sucrose. The resulting mixture has the general formula of GF_n, 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. Because of the configuration of their

glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group ...

s, fructooligosaccharides resist

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

by salivary and intestinal

digestive enzyme Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anima ...

s. In the colon they are fermented by

anaerobic bacteria An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

. In other words, they have a lower caloric value, while contributing to the dietary fiber fraction of the diet. Fructooligosaccharides are more

soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

than inulins and are, therefore, sometimes used as an additive to

yogurt Yogurt (; , from tr, yoğurt, also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as ''yogurt cultures''. Fermentation of sugars in the milk by these bac ...

and other ( dairy) products. Fructooligosaccharides are used specially in combination with high-intensity artificial sweeteners, whose sweetness profile and aftertaste it improves.

Food sources

FOS is extracted from the

plant as well as fruits and vegetables such as bananas,

onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onio ...

root, garlic,

asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial flowering plant species in the genus '' Asparagus''. Its young shoots are used as a spring vegetable. It was once classified in ...

jícama ''Pachyrhizus erosus'', commonly known as jícama ( or ; Spanish ''jícama'' ; from Nahuatl ''xīcamatl'', ) Mexican turnip, is the name of a native Mexican vine, although the name most commonly refers to the plant's edible tuberous root. Jíca ...

, and leeks. Some grains and cereals, such as

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

and

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...

, also contain FOS. The

and its relative yacón together with the blue agave plant have been found to have the highest concentrations of FOS of cultured plants.

Health benefits

FOS has been a popular sweetener in Japan and

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

for many years, even before 1990, when the Japanese government installed a "Functionalized Food Study Committee" of 22 experts to start to regulate "special nutrition foods or

functional food A functional food is a food claimed to have an additional (often one related to health promotion or disease prevention) by adding new ingredients or more of existing ingredients. The term may also apply to traits purposely bred into existing edib ...

s" that contain the categories of fortified foods (e.g., vitamin-fortified wheat flour), and is now becoming increasingly popular in Western cultures for its prebiotic effects. FOS serves as a substrate for microflora in the large intestine, increasing the overall gastrointestinal tract health. It has also been proposed as a supplement for treating

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...

infections. Several studies have found that FOS and inulin promote calcium absorption in both the animal and the human gut. 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. FOS can be considered a small dietary fibre with (like all types of fibre) low caloric value. The fermentation of FOS results in the production of gases and acids. The latter provide some energy to the body.

Side-effects

All inulin-type prebiotics, including FOS, are generally thought to stimulate the growth of '' Bifidobacteria'' species. Bifidobacteria are considered beneficial bacteria. This effect has not been uniformly found in all studies, either for bifidobacteria or for other gut organisms. FOS are also fermented by numerous bacterial species in the intestine, including ''

Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' species are found everywhere in nature. This is thought to be due to distinct sublineages developi ...

'', '' E. coli'' and many '' Clostridium'' species, which can be pathogenic in the gut. These species are responsible mainly for the gas formation (hydrogen and carbon dioxide), which results after ingestion of FOS. Studies have shown that up to 20 grams/day is well tolerated.

Regulation

US FDA regulation

FOS is classified as generally recognized as safe (GRAS).

NZ FSANZ regulation

The Food 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.Inulin, FOS and GOS assessed in Australia, NZ
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EU regulation

FOS use has been approved in the European Union; allowing addition of FOS in restricted 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.

Canadian regulations

FOS is currently not approved for use in baby formula.

References

{{carbohydrates Oligosaccharides Prebiotics (nutrition) Sugar substitutes