 | |
| Identifiers | |
|---|---|
| ChEBI | |
| Properties | |
| (C6H10O5)n | |
| Molar mass | Variable |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Galactooligosaccharides (GOS), also known asoligogalactosyllactose,oligogalactose,oligolactose ortransgalactooligosaccharides (TOS), belong to the group ofprebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of beneficial bacteria in the colon. GOS occurs in commercially available products such as food for both infants and adults.
The composition of the galactooligosaccharide fraction varies in chain length and type of linkage between the monomer units. Galactooligosaccharides are produced through the enzymatic conversion oflactose, a component of bovine milk.
A range of factors come into play when determining the yield, style, and type of GOS produced. These factors include:
GOS generally comprise a chain of galactose units that arise through consecutive transgalactosylation reactions, with a terminal glucose unit. However, where a terminal galactose unit is indicated, hydrolysis of GOS formed at an earlier stage in the process has occurred. Thedegree of polymerization of GOS can vary quite markedly, ranging from 2 to 8 monomeric units, depending mainly on the type of the enzyme used and the conversion degree of lactose.
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Because of the configuration of their glycosidic bonds, galactooligosaccharides largely resist hydrolysis by salivary and intestinaldigestive enzymes.[1] Galactooligosaccharides are classified asprebiotics, defined as non-digestible food ingredients assubstrate for the host by stimulating the growth and activity of bacteria in the colon.[1]
The increased activity of colonic bacteria results in various effects, both directly by the bacteria themselves or indirectly by producingshort-chain fatty acids as byproducts via fermentation. Examples of effects are stimulation of immune functions, absorption ofessential nutrients, and synthesis of certain vitamins.[2][3][4]
Galactooligosaccharides are a substrate for bacteria, such asBifidobacteria andlactobacilli. Studies with infants and adults have shown that foods or drinks enriched with galactooligosaccharides result in a significant increase inBifidobacteria.[1] These sugars can be found naturally inhuman milk, known ashuman milk oligosaccharides.[5] Examples includelacto-N-tetraose, lacto-N-neotetraose, and lacto-N-fucopentaose.[6]
Human gut microbiota play a key role in the intestinalimmune system.[1] Galactooligosaccharides (GOS) support natural defenses of the human body via thegut microflora,[7] indirectly by increasing the number of bacteria in the gut and inhibiting the binding or survival ofEscherichia coli,Salmonellatyphimurium andClostridia.[8][9] GOS can positively influence the immune system indirectly through the production of antimicrobial substances, reducing the proliferation of pathogenic bacteria.[10][11]
Constipation is a potential problem, particularly among infants, elderly andpregnant women. In infants, formula feeding may be associated with constipation and hard stools.[12] Galactooligosaccharides may improve stool frequency and relieve symptoms related to constipation.[13]
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