Galactooligosaccharides

Galacto-oligosaccharides (GOS), also known as oligogalactosyllactose, oligogalactose, oligolactose or transgalactooligosaccharides (TOS), belong to the group of prebiotics. 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 commercial available products such as food for both infants and adults.

The composition of the galacto-oligosaccharide fraction varies in chain length and type of linkage between the monomer units. Galacto-oligosaccharides are produced through the enzymatic conversion of lactose, 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. The degree 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.

GOS have been used as food ingredients in Japan and Europe for at least 30 years and their application has expanded rapidly. It all started in Japan, where Japanese companies like Yakult Honsha (Tokyo, Japan) and Nissin Sugar Manufacturing Company (Tokyo, Japan) produced GOS for food applications. Later on Snow Brand Milk Products (Tokyo, Japan), FrieslandCampina Domo (ex Borculo ingredients and Friesland Foods Domo) in the Netherlands and [ ] (Yunfu, China), (Clasado Ltd in the United Kingdom also started to produce GOS. In contrast, GOS production in the USA remains negligible. Nowadays, GOS is mostly used for application in infant nutrition.

Most of the manufacturers produce several classes of products in terms of GOS purity in either syrup and/or powder format. Yakult is producing three GOS products: Oligomate 55 in syrup form, Oligomate 55P in powder form and TOS-100 a purified version of 99% oligosaccharide content. Nissin is producing Cup-Oligo in syrup (Cup-Oligo H70) and powder format (Cup-Oligo P) and Snow Brand produces GOS that is incorporated into its infant milk formula P7L, without offering sales outside its organization. In Europe, FrieslandCampina Domo is offering Vivinal GOS in a syrup format containing 57% oligosaccharides on dry matter and in a two powder format containing 29% or 71% oligosaccharides on dry matter. Clasado Ltd is offering a powder GOS product, Bimuno, with 52% galacto-oligosaccharide content on dry matter, as well as a syrup and pastille versions of that product. Besides the differences in purity amongst the commercially offered products, there are differences also in the linkages of the oligosaccharide chain due to the different enzymes used in their production. This can have a direct impact on their potential to affect host's physiology and health. The Oligomate range is produced with enzymes originating from Aspergillus oryzae offering mainly β 1-6 linkages, the Bimuno product is produced using enzymes from a probiotic Bifidobacterium bifidum and contains mainly β 1-3 linkages whilst Cup-Oligo and Vivinal offer mainly β 1-4 linkages as a result of the activity of enzymes from Bacillus circulans for the latter and Cryptococcus laurentii for the former GOS product. Yakult is also considering dual enzymes systems combining the activity of enzymes from A. oryzae and B. circulans to produce GOS mixtures of β 1-4 and β 1-6 linkages.

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