Galactans

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Galactans , also galactans , are a group of branched water-soluble oligo- or polysaccharides that belong to the hemicelluloses and consist mainly of D - galactose or 3,6-anhydro- L- galactose . Some galactans are homoglycans , but most are heteroglycans . Analogously, there is the substance group of fructans from fructose - monomers and glucans from glucose monomers.

structure

The galactans usually have a linear main chain of mostly (1 → 4) -ɑ- or (1 → 3) -β- glycosidically bonded D- galactose or 3,6-anhydro- L- galactose; the side chains differ depending on their origin. They contain neutral monosaccharides such as L - arabinose , D - galactose or L - rhamnose , but also uronic acids such as D - glucuronic acid or D - galacturonic acid ; there are also sulfated ago monomers.

Occurrence and use

Representatives of the substance group of galactans are agar , carrageenan , furcellaran, tragacanth and many other polyoses , e.g. B. made of larch wood . Acacia galactans are mainly (1 → 4) -ɑ-glycosidic, while those from Anogeissus latifolia from the winged family are mainly (1 → 6) -ɑ-glycosidic. They come as structural components together with pectins and arabans in the cell walls of many plants such as lupins ( Lupinus ), sugar beets ( Beta vulgaris subsp. Vulgaris var.altissima ), potatoes ( Solanum tuberosum ) and garlic ( Allium sativum ), certain genera of red algae - where they make up up to 40% of the dry weight of the algae - and are found in the cell wall of mycobacteria .

Agar ( E 406 ), carrageenan ( E 407 ) and tragacanth ( E 413 ) are important as food additives ; they are mainly used as fillers, gelling agents and thickeners .

See also

Individual evidence

  1. ^ Wissenschaft-Online-Lexika: Entry on “Galactans” in the Lexikon der Chemie, accessed on September 1, 2011.
  2. ↑ a b Science Online Lexica: Entry on “Galactans” in the Lexicon of Nutrition, accessed on September 1, 2011.
  3. ↑ Entry on agar (-agar). In: Römpp Online . Georg Thieme Verlag, accessed on September 1, 2011.
  4. ↑ a b Entry on Galactans. In: Römpp Online . Georg Thieme Verlag, accessed on September 1, 2011.
  5. ↑ Entry on larch. In: Römpp Online . Georg Thieme Verlag, accessed on May 25, 2014.
  6. ^ Maurizio Zanetti: The antibodies . Harwood Academic Publishers, Luxembourg 1995, ISBN 0-415-28466-X , p. 78.
  7. ↑ Polysaccharides from L-arabinose, see Foodnews: Glossary of terms relating to food , accessed on February 7, 2016. See also reverso: arabane definition (French), accessed on February 7, 2016.