Galactomannan

A segment of galactomannan showing mannose backbone (below) with a branching galactose unit (top)

Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups (more specifically, a (1-4)-linked beta-D-mannopyranose backbone with branchpoints from their 6-positions linked to alpha-D-galactose, i.e. 1-6-linked alpha-D-galactopyranose).

In order of increasing number of mannose-to-galactose ratio:

• fenugreek gum, mannose:galactose ~1:1
• guar gum, mannose:galactose ~2:1
• tara gum, mannose:galactose ~3:1
• locust bean gum or carob gum, mannose:galactose ~4:1

Galactomannans are often used in food products to increase the viscosity of the water phase.

Food use

Galactomannans are used in foods as stabilisers. Guar and Locust Bean Gum (LBG) are commonly used in ice cream to improve texture and reduce ice cream meltdown. LBG is also used extensively in cream cheese, fruit preparations and salad dressings. Tara is seeing growing acceptability as a food ingredient but is still used to a much lesser extent than guar or LBG. Guar has the highest usage in foods, largely due to its low and stable price. Article on LBG

Clinical use

Galactomannan is a component of the cell wall of the mold Aspergillus^[1] and is released during growth. Detection of galactomannan in blood is used to diagnose invasive aspergillosis infections in humans. This is performed with monoclonal antibodies in a double-sandwich ELISA assay from Bio-Rad Laboratories was approved by the FDA in 2003 and is of moderate accuracy.^[2] The assay is most useful in patients who have had hemopoetic cell transplants (stem cell transplants).

The tears of the eye can be supplemented with artificial lubricants to improve eye comfort. An independent clinical trial ^[3] has shown that lubricant eye drops containing HP Guar provide significant improvement of comfort in people with "dry-eye".

References