Galactoglucomannan Galactomannan

In describing and interpreting some of the more important properties of plant galactomannans, comparisons will be made with structurally similar polysaccharides, including the closely related glucomannans and galactoglucomannans, and those based on (1 — 4)-/3-D-xylan main-chains (for example, the arabinoxylans) and (1 — 4)-/3-D-glucan main-chains [for example, the amyloids and sodium 0-(carboxymethyl)cellulose]. 

Since crystalline mannan I is not hydrated, it seems clear that the role of the (l- -6)-a-D-gal actose substituent is to encourage hydration and plasticity. In wood cells where the galactoglucomannan (glucose present in the backbone) is a matrix substance, plasticization is probably the desired property. In seeds where galactomannan is a constitutent of an endosperm, controlled hydration to facilitate attack by some enzyme is probably the important feature. The facility of hydration can control the specific time of germination of seeds especially in a desert enV i ronment. 

Obviously, Meier s results may equally well be interpreted in terms of a triheteropolymer galactoglucomannan. Glucomannans are well known for their insolubility in water and their limited solubility in certain aqueous alkalis, whereas galactomannans are water-soluble. A glucomannan and a galactomannan, if really present, should be separable. It also appears... 

Other hemicelluloses, composed mainly of hydrocolloids, are used primarily as an extracellular energy, raw materials storage system, and as a water retention mechanism in seeds. Galactoglucomannans, glucomannans, galactomannans, and h-glucans tend to be heavily hydrated and have fewer, if any, ester-linked side chains [57]. 

Figure 5.10 A. A Simple Galactomannan. The number of branches is very variable. B. Part of a galactoglucomannan.

Gluco- mannans (Mannans) D-Mannose D-Glucose P-1.4 D-Galactose Glucomannans Galactoglucomannans (Mannans) (Galactomannans)... 

Reproduced with permission from T. Hannuksela and B. Holmbom, Stabiiization of wood resin emulsions by dissolved galactoglucomannans and galactomannans, ]. Pulp Pap. Sci., 30,159-164 (2004). 

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