Legumes, galactomannans

Like guaran, and the endosperm polysaccharides of other legumes, locust bean (carob)gum [900040-2] is also a galactomannan. Like guaran, it has a linear backbone of (1 — 4)-linked p-D-mannopyranosyl units. However, in locust bean gum, approximately one of every 3.9 p-D-mannopyranosyl units, on the average, is substituted with an a-D-galactopyranosyl unit attached at 0-6. 

The polysaccharidic galactomannans which occur94 in the endosperms of guar, locust bean, carob bean, and many other legumes have been... 

The plentiful occurrence of these galactomannans in certain members of the legume family, and the widespread (perhaps universal) distribution of the raffinose oligosaccharides in legumes, make it tempting to suggest that there may be a close biogenetic relationship between these two types of saccharide. 

I inked D-mannose is the backbone of a major group of cell storage-polysaccharides in seeds. Galactomannans with different amounts of terminal a-galactose residues are typical of legume seeds.121... 

The modes of action of jS-o-mannanases of diverse origin on legume seed galactomannans have been reported. The enzymes have different abilities to hydrolyse galactomannans especially when the backbone is highly substituted with D-galactose residues. 

Finally a word about the endospermic legumes. As we have mentioned previously, the galactomannan reserves of the endosperm of these seeds might be more important for retention of water within the seed to allow early embryo growth than for the provision of nutrients. The cotyledons of these legumes are usually rich in fats and protein but their mobilization does not appear to have received any attention. 

Soluble dietary fibre includes a certain proportion of hemi-ceUuloses. For example, about one third of cereal structural arabinoxylans are soluble. Also, one quarter to about one half of barley fl-glucans are soluble, and even a certain proportion of glucomannans and galactomannans of legumes are soluble. Other soluble polysaccharides are pectins, plant mucilages, seaweed polysaccharides, modified starches and modified celluloses (Table 4.21). 

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