Endosperm, galactomannans

Anderson, D. M. W., Howlett, J. F., and McNab, C. G. A. (1986). The amino acid composition of the proteinaceous components of konjac mannan, seed endosperm galactomannans and xanthan gum. Food Hydrocoll. 1 95-99. 

It has been known for some time that the albuminous seeds of the family Leguminosae contain, in the endosperm, galactomannan as the reserve polysaccharide. The exalbuminous seeds, on the other hand, have the main reserve in the cotyledon in the form of starch, oil, and proteins.198,199 The seed galactomannan-reserves are generally mobilized during the process of germination.43,57,81,82,199-205 Detailed study... 

Seed germination is a phenomenon which requires moisture, hence hydration of the polysaccharide in the endosperm. Galactomannans seem tailored to adapt to the environmental requirements of plants located in tropical areas where moisture is seasonal. By comparison, starch hydration is probably more gradual and reversible, a situation more in keeping with a temperate climate. 

Locust Bean Gum. Locust bean gum [9000-40-2], also known as catob seed gum, is a galactomannan extracted from the endosperm of the catob tree seed which is cultivated in the Mediterranean area. The primary use of locust bean gum is in dairy appHcations such as ice cream. It is often used in conjunction with carrageenan because the chemical stmctures of the two enable them to cross-link and form a gel (85). 

Analogies may be drawn between galactomannans and xylo-glucans. The latter polysaccharides, often referred to as amyloids, are found in seed endosperms of plants from many different fami-... 

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... 

Locust bean or carob Thickener exhibits Galactomannan Endosperm of locust... 

Fig. 1.—A Cross-section of the Outer Part of a Seed of Trigonella foenum-graecum Before Mobilization of the Galactomannan, Showing the Three-layered Seed-coat (S) and a Small Part of the Cotyledon (C), with the Endosperm in Between. [The aleurone layer (A) is the outer cell-layer of the endosperm, and the rest of the endosperm is composed of large cells that have thin, primary walls and are completely filled with the dark-stained galactomannan (G). Stained with the periodic acid-Schiff reagent x300 (reproduced, by permission, from Ref. 199).]...

Reid and Meier83 performed a histological examination of the process of deposition of galactomannan in the endosperms of maturing fenugreek-seeds. There was no galactomannan in the very young seeds (2 weeks after anthesis), and the endosperm was not... 

Fig. 4.—Disappearance of Galactomannan from the Endosperm, and Appearance of Starch in the Cotyledon, During Germination of Seeds olTriganella foenum-graecum that had Already Been Soaked for 24 Hours at 24-26°. (Adapted from Figs. 5 and 6 of Ref. 199.)...

During the third, and final, phase (24 h following the second phase), galactomannan is absent (see Fig. 5), and the endospermic carbohydrates of low molecular weight also disappear completely and rapidly. Cotyledons, however, have a high level of starch (see Fig. 4). 

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