Structure of Gum

The main composition of gum is mannogalactan. Carbohydrate can be divided into monosaccharide, polyose, and glycan. Monosaccharide can be further divided into pentose and hexose. For example, glucose, mannose, and galactose belong to hexoaldose. The structures of glucose, mannose, and galactose are as follows  

Saccharides appear in the form of ringlike structure. For example, the ringlike structure of glucose is as follows  

The famous Arabic gum is a mixture of various salts (Ca, Mg and K) of arabonic acid. It consists of 1-D-hexonicacid, 3-D-galactose, 2-L-arabinose, and 1-L-rham-nose. The structure of Arabic gum is as follows  

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Over thirty publications resulted from Tipson s work in Levene s laboratory. Along with the work on nucleic acid components, he also studied the structures of gum arabic and other plant gums, and conducted a range of synthetic investigations on sugars, with particular emphasis on uronic acids and 5-carbon ketoses. His 1939 observation that acetylated glycosyl halides... 

One remarkable feature of plant gums is the striking uniformity in the structure of gums isolated from different trees of the same type. For example, damson plum trees produce a gum whose properties do not vary from tree to tree. The same has been said by O Sullivan about gum arabic from acacia trees. 

The gum phenomenon was studied in detail 10-25 years ago. The composition of "gum deposits" was studied by extracts of deactivated catalysts. Jackson et al, 10) found that the chemical structure of gum deposits on catalysts deactivated in laboratory tests was independent of the reacting hydrocarbons and consisted of -CH2-polymers, whereas Bhatta and Dixon (77) found aromatics in extracts from... 

Numerous examples further illustrate the great value of the Smith degradation in determinations of the fine structure of polysaccharides. They include studies on arabinoxylans, mesquite gum, an exocellular yeast mannan, and a type-specific bacterial polysaccharide. Branching patterns in complex types of glycoproteins from several different origins have been elucidated, and detailed structures of gum exudates, seed polysaccharides, and pectic sub-... 

Figure 14.15 Molecular structure of Gum agar. Adapted with permission from [81] Copyright 2011 Elsevier.

The structure of gum arabic is relatively complex, with a main chain of d-galactopyranosyl units linked P-1 -> 3 and P-1 6, along with D-glucopyra-nosyl uronic acid units linked P-1 6. The nonreducing ends are terminated with... 

D-galactose, C HiiOe. Crystallizes in the pyranose form m.p. 1I8-120 C (monohydrate), 165-5" C (anhydrous). An isomer of glucose which is fairly widely distributed in plants. It is a constituent of raffinose and slachyose, of hemicelluloses, of pectin, of gums and mucilages, and of some glycosides. In animals it forms half the lactose molecule and is the sugar found in the brain. Chemically it is very similar to glucose. It has the structure... 

As investigations with polysaccharides of microbiological, plant, and animal origin revealed the presence in these substances of uronic acids, it became necessary to know more about the acids. Moreover, the occurrence of uronic acids in plant gums and pectic substances, and the structures of urinary... 

Funami, T., Noda, S., Nakauma, M., Ishihara, S., Takahashi, R., Al-Assaf, S., Ikeda, S., Nishinari, K., and Phillips, G. O. (2008). Molecular structures of gellan gum imaged with atomic force microscopy in relation to the rheological behavior in aqueous systems in the presence or absence of various cations. J. Agric. Food Chem. 56, 8609-8618. 

Gum acacia is a unique polysaccharide, with some peptides as part of the structure and has a range of different uses. It was originally the gum in gum sweets although some gum sweets do contain modified starch as a substitute. The replacement of gum is not because the substitute performs better but because there have been supply problems with gum acacia. Gum acacia is likely to be encountered in bakeries in small quantities when it has been used to make emulsions of citrus oils as a bakery flavour. It is possible to use gum acacia in making dry flavours from oils such as citrus by making an emulsion and then spray drying it. 

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