Polysaccharides plant exudates

Natural gums include plant exudates, seed gums, plant extracts, seaweed extracts, and the extracellular microbial polysaccharides. Plant exudates include gum arabic, gum ghatti, gum karaya, and gum tragacanth. Seed gums include... 

Gum acacia, a natural plant exudate polysaccharide, has historically been used as the wall material of choice. Due to fluctuations in availability and increasing costs of this natural polymer, alternate choices have been examined (9), Worth noting at this point is the 1.5% to 3% protein content associated with this polysaccharide (20). 

Acacia gum A mixture of structurally related polysaccharides, the main one is based on P-D-galactopyranose residues Natural plant exudates solutions are stable at pH 2-7 and display relatively low viscosity Emulsifying or suspending agents, adhesive and binders (in tablets)... 

Polyuronides may be defined as polysaccharides that contain one or more uronic acid units in their molecular structures. They have a frequent and wide occurrence in nature. Much of the carbohydrate material in plants belongs to the group. It includes all pectic materials and plant gums and many plant mucilages, hemicelluloses and gel-forming substances and some microbial polysaccharides. These substances are to be looked for in water-soluble plant exudates and mucilages, as well as in water and alkaline extracts of most plant materials. This review will be limited to the polyuronides occurring in plants. 

Astragalus gummifer. Exudate gums are a plants defense mechanism. These polysaccharides are exuded from plants as a result of injury or fungal attack. 

Other gums (plant exudates consisting of high polymer polysaccharides, some with a low nitrogen content) as karaya, acacia (gum arabic), and gum tragacanth may occasionally act as sensitizers (Nilsson 1960). 

Tragacanth is a plant exudate from certain legumes. It is a mixture of various polysaccharides, predominantly with D-galacturonic acid residues. It is used as a thickener in foods, e.g., in salad sauces, ice cream, etc. 

As technically employed in industry, the term gum usually refers to polysaccharides (long chains of simple sugars) or their derivatives, which are dispersible in either hot or cold water to produce viscous mixtures. Gums also may include water-soluble derivatives of cellulose and modifications of other polysaccharides which in their natural form are insoluble. The original definition of gums applied only to the sticky gummy natural plant exudates. 

Exudate gums are polysaccharides produced by plants to seal wounds in their bark. The plant exudes an aqueous solution of polysaccharide around a break in the bark, covering the injury. The water evaporates, leaving a polysaccharide that hardens and prevents infection and desiccation of the plant. 

Hydrocolloids are high-molecular-weight hydrophihc biopolymers used as functional ingredients in the food industry for the control of viscosity, gelation, microstructure, texture, flavor, and shelf-hfe. The term hydrocolloid encompasses all the polysaccharides that are extracted from plants, seaweeds, and microbial sources, as well as gums derived from plant exudates, and modified biopolymers made by chemical or enzymatic treatment to be soluble or dispersible in water. The general molecular and functional properties of proteins and polysaccharides are compared in Table 5.1. 

The botanical gums represent a family of polysaccharides obtained from a wide variety of plant sources. They are subdivided into exudate gums, seed gums, and gums obtained by extraction of plant tissue. For a gum to be used in commercial quantities, it must be present in the tissues or be readily extractable in relatively pure form which limits the number of commercial botanical gums. 

An attempt has been made to classify gums into two main groups (a) real gums which are those plant products which form a clear solution in water and (b) vegetable mucilages which are those which swell but do not dissolve completely in water. This classification is useful but not entirely satisfactory since there are exceptions. Thus gum traga-canth, a tree exudate and a true plant gum, is only partially soluble in water and exhibits those properties normally attributed to mucilages. In this section of the article the term plant gum will be restricted to those complex acid polysaccharides which are exuded from trees either spontaneously or after mechanical injury. 

Reference should also be made in this section to the recent advances in the chemistry of mesquite gum, an exudate from mesquite trees (Prosopia julijlora DC. and related species). The naturally occurring plant gum is the salt of a complex acid polysaccharide as is the case with... 

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