What is gum and what is it made of? The properties and uses of gums. Information about gum.
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Gum; is a high-molecular-weight substance that is gelatinous when moist, but becomes hard when dry. Gums may be natural polymers, such as proteins and polysaccharides; derived polymers obtained from natural polymers by chemical modification, such as methylcellulose; or synthetic polymers obtained by synthesis from low-molecular-weight substances, such as polyvinyl alcohol.
Commercially, the term “gum” usually refers to plant polysaccharides ( polymers of simple sugars) and their derivatives. These gums are water-soluble or -dispersable and can be either linear or branched, ionic or neutral. They can be further classified as seaweed extracts, such as algin and agar; plant exudates, such as gum arabic and gum tragacanth; seed extracts, such as guar gum and locust bean gum; other plant extracts, such as larch arabinogalactan and pectin; starches and their derivatives, such as starch dextrins and hydroxyethylstarches; and cellulose derivatives, such as methylcellulose and sodium carboxymethylcellulose. Other water-soluble gums include synthetic gums, such as polyacrylamide and ethylene oxide polymers (polyethylene glycols); and proteins, such as gelatin and casein, which is used in certain glues.
Gums have a large number of commercial uses. Polysaccharide gums are useful mainly because of their thickening power which makes them important as thickeners, adhesives, gelling agents, emulsifiers, and stabilizers. Some gums have film forming properties that make them useful in the paper and textile industries as coating agents and sizing; some exhibit protective colloid action and can be used, for example, in ore refining; and some have the additional property of making dispersions that are sticky ( tacky ) or slimy (mucilaginous). Gums are used extensively in foods—for example, in ice cream to prevent ice crystal growth, in bakery products, and in sauces and meat specialties. They are also used in pharmaceuticals as demulcents, emollients, lubricants, and bulking agents; in adhesives, cosmetics, and oil-well drilling fluids; in lithography and photography; and in the mining industry.
Water-insoluble substances, such as chicle, rubber and other elastomers, and high-molecular-weight hydrocarbons, are less commonly called gums. Some substances that are frequently called gums are resins; for example, gum dammar, pon-tianak gum, and sandarac gum. Other substances that are called gums are mixtures of a true polysaccharide gum, a resin or oleoresin, and essential oils—for example, gum ammoniac and gum myrrh.
