Gums, resins and latexes of plant origin

GLOSSARY OF TECHNICAL TERMS 

Absolute

A highly concentrated extract, usually liquid but occasionally semi-solid or solid, prepared by alcohol extraction of a material which is either (a) already in the form of a natural balsam or oleoresin, (b) is a resinoid or (c) has previously been prepared by extraction of plant material with a hydrocarbon solvent. Absolutes are much used in perfumery.

Balsam

A resin or oleoresin exudate characterized by a high content of benzoic or cinnamic acids and their esters. They have a characteristic "balsamic" odour.

Gum

Vegetable gums, i.e., those gums obtained from plants, are solids consisting of mixtures of polysaccharides (carbohydrates) which are either water-soluble or absorb water and swell up to form a gel or jelly when placed in water. They are insoluble in oils or organic solvents such as hydrocarbons, ether and alcohol. The mixtures are often complex and on hydrolysis yield simple sugars such as arabinose, galactose, mannose and glucuronic acid.
Some gums are produced by exudation, usually from the stem of a tree but in a few cases from the root. The exudation is often considered to be a pathological response to injury to the plant, either accidental or caused by insect borers, or by deliberate injury ("tapping"). Seed gums are those isolated from the endosperm portion of some seeds. (Other vegetable gums can be isolated from marine algae (seaweeds) or by microbial synthesis but these are not discussed in this report).
The term "gum resin" is occasionally found in the literature but it has no precise meaning (and is best avoided) although it is generally used to describe a resinous material which contains some gum. The coagulated part of some commercially important latexes such as chicle and jelutong are often referred to as non-elastic gums or masticatory (chewing) gums, but they are not gums in the proper sense of the word.

Latex

A fluid, usually milky white in colour, which consists of tiny droplets of organic matter suspended or dispersed in an aqueous medium. The most well-known example is rubber latex, in which the solids content is over 50% of the weight of the latex. The solids can normally be coagulated to form a solid mass by boiling the latex. The principle components of the coagulum are cis or trans polyisoprenes and resinous material. If the polyisoprene is mainly cis, it confers elasticity to the solid and makes it rubber-like; if it is mainly trans, the solid is non-elastic and gutta-like. 1 ^/
Latexes are usually obtained by cutting the plant to make it bleed. Latex-yielding plants occur in fewer families than those which produce gums and resins; Apocynaceae, Euphorbiaceae and Sapotaceae are among the important ones.  

Oleoresin

A resin which, because of a high content of volatile oil, is softer than one which contains little or no oil. The term is, nevertheless, sometimes shortened to resin when describing soft resins. (The term is also used in another context to describe prepared extracts of spices or other plant materials - after evaporation of the solvent used to extract the spice a soft extract, or oleoresin, remains.) 

Resin (natural) 

A solid or semi-solid material, usually a complex mixture of organic compounds called terpenes, which is insoluble in water but soluble in certain organic solvents. Oil-soluble resins are soluble in oils and hydrocarbon-type solvents; spirit-soluble resins are soluble in alcohols and some other solvents. 
Resins are very widely distributed in the plant kingdom although a few families are notable in accounting for a large proportion of the resins of commerce (e.g., Leguminosae, Burseraceae and Pinaceae). Resins can occur in almost any organ or tissue of the plant; a few (such as lac) are produced from insects. Most resins of commerce are obtained as exudates by tapping.  

Resinoid

A viscous liquid, semi-solid or solid prepared from a natural resin by extraction with a hydrocarbon-type solvent. They contain any volatile oils originally present in the resin and are often used for fragrance purposes.  
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^1/ The terms cis and trans denote the particular molecular geometries exhibited by certain types of chemical compound, in this case the polyisoprene. The term gutta is a short form of gutta percha, the coagulated latex obtained from Palaquiumspp. 

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