Gum Constituents: The normal composition of gums is carbon, hydrogen, oxygen with small quantities of mineral matter ash constituents, nitrogen and small quantities of tannin. Gums can be derived into two types soluble and insoluble. Soluble gums dissolve in water or form transparent, adhesive and viscous solutions as in Indian gum Arabic. Insoluble gums do not dissolve in water. A third group is there, which can be termed as semi-insoluble gums. These gums on heating decompose completely without melting.
Resin Formation: Resins can be generalized as oxidation products of various essential oils. They are chemically related to the terpenes or the essential oils.
Gum characteristics: Gums are edible, not usually fragrant, and do usually do not burn
Resin Characteristics: Resins are not edible, are aromatic, flammable, soften and then melt to a clear stick fluid when heated, and Insoluble in water. Usually dissolves readily in alcohol, ether, or other solvents.
Categories of Resins: Resins can broadly be classified into 3 types. They are Oleoresins, gum resins and hard resins.
Oleoresins: These are soft an doily resins with distinct aroma and contains considerable amount of essential oil
Gum resins: These are mixtures of gums and resins and contains small amount of essential oils. These are usually produced by plant species in dry regions. Myrrh, frankincense, asafoetida and galbanum are important gum resins.
Hard resins: These contain very little of essential oils and are usually solid, more or less transparent, brittle substances with no peculiar odour or taste. The most important commercial resins in this category are copals, dammers, amber, lacquer, shellac and mastic.
Physical Properties Gum/Resin:
Viscosity: Viscosity or the “thickness” of a solution that a gum forms with water is of paramount importance in determining the quality of gum. It is said that the higher the viscosity the better the gum particular in case of medicinal use.
Shape: Gums is either tear or globular in shape
Value: The market traders take light colored gums to be of higher quality. So the darker the colour, the lower the commercial value. Reasons for discriminating include the fact that a lighter color indicates a higher percentage of essential oil in the gum. Which allows for an increased amount of fragrance produced when the gum is burned. The lighter color often is valued aesthetically as well.
Colloidal nature: This property makes gums valuable in manufacturing processes, notably in the textile,cosmetic, pharmaceuticals and food industry. Colloidal nature exhibits swelling pressures and form gel structures at very low concentrations and over a wide range of concentrations. They have low surface tension, do not crystallize and act as protective colloids and stabilizing agents. In effect they prevent the agglomeration.
Taste and smell: The true gums are nearly scentless and in this sense differ markedly from some of the resins and oleo-resins that are so distinctive in smell. They may be tasteless, and are in fact generally devoid of any characteristic taste. But some are slightly sweet or bitter according to botanical origin. In some gums there is distinctively bitter taste. This is a serious disadvantage in a gum required for edible purposes.
Hardness: Gums vary in hardness. Hardness is obviously governed partly by the amount of moisture present. Density also provides variable in one and the same gum according to the amount of air that may have been incorporated in it when it was formed. Most gums break with a clear glassy fracture when properly dried, and may be readily pulverized.
Compiled By: Raqib Zaman