Gum Karaya

Introduction

Gum Karaya is the dried exudate of the Sterculia Urens tree. These are large bush trees that grow about 9 metres high. In order to produce the gum, the trees are tapped and exudation begins immediately and continues for several days forming irregular lumps (or tears) which may weigh up to 5 pounds. The exudate is allowed to dry on the tree and is later collected, broken, cleaned and sorted. On average, a tree can be tapped about 5 times during its lifetime.

The highest quality of raw gum collected is during the hot months of April, May and June right before the monsoon. High grades are white to tan in colour, translucent and nearly free of organic matter and bark.

Manufacturing Process

Gum Karaya is initially processed to remove impurities such as bark, stones, fibres and sand. It is then milled, blended and classified according to mesh, viscosity, and purity.

Properties

Gum Karaya is a complex acetylated polysaccharide consisting mainly of D-galacturonic acid, D-galactose and L-rhamnose. Its powder is light gray to pinkish gray and has a slight acetic taste and odour.

Unlike other water soluble gums, it does not dissolve in water but absorbs it to form a viscous colloidal solution. Viscosity stability depends on time of harvest, climate during harvest, storage conditions including temperature/humidity and may decrease after storage over 6 months.

Low concentrations in cold solutions are more viscous rather than in hot solutions. High concentrations require cooking of the gum to aid in solubility which could reduce the viscosity.

Applications

Pharmaceutical:

Its adhesive property is used in dental compounds and colostomy rings. Acting as mucilage it is also used as a bulk laxative.

Food:

It is used as a binder, emulsifier and stabilizer.

Grades

Gum Karaya is offered as granules or in powder form. The granule size ranges from 4-8 mesh and 8-14 mesh and powder size is 160 mesh with viscosity ranging from 500-1200 cps.