Karaya gum is a polysaccharide obtained from the secretion of karaya or silk cotton trees. It occurs as light gray or brown lumps with an acetic acid odor. When added to water, it forms a viscous solution and when added to an ethanol-water mixture, it swells. Karaya gum must not contain more than 3% hydrochloric acid insoluble matter, heavy metals above certain limits, or microbial contaminants above specified levels to be considered pure.

1. Karaya Gum
〔9000-36-6〕
Definition Karaya Gum mainly consists of polysaccharides, obtained from the
secretion of karaya trees or silk cotton trees.
Description Karaya Gum occurs as a light gray to light red-brown lumps, and has
acetic acid odor.
Identification (1) To 1 g of powdered Karaya Gum, add 50 ml of water and mix. A
viscous solution is produced and it is acidic.
(2) Add 0.4 g of powdered Karaya Gum to 10 ml of an ethanol−water mixture (3 :
2), and mix. The powder is swelling.
Purity (1) Hydrochloric acid insoluble matter Not more than 3.0 %.
Weigh accurately about 5.0 g of Karaya Gum, transfer into a 500-ml Erlenmeyer
flask added 100 ml of diluted hydrochloric acid (10 → 100), and dissolve. Cover with
watch dish, heat gradually until gum substances dissolve, and boil. Measure the weight
of a glass filter(1G3) previously dried at 105℃ for 1 hour, filter using the glass filter
while warming, and wash the residue well with warm water. Dry the residue with the
glass filter at 105℃ for 1 hour, and weigh.
(2) Starch and dextrin Add 0.2 g of Karaya Gum to 10 ml of water, and boil.
Allow to cool, and add 2 drops of Iodine TS. No dark blue or red purple color develops.
(3) Heavy metals Not more than 40 µg/g as Pb (0.50 g, Method 2, Control
solution Lead Standard Solution 2.0 ml).
(4) Lead Not more than 10 µg/g as Pb (1.0 g, Method 1).
(5) Arsenic Not more than 4.0 µg/g as As2O3 (0.50 g, Method 3, Apparatus B).
Loss on Drying Not more than 20.0 % (105℃, 5 hours).
Ash Not more than 8.0 %.
Acid insoluble ash Not more than 1.0 %.
Microbial Limits Proceed as directed under the Microbial Limit Tests. The total
viable aerobic count is not more than 10,000/g and no Escerichia coli is observed.