E 425(i) KONJAC GUM

Commission Directive 2001/30/EC

Definition Konjac gum is a water-soluble hydrocolloid obtained from the Konjac flour by aqueous extraction. Konjac flour is the unpurified raw product from the root of the perennial plant Amorphophallus konjac The main component of Konjac gum is the water-soluble high-molecular-weight polysaccharide glucomannan, which consists of D-mannose and D-glucose units at a molar ration of 1,6:1,0, connected by β(1-4)-glycosidic bonds. Shorter side chains are attached through β(1-3)-glycosidic bonds, and acetyl groups occur at random at a ratio of about 1 group per 9 to 19 sugar units

Molecular weight The main component, glucomannan, has an average molecular weight of 200 000 to

2 000 000

Assay Not less than 75 % carbohydrate

Description A white to cream to light tan powder

Identification

A. Solubility Dispersible in hot or cold water forming a highly viscous solution with a pH between 4,0 and 7,0

B. Gel formation Add 5 ml of a 4 % sodium borate solution to a 1 % solution of the sample in a test tube, and shake vigorously. A gel forms

C. Formation of heat-stable gel Prepare a 2 % solution of the sample by heating it in a boiling water bath for 30 min, with continuous agitation and then cooling the solution to room temperature. For each g of the sample used to prepare 30 g of the 2 % solution, add 1 ml of 10 % potassium carbonate solution to the fully hydrated sample at ambient temperature. Heat the mixture in a water bath to 85 °C, and maintain for 2 h without agitation. Under these conditions a thermally stable gel is formed

D. Viscosity (1 % solution) Not less than 3 kgm^-1s^-1 at 25 °C

Purity

Loss on drying Not more than 12 % (105 °C, 5 h)

Starch Not more than 3 %

Protein Not more than 3 % (N x 5,7)

Determine nitrogen by Kjeldahl method. The percentage of nitrogen in the sample multiplied by 5,7 gives the percent of protein in the sample

Ether-soluble material Not more than 0,1 %

Total ash Not more than 5,0 % (800 °C, 3 to 4h)

Arsenic Not more than 3 mg/kg

Lead Not more than 2 mg/kg

Salmonella spp. Absent in 12,5 g

E. coli Absent in 5 g