E 425(ii) – Konjac glucomannan – EU specification

COMMISSION REGULATION (EU) No 231/2012 of 9 March 2012



Konjac glucomannan is a water-soluble hydrocolloid obtained from Konjac flour by washing with water-containing ethanol. Konjac flour is the unpurified raw product from the tuber of the perennial plant Amorphophallus konjac. The main component is the water-soluble high molecular-weight polysaccharide glucomannan, which consists of D-mannose and D-glucose units at a molar ratio of 1,6:1,0, connected by β(1-4)-glycosidic bonds with a branch at about each 50th or 60th unit. About each 19th sugar residue is acetylated


Chemical name:

Chemical formula:

Molecular weight: 500 000 to 2 000 000

Assay: Total dietary fibre: not less than 95 % on a dry weight basis


White to slightly brownish fine particle size, free flowing and odourless powder


Solubility: Dispersible in hot or cold water forming a highly viscous solution with a pH between 5,0 and 7,0. Solubility is increased by heat and mechanical agitation

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


Loss on drying: Not more than 8 % (105 °C, 3 hours)

Starch: Not more than 1 %

Viscosity (1 % solution): Not less than 20 kgm – 1 s – 1 at 25 °C

Protein: Not more than 1,5 % (N × 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 0,5 %

Sulphite (as SO 2 ): Not more than 4 mg/kg

Chloride: Not more than 0,02 %

50 % Alcohol-soluble material: Not more than 2,0 %

Total ash: Not more than 2,0 % (800 °C, 3 to 4 hours)

Lead: Not more than 1 mg/kg

Microbiological criteria

Salmonella spp.: Absent in 12,5 g

Escherichia coli: Absent in 5 g