E 425(ii) KONJAC GLUCOMANNAN
Commission Directive 2001/30/EC
Definition 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 ration 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
Molecular weight 500 000 to 2 000 000
Assay Total dietary fibre: not less than 95 % on a dry weight basis
Description White to slightly brownish fine particle size, free flowing and odourless powder
Identification
A. 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
B. 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
C. Viscosity (1 % solution) Not less than 20 kgm-1s-1 at 25 °C
Purity
Loss on drying Not more than 8 % (105 °C, 3h)
Starch Not more than 1 %
Protein Not more than 1,5 % (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 0,5 %
Sulphite (as SO2) Not more than 4 mg/kg
Chloride Not more than 0,02 %
50 % Alcohol-soluble Not more than 2,0 % material
Total ash Not more than 2,0 % (800 °C, 3 to 4h)
Lead Not more than 1 mg/kg
Salmonella spp. Absent in 12,5 g
E. coli Absent in 5 g