Konjac mannan

Konjac gel has been a popular traditional Japanese food (konnyaku) for over 1000 years. It is also used to produce noodles and jelly dessert. Noodles are produced by pumping an aqueous solution of the konjac marman through a spinneret immersed in a hot alkaline solution. Gelation occurs yielding strings of konjac gel. 

As noted above, konjac mannan modifies the properties of kappa carrageenan gels and interacts with xanthan gum to form thermally reversible gels. 

Whistler, R.L. and BeMiUer, J.N. (1993) Industrial Gums Polysaccharides and Their Derivatives, 

Stephen, A.M. (1995) Food Polysaccharides and Their Application. Marcel Dekker, New York. 

Lapasin, R. and Pricl, S. (1995) Rheology of Industrial Polysaccharides Theory and Applications. Blackie Academic and Professional, Glasgow. 

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In the linear konjac mannan, the degree of acetylation profoundly affects the solubility and flow properties of this hydrocolloid. The acetyl substitution prevents self-association of the mannan chains, but following deacetylation chain interactions become more energetically favorable [230]. 

Anderson, D. M. W., Howlett, J. F., and McNab, C. G. A. (1986). The amino acid composition of the proteinaceous components of konjac mannan, seed endosperm galactomannans and xanthan gum. Food Hydrocoll. 1 95-99. 

Kato, K., and Matsuda, K. (1973). Isolation of oligosaccharides corresponding to the branching point of konjac mannan. Agric. Biol. Chem. 37 2045-2051. 

Konjac mannan (Glucomannan) Araceae Amorphophallus konjac Koch Der Marderosian and Beutler (2002)... 

Polysaccharides have been isolated which contain both D-glucose and D-mannose, for example, the glucomannan of Amorphophallus konjacJ From this Konjac mannan ([a] o —42.8°) has been isolated a disaccharide composed of D-glucose and D-mannose units. The polysaccharide from the corms of Amorphophallus oncophyllus is a fibrous substance which contains 49 % of anhydroglucose, 41 % of anhydromannose, and 4 % of uronic anhydride, and yields 2 % of pentosans. This substance is an excellent beater additive when used in paper manufacture. 

Interaction of xanthan with guar gum in solution leads to enhanced viscosity, whereas elastic thermo-reversible gels are obtained with LEG and konjac mannan sofP (Figure 26.5). Since xanthan may contain cellulases, it cannot be used with cellulose derivatives. 

Williams PA, Clegg SM, Langdon MJ, Nishinari K, Piculell L. Investigation of the gelation mechanism in K-carrageenan/konjac mannan mixtures using differential scanning calorimetry and electron spin resonance spectroscopy. Macromolecules 1993 26 5441-5446. 

Konjac mannan contains acetate residues linked to the polysaccharide by ester bonds. One acetate group is present for every 19 residues of D-mannose and acetic acid is the only acid present. A series of water-soluble methylated glucomannans from Konjac have been prepared. The polysaccharides with the maximum viscosity had a degree of substitution of 0.45. 

Undergoes a coil-helix transition and forms highly elastic thermoreversible gels on cooling in the presence of locust bean gum and konjac mannan. Strong gels, which melt at 50°C are produced in water. In the presence of electrolyte the gels formed are weaker and form at lower temperatures ( 40°C). 

Figure 4.6 DSC cooling curves for kappa carrageenan/konjac mannan mixtures (total polymer concentration 0.6%) in the presence of 50 mM KCI. A 0.1/0.5 B 0.2/0.4 C 0.3/0.3 D 0.4/0.2 E 0.45/0.15 F 0.5/0.1 and G 0.6/0. Reprinted with permission from [18]. Copyright 1993 American Chemical Society.

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