Konjac gum

Blends of starch and konjac gum (Tye, 1991) and of some modified celluloses (Hercules, Inc., 1980) are synergistic. A ternary dispersion of 1% methylcellulose and 2.9% starch had almost 2.5 times the viscosity of a blend of 0.5% methylcellulose and 2.9% starch, and approximately 20 times the viscosity of 3.9% starch (Hegenbart, 1989). Methylcellulose-starch viscosity synergism was suggested as a formula to decrease caloric content (Henderson, 1989). Guar gum can increase starch paste viscosity tenfold (Christianson et al., 1981). 

This group of polysaccharides is represented by locust bean and guar gums (1,4-P-D-mannan with 1,6-a-D-galactose substituents) and konjac gum (l,4-(3-D-glucomannan). These gums are remarkable for the synergistic effect they have on other polysaccharides and proteins and their tendency to self-associate. Locust bean gum is also called carob gum. 

Konjac tubers are washed, peeled, sliced, and dried. The dried slices are milled into flour and air classified (Konjac flour). Konjac flour contains about 70% glucomannan. Konjac flour cau be further purified by alcohol to remove soluble starch to produce Konjac gum. 

Neiss and Cheng have studied the microstructure of alginates and related it to the action of enzymes (69). Baianu and Ozu have examined the gelling mechanism of konjac gum and its interactions with proteins (63). Other studies include bacterial exopolysaccharides (86) and oligosaccharides (83,87),... 

Synonyms Konjac Konjac glucomannan Konjac gum Konnyaku... 

H, defined as the hydrophilicity, is the weight of hydrocolloidal water in grams adsorbed per gram of solute in 102 g of dispersion (3 is the slope of the Vt vs Cj graph. Equation (7.13) is based on the proportional nonsolute volume increase when increments of a hydrophilic polysaccharide are added to initially pure water. Not all gums showed the linearity expressed in Eq. (7.13). When there is nonlinearity, e.g., in one sample of konjac flour gum... 

The manufacturer has since recalled and reengineered konjac flour gum. 

Konjac flour gum is reported to be pH- and cation- (sodium, potassium, and calcium ions) insensitive this is consistent with its nonionic character (FMC, 1989), but an isolate did not show a characteristic linear viscosity-concentration profile in water it did show linearity in the presence of electrolytes (Jacon et al., 1993). The apparent partial specific volume of a 0.2-0.4% dispersion was constant over a wide pH range and increased with increasing temperature from 5 to 50°C it then remained constant (Kohyama and Nishinari, 1993). 

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. 

B. Gel Test At room temperature, add 5 mL of a 4% sodium borate solution to a 1% solution of sample in a test tube, and shake vigorously. A gel forms. (Konjac Flour solutions gel in the presence of sodium borate, similar in reaction to that of galactomannans such as guar gum and locust bean gum)... 

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