Introduction
Konjac glucomannan (KGM) is a highly polymerized dietary fibre obtained from the roots and tubers of the plant Amorphophallus konjac C. Koch The plant is commonly called the konjac yam, devil’s tongue yam or elephant yam. Konjac glucomannan is also extracted from other Amorphophallus including Amorphophallus muelleri.
The main component of KGM is a non-ionic, high molecular weight polysaccharide of mannose and glucose units, with a small number of branched side chains. The units are connected by β-1,4-glycosidic linkages with a mannose: glucose molar ratio of approximately 1.6 to 4:1. Acetyl groups along the glucomannan backbone contribute to solubility properties and are located every 9 to 19 sugar units.
Functional Benefits Of Konjac Glucomannan
Konjac gum has three unique functionalities. It can form an extremely viscous solution, has great water binding capabilities, and can form a reversible or a non-thermo-reversible gel. To create such an ingredient, a weak base, such as potassium carbonate, is added to hydrated konjac gum, and the solution is heated. Raising the pH to 9 or 10 creates a gel that is stable over a range of food temperatures, from freezing to cooking. The gel retains its stability when incorporated into food products with a lower pH. .
Konjac glucomannan can absorb up to 50 times its weight in water and can produce a very viscous gel which measures from 12,000 to 20,000 centipoise.
When the food product has an acid or neutral pH, it forms a thermo-reversible gel. It is ideal for product developers creating stable gels that wont breakdown as the temperature increases.
Nutritional Benefits Of Konjac Glucomannan
KGM has a number of useful physiological and nutritional benefits (Chua et al., 2010; Behera & Ray, 2016). It can reputedly act as a:-
- antigenotoxic agent,
- antioxidant,
- antibacterial agent,
- reduces obesity,
- antidiabetic agent,
- anticoagulant,
- anti‐inflammatory agent,
- regulates in lipid metabolism,
- laxative,
- prebiotic,
- antitumor activities
Glucomannan is used for treating a variety of conditions which include constipation, weight loss, diabetes, high cholesterol, overactive thyroid (hyperthyroidism), high blood pressure, and stomach conditions called dumping syndrome and functional gastrointestinal disorder.
It is used in foods as a thickener and gelling agent. Other konjac derivatives include konjac flour which is commonly found in vegan foods and konjac or shirataki noodles for weight-loss products.
Konjac Flour
The flour is used to prepare a famous noodle known as shirataki noodles. These are famous noodles from Japan. Using the flour means this product has a high dietary fiber content.
The proximate composition of konjac glucomannan flour obtained from Amorphophallus muelleri contains 86.8% glucomannan, 0.2% other carbohydrates, 3% protein, 0.1% lipids, 3.3% ash, and 6.6% moisture content (Impaprasert et al., 2014).
How Does It Work?
Glucomannan probably absorbs water in the stomach and intestines which is in keeping with other types of soluble fibre. The bulking activity helps relieve constipation.
Management Of Diabetes
Glucomannan mixed with American ginseng has been shown in research to produce a moderate improvement in type 2 diabetes management (Jenkins et al., 2018).
Cholesterol Management
Taking glucomannan supplements may help in regulating cholesterol levels. A 2008 study found that glucomannan has a beneficial effect on the overall cholesterol levels (Sood et al., 2008). The dose suggested to help improve cholesterol levels is 3 grams per day (Ho et al., 2017).
Regulatory Status of Glucomannan
The US Food and Drug Administration was granted by a successful citizen petition from The Food Lawyers in late 2019 that glucomannan be listed as a dietary fiber. The FDA states that dietary fiber can be declared on the Nutrition and Supplement Facts labels. This includes naturally occurring fibers that are intrinsic and intact in plants along with added isolated or synthetic non-digestible soluble and insoluble carbohydrates. These must also have be a recognised and determined physiological benefit to human health.
The definition that glucomannan is dietary fiber comes from the FDA’s 2016 Nutrition Facts label final rule. They acknowledged that there was enough scientific evidence to suggest that glucomannan helped to reduce blood cholesterol levels.
Products Containing Konjac
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Amended article to include new FDA regulatory status of glucomannan as a dietary fiber and that it could be listed as such (17th February, 2020).
References
, & (2016). Konjac glucomannan, a promising polysaccharide of Amorphophallus konjac K. Koch in health care. International Journal of Biological Macromolecule, 92, pp. 942–956. (Article).
, , , & (2010). Traditional uses and potential health benefits of Amorphophallus konjac K. Koch ex NE Br. Journal of Ethnopharmacology, 128, pp. 268–278 (Article).
Ho, H. V. T., Jovanovski, E., Zurbau, A., Blanco Mejia, S., Sievenpiper, J. L., Au-Yeung, F., … & Vuksan, V. (2017). A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B. The American Journal of Clinical Nutrition, 105(5), pp. 1239-1247.
Impaprasert, R., Borompichaichartkul, C., Srzednicki, G. (2014) A new drying approach to enhance quality of konjac glucomannan extracted from Amorph. Muelleri. Dry. Technol. Int. J. 32, pp. 851–860. (Article) .
Jenkins, A. L., Morgan, L. M., Bishop, J., Jovanovski, E., Jenkins, D. J., & Vuksan, V. (2018). Co-administration of a konjac-based fibre blend and American ginseng (Panax quinquefolius L.) on glycaemic control and serum lipids in type 2 diabetes: A randomized controlled, cross-over clinical trial. European Journal of Nutrition, 57(6), pp. 2217-2225 (Article).
Sood, N., Baker, W. L., & Coleman, C. I. (2008). Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. The American Journal of Clinical Nutrition, 88(4), pp. 1167-1175 (Article).
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