What Is Glucomannan?
Glucomannan is an organic compound classified as a water-soluble neutral polysaccharide.
It is a polysaccharide composed of D-glucose and D-mannose in a 1:1.6 ratio of β-1,4 bonds, with one branch per 50~60 sugars. In the branches, β-1,6 bonds are formed.
The molecular weight of glucomannan is very large, exceeding 1 million in some cases. At room temperature, it is an odorless white powder. It is relatively stable and insensitive to salt, pH, and heat.
It is also known as konjac glucomannan because it is the main ingredient of konjac.
It is a type of soluble dietary fiber and is known for its ability to swell by water absorption and to gel when heated under alkaline conditions.
Uses of Glucomannan
The main uses of glucomannan are as a gelling agent, thickening agent, and water retention agent in foods and beverages. As a general food and beverage additive (thickening stabilizer and manufacturing agent), it is approved for use as a food additive.
Since it expands by water absorption, it is often used in diet foods in recent years to make people feel full with a small amount of food. As an ingredient in cosmetics, glucomannan is sometimes used as a skin conditioning and protective agent.
Characteristics of Glucomannan
Glucomannan has the property of absorbing water and swelling greatly. For example, it exhibits high viscosity of more than 30,000 mPa-s in a 1% solution.
It is used as a food additive, but has little taste or odor.
Types of Glucomannan
There are several types of glucomannan, including konjac mannan and wood glucomannan, but most commonly sold glucomannan is konjac mannan.
There are a variety of glucomannan powder products on the market, but most of them are made by extracting and refining glucomannan from konjac potatoes. The degree of refinement varies from product to product, so it is necessary to make a selection according to the intended use.
In addition, various forms of glucomannan, such as powders and gels, are sold, and products are offered to meet a wide range of needs.
Other Information on Glucomannan
1. Gelation of Glucomannan
When a coagulant (calcium hydroxide) is added to a solution of glucomannan and heated, a thermo-incompatible gel is formed.
The mechanism of this reaction is as follows. The same principle is used in the production of konjac in general.
- When glucomannan is dissolved in water, it first forms a hydrophilic colloid and then a sol. In other words, many water molecules are hydrated between the macromolecules.
- When a basic salt solution is added and heated, the macromolecules aggregate to form an irreversible gel.
2. Interaction of Glucomannan With Other Polysaccharides
Glucomannan interacts with carrageenan through hydrogen bonds to form cross-linked regions. In fact, it has been found that the gel strength increases synergistically when glucomannan is used in combination with xanthan gum + carrageenan gel.
In addition, what is sold as konjac jelly is a product that uses cross-linking by hydrogen bonding between glucomannan and carrageenan. Unlike the normal konjac manufacturing process described in the previous section (irreversible gelation of glucomannan under alkaline conditions), konjac jelly is dissolved in boiling water without using a coagulant, and then cooled and hardened.
It also differs from konjac in that it dissolves again upon reheating.
Health Benefits of Glucomannan
Glucomannan is a type of dietary fiber that is known to improve bowel movements. It cannot be digested by human digestive enzymes and is said to absorb water in the stomach, causing it to swell dozens of times. However, excessive intake may cause diarrhea or over-expansion in the gastrointestinal tract, which can be harmful, so care should be taken regarding intake.
Recently, it has also been reported that glucomannan helps lower LDL cholesterol and blood sugar levels, suggesting that glucomannan may be effective in improving these factors that cause lifestyle-related diseases.