Glucomannan
Glucomannans (or glucomannans ) are starch -like substances from branched carbohydrate chains. The main chain consists of D - mannose and D - glucose, with different distances ( short ) side chains occur.
Main component of the devil's tongue Amorphophallus konjac in the family Araceae, also called konjac root, from which the food thickener and the satiety agent konjac ( konjac, Japanese = konnyaku ) is produced, is a glucomannan.
Structure
The main chain of the polysaccharide is comprised of 1,4- α - glycosidically linked monosaccharide units D- glucose, and mannose, in the ratio of approximately 2:1. This main chain takes analogous to amylose starch a helical coil structure. On this main chain α -1 ,6 -glycosidic monomers or short side chains of sugar residues are attached, which make up about 8 % of the molecular mass, so that there is a complex branched polymer, but which appears essentially as an unbranched ( figures refer on glucomannan konjac ). If the " side chain" mostly from individual galactose residues, one speaks of galactoglucomannan.
The molecular mass of Glucomannan from Konjac is given as 200 to 2000 kDa.
Occurrence
In the cell walls of softwood glucomannan is next to cellulose as firming matrix substance ( note here is that cellulose consists only of β -glycosidically linked glucose residues without side branches ).
The dry rhizome of devil's tongue contains about 40 % glucomannan and is the most important Glucomannanquelle for human consumption.
Galactoglucomannan is in softwood (eg spruce ) quantitatively the second most abundant polysaccharide after cellulose.
Properties and Uses
The ground rhizome of devil's tongue gives the konjac flour. It is approved as a food additive in Europe under E 425, but only under certain quantitative restrictions. Especially glass noodles ( Shirataki noodles ) can and may contain higher Glucomannananteile. In the food konjak is used as a thickening agent to gel, and as a filler. In Asian cuisine konjac has been used for about 1500 years.
Glucomannan is considered as a valuable dietary fiber and positive for intestinal health. However, its consumption lead to bloating, as it comes with incomplete digestion to metabolism by the intestinal flora, where carbon dioxide is released.
Konjac swells in water slowly sometimes very firm gels that have a high tear strength and printability. In the form of a solid gel, it is also referred to as konjak gum.
Konjac has the highest known water binding capacity of all natural products, it can bind to 50 times the amount of water of its own weight. Therefore, it is increasingly being used also to saturation in dietary products. Due to its strong hygroscopic properties without enough water intake can lead to obstruction of the esophagus.
The European Authority for Food Safety Authority (EFSA ) assessed on 9 December 2010 in the implementation of the Health Claims Regulation, the following health claim as scientifically justified: "Reduction of body weight when at least 3 g daily in 3 doses of at least 1 g each 1-2 glasses of water is taken before each meal by an overweight person. "
The following health claims were not recognized due to insufficient data by EFSA:
- Reducing the glycemic load after food intake ( "post- prandial glycemic response " )
- Maintaining normal blood sugar levels
- Maintaining normal blood triglyceride levels
- Maintenance of normal blood cholesterol levels
- Maintaining normal bowel movement
- Reduction possibly pathogenic microorganisms in the digestive tract