Konjac, also called konnyaku, is a kind of herbaceous perennial rhizomatous herb and is native to Eastern India and Sri Lanka. Konjac with about 130 species in the world is widely cultivated in tropical and subtropical Asian countries. Konjac is probably strange to many people, but it contains a lot of manna, vitamins, plant fibers, and a certain amount of mucin, which display peculiar health effects and medical potencies. The main ingredient of konjac is glucomannan and meanwhile it contains more than 10 kinds of amino acids and trace elements. Up to now, konjac is the only uncovered economic crop to provide large amount of glucomannan, and the application value of konjac in food and medicine has been continuously developed. Konjac has the characteristics of low protein, low fat, high fiber, strong water absorption and high expansion rate and is not easy to be digested and absorbed after ingestion. Konjac food has been identified as “valuable natural health food” by the Food and Health Organization of the United Nations.
Accompanied with nearly more than 10 years of research, konjac tuber has been processed into konjac powder for consumption, which is not only tasty and pleasant, but also has been proved with various medicinal effects, such as reducing weight, treating disease and resisting cancer. Therefore, it has been popular all over the world in recent years with great reputation of “magic food”, “healthy food” and so on.
The absorption of fat, cholesterol and bile juice acid in cardiovascular system can be retarded or suppressed by the medicinal component of konjac powder, thus reducing blood pressure and lowering the risk of cardiovascular diseases. Dietary fiber of konjac powder can enhance intestinal peristalsis, promote defecation and shorten the residence time of food in the intestine, which consequently reduces the harm of detrimental substances in the stool to the body. The volume expansion coefficient of konjac powder is very large, and could lead to a maximum volume being 100 times larger than its own volume after water absorption. Once swollen in the stomach, konjac powder will make people feel full, thus enabling people have no appetite for more other foods. It is exactly the reason that konjac powder can be used as a raw material for slimming food. Since the monosaccharide of glucomannan in konjac powder has a similar bonding way to cellulose, it cannot be degraded into monosaccharide to be absorbed in the small intestine. Hence, it is suitable for people who can’t intake too many carbohydrates. The soluble dietary fiber in konjac powder is also effective in suppressing postprandial blood glucose and thus eases pancreatic burden. Consequently, konjac flour and its products are ideal hypoglycemic foods for diabetics. It is particularly conspicuous that the contained gel can form various semi permeable membranes with different pore size in the intestine to form a defense barrier on the intestinal mucosa, which further blocks the invasion of carcinogens and play a role in cancer prevention. In addition, konjac powder also has the functions of calcium supplementation, salt balance, stomach cleaning, and detoxification. Long term consumption of konjac flour products is not only conducive to obesity, but also good for constipation, hyperlipidemia and the prevention of gastric carcinoma and intestinal cancer. Therefore, konjac powder plays a significant role in disease prevention and health care, and regular consumption of konjac food is of great benefit to the body. It is noteworthy that raw konjac has been proved to be poisonous and must be boiled for 3 hours or more before eating or brewing. Konjac powder also exhibits great potentiality in industry and agriculture fields by fabricating it into adhesive additives, colloid, cotton and so on.
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