Konjac flour is obtained from the tubers of various species of Amorphophallus.It is a soluble dietary fiber that is similar to pectin in structure and function.
konjac flour consists mainly of a hydrocolloidal polysaccharide, glucomannan. Glucomannan is composed of glucose and mannose subunits :inked with B-1 ,4 linkage at a molar ratio of i .O:1 .6. It is a slightly branched polysaccharide having a molecular weight of 200,000 to 2,000,000 daltons. Acetyl groups along the glucomannan backbone contribute to solubility properties and are located, on average. every 9 to 19 sugar units. In general, the konjac tuber is ground and milled, and its impurities are separated by either mechanical separation, water Wash, or aqueous ethanol wash to produce konjac flour. All processes are similar and result in a flour that is enriched in glucomannan and meets the specification listed in the Food Chemicals Codex.
konjac flour has a long history of safe use. The first documented use of konjac tuber as a source of food In China and Japan was In the ancient Japanese written work entitled, "Man-you-shuu." which was edited In the sixth century AD. A comprehensive collection of historical materials, which reference konjac in novels, essays and poems, was published by the Japanese Konjac Society in April 1985. The collection of materials document that its use as food is deeply rooted in the lives and customs of the people in Japan and China for centuries, Historical[y, konnyaku, the alkalitreated konjac flour, was used to cleanse one's digestive tract of irritating and poisonous substances and keep one's internal organs clean. The konjac tuber was introduced into Hawaii in 1858 and konnyaku was commonly eaten as food once or twice a week by Japanese in Hawaii. Assuming a worse-case estimate of consumption for konnyaku once a week for eaters only, the estimated consumption of konnyaku as a food is 20 g/day.
The Food Chemicals Codex lists the current uses of konjac flour in the United States as a gelling agent, thickener, film former, emulsifier. and stabilizer. Assuming that konjac flour would replace all uses of pectin, modified pectin, and gelatin. a worse case estimate for konjac flour consumption as a food ingredient In finished foods would be I .2 g/person/day. However, because use of konjac flour is self limiting and would not substitute for all uses of pectin and gelatin,a more reasonable estimate would be that konjac flour would substitute for one third of the uses and, thus. would be consumed at a level of about 0.4 g/person/day.
The major component of konjac flour. Feeding studies with rats and dogs indicate that the no-observed effect level for glucomannan was 2.5%of the diet. There are several studies which deal with the effects of glucomannan on aspects of the biochemical dynamics of cholesterol, triglyceride, phospholipid, bile acid, glucose and insulin in the,e.experimental animals, While none of these studies can be called a safety study, they provide, some information on the safety of glucomannan in that they do not mention any adverse toxicological effects associated with the administration or glucomannan. These studies, in total, demonstrate that glucomannan has the ability to lower serum cholesterol levels and to delay glucose absorption.
Studies using glucomannan have been tested on humans, principally to study its influence on cholesterol and glucose absorption from the gastrointestinal tract. These studies indicate that glucomannan has the ability to lower serum cholesterol and may lower serum triglyceride and bile acid level as well. Glucomannan may also have an influence on glucose tolerance and glucose absorption. These findings have also been seen in the animal studies, mentioned above. While these studies cannot be deemed to be human safety studies they do indicate that no adverse toxicological effects were associated with the administration of glucomannan.
In addition, the results from several in vitro iron absorption studies demonstrate that glucomannan, the major component of konjac flour, does not bind iron.