Isomaltooligosaccharide, more commonly known as isomalto-oligosaccharide, is a mixture of short-chain carbohydrates which may have a digestion-resistant property. IMO is found naturally in some foods, as well as being manufactured commercially. Although isomaltose is found in some foods, such as honey, as a disaccharide, it behaves like all other disaccharides and is easily digested. Because of a confusion over nomenclature, such disaccharides have frequently been described as IMO, however to truly be called an "oligosaccharide" the molecules must have a degree of polymerization of three or more. Historically, the best documented source of IMO was found in sourdough breads wherein proper oligosaccharides are produced. IMO is currently produced by two distinctly different methods. One is based on a conversion of starch using enzymes. The raw material used for manufacturing IMO is starch, which is enzymatically converted into a mixture of isomaltooligosaccharides. However, IMOs produced via this method result in a very high proportion of isomaltose disaccharides and a majority of panose as the end product. These IMO preparations have been shown to be highly digestible and generally do not exhibit much if any, digestion resistance. The second method uses bacterial fermentation and bio-conversion of sugar and starch to create an IMO variant maltosyl-isomaltooligosaccharide. Typically the end product ranges in molecular complexity from DP3 to DP9 with an average molecular weight near DP5. MIMO preparations exhibit very good digestion resistance and also intestinal microbiota selectivity.
Chemistry
The term "oligosaccharide" encompasses carbohydrates that are larger than simple di- or tri-saccharides, but smaller than polysaccharides. Isomalto-oligosaccharides are glucose oligomers with α-D--linkages, including isomaltose, panose, isomaltotriose, isomaltotetraose, isomaltopentaose, nigerose, kojibiose, and higher branched oligosaccharides. Depending on production method, the structure of the IMO molecules can vary significantly. While human intestinal enzymes readily digest α-glycosidic bonds, longer change IMO with α-linkages are not easily hydrolyzed and exhibit a digestion-resistant property. Therefore, some IMO preparations are only partially digested in the upper gastrointestinal tract. Isomalto-oligosaccharides are a normal part of the human diet and occur naturally in fermented foods, such as fermented sourdough breads and kimchi. The disaccharide isomaltose is also present in rice miso, soy sauce, and sake. Isomaltose, one of the α-linked disaccharide components of IMO, has been identified as a natural constituent of honey and although chemically related, it is not and IMO. IMO is a sweet-tasting, high-density syrup which could be spray-dried into powder form.
Manufacturing
For manufacturing IMO on a commercial scale, food industries use starch processed from cereal crops like wheat, barley, pulses, oats, tapioca, rice, potato and others. This variety in sources could benefit consumers who have allergies or hypersensitivity to certain cereal crops. The manufacturing process controls the degree of polymerization and the α-linkages to ensure a consistent quality of IMO from different starch sources. The starch is first converted, by means of simple enzymatic hydrolysis, into high maltose syrup with di-, tri and oligosaccharides having α-glycosidic linkages which are readily digestible in the human intestine. These α-glycosidic linkages are further converted into digestion-resistant α-glycosidic linkages, creating "iso" linkages between glucose moieties and forming Isomalto-oligosaccharide.
The majority of oligosaccharides found in IMO consist of three to six monosaccharide units linked together. However, disaccharides, as well as longer polysaccharides, are also present. The disaccharide fraction of IMO consists mainly of α-linked isomaltose, while maltotriose, panose, and isomaltotriose make up the trisaccharide fraction. A mixture of isomaltotetraose, isomaltopentaose, maltohexaose, maltoheptaose, and small amounts of oligomers with 8 or more degrees of polymerization, comprise the remaining oligomers in IMO. Longer oligomers do not have 100% α-linkages; the ratio of α- to α-linkages is variable.
Health claims for oligosaccharides
Health claims for the various classes of oligosaccharides have been investigated by the European Food Safety Authority and found to be insufficiently substantiated. Therefore, health claims for oligosaccharides and prebiotics are prohibited in the European Union.
Health benefits
IMO is a multifunctional molecule which exerts positive effects on human digestive health; it acts as a prebiotic, decreases flatulence , has a low glycemic index , and prevents dental caries in animals. Prebiotics are defined as "non-digestible food ingredients that may beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon". Oligosaccharides that are not digested and absorbed in the small intestine, pass through to the colon where they are fermented by Bifidobacteria, thus enhancing the proliferation of the bacteria. In this respect, fermentable oligosaccharides may be considered prebiotics. The oligosaccharides in IMO mixtures are, at least partially, fermented by bacteria in the colon and may, therefore, stimulate the growth of bacterial subpopulations. Short chain oligosaccharides which confer prebiotic properties also produce short-chain fatty acids as end-products of fermentation. These molecules decrease the intra-luminal pH, directly inhibiting the growth and activity of harmful micro-organisms. This stimulates the growth of Bifidobacteria, which compete with the enteropathogens for nutrients and epithelial adhesion sites. The beneficial effects of IMO have been found in infants, children, and the elderly. Dental caries is caused by the formation of insoluble glucan on the surface of teeth, and the production of acids by bacteria in the plaque. These acids attack the hard tissues of the teeth. Studies with animal models showed that IMO, in place of sucrose, reduces the amount of plaque formed and also reduces the amount of enamel-attacking acids formed. Therefore, IMO acts as an anti-caries agent. The reported Glycemic Index for IMO is 34.66±7.65 which represents a low GI. Consumption of IMO effectively improved bowel movements, stool output and microbial fermentation in the colon without any adverse effects in elderly people. The American Association of Cereal Chemists defines soluble fiber as "the edible parts of plants or similar carbohydrates resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine". Dietary fiber consists of many plant components including oligosaccharides. For a dietary substrate to be classified as a fiber, it must be resistant to digestion and absorption in upper GI tract, and cause a bulking effect in defecation. IMO is considered a dietary fiber for the following reasons: it consists of glucose units linked together by digestion-resistant linkages; it has a prebiotic effect; it retains moisture, producing a bulking effect and helping to move the stool forward.
Usage
IMO is finding global acceptance by food manufacturers for use in a wide range of food products, especially beverages and snack/nutrition bars. In the United States, IMO is used mostly as a source of dietary fiber. However, IMO is also used as a low calorie sweetener in a variety of foods like bakery and cereal products. Since IMO is about 50% as sweet as sucrose, it cannot replace sugar in a one-to-one ratio. However, IMO has few side effects compared to other oligosaccharides of the same class. Therefore this carbohydrate molecule is receiving growing attention by food manufacturers across North America, as well as in Europe.
Side-effects
Generally, all digestion-resistant oligosaccharides, including IMO, have adverse side effects when consumed in amounts greater than permissible levels. The maximum permissible dose of IMO is 1.5 g/kg body weight, which is higher than for any other sugar substitute. However, the U.S. Food and Drug Administration has recommended a maximum consumption of 30 g/day for IMO. Higher dosages, can cause gastrointestinal symptoms like flatulence, bloating, soft stool or diarrhea.
Regulatory information
IMO and other oligosaccharides have long been approved in China and Japan. In Japan, IMO is on the list of Foods for Specified Health Use for more than 10 years. In 2002, over 50% of the FOSHU foods in Japan incorporated oligosaccharides as the functional component. The list includes many types of foods: soft drinks and other beverages, frozen yogurt, confectionery products, sweeteners, cookies, coffee drink mixes, bread, tofu, chocolate, and soup mixes. IMO has been imported into the United States for the last few years but has never been manufactured there or formally approved by the FDA. In 2009, a Canadian-based company, BioNeutra, received FDA-GRAS and Health Canada approval for IMO. The European Food Safety Agency recently authorized xylo‐oligosaccharides as a novel food pursuant to Regulation 2015/2283.
Commercial availability
IMO is commercially manufactured mostly in China and Japan. However, most of this product is consumed locally or exported to neighboring Asian countries. In Japan, Meiji Dairies is one of the biggest IMO producers. IMO is marketed under several trade names like IMO-900 and IMO-800. Being a novel food ingredient, there wasn't a producer of IMO in North America and Europe until recently when BioNeutra North America, Inc. began to manufacture this product with the VitaFiber IMO trademark. US-based companies have been in producing other kinds of oligosaccharides, like GOS, FOS, and XOS.
