Isomaltooligosaccharide (IMO) is a mixture of short-chain carbohydrates which has a digestion-resistant property. IMO is found naturally in some foods, as well as being manufactured commercially. The raw material used for manufacturing IMO is starch, which is enzymatically converted into a mixture of isomaltooligosaccharides.
The term "oligosaccharide" encompasses carbohydrates that are larger than simple di- or tri-saccharides, but smaller than polysaccharides (greater than 10 units). Isomalto-oligosaccharides (IMO) are glucose oligomers with α-D-(1,6)-linkages, including isomaltose, panose, isomaltotriose, isomaltotetraose, isomaltopentaose, nigerose, kojibiose, and higher branched oligosaccharides. [1] Depending on production method, the structure of the IMO molecules can vary significantly. While human intestinal enzymes readily digest α(1,4)-glycosidic bonds, longer change IMO (e.g. >= DP4) with α(1,6)-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. [2] [3] [4] Isomaltose, one of the α(1,6)-linked disaccharide components of IMO, has been identified as a natural constituent of honey and although chemically related, it is not an IMO . [5] IMO is a sweet-tasting, high-density syrup which could be spray-dried into powder form.
For manufacturing IMO on a commercial scale, food industries use starch processed from cereal crops like wheat, barley, pulses (peas, beans, lentils), 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 (dp) and the α(1,6)-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 (2, 3 or more glucose units) having α(1,4)-glycosidic linkages which are readily digestible in the human intestine. These α(1,4)-glycosidic linkages are further converted into digestion-resistant α(1,6)-glycosidic linkages, creating "iso" linkages between glucose moieties and forming Isomalto-oligosaccharide (IMO).
The majority of oligosaccharides found in IMO consist of three to six monosaccharide (glucose) units linked together. However, disaccharides, as well as longer polysaccharides (up to nine glucose units), are also present. The disaccharide fraction of IMO consists mainly of α(1,6)-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(1,6)-linkages; the ratio of α(1,4)- to α(1,6)-linkages is variable.
Animal studies describe IMO as a multifunctional molecule which exerts positive effects on digestive health; it acts as a prebiotic, decreases flatulence, has a low glycemic index, and prevents dental caries in animals. [6] [7] [8] [9] [10]
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". [11] 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. [12] [13] [14] [15] [16]
Dental caries is caused by the formation of insoluble glucan (plaque) 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. [17]
The reported Glycemic Index (GI) for IMO is 34.66±7.65 (on a scale of 1–100) which represents a low GI. [18] Consumption of IMO effectively improved bowel movements, stool output and microbial fermentation in the colon without any adverse effects in elderly people. [19]
Health claims for the various classes of oligosaccharides have been investigated by the European Food Safety Authority (EFSA) and found to be insufficiently substantiated. Therefore, health claims for oligosaccharides and prebiotics are prohibited in the European Union. [20]
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 (sugar), it cannot replace sugar in a one-to-one ratio. However, IMO has few side effects compared to other oligosaccharides of the same class. [21] Therefore this carbohydrate molecule is receiving growing attention by food manufacturers across North America, as well as in Europe.
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. [21] However, the U.S. Food and Drug Administration (FDA) has recommended a maximum consumption of 30 g/day for IMO. [22] Higher dosages (greater than 40 g/day), can cause gastrointestinal symptoms like flatulence, bloating, soft stool or diarrhea.
IMO and other oligosaccharides have long been approved in China and Japan. In Japan, IMO has been on the list of Foods for Specified Health Use (FOSHU) for more than 10 years. In 2002, over 50% of the FOSHU foods in Japan incorporated oligosaccharides as the functional component. [23] [24] 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. [25] The European Food Safety Agency (EFSA) recently authorized xylo‐oligosaccharides (XOS) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. [26]
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 (Meiji Food Company) 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 BioNeutra North America, Inc. began to manufacture this product with the VitaFiber IMO trademark, [27] which was approved for use in Canada by Health Canada in 2012. [28] US-based companies have also been producing other kinds of oligosaccharides, like GOS, FOS, and XOS.
In organic chemistry, a carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 and thus with the empirical formula Cm(H2O)n. However, not all carbohydrates conform to this precise stoichiometric definition, nor are all chemicals that do conform to this definition automatically classified as carbohydrates.
A disaccharide is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lactose, and maltose.
Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin.
Fructose, or fruit sugar, is a ketonic simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed by the gut directly into the blood of the portal vein during digestion. The liver then converts both fructose and galactose into glucose, so that dissolved glucose, known as blood sugar, is the only monosaccharide present in circulating blood.
Maltose, also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two-unit member of the amylose homologous series, the key structural motif of starch. When alpha-amylase breaks down starch, it removes two glucose units at a time, producing maltose. An example of this reaction is found in germinating seeds, which is why it was named after malt. Unlike sucrose, it is a reducing sugar.
Maltase is one type of alpha-glucosidase enzymes located in the brush border of the small intestine. This enzyme catalyzes the hydrolysis of disaccharide maltose into two simple sugars of glucose. Maltase is found in plants, bacteria, yeast, humans, and other vertebrates. It is thought to be synthesized by cells of the mucous membrane lining the intestinal wall.
Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants that synthesize and store inulin do not store other forms of carbohydrate such as starch. In the United States in 2018, the Food and Drug Administration approved inulin as a dietary fiber ingredient used to improve the nutritional value of manufactured food products. Using inulin to measure kidney function is the "gold standard" for comparison with other means of estimating glomerular filtration rate.
A reducing sugar is any sugar that is capable of acting as a reducing agent. In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a reaction, the sugar becomes a carboxylic acid.
Fructooligosaccharides (FOS) also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially prepared syrups. It occurs naturally, and its commercial use emerged in the 1980s in response to consumer demand for healthier and calorie-reduced foods.
Prebiotics are compounds in food that induce the growth or activity of beneficial microorganisms such as bacteria and fungi. The most common example is in the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome.
Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. It is a hemicellulose component in the cell walls of some plant species. Glucomannan is a food additive used as an emulsifier and thickener. It is a major source of mannan oligosaccharide (MOS) found in nature, the other being galactomannan, which is insoluble.
Polydextrose is a synthetic polymer of glucose. It is a food ingredient classified as soluble fiber by the US FDA as well as Health Canada, as of April 2013. It is frequently used to increase the dietary fiber content of food, to replace sugar, and to reduce calories and fat content. It is a multi-purpose food ingredient synthesized from dextrose (glucose), plus about 10 percent sorbitol and 1 percent citric acid. Its E number is E1200. The FDA approved it in 1981.
A fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides. Fructans can be found in over 12% of the angiosperms including both monocots and dicots such as agave, artichokes, asparagus, leeks, garlic, onions, yacón, jícama, barley and wheat.
Isomaltulose is a disaccharide carbohydrate composed of glucose and fructose. The glucose and fructose are linked by an alpha-1,6-glycosidic bond. Isomaltulose is present in honey and sugarcane extracts. It tastes similar to sucrose with half the sweetness. Isomaltulose, also known by the trade name Palatinose, is manufactured by enzymatic rearrangement (isomerization) of sucrose from beet sugar. The enzyme and its source were discovered in Germany in 1950, and since then its physiological role and physical properties have been studied extensively. Isomaltulose has been used as an alternative to sugar in foods in Japan since 1985, in the EU since 2005, in the US since 2006, and in Australia and New Zealand since 2007, besides other countries worldwide. Analytical methods for characterization and assay of commercial isomaltulose are laid down, for example, in the Food Chemicals Codex. Its physical properties closely resemble those of sucrose, making it easy to use in existing recipes and processes.
Isomaltose is a disaccharide similar to maltose, but with a α-(1-6)-linkage instead of the α-(1-4)-linkage. Both of the sugars are dimers of glucose, which is a pyranose sugar. Isomaltose is a reducing sugar. Isomaltose is produced when high maltose syrup is treated with the enzyme transglucosidase (TG) and is one of the major components in the mixture isomaltooligosaccharide.
Galactooligosaccharides (GOS), also known as oligogalactosyllactose, oligogalactose, oligolactose or transgalactooligosaccharides (TOS), belong to the group of prebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of beneficial bacteria in the colon. GOS occurs in commercially available products such as food for both infants and adults.
Xylooligosaccharides (XOS) are polymers of the sugar xylose. They are produced from the xylan fraction in plant fiber. Their C5 structure is fundamentally different from other prebiotics, which are based upon C6 sugars. Xylooligosaccharides have been commercially available since the 1980s, originally produced by Suntory in Japan. They have more recently become more widely available commercially, as technologies have advanced and production costs have fallen. Some enzymes from yeast can exclusively convert xylan into only xylooligosaccharides-DP-3 to 7.
Neopullulanase is an enzyme of the alpha-amylase family with systematic name pullulan 4-D-glucanohydrolase (panose-forming). This enzyme principally catalyses the following chemical reaction by cleaving pullulan's alpha-1,4-glucosidic bonds:
Lacto-N-tetraose is a complex sugar found in human milk. It is one of the few characterized human milk oligosaccharides (HMOs) and is enzymatically synthesized from the substrate lactose. It is biologically relevant in the early development of the infant gut flora.
Kestose is a class of sugars that belongs to a group of fructooligosaccharides.
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