Inulin

^{[MNP Dewick]}

"Inulins are a group of naturally occurring polysaccharides produced by many types of plants,[1] industrially most often extracted from chicory.[2] 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."^[Wiki] "Inulin is a natural storage polymer found widely in plants such as chicory, artichoke, and banana. Inulin is a polydisperse fructan that ranges in its degree of polymerization (DP) from 2 to 60, or higher." ^{[Sirisansaneeyakul et al.,2007]}

"...it is well established that probiotic usage should be complemented by the ingestion of prebiotics, which are mainly oligosaccharides (as oligofructose) that improve probiotic viability, both in the dairy product (to which these compounds are most often added) and in the gut. Inulin is a term applied to a heterogeneous blend of fructose-based polymers widely distributed in nature as plant storage carbohydrates. Oligofructose is an anologue of inulin, with a polymerisation degree >10. The criteria used for classifying a food component as a prebiotic are its resistance to digestion, hydrolysis, the ability to be fermented by colonic microbiota and, most importantly, selective growth stimulation of one or a limited number of bacteria in the human colon. This last criterion makes the distinction between a prebiotic and a normal dietary fibre (Ziesenitz et al. 2012)."^{[Delgado CMD]}

"Temperate, cold tolerant grasses like oats, barley, wheat, and rye typically contain fructans and sucrose as the primary carbohydrate reserves. Tropical, warm-loving, and cold-intolerant grasses, such as maize, contain starch and sucrose as the primary reserve carbohydrates."^{[T&F NPP]}

Origin and History

"Inulin is a natural storage carbohydrate present in more than 36,000 species of plants, including wheat, onion, bananas, garlic, asparagus, sunchoke and chicory. For these plants, inulin is used as an energy reserve and for regulating cold resistance.[4][5] Because it is soluble in water, it is osmotically active. The plants can change the osmotic potential of cells by changing the degree of polymerization of inulin molecules with hydrolysis. By changing osmotic potential without changing the total amount of carbohydrate, plants can withstand cold and drought during winter periods.[6] " ^[Wiki]

Chemical Structure & Properties

"Because of the B(2,1) linkages, inulin is not digested by enzymes in the human alimentary system, contributing to its functional properties: reduced calorie value, dietary fiber and prebiotic effects. Without color and odor, Inulin has little impact on sensory characteristics of food products. Oligofructose has 35% of the sweetness of sucrose, and its sweetening profile is similar to sugar. Standard inulin is slightly sweet, while high performance inulin is not. Its solubility is higher than the classical fibers. When thoroughly mixed with liquid, inulin forms a gel and a white creamy structure, which is similar to fat." ^[Wiki] "It is only slightly soluble in cold water, but dissolves readily in hot water." ^{[Jacques AT]} "Inulin contains 35 fructose residues with the possible addition of a terminal glucose." ^{[Pengelly TCMP]}

"It is found to bear a close resemblance to starch except that it is a levulan rather than a dextran. The following characteristic features make it altogether different from starch, namely: Gives yellow colouration by iodine; Does not gelatinize with water." ^[PCPB]

Inulin "... does not undergo hydrolysis by the amylases." ^[PCPB]

Hazards

• "Inulin fermentation increases gas production and thereby provokes intestinal discomfort in some people." ^[EMNMPV.7]
• "A series of clinical studies had been reported showing that up to 20 g/day of inulin and/or oligofructose to be well tolerated." ^[EMNMPV.9]

Uses

Processed Foods

"Inulin is increasingly used in processed foods because it has unusually adaptable characteristics. Its flavour ranges from bland to subtly sweet (approx. 10% sweetness of sugar/sucrose). It can be used to replace sugar, fat, and flour. This is advantageous because inulin contains 25-35% of the food energy of carbohydrates (starch, sugar).[12] In addition to being a versatile ingredient, inulin has many health benefits. Inulin increases calcium absorption[13] and possibly magnesium absorption,[14] while promoting the growth of beneficial intestinal bacteria. Chicory inulin is reported to increase absorption of calcium in girls with lower calcium absorption[15] and in young men.[16] In terms of nutrition, it is considered a form of soluble fiber and is sometimes categorized as a prebiotic. Conversely, it is also considered a FODMAP, a class of carbohydrates which are problematic for some individuals through causing overgrowth of intestinal methanogenic bacteria. The consumption of large quantities (in particular, by sensitive or unaccustomed individuals) can lead to gas and bloating, and products that contain inulin will sometimes include a warning to add it gradually to one's diet." ^[Wiki]

"Chicory inulin has 10% of the sweetness of sugar and is used as a fat and sugar replacement, fiber, and prebiotic in dairy products, frozen desserts, fruit preparations, breads and baked goods, and dietetic products; also as a fat replacement in table spreads, salad dressings, meat products, and fillings; as a fiber and prebiotic in breakfast cereals; sugar replacement and fiber in chocolate; also used to provide form stability, moisture retention, texture improvement, texture, crispness, and mouthfeel in diverse foods.21" ^{[Lung ECNI]}

"Due to the body's limited ability to process fructans, inulin has minimal increasing impact on blood sugar. It is considered suitable for diabetics and potentially helpful in managing blood sugar-related illnesses.[citation needed]" ^[Wiki]

Examples

"Some traditional root vegetables, like camas bulbs (Camassia spp.) and onions (Allium spp.) in Liliaceae, and balsamroot (Balsamorhiza sagittata) and thistles (Cirsium spp.) in Asteraceae, contain large proportions of inulin, a complex carbohydrate that becomes sweet upon cooking due to a partial conversion to the sugar fructose. Some of these species are traditionally cooked in underground pits, or earth ovens, flavored with various types of plants that also apparently enhance their conversion to fructose and fructans (Peacock, 1998; Konlande and Robson, 1972)." ^[ETWP] "The bulbs almost always pit-cooked, usually for 24 hours or more. The Blackfoot left them in the pit with a fire burning overtop for up to 70 hours (Johnston, 1987). Because most of their carbohydrate is in the form of a long-chain sugar, inulin, which is not very digestible, nor very palatable, long term cooking was necessary to chemically break down the inulin into its component fructose molecules." ^{[Turner&Kuhnlein]}

"Higher amounts of inulin could be extracted from D. esculenta compared to other tubers (Harmayani et al. 2011). They demonstrated the production of inulin powder from D. esculenta by the foam mat drying method using maltodextrin and egg white as filler and foaming agent.... From start of storage till sprouting, the total increase of sucrose content was 33.75 %, the total increase of glucose content was 92.2 % and total increase of fructose content was 69.2 %." ^[EMNMPV.10]

"A classical character is for example the presence of polyfructane (inulin), a characteristic constituent of Compositae which completely replaces starch as areserve polysaccharide (see e. g. Percival, 1966). This substance is also distributed in some more or less related families (see Hegnauer, 1964), as for example in Campanulaceae, and it is of no further significance for the internal classification of Compositae" ^{[Wagner PP]}

Agave Sp.

• "When producing 100% agave tequila, the only source of carbohydrate is the inulin hydrolyzed from agave in the cooking step." ^{[Jacques AT]} "Tequila is produced by the distillation of fermented juice from the heads (i.e., leafless stem) of Agave tequilana A. Weber and up to 49% additional sugars (sugar cane, molasses, hydrolyzed maize syrup). Tequilas differ as a result of variation in the proportion of agave material (i.e., 51 - 100%), strain of fermenting bacteria, production processes, distillation equipment, aging times, and growing conditions. The ethanol content ranges from about 40% to 55%. The production process involves cooking to hydrolyze inulin to fructose in stone ovens or autoclaves, extraction of sugars from the cooked agave by milling, bacterial fermenting to convert the sugars to ethanol and organoleptic compounds, and a two - step distillation of the fermented wort using pot stills or rectification columns.2 The head of an 8 - to 9 - year - old Agave tequilana contains high concentrations of the linear fructose polymer, inulin, compared with other Agave species." ^{[Barceloux MTNS]}
• Tequila Making
  • The cooking step: hydrolysis of inulin;"In the pre-Hispanic era, agave was cooked in holes filled with stones heated using wood for fuel. The stones retained the heat for the time needed to cook the agave. Nowadays some distillers have replaced the heated stone holes with brick ovens and heating is accomplished by steam injection after the chopped raw agave has been introduced into the oven. Oven cooking is slow, and steam injection lasts around 36-48 hrs to obtain temperatures of 100^oC. After that period, the steam is shut off and the agave is left in the oven for a further two days to complete the cooking process. During this step, a sweet liquid called 'cooking honey' is collected and used later as a source of free sugars, mainly fructose. Also during this step some of the sugars are caramelized; and some of the compounds that contribute significantly to the aroma and flavor in wort formulation are due to its high content of fermentable sugars (>10% w/v). Finally, the oven door is opened to allow the cooked agave to cool. The agave is then ready for milling." ^{[Jacques AT]}
  • Extraction of agave juice: milling; " In ancient days cooked agave was crushed with wood or steel mallets to extract the juice. Later, a rudimentary mill consisting of a large circular stone 1.3 m in diameter and 50 cm thick was used. Driven by animals, the stone turned in a circular pit containing cooked agave and extracted the juice. The resulting juice was collected by hand in wooden basins and carried to fermentation tanks. By the 1950s modern systems were implemented in which cooked agave was passed through a cutter to be shredded (except in factories that did this operation before cooking); and with a combination of milling and water extraction, sugars were extracted." ^{[Jacques AT]}
    • "The milling step generates a by-product called bagasse, which represents about 40% of the total wet weight of the milled agave. Bagasse composition (dry weight basis) is 43% cellulose, 19% hemicellulose, 15% lignin, 3% total nitrogen, 1% pectin, 10% residual sugars and 9% other compounds. The bagasse, mixed with clay, is used to make bricks; but it is also the subject of research to find alternative uses. Examples are use of bagasse as an animal feed or as a substrate on which to grow edible fungi (Iñiguez et al., 1990; 2001)." [Jaques AT]
  • Fermentation; "To produce 100% agave tequila, only agave may be used and the initial sugar concentration ranges from 4 to 10% w/v, depending on the amount of water added in milling. When other sugars are employed, they are previously dissolved and mixed with agave juice to obtain an initial sugar concentration of 8-16%, depending on sugar tolerance of the yeast strain.... Some companies do not inoculate a specific strain of S. cerevisiae and instead allow natural fermentation to proceed. Others inoculate the wort with fresh packages of baker's yeast or a commercial dried yeast.... The dried yeasts were originally prepared for wine, beer, whisky or bread production; and sometimes the quality of the tequila obtained using these yeasts is not satisfactory.... Although inoculation with commercial yeast greatly improves yield and turnover time, some companies prefer a more complex (in terms of the microbial diversity) fermentation. While yields might be lower and turnover time higher, the range of microorganisms produces more compounds contributing to a more highly flavored tequila....If an inoculum is not added, the fermentation could last as long as seven days. With an inoculum the fermentation time ranges from 20 hrs in the faster process to three days in the slower one.... The alcohol content at the end of fermentation is between 4 and 9% v/v, depending on the initial sugar concentration. In order to increase the fermentation yield, in addition to selection of a good yeast strain, another option is the use of enzymes or enzyme complexes, to convert residual polymers from agave into fermentable sugars, which are converted mainly into alcohol improving the productivity of tequila production.... Alcohol losses may be significant because many fermentation tanks are open, allowing evaporation of alcohol with carbon dioxide. Some of the largest distilleries have a cooling system that keeps fermentation temperature within a tolerable range for yeast, but small producers do not have these systems. The fermentation temperature can exceed 40^oC, causing the fermentation to stop with an accompanying loss of ethanol and flavors that consequently decreases yields and affects the quality of the tequila. Fermentations carried out with pure agave juice tend to foam, sometimes requiring the addition of silica. In worts with added sugars, foaming is usually not a problem. Non-aseptic conditions are employed in fermentation, and in consequence bacterial activity may increase. The size of the bacterial flora depends on a number of factors including the extent to which bacteria grow during yeast propagation (if used), the abundance of bacteria on the raw materials and hygiene standards in the distillery.... Occasionally, the size of the bacterial population in fermenting wort may become too large..., in which case the bacteria use the sugars, decreasing ethanol yields and sometimes excreting undesirable compounds. The same compounds used in the propagation step may be used here to decrease common bacterial contaminants found in tequila worts. Lactobacillus, Streptococcus, Leuconostoc, and Pediococcus are the most common contaminants, but Acetobacter may be found in fermented worts that are left inactive for a long time prior to distillation.... It is also recognized that when non-100% agave tequila is made, a poorer bouquet is obtained because a more defined medium yields a more defined product.... It is of great importance to have a good yeast strain and nutritionally balanced wort for tequila production, as losses can be as high as 35% of the total production if inefficient yeast is used or nutrients are not present in the right proportions." ^{[Jacques AT]}
  • Distillation: "First the fermented wort is distilled to increase the alcohol concentration to 20-30% by volume, separating out the first fraction called 'heads', and the last fraction, called 'tails'. Composition of these fractions varies depending on many factors including the yeast strain employed, wort nutrient composition, fermentation time and distillation technique; but in general, heads are rich in low boiling point compounds such as acetaldehyde, ethyl acetate, methanol, 1- propanol, 2-propanol, 1-butanol, and 2-methyl propanol, which give a very pleasant flavor and taste to tequila. Heads are normally mixed with the wort being distilled. The tails contain high boiling point components such as isoamyl alcohol, amyl alcohol, 2-furaldehyde, acetic acid and ethylactate, giving a strong taste and flavor to the tequila; and when the concentration is above 0.5 mg/ml, the final product becomes unpleasant. This fraction is not used. In the second step, the liquid obtained from the first stage is re-distilled in a similar pot still in order to obtain a final product that is 110^o proof if it is sold in bulk (reducing transport costs) or 80^o proof if it is to be bottled. Some companies obtain high proof tequila and dilute it with demineralized water or water purified by reverse osmosis." ^{[Jacques AT]}
  • Maturation: "At the end of the distillation process white tequila is obtained. Maturation, the last stage, in white oak barrels is required for rested or aged tequila. The minimum maturation times are 2 and 12 months, respectively, for rested and aged tequila as required by government regulations." ^{[Jacques AT]}
• "Pulque is a viscous fermentation product of several Agave species (A. atrovirens Karw. ex Salm - Dyck, A. salmiana Salm - Dyck) that results from the actions of a complex series of yeasts and bacteria. Because the product is not distilled or pasteurized, pulque deteriorates relatively quickly. The ethanol content of this fermentation product ranges from approximately 4 - 6%.3" ^{[Barceloux MTNS]}
  • "The carbohydrate structure of agave plants and aguamiel is rather complex, combining the fructose polymer structure found in inulins and levans as described a few years ago by Mancilla-Margalli and Lopez (2006). Actually, the term agavins has been proposed by these authors due to the clear structural differences with inulin found in agave fructans. Most distilled agave fermented beverages rely on the total hydrolysis of sugars, while pulque fermentation properties are based in the amount of sucrose and monosaccharides found in aguamiel." ^{[Hui HPBFFBT]}
  • "Surprisingly, Ortiz-Basurto et al. (2008) detected only minor differences in aguamiel composition among samples collected at different time intervals during the 3-6 months aguamiel harvest period of an A. mapisaga plant. Actually, the analyzed aguamiel contained 11.5 wt% of dry matter, which was composed mainly of sugars (75 wt%). Among these, 10 wt% were fructo-oligosaccharides."^{[Hui HPBFFBT]}

Cynara cardunculus - Globe Artichoke

• Inulin Content: "At harvest the total biomass and root production, averaged for all Cynara cardunculus genotypes, were 20.4 and 9.8 t DM/ha; they were influenced by genotype (Raccuia and Melilli 2004). On average for all of the genotypes, the roots showed a total sugar content of 367 g DM/kg, with a cv. of 17.1 %; the main compound was inulin (85.0 % of total sugars). The wild cardoon 'SR1' showed the highest total sugar content (470 g/kg DM). On average for all of the genotypes, the total sugar and inulin yields were 3.6 and 3.0 t/ha, respectively. Studies showed that globe artichoke (Cynara cardunculus subsp. scolymus) crop for heads utilization, at the end of their harvest, gave a remaining above-ground biomass production, on average of all genotypes, of 10.3 t/ha DM with a range of 5.7 to 15.7 t/ha of DM, partitioned between leaves (53.4 %) and stalks (47.6 %) ( Raccuia et al. 2004b). The root yield resulted on average of all genotypes 5.7 t/ha of DM. The total extracted sugars from roots resulted on average of all genotypes, 249 g/kg of DM, where inulin accounted for 89.4 % of total sugars. Root total sugars yield resulted on average of all genotypes 1.41 t/ha" ^[EMNMPV.7]
• Similarity to Chichory: "The main constituent monosaccharide in artichoke inulin was fructose, and its degradation by inulinase indicated that it contained the expected beta-2,1-fructan bonds. Its FT-IR spectrum was identical to that of chicory inulin." ^[EMNMPV.7]
• Prebiotic/Probiotic: "The health-promoting prebiotic effects of artichoke inulin were demonstrated in an extensive microbiological study showing a long-lasting bifidogenic effect on Bifi dobacterium bifi dum cultures and also in mixed cultures of colonic bacteria (Lopez-Molina et al. 2005). Valerio et al. (2006) found that probiotic strains of Lactobacillus plantarum and Lactobacillus paracasei were able to survive on artichokes for at least 90 days in simulated gastrointestinal digestion. Further, when L. paracasei ... was used in an artichoke human feeding study involving four volunteers, the organism could be recovered from stools." ^[EMNMPV.7]
• Breakdown of Inulin Over Time: "The scientists found that eating stored artichoke led to consumption of an inulin quantity that did not provoke unwanted symptoms related to gas production but sufficient to have a prebiotic effect. Storage time caused a decrease in inulin content and an average degree of polymerization, accompanied by an increase of free fructose and sucrose due to depolymerization of inulin." ^[EMNMPV.7]

Helianthus tuberosus - Jerusalem artichoke

• "It is interesting that in the shoots of temperate-zone grasses and in the tubers of Jerusalem artichoke (Helianthus tuberosus), fructan synthesis accelerates under the low-temperature conditions of autumn. Then, the stored fructans become hydrolyzed through the action of fructan hydrolase in the spring, when temperatures warm and shoot and root growth begins. This appears to provide the plant with a source of energy for a head start on growth in the early spring." ^{[T&F NPP]}
• "Jerusalem artichoke tubers are frequently eaten by humans as a potato substitute (but not starch substitute). Humans cannot digest the inulin fructan present in these tubers because of the absence of the gene that makes the fructan-specific hydrolase in humans. Furthermore, the ubiquitous intestinal colon bacterium, Escherichia coli, cannot hydrolyze fructan. This would make one think that these tubers would be perfect food for dieters. However, there is recent evidence from Japanese studies that Bifidobacteria, found in intestinal microflora, can digest fructan; in fact, when fructans are eaten, populations of this microbe in the large intestine increase significantly. This being the case, enrichment of the human diet with fructans from plants such as rye (Secale cereale), onions (Allium cepa), Jerusalem artichoke tubers, and garlic (Allium sativum) may be beneficial, not because they are hydrolyzed in the small intestine, but because they are hydrolyzed in the large intestine. There is also evidence that fructans from plant sources may be beneficial in the diets of swine and poultry (see “Fructans in Human and Animal Diets” by Farnworth in Suzuki and Chatterton, 1993)."^{[T&F NPP]}

Murnong (Microseris lanceolata)

• "Murnong root is of dietary interest as it is a carbohydrate-rich resource that contains a large amount of inulin, a polysaccharide that is utilised by the plant as a food reserve. "^{[Cheryll_Williams]}

Industrial/Commercial Utilization

"Nonhydrolyzed inulin can also be directly converted to ethanol in a simultaneous saccharification and fermentation process, which may have great potential for converting crops high in inulin into ethanol for fuel.[19]" ^[Wiki] " France may really be considered as its secondary gene centre. There 150,000 ha are planted with different clones, between Poitiers, Limoges and the Atlantic coast; mostly as forage for cattle, but also for alcohol production in the cognac industry (Delhay 1979)." ^{[Brucher UPNO]}

"Inulin is commercially recovered from chicory roots and Jerusalem artichoke tubers (Hoebregs 1997 ; Frank and Leenheer 2002 ; Rhee et al. 2002 ; Stolzenburg 2005 ). It is used as a mostly indigestible soluble dietary fibre and thickener in foods." ^{[Sirisansaneeyakul et al.,2007]}

"A high-quality fructose syrup can be produced from Jerusalem artichoke tubers (Fleming and GrootWassink 1979). They reported that Jerusalem artichoke had the potential to produce more sugar per acre than corn or sugar beets." ^[EMNMPV.9] Jerusalem artichoke; "Tubers can be processed to fructose syrup, also to alcohol." ^{[Brucher UPNO]} "The tuber can be used to produce a highfructose syrup (70-80% fructose, 20-30% glucose)" ^{[Cheryll_Williams]}

Harvesting and extraction of inulin

"Chicory root, grown as a root crop in Holland, Belgium and France, is the main source of extraction for commercially produced inulin. The extraction process involves soaking the fresh or dried root in a solvent, the inulin is then mechanically isolated, purified and spray dried.[citation needed]" ^[Wiki]

Inulinases

"Inulinase from various yeasts has the capability to produce fructose in high concentration from inulin in Jerusalem artichokes and chikory." ^{[Zhiqiang HIM]}

"Inulin is hydrolysed by enzymes known as inulinases. Inulinases are classified into endo- and exo- inulinases, depending on their mode of action.... Inulinases are encountered in plants and many microorganisms. Among fungi, some well-known sources of these enzymes include A. niger , Aspergillus ficuum , Chrysosporium pannorum and Penicillium purpurogenum . Among yeasts, the best-known producers are Kluyveromyces marxianus , Candida kefyr , De- baryomyces cantarellii and Pichia polymorpha .These yeasts appear to produce only exo-inulinases whereas most inulin-hydrolysing molds produce both endo- and exo-inulinases (Guiraud and Galzy 1990 ; Frank and Leenheer 2002 ; Barta 1993 ; Hensing et al. 1993 ).... the 5:1 mixture of enzymes was distinctly better than the yeast enzymes alone, in terms of the fructose concen- tration obtained, the proportion of the initial inulin hydrolysed, the yield of fructose on inulin and the productivity of fructose. The 5:1 enzyme mixture was measurably better than the mold enzymes alone, but the difference was not very large. A 1:1 mixture was distinctly poorer than the mold enzymes alone, but still outperformed the yeast enzymes used alone." ^{[Sirisansaneeyakul et al.,2007]}

• Kluyveromyces marxianus (Syn: K. fragilis and asexual state Candida kefyr) ^{[Jacques AT]}
  • "K. marxianus is often associated with spoilage of commercial yogurt and has been commonly isolated from other dairy products such as milk and cheese, pressed commercial yeast, effluent of sugar refineries, bread doughs, beer, fermenting figs, sewage, infected humans and infected milk cows, where it causes bovine mastitis. In spite of the association of K. marxianus with infected humans and dairy cows, it is considered GRAS and frequently referred to as the 'dairy yeast'."^{[Jacques AT]}
  • "Interesting characteristics of this yeast include the production of killer factors and growth and production of ethanol from cheese whey and inulin at 45^oC to a final concentration of 7.0% (w/v) (Balletsteros et al., 1993; Singh et al., 1998; Banat et al., 1995)." ^{[Jacques AT]}
• Ectomycorrhizal Fungi
  • "The ectomycorrhizal fungi can be isolated from short roots, spores and sporophores. Ectomycorrhizal fungi grow well in modified Melin-Norkran's medium and potato dextrose agar (PDA) medium (Bakshi, 1966). They are highly specialised in their nutritional requirements. They require soluble carbohydrates, vitamins and amino acids which they derive most, if not all, from the symbiotic niche in the primary tissues of roots. The majority of mycorrhiza form estimated by Melin (1925) required sugars such as glucose as a source of carbon and some made fair growth on maltose, xylose and mannitol. They grew strongly on starch and inulin and no growth occured on cellulose." ^{[Rai PM]}

Resorcinol Test for Ketones (Selivanoff's Test)

"A crystal of resorcinol is added to the solution and warmed on a water bath with an equal volume of concentrated hydrochloric acid. A rose colour is produced if a ketone is present (e.g. fructose, honey or hydrolysed inulin)." ^{[Shah TPP]}