SUGAR ALCOHOLS

A. Rapaille , ... Yard. Heume , in Encyclopedia of Food Sciences and Nutrition (2nd Edition), 2003

Sensory and Nutritional Properties

Compared to sucrose, sugar alcohols accept slightly reduced sweetness values, as shown in Tabular array 2. Carbohydrate alcohols produce a characteristic mouth-cooling effect which is directly related to their heats of solution and their solubility in water (Table 1). Sugar alcohols, also known as polyols, may give particular advantages with regard to diet control and dental health (Tabular array 3). The benefits that polyols tin can give in reducing caloric intake is due to their different metabolic behavior afterward oral ingestion compared to other carbohydrates. Considering polyols may have a mono-, di-, or oligosaccharide carbohydrate structure, small differences can occur with regard to their metabolic fate in the human body.

Table 2. Sugariness values of sugar alcohols

Compound Relative sweetness
Polyol a
  Xylitol 80–100
  Sorbitol fifty–lx
  Mannitol 50–60
  Maltitol fourscore–90
  Lactitol 30–40
  Isomalt 40–50
  Erythritol sixty–seventy
Sucrose a 100
a
ten% in H2O: xx   °C.

Table iii. Absorption characteristics of sugar alcohols

Polyol Absorbed from the small intestine (%) Excreted (%) Fermented (%) Calorific value (kcal 1000−1)
Urine Carrion
Xylitol 25–40 0 <   1 60–75 2.9
Sorbitol xv–20 0 <   one 80–85 2.6
Mannitol 15–twenty xv–xx <   1 80–85 one.9
Maltitol 45–60 0 <   1 40–55 3.2
Lactitol <   1 0 <   1 99 2.3
Isomalt 35–45 0 <   ane 55–65 3.0

Except for maltitol-containing syrups (55–75% maltitol), in which a modest fraction of oligomeric structures occurs, polyols are not degraded past saliva enzymes (amylases) upon oral ingestion. In the stomach slight acid hydrolysis of the di- and oligosaccharide polyols may occur. However, once the small intestine is reached, extensive hydrolysis by α-amylases of the mucosa occurs and upwardly to 60–lxxx% of the maltitol and isomalt is hydrolyzed. A 50% glucose/50% sorbitol or a 50% glucose/25% sorbitol/25% mannitol mixture respectively is obtained. The other disaccharide polyol lactitol is well-nigh unchanged because the required β-galactosidase is only present in trace amounts. Sorbitol, mannitol, and xylitol reach the small intestine unchanged. (See ISOMALT.)

In the pocket-sized intestine the monosaccharide polyols are partly absorbed into the blood stream past a passive diffusion process at rates depending upon their molecular weight (Table 3). Besides, the applied dose and the bodily abdominal transit fourth dimension affect the charge per unit of absorption. The absorbed fraction of sorbitol and xylitol is channeled into the normal liver metabolism and contributes free energy to the same extent as glucose.

The unabsorbed polyols finally achieve the large intestine where the microflora ferments them nearly completely to volatile fat acids (VFAs). From the energy contained in the fermented fraction, 20% is used by the bacteria for growth. The remainder is absorbed from the gut as VFAs which are then transported in the blood to exist metabolized by the liver into fat constituents. In total, about l% of the energy of the fermented polyols is available to the human body.

Based on the above metabolic behavior, the calorific value of polyols can approximately be calculated (Table 3). However, depending upon the methodologies used, values vary over a wide range. Therefore, and considering many polyols are used in combination with each other, a European Spousal relationship Directive has laid down an boilerplate calorific value of 2,4   kcal   g−iv for all polyols.

Considering of the reduced digestibility of polyols, their intake level is recommended to be restricted to 40–50   g   day−1 (adults) and 30   k   day−ane for children in lodge to avoid gastrointestinal discomfort. College doses may crusade an osmotic diarrhea or increased flatulence due to deadening assimilation and extensive fermentation, respectively, but tolerance levels improve upon accommodation. On the other hand polyols are very suitable for diabetics, considering rapid glycemic or insulinemic response is avoided. For the same reason sorbitol and xylitol are often practical in parenteral diet to provide a more than controllable carbohydrate energy source compared to glucose or fructose.

Concerning dental health, polyols have long been known to accept no adverse effect on teeth. This is due to the fact that oral fissure bacteria are unable to ferment polyols, thereby fugitive the product of enamelsolubilizing acids. With the intraplaque pH telemetry exam, it was shown that eating polyol-based sweets did not decrease the plaque pH beneath the critical value of five.7. Additionally, for xylitol, there is ample proof of a cariostatic issue. In several studies, of which the Turku study (Finland) is near famous, the incorporation of xylitol in a normal nutrition was proved to reduce the occurrence of dental carics. Nigh probably, xylitol selectively discriminates against the growth of Streptococcus mulans, the major organism involved in dental caries. (Encounter DENTAL DISEASE | Role of Nutrition.)

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Carbohydrate Basics: Sugars, Starches and Fibers in Foods and Wellness

Jacqueline B. Marcus MS, RD, LD, CNS, FADA , in Culinary Nutrition, 2013

Sugar Alcohols

A carbohydrate booze is a saccharide with an alcohol grouping attached to it. They include erythritol, lactitol, maltitol, mannitol, sorbitol and xylitol—identified past their "ol" suffix.

Sugar alcohols are reduced-calorie sweeteners. They are non every bit sweet as white carbohydrate and they have fewer calories. On the boilerplate, saccharide alcohols provide about one-half of the calories of white saccharide. Sugar alcohols are poorly absorbed into the bloodstream from the minor intestine, so they only cause a small change in blood sugar. This is meaningful to diabetics. Foods and beverages with sugar alcohols should be taken into account when estimating the total amount of carbohydrates in a diabetic nutrition. The American Diabetes Association offers guidelines [17].

Due to their poor absorption, if as well many carbohydrate alcohols are ingested, they can pb to gas or diarrhea. This may be the case if sugar alcohols are overconsumed in beverages and sweets.

Carbohydrate alcohols are non broken down past the leaner in the oral cavity, so they do not lead to dental cavities. That is why chewing sugarless gum really prevents teeth from decay, and due to the chemic construction of carbohydrate alcohols, they actually leave the mouth feeling absurd! Too chewing gum, sugar alcohols are plant in some candies, cookies, ice foam and puddings. Sugar alcohols do not brown, nor practise they caramelize when heated, so they have limited value to cooks. In nutrient product evolution, saccharide alcohols are sometimes used to mask the bitter palatableness of other sweeteners.

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GENETIC MODIFICATION OF Principal METABOLISM | Carbohydrates

R.Due north. Chibbar , M. Båga , in Encyclopedia of Applied Plant Sciences, 2003

Carbohydrate Alcohols

Sugar alcohols are main photosynthetic products that are accumulated temporarily in leaves during light and are translocated to other plant organs during nighttime. As compared to the corresponding sugar, sugar alcohols have an additional hydroxyl grouping ( Figure 1), and, therefore, are also designated as polyols, polyalcohols, or polyhydric alcohols. Mannitol, sorbitol, galactitol, and gluctinol are the chief sugar alcohols that have been studied in plants. These compounds are rare in monocotyledons but contribute significantly to transported and stored carbon in some horticultural plants, such as members of the Rosaceae, Rubiaceae, and Plantaginaceae families. Sugar alcohols take been implicated in abiotic stress tolerance. As compared to sucrose, saccharide alcohols are more metabolically sequestered, and this has important implications in their physiological role in translocation and storage of carbohydrates.

Carbohydrate alcohols are synthesized from hexoses or hexose-phosphates, through the consecutive activeness of reductases and phosphatases. In green celery (Apium graveolens) tissues, three cytosolic enzymes, mannose-six-phosphate isomerase (EC 5.iii.1.8), NADPH-dependent mannose-6-phosphate reductase (EC 1.1.1.224), and mannitol-ane-phosphate phosphatase (EC 3.1.3.22) catechumen fructose-half-dozen-phosphate to mannose-6-phosphate, mannitol-1-phosphate, and mannitol, respectively. Glucitol is similarly synthesized from glucose-6-phosphate by the action of a glucose-six-phosphate reductase (EC ane.1.one.200) and a sorbitol (glucitol)-half-dozen-phosphate phosphatase (EC 3.one.3.l). The genes for some of the sugar alcohol biosynthetic enzymes have been isolated from bacterial species and plants like celery and apple (Malus spp.), and used to genetically engineer elevated concentrations of sugar alcohols in tobacco, apple tree, persimmon (Diospyros spp.), and Arabidopsis. Some of the transgenic lines producing elevated levels of sugar alcohols testify enhanced tolerance to drought, salinity, or oxidative stress.

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Uncomplicated Carbohydrates

N.Five. BHAGAVAN , in Medical Biochemistry (4th Edition), 2002

Sugar Alcohols

Saccharide alcohols are polyhydric alcohols (or polyols) formed when the carbonyl group of the monosaccharide is reduced to a hydroxyl grouping ( Figure nine-11). For example, reduction of glyceraldehyde or dihydroxyacetone yields glycerol, a component of triacylglycerols (fatty acid esters of glycerol) and of phospholipids. D-Sorbitol (also known as D-glucitol) is formed when D-glucose is reduced. Keto sugars of more three carbons tin can yield more than than ane carbohydrate alcohol. For example, the chemic reduction of D-fructose yields a mixture of D-sorbitol and D-mannitol (sugar alcohol of D-mannose) considering of the cosmos of a new asymmetrical eye at C2 when the

group is converted to a

OH group.

FIGURE nine-11. Structures of selected carbohydrate alcohols and myo-inositol.

Sorbitol, with well-nigh 35-60% of the sweetness of sucrose, is used as a sweetener and flavoring agent. Information technology is hygroscopic and therefore is used as a humectant. Sorbitol (and other saccharide alcohols) can accumulate in tissues such as the lens, sciatic nerve, and renal papillae in certain disorders (e.g., diabetes mellitus and galactosemia) and can lead to pathological changes. In these instances, the intracellular accumulation of sugar alcohols is due to the loftier levels of precursor sugars in the plasma, which are converted enzymatically to the respective saccharide alcohols in the cytoplasm. Saccharide alcohols are not metabolized as rapidly every bit their precursors, and reconversion to the precursor is also slow.

Mannitol is widely distributed in nature and occurs in the exudates of many plants. Information technology has about one-half the sugariness of sucrose. Clinically, mannitol is administered intravenously as an osmotic diuretic in patients with acute renal failure. Information technology is not metabolized appreciably, is filtered by the glomerulus, and is non reabsorbed by the tubules; hence, it is excreted in urine (Affiliate 39). The nonreabsorbable solute holds water, limits back-improvidence, and thus maintains urine volume in the presence of decreased glomerular role. Intravenous mannitol is also used to relieve an increase in force per unit area and in book of cerebrospinal fluid.

Xylitol, a five-carbon polyol, is widely distributed in the establish kingdom. It has about twice the sugariness of sucrose. A potential benefit of xylitol and other saccharide alcohols used as sucrose substitutes may exist the prevention of dental caries. The beneficial event may be due to the disability of the oral microorganisms to utilize the sugar alcohols. Saccharide alcohols, though derived from reducing monosac-charides, are not reducing agents and exist only in the directly-chain class, since they cannot form cyclic hemiacetal or hemiketal linkages. Nevertheless, circadian compounds related to saccharide alcohols do exist, east.g., myo-inositol, a component of some phospholipids (Figure ix-11).

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FUNCTIONAL FOODS

F. Rincón-León , in Encyclopedia of Food Sciences and Nutrition (2d Edition), 2003

Sugar Alcohols and Other Alcohols

Sugar alcohols are 'polyols.' This term refers to chemical compounds containing three or more than hydroxyl groups. Polyols tin can exist divided into acyclic polyols (alditols or glycitols, which are true sugar alcohols), and cyclic polyols. An instance of the first group is xylitol, and an example of the 2nd is myo-inositol. In general, different functional properties accept been attributed to these groups of substances, such as low caloric intake by incomplete assimilation, sweeteners in diabetic diet and caries-reducing agents.

The most ubiquitous saccharide alcohols are sorbitol and d-manitol, and their concentrations in some plants and constitute exudates may exist very high. Fruits belonging to the family Rosaceae, such as pears, apples, cherries, plums, peaches, apricots, etc., contain appreciable amounts of sorbitol. Xylitol is a naturally occurring five-carbon sugar alcohol that tin can be found in many fruits and berries, beingness most abundant in xanthous plums and greengages. Some research papers have documented the noncariogenic and anticariogenic effects in addition to sweetener properties, and recent studies take indicated that xylitol may have prebiotic properties and other effects on health.

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SWEETENERS

M.C. Yebra-Biurrun , in Encyclopedia of Analytical Science (2d Edition), 2005

Sugar alcohols, polyhydric alcohols, or hydrogenated sugars

Sugar alcohols or polyols differ from sugars in that the aldehyde or ketone function of the saccharide molecule is reduced to an booze. They can also be categorized as carbohydrate substitutes because they can replace saccharide sweeteners. Nearly mutual every bit bulk sweeteners are sorbitol, mannitol, xylitol, and erythritol (monosaccharides); isomalt, maltitol, and lactitol (disaccharides); and hydrogenated starch hydrolyzates (HSH, a mixture of carbohydrate alcohols). Many saccharide alcohols are found in nature, only it is not commercially feasible to isolate and concentrate them from their sources. Sorbitol, mannitol, maltitol, and the HSH are produced past enzymatic hydrolysis of a starch. Lactitol, xylitol, and isomalt are produced in a like fashion, except that they are not derived from starch. Erythritol has been commercially produced past a fermentation process. All retain sweetness through heating and their bulking backdrop are like to those of sucrose. All polyols are captivated slowly and incompletely from the intestine past passive improvidence. Therefore, these sweeteners provide low energy and offer potential wellness benefits (due east.g., reduced glycemic response and reduced dental caries risk). All these sweeteners except mannitol do non represent a take chances to health and the Bring together Expert Committee on Food Additives of the Agriculture Organization/World Health Organization (JECFA) accounted it not necessary to assign a numerical value for ADI, but instead assigned the most favorable term 'not specified'. Furthermore, in the USA they are considered Generally Recognized every bit Rubber. Nevertheless, an excess consumption of mannitol may have a laxative effect, and for this reason, JECFA has allocated a temporary ADI of l  mg   per   kg.

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CARBOHYDRATES | Sugar Alcohols

M.East. Legaz , C. Vicente , in Encyclopedia of Analytical Scientific discipline (Second Edition), 2005

Special Considerations in Sample Handling and Storage of Samples

Sugar alcohols should be extracted immediately from fresh material to avoid their enzymatic degradation. Air-stale plant material and even material stored at deep freeze temperatures (−25°C) over a long period should be avoided for the same reason. Plant material must exist free of microbial infection and contagion.

Fractionation of the textile is recommended because certain substances interfere with some detection methods. Percolation with petroleum ether removes lipophilic substances. Proteins and mucilages tin exist removed by precipitation with metal ions or 5% (w/five) trichloroacetic acrid (TCA). Discoloration of biological materials is achieved with charcoal. Owing to the insolubility of benzylidine derivatives of sugar alcohols in water, they tin easily exist crystallized and purified from adhering thing by washing with water.

Homo plasma and cerebrospinal fluid (CSF) samples must exist frozen immediately after they are collected, and must exist stored at −lxx°C until analyzed. For plasma and CSF, borosilicate drinking glass examination tubes must be silanized with five% (w/v) trimethylchlorosilane in hexane for thirty   min at 75°C and unreacted reagent is removed by rinsing with methanol.

Glucose, sucrose, and polyhydric alcohols, glycerol, sorbitol, and mannitol, brandish nucleophilic reactivity with simple activated esters in aqueous solution buffered at neutral to alkali metal pH. This nucleophylic reactivity is attributed to the anion resulting from ionization of a hydroxyl grouping. These polyhydric alcohols accept been shown to exist catalytically agile in the hydrolysis of cephalosporins in aqueous solution. The reaction mechanism involves opening of the β-lactam moiety past an alkoxide ion derived from proton ionization of one of the hydroxyl groups generating an intermediate ester which undergoes further hydrolysis.

Glucose may interfere with sorbitol and galactitol estimation by gas–liquid chromatography (GLC) and therefore it must be removed prior to analysis past incubating samples with glucose oxidase. Information technology is also recommended that monosaccharides be converted to the corresponding methyloxime derivatives prior to acetylation in order to avoid interferences in galactitol and mannitol estimation when using GLC equally separation method. When GLC is chosen equally belittling procedure, pyridine tends to mask polyol peaks with brusque retention time values. In such cases, the reacted sample may be stale down and redissolved in a more volatile solvent such as chloroform, hexane, or heptane.

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Extraction Techniques and Applications: Food and Beverage

F. Temelli , ... L. Comin , in Comprehensive Sampling and Sample Preparation, 2012

4.18.iii.iv.1 Polyols

Sugar alcohols, or polyols, have many applications in the nutrient and drink industry. Mannitol ( Figure ix) is a popular polyol, which is used to sweeten products without the apply of saccharide, and results in a reduced rising in blood glucose and insulin response. It can act as a plasticizer, a laxative, and a cooling amanuensis, and is commonly used in the pharmaceutical manufacture. 112,113 Mannitol can be produced through bacterial fermentation, or it can be extracted from natural sources, such equally the olive tree. Such an extraction is unremarkably carried out using hot ethanol, h2o, or methanol, 113 but mannitol extraction using SC-COii has likewise been investigated. 112

Effigy 9. Chemical structure of mannitol.

Every bit is common with polar compound extractions, the extraction of mannitol from olive leaves using SC-CO2 increased with the addition of a polar co-solvent, like ethanol, and the optimum level was found to exist 20%, five/five. When ethanol level was increased from 10 to 20%, 5/v, extraction yields increased 136.eight%. 112 Mannitol yields were negligible at ethanol levels of less than 10%. Increasing force per unit area and decreasing temperature increased mannitol yield; an increase from 25 to 30   MPa increased yield 405%, while the divergence in yields obtained at 80 °C and 40 °C was 381%. 112 These results would indicate that the crossover of the solubility isotherms does not occur within the operating pressures investigated up to 35   MPa. Although final yields of SC-CO2 extraction were lower than that obtained by solid–liquid extraction, less ethanol was used during SC-COii extraction per thousand of olive leaves to recover mannitol, 35.four   chiliad vs. 194.iv   g, respectively. 112

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Properties and Composition of Normal Cerebrospinal Fluid

David N. Irani , in Cerebrospinal Fluid in Clinical Practise, 2009

Polyols

Polyols are ubiquitous sugar alcohols, formed by the reduction of aldoses and ketoses during intermediary carbohydrate metabolism. myo-Inositol is involved in bespeak transduction when released from phospholipids as inositol-1,4,five-triphosphate, and mannitol and sorbitol are organic osmolytes. The function of other polyols in mammalian tissues is otherwise unknown, even though studies accept gone to substantial lengths to quantify them in normal human plasma and CSF. Shetty et al. reported the following polyol concentrations in the CSF of 12 healthy adults: myo-inositol, 23.97 ± 3.90 μg/ml; 1,5-anhydrosorbitol, 15.32 ± 3.54 μg/ml; arabitol, three.72 ± 0.87 μg/ml; ribitol, 0.57 ± 0.11 μg/ml; galactitol, 0.33 ± 0.12 μg/ml; sorbitol, two.37 ± 0.64 μg/ml; and mannitol, 0.84 ± 0.24 μg/ml. 97 Similar CSF concentrations accept been reported in other studies. 96 Furthermore, all of these compounds have CSF:plasma concentration ratios greater than i.0 (most are in a higher place v.0); 97 this indicates that polyols are either being quickly transported into CSF, or more likely that they are produced within the brain or at the choroid plexus. With the exception of myo-inositol, polyols are formed in unmarried-step reductions from their respective sugars, pregnant that their precursors turn over very quickly in the brain. An inborn fault of metabolism causing high CSF and brain polyol levels and leukoencephalopathy has recently been described. 98

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Examples of Pathway Manipulations: Metabolic Engineering in Practice

Gregory N. Stephanopoulos , ... Jens Nielsen , in Metabolic Engineering, 1998

vi.3.7. PENTOSES: XYLITOL

Xylitol, a sugar alcohol, is a good anticariogenic sweetener that does not require insulin for its digestion by diabetics (Emodi, 1978). In nature xylitol is found in certain fruits and vegetables in minor amounts, making its quantitative extraction difficult and uneconomical. Currently xylitol is manufactured chemically in alkali metal conditions by catalytic reduction of xylose derived from hemicellulose hydrolysates. Lately, much attention has focused on the microbial production of xylitol from D-xylose. Xylitol has been reported to exist produced by yeasts, especially species of genus Candida, such every bit C. pelliculosa (Nishio et al., 1989), C. boidinii (Vongsuvanlert and Tani, 1989), C. guillliermondi (Meyrial et al., 1991), and C. tropicalis (Gong et al., 1981), Petromyces albertensis (Dahiya, 1991), by bacteria such as Enterobacter liquefaciens (Yoshitake et al., 1973), Corynebacterium sp. (Yoshitake et al., 1971), and Mycobacterium smegmatis (Izumori and Tuzaki, 1988). Yeasts by and large possess the first two enzymes needed for the metabolism of xylose: xylose reductase (XR) and xylitol dehydrogenase (XDH) (Fig. six.seven). Efforts to increment xylitol productivities and yields through culture optimization have yielded moderate results (0.32-two.67 yard L−1 h−1) (Horitsu et al., 1992). Therefore, emphasis has been placed on genetic modifications that would enhance both the yield and productivity of xylose conversion to xylitol.

In an initial written report, the P. stipitis XR was chosen for the construction of xylitol-producing recombinant yeasts (Hallborn et al., 1991). The choice was based on the high specific activity of XR and the fact that this detail XR uses both NADH and NADPH as cofactors (Verduyn et al., 1985). Due to the lack of XDH (needed for NADH regeneration), the recombinant strain was studied on medium containing both glucose and xylose. Xylose utilization commenced after glucose burnout and proceeded to give nigh 97% theoretical yield conversion of xylose to xylitol at a specific productivity of 0.08 g (gcells h)−one. A later report, aimed at expanding the substrate utilization range of ethanologenic S. cerevisiae past overexpressing the P. stipitis genes for XR and XDH, fortuitously resulted in the product of 35 g L−1 xylitol (Tantirungkij et al., 1993).

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