Carbohydrates.2007

This problem tri and tetrasaccharides

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Unformatted text preview: es Poorly absorbed in small intestine Poorly and indigestible and Gal Glu Fru We cant hydrolyze the α 1-6 We linkage linkage Bacteria in intestines use it and Bacteria produce gas Cause of flatulence flatulence “Flatulence is not socially Flatulence acceptable in some societies” really? really? Gal Gal Glu Fru Possibly inhibited by phenolic Possibly compounds compounds How do we minimize this problem? Some properties of mono and oligosaccharides oligosaccharides RELATIVE SWEETNESS SUGAR RELATIVE SWEETNESS 175 100 40-79XYLITOL <40 27 --59 BITTER 16-38 48 46-52 SUGAR RAFFINOSE STACHYOSE 90 SORBITOL GALACTITOL MALTITOL LACTITOL 63 58 68 35 RELATIVE SWEETNESS 23 --- D-FRUCTOSE SUCROSE α -D-GLUCOSE β -D-GLUCOSE -D-GLUCOSE α -D-GALACTOSE β -D-GALACTOSE -D-GALACTOSE α -D-MANNOSE -D-MANNOSE β -D-MANNOSE α -D-LACTOSE -D-LACTOSE β -D-LACTOSE β -D-MALTOSE Some properties of mono and Some oligosaccharides oligosaccharides RELATIVE SWEETNESS RELATIVE Sweetness of molecules is explained in part by the AH-B theory Sweetness AH-B Level of sweetness depends on how strongly certain receptors in Level our tongue interact with molecules our Depends on: Type of chemical groups Spatial arrangement Spatial Polarity Distance between groups Distance Electron density Hydrogen and hydrophobic bonding Some properties of mono and oligosaccharides oligosaccharides RELATIVE SWEETNESS Artificial sweeteners Much sweeter than natural sugars Cyclamate Cyclamate Aspartame Aspartame Acesulfame K Acesulfame Saccharin Saccharin Sucralose Sucralose – 30 times sweeter 30 – 200 200 – 200 200 – 300 300 – 600 600 Problem they are all very bitter Problem Another bond (γ) iis apparently needed for good sweetness s (lipophilic interaction) (lipophilic Reason why artificial sweeteners taste bitter Reason Sucralose, derived from sucrose, is believed to give the most Sucralose, “natural” sweet taste of them all “natural” Some properties of mono and oligosaccharides oligosaccharides WATER ADSORPTION AND AW CONTROL SUGAR WATER ADSORPTION 0.07 0.28 0.04 5.05 0.80 5.05 0.54 D-GLUCOSE D-FRUCTOSE SUCROSE MALTOSE (HYDRATE) MALTOSE (ANHYDROUS) LACTOSE (HYDRATE) LACTOSE (ANHYDROUS) OH-groups in sugars reason for water-binding and solubility E.g. 4-6 per sucrose More H2O binding = more reduction in aw as well as increased viscosity Water-binding and solubility is temperature dependent Water-binding Chemical reactions Chemical MUTAROTATION Process by which various anomeric forms attain Process an equilibrium in solution an First established studying spectral properties of First sugars sugars Rotation of plane polarized light by an asymmetric Rotation center center Rotation varies from sugar to sugar and anomere Chemical reactions Chemical MUTAROTATION α = +112 +112 β = +18.7 +18.7 Equilibrium = +52.7 At equilibrium: 37% α 37% 63% β 63% For any sugar - the occurrence of mutarotation implies that a small amount of the straight chain form must be present Chemical reactions Chemical MUTAROTATION ~37% <<1% 0.0026% ~63% Chemical reactions Chemical HYDROLYSIS (Disaccharides and beyond…) Low pH and high temperature favor reaction Usually stabl...
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