Carbohydrates (1. LF UK, NT)

Classification
According to the number of sugar units By attachment:
 * Monosaccharides
 * Oligosaccharides (2–10 monosaccharide units)
 * Polysaccharides ( more than 10 monosaccharide units)
 * Complex (conjugated) carbohydrates
 * loosely
 * bound
 * homoglycosides
 * heteroglycosides
 * aglycone (non-sugar component)

Monosaccharides

 * polyhydroxyalkyl substituted aldehydes and ketones, derived compounds
 * main nutrients, biologically and sensorially active substances
 * characteristic: sweet taste

Structure and classification

 * According to the type of carbonyl group


 * aldos
 * ketosis
 * By number of carbon atoms (3–8), (multiples of CH2O (formaldehyde))


 * trios
 * D-(+)-glyceraldehyde (D-glycero-triose)
 * L-(-)-glyceraldehyde
 * 1,3-dihydroxyacetone (1,3-dihydroxypropan-2-on)
 * tetros
 * pentoses
 * hexoses
 * D-glukose (D-gluko-hexose) = dextrose, grape sugar
 * D-fructose (D-arabino-hex-2-ulose) = levulose, fruit sugar
 * According to the arrangement of the string


 * with a direct chain
 * with a branched chain
 * According to the type of lactol


 * furanoses
 * pyranoses

Mutarotation

 * anomers, anomeric C, anomeric OH

Conformation

 * furanoses (envelope E, crossed T)
 * pyranoses (chairs 4C1, 1C4)
 * acyclic forms (conformation cik-cak)

Occurrence
(abbreviations: glucose Glc, furanose f, fructose Fru, pyranose p, mannose Man, acid A, apiose Api, sorbose Sor, β-D-glucopyranose β-D-Glcp)
 * component of almost all foods
 * atypical monosaccharides
 * D-apiosa (branched sugar), root vegetables
 * L-sorbose (L-series sugar), rowan berries
 * D-manno-hept-2-ulose (ketoheptose), avocado

Derivates of monosaccharides

 * chemical reactions of their formation:


 * oxidation (rearrangement)  – sugar acids, ketoaldoses, diketoses
 * reduction – sugar alcohols, deoxysugars
 * dehydration – anhydrosugars
 * reaction with other compounds – glycosides, ethers, esters

Sugar acids

 * aldonic (glykonic) – (glucose oxidase, Ca-gluconan (medicine), δ-lactone (fermented salami, 0.1%)
 * alduronic (glycuronic) – polysaccharides: D-GlcA6 (glycoproteins), D-GalA6 (pectins), D-ManA6 and L-GulA6 (alginates)
 * aldaric (glycaric), e.g. tartaric and malic acid
 * content in chicory and malt

Ketoaldoses, diketoses

 * key products of the Maillard reaction and oxidation
 * 3-deoxyglykosulose, 1-deoxyglykodiulose, 4-deoxyglykodiulose

Sugas alcohols

 * alditols, glycitols (glycerol derivatives)
 * reduction of hemiacetal hydroxyl of mono- and oligosaccharides


 * natural food ingredients
 * ribitol – riboflavin
 * arabinitol – mushrooms
 * xylitol – mushrooms
 * D-glucitol – plums, rowanberries, pears
 * D-mannitol – mushrooms, rowan berries, celery, green coffee
 * galaktitol – mushrooms, fermented milk products
 * synthetic (reduction of H2/cat., NaHgx, substitute sweeteners)
 * xylitol, D-glucitol

widespread, phospholipids, phytates, pseudo-oligosaccharides (legumes)
 * cyclitols - content
 * cyklohexane-1,2,3,4,5,6-hexols (inositols, cykloses)
 * myo-inositol (meso-inositol)

Deoxysugars
2-deoxysugars 6-deoxysugars (6-deoxyhexosis = methylpentosis)
 * reduction of primary / secondary hydroxyl - natural, Maillard reaction
 * 2-deoxy-D-ribose (thyminose), deoxyribonucleic acid

Anhydrosugars
sugar anhydrides, glycosans, elimination of water, mainly hemiacetal and other OH
 * natural polysaccharide components CH2O
 * 3,6-anhydro-α-D-galaktopyranose ( carrageenans )
 * 3,6-anhydro-α-L-galaktopyranose (agar)
 * products of thermal reactions
 * 1,6-anhydro-β-D-glukopyranose (β-glucosan, levoglucosan) (caramel)

Glycosides, ethers, esters and other derivates

 * O-glycosides – very widespread
 * ethers: 4-O-methyl-D-GlcpA (hemicelluloses), 2-O-methyl-D-Xylp (pectins)
 * esters – natural (phosphates, acetates, benzoates, etc.), synthetic (fatty acids, emulsifiers)
 * S-glycosides – glucosinolates
 * N-glycosides - natural (ATP, NADH), Maillard reaction (glycosylamines)
 * aminodeoxysugars – natural (chitosamine), Maillard reaction (Amadori products)
 * C-glycosides

Oligosaccharides

 * homoglycosides
 * pentoses, hexoses, sugar acids, etc. derivatives
 * furanoses, pyranoses

Classification
By number of monosaccharides (monos, 2-10) According to the presence of hemiacetal OH According to the predominant monosaccharide According to digestibility According to biological effects
 * disaccharides (bioses) – decasaccharides (decaoses)
 * reducing (glycosides)
 * non-reducing (glycosylglycosides)
 * glucooligosaccharides
 * maltose, maltooligosacharides
 * fructooligosaccharides
 * sucrose
 * galactooligosaccharides
 * lactose, α-galactosides
 * digestible
 * indigestible
 * prebiotic effects (stimulate growth and metabolism of desirable microflora)
 * probiotic effects (with fiber they influence and regulate peristalsis)
 * synbiotic effects (both prebiotic and probiotic)

Nomenclature

 * maltose
 * α-D-glukopyranosyl-(1→4)-D-glukopyranose,
 * 4-O-α-D-glukopyranosyl-D-glukopyranose
 * α-D-Glcp-(1→4)-D-Glcp
 * α,α-trehalose
 * α-D-glukopyranosyl-α-D-glukopyranoside
 * α-D-Glcp-(1↔1)-α-D-Glcp

Gluco-oligosaccharides
maltose = α-D-Glcp-(1→4)-D-Glcp (malt sugar )

Occurrence Production
 * starch hydrolysis product, glucose reversion
 * malt, bread (1.7-4.3%), honey (2.7-16%)
 * maltose (85%), glucose syrups (acids, enzymes)
 * maltose
 * isomerization to maltulose, α-D-Glcp-(1→4)-D-Fruf
 * reduction to maltitol, α-D-Glcp-(1→4)-D-glucitol

Frukto-oligosaccharides
sacharóza = α-D-Glcp-(1↔2)-β-D-Fruf (beet sugar)

Occurence
 * cuttings extraction (diffusion)
 * purification (epuration) of raw juice, clarification of Ca(OH)2
 * CO2 saturation
 * filtration, light juice
 * thickening - heavy juice (61-67% sucrose, 68-72% solids)
 * raw (brown) sugar - 96% sucrose, 2-3% non-sugars, 1-2% water (1.0-1.2% organic, 0.8-1.0% inorganic)
 * affinade
 * refining – molasses (feed, substrate for fermentation processes), production of invert sugar, other products

Galakto-oligosaccharides
laktosis = β-D-Galp-(1→4)-D-Glcp (milk sugar)

Occurrence Production (from whey) other β-galactooligosaccharides of milk
 * cow's milk 4-5%
 * human milk 5.5-7%
 * by ultrafiltration
 * after thickening by crystallization – production of galactose, galactitol, lactulose, lactitol

α-galaktooligosacharides of legumes
content

Reactions of saccharides
Non-enzymatic browning reaction Reaction of carbohydrates Main reactions of monosaccharides (reactions catalyzed by acid-base) Formation and hydrolysis of glycosides Hydrolysis (inversion) Formation (reversion, Fischer reaction) Dehydratation Anhydrosugars Deoxysugars Formation of reductones Isomeration Isomerization of disaccharides Changes to acids Fragmentation
 * complex enzymatic and non-enzymatic reactions
 * carbonyl, anomeric OH, primary OH, secondary OH
 * reactions of the carbohydrates themselves
 * Maillard reaction (reaction with proteins, amino compounds)
 * caramelization
 * Reactants
 * reducing mono- and oligosaccharides
 * non-reducing oligo- and polysaccharides after hydrolysis
 * in an acidic environment (other factors: temperature, time)
 * formation (hydrolysis) of glycosides, dehydration, formation of reductones
 * in an alkaline environment
 * mutarotation, isomerization, rearrangements, fragmentation, oxidation
 * reaction of hemiacetal OH
 * production of starch syrups
 * invert sugar
 * galaktose
 * inversion by-products (starch syrups: 5-6%)
 * byproducts of caramelization
 * low energy products
 * counterfeit indicators
 * reaction of hemiacetal OH and other OH
 * hemiacetal OH / other OH → anhydrosugars (glycosans)
 * another OH / another OH → deoxysugars
 * β-D-Glcp → 1,6-anhydro-β-D-Glcp (β-glukosan)
 * inversion by-products (glucose < 1%)
 * byproducts of caramelization (more)
 * 1,2-enolisation (series of isomerisations and dehydrations)
 * 2,3-enolisation (caramel aroma)
 * antioxidants
 * reduction of organic substances, metal ions
 * pH < 6 (similar to enediolates) monoanionts
 * pH > 6 dianionts
 * aldose → ketose
 * aldose → aldose ( epimerization).
 * laktosis – β-D-Galp-(1→4)-D-Glcp
 * laktulosis – β-D-Galp-(1→4)-D-Fruf
 * epilaktosis – β-D-Galp-(1→4)-D-Manp
 * 1-ene-1,2-diol, Cannizzaro reaction, benzyl rearrangement
 * formation of very reactive compounds
 * retroaldolization
 * by oxidation (after isomerization, dehydration)

non-enzymatic browning reaction
Reactants Reaction conditions Consequences positive, negative Reaction mechanisms – 3 reaction phases
 * sugars (carbonyl compounds)
 * monosaccharides and reducing oligosaccharides
 * (non-reducing oligosaccharides, polysaccharides, glycosides)
 * triosa > …. > pentose > hexose (acyclic form)
 * aldose > ketose
 * α-dicarbonyls > aldehydes > ketones > carbohydrates
 * proteins (amino compounds)
 * ε-NH2 Lys, N-terminal NH2, guanidyl Arg, SH Cys
 * free amino acids, amines, ammonia
 * ε-NH2 > …. > β-NH2 > α-NH2
 * NH3 > R-NH2 > amino acid
 * water activity (aw 0.3–0.7)
 * pH (9–10)
 * other (temperature, reaction time, other components)
 * formation of aromatic substances
 * formation of yellow, brown, black melanoidin pigments
 * reduction of nutritional value
 * potentially toxic products
 * in vivo reaction (glycosylation of proteins)
 * initial phase
 * formation of glycosylamine (Amadori rearrangement) and aminodeoxysugar (Amadori product)
 * middle phase
 * breakdown of carbohydrates, glycosylamines, aminodeoxysugars (dehydration, fragmentation)
 * breakdown of amino acids (Strecker degradation)
 * final stage
 * reaction of products and decomposition products, formation of aromatic, taste and colored substances (melanoidins)

Glykosylamines and aminodeoxysugars

 * ketoses → ketosylamine → aldosamine (2-amino-2-deoxyaldose), Heyns' p.

Decomposition of aminodeoxysugars Analogy with the reactions of sugars themselves parallel breakdown of the sugars and amino acids themselves
 * mechanisms (reactions of acyclic forms)
 * 1,2-enolization, acidic environment
 * 2,3-enolization, neutral and alkaline environment
 * the formation of glycosulos and glycodiulos (aldoketos and diketos)
 * lower activation energy
 * products contain N and S
 * qualitatively and quantitatively more products

Important heterocyclic products

Malliard reaction in major commodities
technology (aroma, taste, color, nutritional value) Reaction during milk processing unusable (blocked) Lys Maillard reaction inhibition
 * positive and negative consequences, desirable and undesirable reactions
 * roasting
 * cooking, baking, frying
 * drying
 * extrusion, microwave heating
 * milk, dairy products - Lys: 10-30% traditional drying, 3% spray drying
 * cereals, cereal products - Lys: 70% bread crust, 10% total
 * meat, meat products – mutagens
 * fruit vegetables
 * coffee, cocoa, nuts
 * isomerization of lactose → lactulose + epilactose
 * lysinoalanine
 * creating unfavorable conditions
 * water content (activity), temperature reduction, pH adjustment
 * removal of one of the partners
 * use of inhibitors

Caramelization

 * sugars (sucrose, glucose, fructose, starch syrups, invert sugar)
 * temperature 150–190 °C (240 °C)
 * reaction time 5-10 hours
 * catalyst


 * caramel – a solid product
 * cooler - solution

Source

 * DAVÍDEK, Jiří. 5. CARBOHYDRATES [online]. [cit. 2012-03-12]. < https://el.lf1.cuni.cz/p46134582/ >