o oligosaccharides - research university | purdue university
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Oligosaccharide-Introduction
Oligo--Greek, few Definition: 2-20 monosaccharide units More than 20 monosaccharide units is a
polysaccharide Poly--Greek, many
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Oligosaccharides
In the disaccharides, the aglycon is a monosaccharide unit
Higher order oligosaccharides are named tri-, tetra-, penta-, etc.
Structures may be predominately linearor branched
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Structural features
Linear– Features a head-to-tail linkage– 1 reducing end– 1 non-reducing end
Branched– 1 reducing end– Several to many non-reducing ends
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Reversion
If this reaction continues, the oligomers produced will tend to be highly branched and contain a variety of anomers and linkages
Readily occurs under water-limiting conditions (nearly dry)
A good commercial example of this is the bulking agent Polydextrose
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Polydextrose
Polydextrose is produced by the reversion reaction between D-glucose, sorbitol, and citric acid
This mixture is heated to produce the oligomer Polydextrose
The degree of polymerization (DP) is fairly low
Sold commercially as Litesse (and under other names as well)
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Polydextrose
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OOH
OHHO
CH2ORO
OH
OHHO
CH2OR
O O
O
O
O
OO
O
OCH2
OHHO
O
OH
HOCH
CH2OH
HO
OCH2
HOOH
OH
O
OH
OH
CH2
O
CH2
OHHO
OHOCH2
HOOH
O
O
OH
OH
HOCH2
OH
OHHO
HOCH2
OH
OHHO
O
CH2
O
OR
R = H, D-glucose, sorbitol, citric acid, or polydextrose moieties
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Maltose
Obtained from starch by the action of -amylase (from Bacillus bacteria)
Yield = 80%
-amylaseNon-reducingend
Maltose Maltose Maltose
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Maltose
Maltose may also be prepared by the action of debranching enzyme and then -amylase on amylopectin
Maltose crystallizes from aqueous solution as -maltose.H2O
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Maltose uses
A mild sweetener in foods and pharmaceuticals
A parenteral injectable for slow release of D-glucose
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Maltose
Proper name: 4-O-(-D-glucopyranosyl)-D-glucopyranose
Exists as and -anomers Reducing sugar It’s glycosidic linkage is acid labile
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Acid hydrolysis of glycosides
Acid Hydrolysis of a Glucoside
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Lactose
Milk sugar– [lactose] in nature: 2.0-8.5%– Cow/goat: 4.5-4.8%– Human: 7.0%
Provides 40% of the energy obtained during nursing
To utilize, lactose must be broken down to D-glucose and D-galactose
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Lactose production
Cow’s milk
Coagulated casein
Curd
Whey
Crystalline lactose
Adjust to IEP;heat or rennin ultrafiltration
Ion exchange
Concentration
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Lactose production
Crystallizes as -lactose monohydrate Potential lactose from whey is 23 billion
pounds per year So far its potential production has far
outstripped its commercial use
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Lactose characteristics
Name: 4-O-(-D-galactopyranosyl)-D-glucopyranose
Reducing sugar Hydrolyzable Multiple anomeric forms
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Lactose uses
Food– Toppings– Icings– Pie fillings– Confections– Ice creams
In food, lactose contributes body but little (20% of sucrose) sweetness
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Pharmaceutical uses
Provides bulk and rapid dissolution– Present in 20% of prescription drugs– Present in 6% of over the counter (OTC)
drugs
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Natural occurrence
Lactose is relatively high in milk and milk products but lower in fermented dairy products such as yogurt and some cheeses
During fermentation some lactose is converted to L-lactate
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Lactate production in food
Lactose D-Glucose + D-Galactose
-galactosidaseof bacteria
Fermentation bybacteria
CH3
OH H
O O-
L-lactate
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Lactose digestion
Digestion in gut mediated by lactase, a -galactosidase that occurs in brush border epithelial cells
The monosaccharides so produced are rapidly absorbed and enter the blood stream
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Lactose intolerance
If lactose is not completely hydrolyzed and absorbed in the small intestine, it will proceed into the large intestine
Here anerobic bacteria ferment the lactose to lactic acid and other short chain acids, in addition to CO2, H2, and methane
This causes the symptoms of lactose intolerance
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Lactose intolerance
Usually not seen in children until 6 years of age
After 6 years of age, the percent of lactose intolerant people increases with increasing age, with the greatest incidence among the elderly
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Genetic control
Lactose intolerance tends to be high among African Americans, Native Americans, Asian Americans, and Mexican Americans
Relatively lower in Western European Americans
Suggests that production of lactase is under genetic control
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Dealing with lactose intolerance
Reduce/remove lactose by fermentation– Yogurt, buttermilk
Add lactase to food (or consume lactase) just before consuming lactose containing food– This may increase the sweetness of the food
slightly when the extent of hydrolysis reaches 80%
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Other incompletely digested oligosaccharides Mostly from legumes, especially beans
– Raffinose, a trisaccharide– Stachyose, tetrasaccharide
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Lactose chemistry
Lactose can be reduced to lactitol with hydrogen gas and Raney nickel
Lactitol is not absorbed from the small intestine
It is fermented in the large intestine to lactic and acetic acid
Due to the water attracting properties of these acids, they soften stools and facilitate bowel function
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Lactose chemistry
Lactose can be isomerized in alkali to the keto sugar lactulose
Lactulose is similar in its physiological effect to lactitol, that is it facilitates bowel function
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Sucrose
One of the principal sugars in fruits and honey
Isolated from sugar cane Produced in China during the 1st century
B.C. In ancient days it was very expensive
and, thus, reserved for the nobility
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Sucrose utilization
Per person per day disappearance data: 160 grams
Per person per day consumption data: 55 grams
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Sucrose structure
Odd as it is a “head-to-head” type structure (anomeric carbon to anomeric carbon)
Non-reducing The glycosidic bond is high energy, thus
unstable– Easily hydrolyzed in dilute acid or enzymes
(sucrase or invertase)
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Sucrase and invertase
Human sucrase(-glucosidase)
Yeast and bacterialinvertase(-fructofuranosidase)
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Sucrose synthesis
Synthesized mainly in plants leaves, then transported throughout the plant
Stored in root or tuber structures
Sucrose phosphate
Sucrose
UDPGlucose +Fructose-6-phosphate
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Sucrose from sugar cane
Isolation involves processing 12-18 month old sugar cane through a series of steps that involve crushing, treating with lime, heating, filtration, and crystallization
This produces raw sugar and blackstrap molasses
The raw sugar is further cleaned up by treating with lime and phosphate, decolorizing, and crystallizing
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Sucrose from sugar beet Utilizes countercurrent
extraction of sugar beet slices (called cosettes)
The extracting solution (12% sugar) is then treated with lime, carbon dioxide, filtered, decolorized with SO2, and concentrated to crystallize the sugar
Impurities: raffinose and stachyose
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Other sugar products Brown sugar
– Incompletely purified table sugar or (more commonly) made by adding back cane sugar molasses to table sugar to get desired brownness and taste
– Industry refers to this as soft sugar
Powdered sugar– Pulverized table sugar +
3% corn starch as an anti-caking agent
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Other sugar products (cont.) Fondant sugar
– Very fine sucrose crystals surrounded with a saturated solution of invert sugar, corn syrup, or maltodextrin
– Used in icings and confections
Transformed sugar– Agglomerated sucrose
crystals– Low density, rapid
dissolving Liquid sugar
– Refined aqueous solution of sucrose
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Sucrose crystal and solution properties Sucrose can form highly concentrated
solutions– Syrups– Honey
Uses– Sweetener– Preservative– Humectant
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Cryoprotectant function
In a solution of sucrose, as freezable water freezes, the [sucrose] increases
Thus, freezing point decreases As [sucrose] increases, viscosity increases Eventually the liquid phase solidifies as a
glass– This explains how some carbohydrates can
protect against dehydration (via crystallization) that destroys structure and texture on freezing
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Sucrose solution structure
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OO
OH
OHHOH2C
O
OH
OH
H
OH
OH
In solution andcrystal state
In crystal stateonly
6’
1’
2
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Derivatives of sucrose Sucrose esters
– Low derivatization (1, 2, 3 fatty acids) Surfactants
(emulsifiers)– Octaacetate
Very bitter Used to denature
ethanol– Longer fatty acids
6-8 fatty acids (stearic, palmitic, oleic)
Olestra (frying oil fat substitute from Proctor and Gamble)Not metabolized or absorbed
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Sucralose 650x sweeter than sucrose Good taste quality and
intensity Adequate water solubility Not hydrolyzed in small
intestine 60 times more stable to acid
than sucrose Approved for use in the US
on 4/1/98
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Sucralose uses
Tabletop sweetener (Splenda) Beverages Baked goods Chewing gum Dry mixes Fruits spreads Frozen desserts
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Isomaltulose
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OHOH
OHHOH2C
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OHOH
OH
CH2OH
OIsomaltulose
50% as sweetas sucrose
-D-Glucopyranosyl-(16)-D-fructofuranose
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Isomaltulose preparation
Prepared enzymatically from sucrose Enzyme is from Protaminobacter rubrum Transfers glucose in sucrose from O-2’ to
O-6’
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Palatinit
Hydrogenation of isomaltulose with hydrogen and a catalyst produces Palatinit
About 45% as sweet as sucrose Crystalline
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Leucrose
Derived from sucrose by treatment with Leuconostoc mesenteroides
50% of the sweetness of sucrose
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Neosugar preparation
A concentrated solution of sucrose is treated with invertase or a fungal transferase
This causes the transfer of D-fructosyl units onto sucrose, thus producing kestose and the other neosugars
50% as sweet as sucrose Non-cariogenic Approved for use in Japan
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Trehalose
Occurs widely in nature– Mushrooms– Honey– Lobster– Shrimp– Certain seaweeds– Foods produced using yeast
Commercially produced by enzyme catalyzed reaction
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Trehalose
Properties– Stabilizes proteins against freezing and
drying– Maintains texture, flavor and color in frozen
and dehydrated foods, especially in Japan– Reduces retrogradation of starch– Preserves cell structure– Low hygroscopicity– RS 0.45
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Trehalose
Properties– No reactivity in Maillard reaction– Provokes less insulin response– Used in some sports drink and nutrition bars