Introduction lecture polysaccharides
● Functionalities of polysaccharides:
○ Thickening → increase in viscosity.
○ Gel forming properties.
○ Stabilization
■ Emulsification, suspension, foam.
○ Film forming.
○ Aroma binding.
○ Glue properties.
○ Filling agent.
● Polysaccharide functionality depends on:
○ Chemical structure.
■ Sugar building blocks.
■ Charge.
■ Non-glycosidic substituents.
○ Branched vs. linear.
○ Molecular weight.
■ polydisperse vs monodisperse.
- Homopolysaccharides: polysaccharides made from one building block (sugar unit).
Cellulose, starch.
- Heteropolysaccharides: polysaccharides made from multiple building blocks (sugar
unit).
● Difference glycan/glucan → glycan is a generic name for all polysaccharides
(glycosidic linkage). Every polysaccharide is a glycan. A glucan is a polysaccharide
made from glucose.
● The polysaccharide structure dictates the shape of the polymer. The type of
monomer linkage plays an important role (a/b, 1-4, 1-2, 1-3).
○ Alpha: the OH group at C1 points downwards.
○ Beta: the OH group at C1 points upwards.
● The properties of polysaccharides are also determined by the presence of charged
groups and/or substituents.
○ Acids → COO-, SO4-- (always charged → not pH dependent), PO4--,
pyruvate.
○ Esters → methyl, acetyl or amide groups.
■ Neutralizing of charge.
■ Acetyl does not add charge to the molecule!
○ Number of charged groups or other substituents and their distribution is
important.
, ● (Pectin) high pH → more charge → more repulsion → higher viscosity.
● (Pectin) low pH → less charge → less repulsion → lower viscosity.
● In solutions, the hydrodynamic volume of the polysaccharides is important.
○ Larger hydrodynamic volume when DP is high.
○ Large hydrodynamic volume for linear polysaccharides than branched.
○ Larger hydrodynamic volume when the polysaccharide is charged.
● In High Performance Size Exclusion Chromatography, larger molecules (elute
more quickly) are less retained by the column than the small molecules.
○ Enzymes decrease the molecular weight.
● Sources of food hydrocolloids:
○ Botanical.
○ Algal.
○ Microbial.
○ Animal.
● Polysaccharide production
from raw (agricultural)
products:
○ Directly from the crop.
■ Starch from
wheat.
■ Enzymes may
degrade the
pectin →
control!
○ From food industry
wastes.
■ Pectin from apple pomace.
● Polysaccharides may be highly variable.
○ Depending on the raw material and processing methods.
● However, a product sheet usually only contains generic information. This info might
thus not be true!
● During food processing, polysaccharide functionality may change.
○ Heating → starch gelatinization, degradation, retrogradation.
○ Polymer degradation → lower Mw → decrease in viscosity.
● Functionalities of polysaccharides:
○ Thickening → increase in viscosity.
○ Gel forming properties.
○ Stabilization
■ Emulsification, suspension, foam.
○ Film forming.
○ Aroma binding.
○ Glue properties.
○ Filling agent.
● Polysaccharide functionality depends on:
○ Chemical structure.
■ Sugar building blocks.
■ Charge.
■ Non-glycosidic substituents.
○ Branched vs. linear.
○ Molecular weight.
■ polydisperse vs monodisperse.
- Homopolysaccharides: polysaccharides made from one building block (sugar unit).
Cellulose, starch.
- Heteropolysaccharides: polysaccharides made from multiple building blocks (sugar
unit).
● Difference glycan/glucan → glycan is a generic name for all polysaccharides
(glycosidic linkage). Every polysaccharide is a glycan. A glucan is a polysaccharide
made from glucose.
● The polysaccharide structure dictates the shape of the polymer. The type of
monomer linkage plays an important role (a/b, 1-4, 1-2, 1-3).
○ Alpha: the OH group at C1 points downwards.
○ Beta: the OH group at C1 points upwards.
● The properties of polysaccharides are also determined by the presence of charged
groups and/or substituents.
○ Acids → COO-, SO4-- (always charged → not pH dependent), PO4--,
pyruvate.
○ Esters → methyl, acetyl or amide groups.
■ Neutralizing of charge.
■ Acetyl does not add charge to the molecule!
○ Number of charged groups or other substituents and their distribution is
important.
, ● (Pectin) high pH → more charge → more repulsion → higher viscosity.
● (Pectin) low pH → less charge → less repulsion → lower viscosity.
● In solutions, the hydrodynamic volume of the polysaccharides is important.
○ Larger hydrodynamic volume when DP is high.
○ Large hydrodynamic volume for linear polysaccharides than branched.
○ Larger hydrodynamic volume when the polysaccharide is charged.
● In High Performance Size Exclusion Chromatography, larger molecules (elute
more quickly) are less retained by the column than the small molecules.
○ Enzymes decrease the molecular weight.
● Sources of food hydrocolloids:
○ Botanical.
○ Algal.
○ Microbial.
○ Animal.
● Polysaccharide production
from raw (agricultural)
products:
○ Directly from the crop.
■ Starch from
wheat.
■ Enzymes may
degrade the
pectin →
control!
○ From food industry
wastes.
■ Pectin from apple pomace.
● Polysaccharides may be highly variable.
○ Depending on the raw material and processing methods.
● However, a product sheet usually only contains generic information. This info might
thus not be true!
● During food processing, polysaccharide functionality may change.
○ Heating → starch gelatinization, degradation, retrogradation.
○ Polymer degradation → lower Mw → decrease in viscosity.
