Polysaccharides

Polysaccharides
FDSC400
Sources of Polysaccharide
Microbial fermentation
Higher plants
seeds,
tree extrudates,
marine plants,
Chemical modification of other polymers

Solubility

Strong interaction with water = solubility
Strong, extended interaction with polymer = insolubility
Local, limited interaction with polymer = gelation
Gelation

Cross links – covalent, ion pairing, co-crystallization
Viscosity
Xanthan gum
Source: Product of bacteria Xanthomonas campestris
Structure: cellulose-like backbone (b-1,4-poly-glucose) with trisaccharide branches (stubs) on alternate monomers on the backbone carrying carboxylic acid residue
Functional Properties: Water soluble, viscous, non-gelling. Viscosity is only slightly temperature dependant

Xanthan: Structure-function
Pectin
Source: Cell walls of higher plants (citrus rind)
Structure: Largely a linear polymer of polygalacturonic acid with varying degrees of methyl esterification. (Also some branches –HAIRY REGIONS)
>50% esterified is a high methoxy (HM) pectin
<50% esterified is a low methoxy (LM) pectin
Functional Properties: High methoxy pectin will gel in the presence of acid and high sugar concentrations. Low methoxy pectin will gel in the presence of calcium.

High and Low Methoxy Pectin
Algin
Source: Seaweed extract
Structure: linear polysaccharide containing two types of residue (i.e., a co-polymer): b-D-mannopyranosyluronic acid and (M) a-L-gulopyrasonic acid (G)
Functional Properties: Viscous in aqueous solution, gels in the presence of Ca2+ (or low pH). Gels are temp stable
PGA (propylene glycol alginate)

“Egg-box” Structure
Cellulose Gums

Carboxymethyl cellulose
-CH2COO-
High viscosity, non-gelling
Carageenan
Source: Seaweed gum
Structure: Linear D-galactopyranosyl chain with alternating 1,3 and 1,4 links. Some residues have one or two sulfate ester residues. Three broad types of repeating structure (i, k, and l carageenan)
Functional Properties: pH independent thickening. Double helix formation in k or i carageenan can lead to gelation.
k-carageenan in dairy foods

Gum Arabic
Extrudate gum of the acacia tree
Expensive – hard to source
Low viscosity, non-gelling
Complexed with a glycoprotein -surface active

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