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


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

Cross links – covalent, ion pairing, co-crystallization
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
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

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

High viscosity, non-gelling

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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