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Polysaccharides

Polysaccharides. FDSC400. Sources of Polysaccharide. Microbial fermentation Higher plants seeds, tree extrudates, marine plants, Chemical modification of other polymers. No calorific value; fiber. Solubility. Strong interaction with water = solubility

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Polysaccharides

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  1. Polysaccharides FDSC400

  2. Sources of Polysaccharide • Microbial fermentation • Higher plants • seeds, • tree extrudates, • marine plants, • Chemical modification of other polymers No calorific value; fiber

  3. Solubility • Strong interaction with water = solubility • Strong, extended interaction with polymer = insolubility • Local, limited interaction with polymer = gelation

  4. Gelation • Cross links – covalent, ion pairing, co-crystallization

  5. Viscosity The radius of gyration is the sphere swept out by the polymer

  6. 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

  7. - - - - - - - - Xanthan: Structure-function Low pH Linear molecule Random coil

  8. 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.

  9. High and Low Methoxy Pectin HMP LMP Gel with acids and low water Gel with Ca2+ 0 50 100 %DE of Pectin

  10. 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)

  11. “Egg-box” Structure Ca2+ G-block Ca2+ M-block Ca2+ Ca2+ Ca2+ Ca2+ Ca2+

  12. Cellulose Gums a1-4 b1-4

  13. Carboxymethylcellulose Methylcellulose (may gel at high T)

  14. Carboxymethyl cellulose • -CH2COO- • High viscosity, non-gelling

  15. 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

  16. 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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