Alginates Flashcards

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1
Q

Alginic acid is a linear copolymer (unbranched) composed of

A
  • D-manuronic acid (M)
  • L-guluronic acid (G)
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2
Q

Alginic acid and calcium alginate are

A

water-insoluble

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3
Q

All the alginate salts are insoluble to

A

fats & oils and organic solvents

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4
Q

Alginate must be dispersed

A

d before dissolution can take place

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5
Q

prepare a uniform aqueous solution of ALGIN before it is utilized

A

as a thickening agent

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5
Q

Poor dispersion in water will occur if

A

sodium alginate is added too rapidly,

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6
Q

Alginates form gels
with a number of

A

divalent cations. E.g. Ca2+ (non-toxiic)

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7
Q

Gelation involved binding of Ca2+

A

in poly-L-guluronate segments (G) (with
chain length of > 20 residues

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8
Q

The amount of G blocks & the average G-block length

A

significantly affect gel formation & gel strength.

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9
Q

High G content and long
G blocks give alginates

A

high calcium reactivity
and the strongest gel forming potential

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10
Q
  • A cavity that acts as a binding site for calcium ions between two diaxially linked G residues is formed
A

produces a 3D structure (‘egg-box’), in which the calcium interacts with the carboxyls and with the electronegative oxygen atoms of the hydroxyl group (OH).

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11
Q

Gelation involves

A

chain dimerization and later aggregation of the dimer

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12
Q

After gelation, the water molecules are
physically entrapped

A

by the alginate matrix/network but retain their ability to migrate

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13
Q

The alginate gel is considered a semi-solid
material,

A

d the junction zones at which
the alginate polymers are bound represent
the solid state

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