Etiket Arşivleri: Gum Arabic

Gum Arabic / Gum Acacia

The dried exudate (gum) from Acacia Senegal and related species (Acacia Seyal)

Gum Arabic

Origin

Collection (origin) and Processing (Europe)

Structure

– chemical composition

Properties

– functional characteristics and influences

Applications

Important Quality Parameters

Comparison of the different grades

Our qualities

Gum Arabic – Origin

South of Sahel zone, mainly Sudan, Chad and Nigeria

Gum Arabic – Collection

Tapping

Cleaning

Sieving

Gum Arabic – Processing

Dry
– powder
– granular

Wet
– spraydrying
– rollerdrying

Gum Arabic – Structure

Complex polysaccharide

– neutral or weakly acid

– containing nitrogenous material (amino acids)

– chemical composition vary slightly

– contained sugar monomers in a ratio of 3:3:1:1 are

• galactose, arabinose, rhamnose and glucoronic acid

– highly branched molecule with great variation in molecular mass

Gum Arabic – Properties

readily dissolves in cold water

odourless

tasteless

viscosity is a function of concentration

Solutions of Gum Arabic below 40 %
– react like Newtonian liquid

• viscosity is shear rate independent

Solutions of Gum Arabic at higher concentrations
– show pseudoplastic characteristics

• shear thinnig
reversible decrease of viscosity with increasing shear forces

weakly acid character in water (pH 4.5)

pH of the solution affects the viscosity

viscosity decreases in the presence of electrolytes (salts)

comparison with other thickening agents shows lower viscosity of Gum Arabic solutions even at higher concentrations

emulsifier for essential oils and flavours

– proteins adsorb on the surface of the oil droplets

– formed emulsions remain stable for a long period of time

Disadvantage:

prolonged heating ( > 70 °C) of Gum Arabic solutions causes precipitation of the proteinous components !!!

Source: http://hobbytakt.com/products/3856466109.pdf

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