Food Chemistry

4.4 Polysaccharides 313

Fig. 4.24.Gel strength of (a) tamarind flour and
(b) pectin from lemons versus saccharose concentration
(according toWhistler, 1973)

4.4.4.11.3 Utilization

The tamarind seed polysaccharide is a suitable
substitute for pectin in the production of mar-
malades and jellies. It can be used as a thickening
agent and stabilizer in ice cream and mayonnaise
production.

4.4.4.12 Arabinogalactan from Larch

4.4.4.12.1 Occurrence,Isolation

Coniferous larch-related woods (Larixspecies;
similar to pine, but shed their needle-like leaves)

contain a water-soluble arabinogalactan of

5–35% of the dry weight of the wood. It can be

isolated from chipped wood by a counter-current

extraction process, using water or dilute acids.

The extract is then usually drum dried.

4.4.4.12.2 Structure,Properties.....................................

The polysaccharide consists of straight chain

β-D-galactopyranosyl units joined by 1→ 3

linkages and, in part, has side chains of galactose

and arabinose residues bound to positions 4

and 6. The suggested structure is given in

Formula 4.146.

In general, the polysaccharide is highly branched.

The molecular weight is 50–70 kdal. The

molecule is nearly spherical in shape, so its

aqueous solution behaves like aNewtonian fluid.

The viscosity is exceptionally low. At a tempera-

ture of 20◦C, the viscosity of a 10% solution

is 1.74 cps, a 30% solution 7.8 cps at pH 4 or

8 .15 cps at pH 11, and a 40% solution 23.5cps.

These data show that the viscosity is practi-

cally unaffected by pH. The solution acquires

a thick paste consistency only at concentrations

exceeding 60%.

4.4.4.12.3 Utilization

Arabinogalactan, due to its good solubility and

low viscosity, is used as an emulsifier and stabi-

lizer, and as a carrier substance in essential oils,

aroma formulations, and sweeteners.

(4.145)

(4.146)