Biomedical Engineering Reference
In-Depth Information
CH
2
-O-R
CH-OR' =
β
-Form
CH
2
-O-P-O-R" =
α
-Form
OH
R" = CH
2
-CH
2
-N
+
(CH
3
)
3
Phosphatidylcholine
" = CH
2
-CH
2
-NH
+
Phosphatidylethanolamine
" = CH
2
-CH(NH
3
)-CO
2
H
+
Phosphatidylserine
" = C
6
H
6
-(OH)
6
Phosphatidylinositol
" = H
Phosphatidic acid
O
R' = -OP-OR" or Fatty acid
OH
R = Fatty acid
FIGURE 7.3
Several groups attached to the phosphate in phospholipids.
the phosphatide molecules at the surface of the oil or water droplets act as barriers
that prevent the droplets from coalescing and then they stabilize the emulsion.
1
The
following discussion deals with the major functional uses of lecithin products:
1.
its functionality as emulsifier in food emulsions
2.
its ability to solubilize various compounds in aqueous systems
3.
its sol dispersing power
4.
its foaming and defoaming activity
Emulsifier in Foam Emulsions
Examples of food emulsions include milk, butter, margarine, puddings, chocolate,
bakery items, cheese, milk, replacers, and ice creams.
Crude lecithins are excellent water-in-oil (dispersed phase is water, continuous
phase is oil) emulsifiers. However, modified lecithins can function to emulsify either
water-in-oil or oil-in-water emulsions, depending on the type of lecithin modification
and the specific parameters of a system. These system parameters can include pH,
types of components, and component ratios as well as solid content. Unlike crude
lecithins, hydroxylated lecithins are stable in acid systems (pH <3.5). Fractionated
lecithins can be manufactured for specific types of emulsion. Since lecithin emul-
sifying activity is dependent on its phosphatide ratios, changing the ratio can alter
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