Dispersion systems inner phase outer phase a emulsion

Dispersion systems Inner phase Outer phase
a. Emulsion liquid liquids
b. Foaming Gaseous liquid
c. Aerosol liquid or solid Gaseous
d. Suspension solid liquid.
*Emulsifying action

*Foams induce stability
*Dispersion of solids or liquids in gases by Aerosols.
*Solid is dispersed in liquid by suspension.
Eg: Chocolate powder in milk
*Lubrication and reduces stickiness.
*Complexing: Surface active agents like mono & diglycerides react with
amylase & prevent retro gradation of amylase. Hence addition of
mono & diglycerides to bread dough before baking can prevent retro
gradation of amylase.
*Shortening: Shortenings are used in bakery & confectionary (2.5%
mono glycerides ) is used.
Emulsions & Emulsifiers:
Emulsions are dispersed systems, usually comprises of two immiscible
liquids, where the outer phase consists of water and the inner of oil, it
is considered as “oil in water” (O/W) type of emulsion. When this is
reversed i.e., water is dispersed in oil, a w/o emulsion exists.
eg., Milk (O/W)
Butter (W/ O)
Visual appearance of an emulsion depends on the droplet diameter.
If the diameter is in the range of 0.15 - 100μm the emulsion appears
milky – turbid. In comparison micro emulsions of diameter 0.015-0.15
μm are transparent and considerably more stable because the
sedimentation rate depends on the droplet diameter.
Emulsifiers are substances because of their molecular structure they
are deposited at the phase (inter phase) and help to stabilize the
phases. Each emulsifier can disperse a limited amount of an inner
phase, i.e., it has a fixed capacity. When the limit is reached further
addition of outer phase breaks down the emulsion.

Mechanism of action of Emulsifiers:
Emulsions are made and stabilized with the aid of a suitable tenside
(surfactant). The emulsifier molecule has at least one group with polar
affinity i.e., hydrophilic soluble in H
2
o and one group with lipophilic or
hydrophobic nature which is soluble in fat. Hydrophobic group is
usually a long chain or alkyl residue or fatty acids while hydrophilic part
of the molecule consists of a dissociable group or number of hydroxyl
or polyglucoether groups. Through the presence of hydrophilic &
lipophilic group in the molecule, emulsifiers interact with water & with
fats or oils.
The emulsifier is oriented at the phase interface with the
hydrophilic component going towards the water and the lipophilic
component towards oil. This causes a film to be formed which reduces
surface tension. In an immiscible system such as oil or water the
emulsifier is located on the interface, where it decreases interfacial
tension. It facilitates a fine distribution of one phase within the other.
The emulsifiers also prevent droplets once formed from aggregating &
coalescing i.e., merging into a single large drop.
CMC (Critical Micelle Concentration)
Or lyotrophic Mesomorphism
 CMC is a function of emulsifier concentration above which the
emulsifier aggregates, reversibly to give spherical micelle,
changing surface tension slightly.