Fig. 26. — A coarse emulsion of oil In egg white. Egg white will not foam If a fat
like butter or lard Is added to It, but with oil both an emulsion and a foam are
formed when beaten with an egg beater. The large light spheres are air bubbles.
The oil Is stained red and appears dark in the photomicrograph. This photomicro-
graph is interesting for it shows the adsorption or concentration of the oil at the
interface between a gas and a liquid (egg white). This adsorption of fat can be
seen In later Illustrations of cake batter.
Magnification approximately x 135.
Lard and Crisco form rather unstable emulsions with egg white, but
both types may be formed.
With a saturated casein solution as the emulsifier, the water-in-oil type
of emulsion predominates when butter, lard, Crisco, and oil are used. The
emulsions are rather coarse and unstable.
EfBciency o£ different substances as emulsifiers. Some emulsify-
ing agents are more efficient than others. No study has been made to
compare the efficiency of the various emulsifiers under different conditions
and for different emulsions. As a class, the hydrophilic colloids seem to be
the most efficient emulsifiers. Clark and Mann have reported the efficiency
of sucrose, dextrin, starch, gum arable, and egg albumin in emulsions of
benzene and kerosene in water. The oils composed 75 per cent of the total
STABILIZATION BY POWDERS 273
volume In each case. The emulsions were made by shaking In a bottle, the
oil being added in 3 parts and a total of 4800 shakes used in making the
emulsion. They examined the emulsions after standing 1, 4, and 7 weeks
and ranked the emulsifiers for stability on a scale of 10.
With benzene and a 1 per cent solution of each emulsifier the order was
as follows: egg albumin, 10; starch, 6; gum arable, 5; dextrin, 3; sucrose,
0. With kerosene the order was as follows: egg albumin, 10; starch, 9;
gum arable, 3 ; dextrin, 2 ; sucrose, 2.
Clark and Mann also determined the efficiency of the above emulsifying
agents in the presence of electrolytes. In some cases the electrolytes in-
creased the viscosity; in others they lowered It. They concluded that "no
one general rule can be made as to the effect which produces the best
emulsions for any one substance nor can any one generalization be made
for the effect which produces the best emulsion for all substances under
all conditions. Those which seem to be of primary importance are viscosity
and film formation."
Brooks reports that egg yolk is four times more efficient in mayonnaise
than egg white.
Types of Emulsifying Agents
Emulsions may be stabilized by different substances. They may be classi-
fied as follows, the basis being upon the type of emulslfier : ( 1 ) those
stabilized by an electric charge, (2) those stabilized by colloids, and (3)
those stabilized by powders.
Stabilization of emulsion by an electric charge. Mineral oil emul-
sions in which the oil is present In very small amounts belong in the group
stabilized by an electric charge. The oil particles are negatively charged.
Hydrophilic sols are stabilized by hydration and an electric charge. Ghosh
and Dhar suggest that emulsions are similar to sols and that the stability,
the separation or coagulation, and the reversal of the emulsion are markedly
Influenced by its electric charge.
Page 220
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Fig. 26. — A coarse emulsion of oil In egg white. Egg white will not foam If a fat
like butter or lard Is added to It, but with oil both an emulsion and a foam are
formed when beaten with an egg beater. The large light spheres are air bubbles.
The oil Is stained red and appears dark in the photomicrograph. This photomicro-
graph is interesting for it shows the adsorption or concentration of the oil at the
interface between a gas and a liquid (egg white). This adsorption of fat can be
seen In later Illustrations of cake batter.
Magnification approximately x 135.
Lard and Crisco form rather unstable emulsions with egg white, but
both types may be formed.
With a saturated casein solution as the emulsifier, the water-in-oil type
of emulsion predominates when butter, lard, Crisco, and oil are used. The
emulsions are rather coarse and unstable.
EfBciency o£ different substances as emulsifiers. Some emulsify-
ing agents are more efficient than others. No study has been made to
compare the efficiency of the various emulsifiers under different conditions
and for different emulsions. As a class, the hydrophilic colloids seem to be
the most efficient emulsifiers. Clark and Mann have reported the efficiency
of sucrose, dextrin, starch, gum arable, and egg albumin in emulsions of
benzene and kerosene in water. The oils composed 75 per cent of the total
STABILIZATION BY POWDERS 273
volume In each case. The emulsions were made by shaking In a bottle, the
oil being added in 3 parts and a total of 4800 shakes used in making the
emulsion. They examined the emulsions after standing 1, 4, and 7 weeks
and ranked the emulsifiers for stability on a scale of 10.
With benzene and a 1 per cent solution of each emulsifier the order was
as follows: egg albumin, 10; starch, 6; gum arable, 5; dextrin, 3; sucrose,
0. With kerosene the order was as follows: egg albumin, 10; starch, 9;
gum arable, 3 ; dextrin, 2 ; sucrose, 2.
Clark and Mann also determined the efficiency of the above emulsifying
agents in the presence of electrolytes. In some cases the electrolytes in-
creased the viscosity; in others they lowered It. They concluded that "no
one general rule can be made as to the effect which produces the best
emulsions for any one substance nor can any one generalization be made
for the effect which produces the best emulsion for all substances under
all conditions. Those which seem to be of primary importance are viscosity
and film formation."
Brooks reports that egg yolk is four times more efficient in mayonnaise
than egg white.
Types of Emulsifying Agents
Emulsions may be stabilized by different substances. They may be classi-
fied as follows, the basis being upon the type of emulslfier : ( 1 ) those
stabilized by an electric charge, (2) those stabilized by colloids, and (3)
those stabilized by powders.
Stabilization of emulsion by an electric charge. Mineral oil emul-
sions in which the oil is present In very small amounts belong in the group
stabilized by an electric charge. The oil particles are negatively charged.
Hydrophilic sols are stabilized by hydration and an electric charge. Ghosh
and Dhar suggest that emulsions are similar to sols and that the stability,
the separation or coagulation, and the reversal of the emulsion are markedly
Influenced by its electric charge.