chloride, calcium chloride, sodium chloride, aluminum chloride, aluminum
sulfate, sodium sulfate, magnesium sulfate, sodium acetate, potassium
tartrate, sodium potassium tartrate, calcium phosphate (monobasic and
secondary), sodium and potassium phosphate. However, some produce a
firmer coagulum than others, for with each salt a definite concentration
brings about optimum coagulation. If the distilled-water custard is heated
to 83°-86° before the salt is added, and the salt is then added, coagulation
occurs; but when the mixture is stirred, curdling occurs to a greater or
lesser extent. A milk-salt mixture, such as the Sherman or Steenbock formu-
las used in animal-feeding experiments, in the right concentration forms a
coagulum in distilled-water custards that is similar in consistency to that
produced by milk custards.
Concentration and valence of added salts. If the effect of electrolytes
upon hydrophobic and hydrophilic colloids is referred to in Chapter I, the
statement is found that the precipitation of the protein is brought about
by the ion having the opposite charge from that of the protein. In general,
the coagulating power of the ion increases with increasing valence, but
there are some exceptions to this rule, some monovalent ions being more ef-
fective than some polyvalent ions. In many cases there is a zone of maximum
coagulating effect. The effect of the concentration of the salt upon the
coagulation of the egg can be shown in the following way. If less than 1/16
teaspoon of ferric or aluminum chloride is added to an egg, a cup of distilled
water and 2 tablespoons of sugar, the custard coagulates on heating to 84°C.,
though the coagulum is not so firm as when milk is used. However, if a
larger quantity of ferric or aluminum chloride is added to the mixture,
about ]/^ teaspoon or more, the custard does not coagulate when heated to
84° C. The reaction of the custard mixture with the small amount of
aluminum or ferric chloride given above is slightly acid to litmus, and
the larger quantities are decidedly acid to litmus. Hence, the larger quantity
of ferric chloride must peptize the egg proteins.
Woodruff and Meyer found that sodium chloride, sodium sulfate, and
calcium chloride, when used in 0.2 M concentration, produced gels of
approximately equal strength and slightly weaker gels than milk. Mag-
nesium chloride and sodium thiocyanate produced stronger gels than milk.
They concluded that the difference in strength of gels formed by various
electrolytes seemed to be a specific function of the cation and anion of
the salt, and independent of the /»H of the solution. Increasing the concentra-
tion of each salt gave gels of greater strength until a maximum strength was
reached, after which further increases of the salt reduced the gel strength.
The relation of reaction to setting of custards. If hydrochloric acid is
added to the egg-distilled-water custard, so that the reaction is adjusted to
a /»H above the isoelectric point of egg albumin, pH 4.8, coagulation occurs
within the range of pH 5 to 6. The coagulum is soft and not quite so firm
336 EGG COOKERY
as when salts are added, but it shows that a definite acidity tends to aid
coagulation.
The coagulation of egg-distilled-water custard with added salt is some-
what similar to the jellying of fruit jells in that it occurs at a definite
range of pH.
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chloride, calcium chloride, sodium chloride, aluminum chloride, aluminum
sulfate, sodium sulfate, magnesium sulfate, sodium acetate, potassium
tartrate, sodium potassium tartrate, calcium phosphate (monobasic and
secondary), sodium and potassium phosphate. However, some produce a
firmer coagulum than others, for with each salt a definite concentration
brings about optimum coagulation. If the distilled-water custard is heated
to 83°-86° before the salt is added, and the salt is then added, coagulation
occurs; but when the mixture is stirred, curdling occurs to a greater or
lesser extent. A milk-salt mixture, such as the Sherman or Steenbock formu-
las used in animal-feeding experiments, in the right concentration forms a
coagulum in distilled-water custards that is similar in consistency to that
produced by milk custards.
Concentration and valence of added salts. If the effect of electrolytes
upon hydrophobic and hydrophilic colloids is referred to in Chapter I, the
statement is found that the precipitation of the protein is brought about
by the ion having the opposite charge from that of the protein. In general,
the coagulating power of the ion increases with increasing valence, but
there are some exceptions to this rule, some monovalent ions being more ef-
fective than some polyvalent ions. In many cases there is a zone of maximum
coagulating effect. The effect of the concentration of the salt upon the
coagulation of the egg can be shown in the following way. If less than 1/16
teaspoon of ferric or aluminum chloride is added to an egg, a cup of distilled
water and 2 tablespoons of sugar, the custard coagulates on heating to 84°C.,
though the coagulum is not so firm as when milk is used. However, if a
larger quantity of ferric or aluminum chloride is added to the mixture,
about ]/^ teaspoon or more, the custard does not coagulate when heated to
84° C. The reaction of the custard mixture with the small amount of
aluminum or ferric chloride given above is slightly acid to litmus, and
the larger quantities are decidedly acid to litmus. Hence, the larger quantity
of ferric chloride must peptize the egg proteins.
Woodruff and Meyer found that sodium chloride, sodium sulfate, and
calcium chloride, when used in 0.2 M concentration, produced gels of
approximately equal strength and slightly weaker gels than milk. Mag-
nesium chloride and sodium thiocyanate produced stronger gels than milk.
They concluded that the difference in strength of gels formed by various
electrolytes seemed to be a specific function of the cation and anion of
the salt, and independent of the /»H of the solution. Increasing the concentra-
tion of each salt gave gels of greater strength until a maximum strength was
reached, after which further increases of the salt reduced the gel strength.
The relation of reaction to setting of custards. If hydrochloric acid is
added to the egg-distilled-water custard, so that the reaction is adjusted to
a /»H above the isoelectric point of egg albumin, pH 4.8, coagulation occurs
within the range of pH 5 to 6. The coagulum is soft and not quite so firm
336 EGG COOKERY
as when salts are added, but it shows that a definite acidity tends to aid
coagulation.
The coagulation of egg-distilled-water custard with added salt is some-
what similar to the jellying of fruit jells in that it occurs at a definite
range of pH.