Dahlberg, Carpenter, and Hening found that the gel strength was
greater in milk than in water, even when the proportion of gelatin added
to the milk was based on the water content of the milk and not on its total
volume or weight. They found that the change in hydrogen-ion concen-
tration did not account for this increase in jelly strength in all the samples.
The other factors that might influence the jelly strength were the salt
and protein content of the milk. They state that the "influence of salts
on gel strength has been observed by other investigators, so it may be one
of the means by which skim milk altered gel strength."
Sugar. Small amounts of non-electrolytes do not appreciably affect
the viscosity of gelatin solutions, but in large quantities sugar increases
the viscosity, as a thick sugar sirup is more viscous than a thin one. Loeb
has reported that cane sugar does not diminish the viscosity of gelatin solu-
tions, but at concentrations of M/S or over may increase it slightly. The
sugar has a similar effect upon the stiffening power. Some concentrations
of sugar do not seem to affect the stiffening power, but others do. Ostwald
186 GELATIN
states that 1 gram of sugar added to 9 cc. of a 6 per cent gelatin solution
accelerates gelation. This would give about 10 per cent of sugar in the
solution. Larger quantities of sugar may retard gelation.
Opacity in gelatin. Edwards states that two factors of prime impor-
tance in gelatin are its strength and clarity of aqueous solution. In regard
to clarity he says that many perplexing problems occur in this connection,
for a gelatin may be clear at one concentration but, if further diluted,
may appear turbid. He says that a complete explanation of the problem
of turbidity has yet to be made, but some causes are as follows : ( 1 ) actual
dirt, particles of animal tissue and fibers, (2) mold, (3) emulsified grease
and calcium salts of fatty acids, (4) protein salts and proteins other than
gelatin which precipitate and remain in suspension when the /)H of the
solution is varied, (5) a calcium sulfate-phosphate complex which is re-
tained in solution by the presence of sulfurous acid, and (6) colloidal sulfur.
Edwards states that the first two enumerated difficulties should not be
present and when detected the gelatin should be condemned. Emulsified
grease is more difficult to remove. It results from the employment of
greasy material, extraction of gelatin at the wrong pH, the agitation of
liquid in the boiling vat, and improper filtration. The presence of proteins
other than gelatin is more likely to occur in a skin gelatin. Mucin and
chondrin are readily soluble in weak alkalies and are thrown out of solu-
tion by acids. Hence they are less likely to be found in acid gelatins.
Cloudiness due to the presence of insoluble calcium sulfate-phosphate com-
plex is more likely to be found in ossein gelatins. Colloidal sulfur is more
likely to be found in glue than in gelatin stock.
Gelatin is used in the meat trade for packing tongues, chickens, and
glazing hams. Sometimes a cloudy precipitate appears which is caused by
too much calcium in the gelatin.
Black mentions that unless the copper content of the gelatin is low a
purplish discoloration may appear with meats and particularly with
chicken and tongues.
Page 151
Presented as published in 1932. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
A modernized reading is not available for this page yet. You are seeing the original text.
Dahlberg, Carpenter, and Hening found that the gel strength was
greater in milk than in water, even when the proportion of gelatin added
to the milk was based on the water content of the milk and not on its total
volume or weight. They found that the change in hydrogen-ion concen-
tration did not account for this increase in jelly strength in all the samples.
The other factors that might influence the jelly strength were the salt
and protein content of the milk. They state that the "influence of salts
on gel strength has been observed by other investigators, so it may be one
of the means by which skim milk altered gel strength."
Sugar. Small amounts of non-electrolytes do not appreciably affect
the viscosity of gelatin solutions, but in large quantities sugar increases
the viscosity, as a thick sugar sirup is more viscous than a thin one. Loeb
has reported that cane sugar does not diminish the viscosity of gelatin solu-
tions, but at concentrations of M/S or over may increase it slightly. The
sugar has a similar effect upon the stiffening power. Some concentrations
of sugar do not seem to affect the stiffening power, but others do. Ostwald
186 GELATIN
states that 1 gram of sugar added to 9 cc. of a 6 per cent gelatin solution
accelerates gelation. This would give about 10 per cent of sugar in the
solution. Larger quantities of sugar may retard gelation.
Opacity in gelatin. Edwards states that two factors of prime impor-
tance in gelatin are its strength and clarity of aqueous solution. In regard
to clarity he says that many perplexing problems occur in this connection,
for a gelatin may be clear at one concentration but, if further diluted,
may appear turbid. He says that a complete explanation of the problem
of turbidity has yet to be made, but some causes are as follows : ( 1 ) actual
dirt, particles of animal tissue and fibers, (2) mold, (3) emulsified grease
and calcium salts of fatty acids, (4) protein salts and proteins other than
gelatin which precipitate and remain in suspension when the /)H of the
solution is varied, (5) a calcium sulfate-phosphate complex which is re-
tained in solution by the presence of sulfurous acid, and (6) colloidal sulfur.
Edwards states that the first two enumerated difficulties should not be
present and when detected the gelatin should be condemned. Emulsified
grease is more difficult to remove. It results from the employment of
greasy material, extraction of gelatin at the wrong pH, the agitation of
liquid in the boiling vat, and improper filtration. The presence of proteins
other than gelatin is more likely to occur in a skin gelatin. Mucin and
chondrin are readily soluble in weak alkalies and are thrown out of solu-
tion by acids. Hence they are less likely to be found in acid gelatins.
Cloudiness due to the presence of insoluble calcium sulfate-phosphate com-
plex is more likely to be found in ossein gelatins. Colloidal sulfur is more
likely to be found in glue than in gelatin stock.
Gelatin is used in the meat trade for packing tongues, chickens, and
glazing hams. Sometimes a cloudy precipitate appears which is caused by
too much calcium in the gelatin.
Black mentions that unless the copper content of the gelatin is low a
purplish discoloration may appear with meats and particularly with
chicken and tongues.