Concentration. With a definite temperature and time, solidification
occurs only with a definite concentration. With increasing concentration
of gelatin the time for setting is shortened. The amount of liquid that
a gram of dry gelatin can bind and hold in the form of a gel is high, 1 to
2 grams forming a gel with 99 to 98 grams of water.
Ostwald states, that the solidification of gelatin in Yi hour depends upon
the mode of preparation, but usually requires about 2 per cent at 15°C.
"SEEDING" GELATIN SOLS 183
and 1 per cent at 0°C. To serve as food the concentration should not be
too high, or the jelly is too stiff to be desirable. Some food gelatins pro-
duce a desirable texture for serving w^ith a 1.5 per cent concentration,
some require 2 per cent, and some may require as much as 3 or 4 per cent.
Manufacturers often place a quantity of gelatin in a packet or envelope
and state the amount of vrater to be used with it. This amount of w^ater
is an average amount required under all conditions for cooling. In some
instances it might be desirable to change it, on account of variation in
proportion of ingredients or variation in temperatures at which it solidifies,
or for other reasons. Recipes containing sauces thickened with egg or
starch do not need so high a concentration of gelatin.
It is preferable to use bulk or sheet gelatin by weight, rather than by
measure. On account of differences in the size of the gelatin particles,
a definite measure does not yield the same weight, hence a different concen-
tration of the gelatin would be used.
Temperature. With a definite concentration and time for setting, solidi-
fication occurs only with a definite temperature. For a high solidifying
temperature a high concentration of gelatin is required. The slower a
gelatin solution is cooled, the higher the temperature at which it solidifies.
A gelatin solution may be cooled down, by packing ice around its container,
to a temperature below that at which setting would occur if a longer
time is allowed. On the other hand, gelatin solutions may be mixed and
left standing for 2 or 3 hours at room temperature. If they are then put
in ice or the refrigerator they set quite rapidly and as if gel nuclei might
have started to form while standing at room temperature. At low tempera-
tures all gelatins become firmer. At high temperatures they are liquid,
for no gel occurs at temperatures above 35 °C. with any concentration of
gelatin. With the same concentration one gel may set at 10°C., another
at 12°, still another at 14° to 16°C., and others require lower tempera-
tures for setting. The gelatins that set at higher temperatures show jellies
of greater firmness than those that set at low temperatures. The ones
requiring lower temperatures than 10°C. to set do not serve very well,
for they also soften at a low temperature.
Page 148
Presented as published in 1932. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
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Concentration. With a definite temperature and time, solidification
occurs only with a definite concentration. With increasing concentration
of gelatin the time for setting is shortened. The amount of liquid that
a gram of dry gelatin can bind and hold in the form of a gel is high, 1 to
2 grams forming a gel with 99 to 98 grams of water.
Ostwald states, that the solidification of gelatin in Yi hour depends upon
the mode of preparation, but usually requires about 2 per cent at 15°C.
"SEEDING" GELATIN SOLS 183
and 1 per cent at 0°C. To serve as food the concentration should not be
too high, or the jelly is too stiff to be desirable. Some food gelatins pro-
duce a desirable texture for serving w^ith a 1.5 per cent concentration,
some require 2 per cent, and some may require as much as 3 or 4 per cent.
Manufacturers often place a quantity of gelatin in a packet or envelope
and state the amount of vrater to be used with it. This amount of w^ater
is an average amount required under all conditions for cooling. In some
instances it might be desirable to change it, on account of variation in
proportion of ingredients or variation in temperatures at which it solidifies,
or for other reasons. Recipes containing sauces thickened with egg or
starch do not need so high a concentration of gelatin.
It is preferable to use bulk or sheet gelatin by weight, rather than by
measure. On account of differences in the size of the gelatin particles,
a definite measure does not yield the same weight, hence a different concen-
tration of the gelatin would be used.
Temperature. With a definite concentration and time for setting, solidi-
fication occurs only with a definite temperature. For a high solidifying
temperature a high concentration of gelatin is required. The slower a
gelatin solution is cooled, the higher the temperature at which it solidifies.
A gelatin solution may be cooled down, by packing ice around its container,
to a temperature below that at which setting would occur if a longer
time is allowed. On the other hand, gelatin solutions may be mixed and
left standing for 2 or 3 hours at room temperature. If they are then put
in ice or the refrigerator they set quite rapidly and as if gel nuclei might
have started to form while standing at room temperature. At low tempera-
tures all gelatins become firmer. At high temperatures they are liquid,
for no gel occurs at temperatures above 35 °C. with any concentration of
gelatin. With the same concentration one gel may set at 10°C., another
at 12°, still another at 14° to 16°C., and others require lower tempera-
tures for setting. The gelatins that set at higher temperatures show jellies
of greater firmness than those that set at low temperatures. The ones
requiring lower temperatures than 10°C. to set do not serve very well,
for they also soften at a low temperature.