3. A cup of juice and ^ cup of sugar.
4. A cup of juice and 1 cup of sugar.
5. A cup of juice and 1J4 cups of sugar.
Some idea of the amount of sugar to use can be obtained from the
alcohol test. With gooseberry juice and using the larger quantity of
alcohol for the test, the approximate proportion of sugar required for a
cup of juice can be estimated from the character of the precipitated pectin.
After mixing, turn the pectin and alcohol out in a dish. If the pectin
precipitate can be picked up in one piece without breaking and feels firm,
about \%. to 1 1/3 cups of sugar will be required; if the pectin precipitate
can be picked up in one piece without breaking but does not feel firm,
about 1 to 1^ cups of sugar will be necessary; but if the precipitate breaks
into two pieces when picked up, about ^ to J^ cup of sugar is required.
If the precipitate is flocculent the juice needs concentrating or only ^2 cup
or less of sugar can be used. A still easier way to determine the best pro-
portion of sugar to add is to determine the viscosity with a jellmeter.
Sugar, pectin, acid, and salt. As can be ascertained from the previous
discussion there is a relation between proportion of pectin, sugar, acid,
and salts, temperature to which the pectin is heated, and time of pouring.
Increases and decreases of constituents may be made within certain limits.
Salts in the fruit juice or added to it may aid jelly formation or hinder
168
JELLY
and delay it, according to whether they tend to precipitate or stabilize the
pectin.
Inversion of sugar in jelly making. The saturation point of a
sucrose solution at room temperature or 20°C. is 67 per cent. Thus
jellies containing more than 67 per cent of sucrose at 20°C. are super-
saturated, unless something has occurred to the sugar. The pectin tends to
keep the sugar from crystallizing from solution, acting as a protective
colloid. But even this protective action would not always be great enough
to keep the sugar from crystallizing wdth a concentration of sugar that
is increased to 70 per cent or over. When sucrose is heated with acid, some
of the sucrose is inverted to dextrose and levulose. The amount of inverted
sugar formed during jelly making depends upon the acidity of the fruit
juice and the length of time of boiling with the sugar. Since there are
three sugars in the finished jelly the percentage or total sugar that can be
held in the finished jelly without crystallization occurring is increased.
Tarr and Baker report that in a solution containing a mixture of sucrose,
dextrose, and levulose, the total maximum solubility is obtained with the
proportions of each sugar show^n in Table 23 (obtained from Bureau of
Standards).
At 20°C. if inversion has occurred to obtain maximum solubility, about
75.7 per cent of sugar is soluble. Thus jelly containing about 70 per cent
of sugar is not necessarily supersaturated. The salts and organic con-
stituents of the fruit juice may also increase the solubility of the sugar
in a given solution.
Rate of inversion in different fruit juices. Tarr and Baker have
determined the rate of inversion of sucrose during jelly making with
equivalent solutions of sulfuric, tartaric, and citric acids. As would be
TABLE 23
Total Maximum Solubility with Cane Sugar and Invert Sugar
{Tarr and Baker)
Temperature,
°C.
Grams of cane sugar
per 100 grams
solution
Page 136
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
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3. A cup of juice and ^ cup of sugar.
4. A cup of juice and 1 cup of sugar.
5. A cup of juice and 1J4 cups of sugar.
Some idea of the amount of sugar to use can be obtained from the
alcohol test. With gooseberry juice and using the larger quantity of
alcohol for the test, the approximate proportion of sugar required for a
cup of juice can be estimated from the character of the precipitated pectin.
After mixing, turn the pectin and alcohol out in a dish. If the pectin
precipitate can be picked up in one piece without breaking and feels firm,
about \%. to 1 1/3 cups of sugar will be required; if the pectin precipitate
can be picked up in one piece without breaking but does not feel firm,
about 1 to 1^ cups of sugar will be necessary; but if the precipitate breaks
into two pieces when picked up, about ^ to J^ cup of sugar is required.
If the precipitate is flocculent the juice needs concentrating or only ^2 cup
or less of sugar can be used. A still easier way to determine the best pro-
portion of sugar to add is to determine the viscosity with a jellmeter.
Sugar, pectin, acid, and salt. As can be ascertained from the previous
discussion there is a relation between proportion of pectin, sugar, acid,
and salts, temperature to which the pectin is heated, and time of pouring.
Increases and decreases of constituents may be made within certain limits.
Salts in the fruit juice or added to it may aid jelly formation or hinder
168
JELLY
and delay it, according to whether they tend to precipitate or stabilize the
pectin.
Inversion of sugar in jelly making. The saturation point of a
sucrose solution at room temperature or 20°C. is 67 per cent. Thus
jellies containing more than 67 per cent of sucrose at 20°C. are super-
saturated, unless something has occurred to the sugar. The pectin tends to
keep the sugar from crystallizing from solution, acting as a protective
colloid. But even this protective action would not always be great enough
to keep the sugar from crystallizing wdth a concentration of sugar that
is increased to 70 per cent or over. When sucrose is heated with acid, some
of the sucrose is inverted to dextrose and levulose. The amount of inverted
sugar formed during jelly making depends upon the acidity of the fruit
juice and the length of time of boiling with the sugar. Since there are
three sugars in the finished jelly the percentage or total sugar that can be
held in the finished jelly without crystallization occurring is increased.
Tarr and Baker report that in a solution containing a mixture of sucrose,
dextrose, and levulose, the total maximum solubility is obtained with the
proportions of each sugar show^n in Table 23 (obtained from Bureau of
Standards).
At 20°C. if inversion has occurred to obtain maximum solubility, about
75.7 per cent of sugar is soluble. Thus jelly containing about 70 per cent
of sugar is not necessarily supersaturated. The salts and organic con-
stituents of the fruit juice may also increase the solubility of the sugar
in a given solution.
Rate of inversion in different fruit juices. Tarr and Baker have
determined the rate of inversion of sucrose during jelly making with
equivalent solutions of sulfuric, tartaric, and citric acids. As would be
TABLE 23
Total Maximum Solubility with Cane Sugar and Invert Sugar
{Tarr and Baker)
Temperature,
°C.
Grams of cane sugar
per 100 grams
solution