Directions for cooling gelatin. The gelatin solutions should be put to cool at the same temperature. Those from the same experiment should be on the same shelf in the refrigerator, as the upper shelves have a higher temperature than the lower ones. A cooling room is a splendid place to put them while cooling. For class work when periods are short the setting may be hastened by putting the containers in crushed ice. The ice should be the same depth around all the containers. It is better to have all the containers for one experiment in the same pan of ice for cooling. The containers should be the same size, shape, and material, for if they are not the same size the surface area for cooling will be greater for some than for others. Enamel or aluminum are good materials for cooling gelatin solutions. Crockery or china cools more slowly than metal.

The proportion of gelatin suggested in the following experiments, 3.5 grams for a cup of liquid, is not the best proportion for all gelatins. With some brands or grades about 2 per cent or about 4.8 grams per cup of liquid will be required for the best results. Find the best proportion of gelatin for the brand that is being used and substitute that amount for the amount given in the experiments. Use the same brand for all the experiments except Experiment 30.

Record the time and temperature when the gelatin is mixed, when it begins to gel around the edges, and when set. If cooled in crushed ice make a record of the temperature every 5 minutes and plot on graph paper. Find the effect on the texture of the gelatin of standing 20 minutes at room temperature. Most gelatins will need to stand at least 20 minutes or longer for serving.

Experiment 29

To determine the effect of dissolving gelatin by different methods on the time required for setting and the temperature at which gelation occurs.

A. Hydrate 3.5 grams of gelatin with 30 cc. of cold water. Add 206.5 cc. of boiling water. Stir until dissolved. Record the temperature when mixed and the time when mixed. Set in crushed ice. Record time and temperature every 5 minutes or more often until set. Plot on graph paper.

B. Hydrate 3.5 grams of gelatin with 30 cc. of cold water. Let stand 5 minutes, then melt over hot water. The temperature of the hot water should be 85 to 90°C. Stir the gelatin until melted, remove from above the hot water and add gradually while stirring 206.5 cc. of cold water. Follow directions for cooling under A.

C. Hydrate 3.5 grams of gelatin with 30 cc. of cold water for 5 minutes. Stir while adding 60 cc. of boiling water. After gelatin is dissolved add 131.5 cc. of cold water. Follow directions for cooling under A. Compare the length of time required for setting, the temperature at which setting occurs, and the ease of dissolving by each method.

What proportion of an ounce is 3.5 grams? What proportion of an envelope of gelatin? What is the measure in teaspoons? A total of 240 grams of liquid and gelatin is used. What proportion of 240 grams is 15 cc. ? What percentage is 3.5 grams?

Gelatin, grams

Gelatin, measure

Gelatin, per cent

Time required to set

Temperature when mixed

Temperature when set

Results and conclusions.

Experiment 30

To determine the stiffening power of different brands of gelatin.

Use as many different brands and kinds of gelatin as you can obtain. Use plain gelatin. If acidulated gelatins are used they should be compared with acidulated gelatins and not with plain ones. Notice the color and odor of each gelatin solution. Use a total of 240 grams of gelatin and liquid. Compare the length of time required to set and the firmness of the jellies. Do any of the gelatins require too long a time to set to serve in a reasonable time? Are any of the gelatins too firm?

1. Hydrate 3.5 grams of gelatin with 30 cc. of cold water. Dissolve by warming over hot water. Add 176.5 cc. of cold water, 30 cc. of lemon juice, and 50 grams of sugar. Follow directions under 29A for cooling.

2. Repeat 30,1, with as many different brands and grades of gelatin as have been obtained.

Brand of gelatin

Gelatin, per cent

Time to set

Temper-ature when mixed

Temper-ature when set

Texture

Color

Odor

Results and conclusions.

Experiment 31

To determine the effect of distilled water, fruit juices, tomato, and vinegar upon the stiffening power of gelatin and upon the time required for gelation. Use a plain gelatin.

A. Water.

1. Use tap water. Hydrate 3.5 grams of gelatin with 30 cc. of cold water. Follow directions for cooling under Experiment 29A.

2. Repeat A1, but use distilled water.

3. Repeat A1, but use softened water if obtainable.

B. Lemon juice.

1. Repeat A1, but reduce the cold water to 191.5 cc. and add 15 cc. of lemon juice.

2. Repeat A1, but reduce the cold water to 176.5 cc. and increase lemon juice to 30 cc.

3. Repeat A1, but reduce the cold water to 146.5 cc. and add 60 cc. of lemon juice.

4. Repeat A1, but reduce the cold water to 86.5 cc. and add 120 cc. of lemon juice.

C. Grape juice.

1. Repeat B1, but substitute grape juice for the lemon juice.

2. Repeat B2, but substitute grape juice for the lemon juice.

3. Repeat B3, but substitute grape juice for the lemon juice.

4. Repeat B4, but substitute grape juice for the lemon juice.

D. Tomato juice.

1. Repeat A1, but substitute tomato juice for the cold water.

E. Vinegar.

1. Repeat B2, but substitute vinegar for the lemon juice.

2. Repeat B3, but substitute vinegar for the lemon juice.

Gelatin, per cent

Time required to set

Temperature when set

Proportion of acid added

Color

Texture

Results and conclusions.

Experiment 32

To determine the effect of varying the percentage of gelatin upon the time required for gelation and the stiffness of the gelatin.

1. Hydrate 3.5 grams of gelatin with 30 cc. of cold water. Dissolve by warming over hot water. Add 176.5 cc. of cold water, 30 cc. of lemon juice, and 50 grams of sugar.

2. Repeat 32,1, but increase the gelatin to 4.8 grams and reduce the cold water to 174 cc. What is the percentage of gelatin used? Its measure?