This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
2. Repeat A1, but have the pint of water in the lower part of the double boiler boiling when the upper part is added. Regulate the heat to keep the water boiling very rapidly. Cook as quickly as possible, but not more than 6 minutes should be necessary. Record the temperature of the custard and the time just before putting the custard over the boiling water. If possible, record the temperature as under A1. The stirring should be rather rapid for the cooking is rapid. It will also take rapid work to remove the custard at the desired temperatures. Remove portions of the custard at temperatures given under A1.
Note the temperature before and during curdling of the slowly and rapidly cooked custards.
Does the temperature lag or drop in some instances? Prepare a time-temperature chart, showing the period of time required for custard for different groups and time intervals as follows. It will be found that the consistency of a given custard at a definite temperature, say 80°C, is directly proportional to the time required to heat it from 76° to 80°C. Compare thickening of custard for different groups, noting time required for each custard to reach a definite temperature. Also note curdling temperature and highest temperature reached.
Time to reach 76°C. Min.
76° to 78°
78° to 80°, etc.
A. Group 1, etc.
B. Group 1, etc.
Compare the consistency of the custards at each temperature. What is the effect of the rate of coagulation upon the amount coagulated at a definite temperature? Would you advise the rapid or the slow cooking? Why? Compare with baked custards heated to the corresponding temperatures.
B. Baked custards.
Prepare 2 times the recipe. Combine all the ingredients and mix thoroughly. Divide into 5 portions, using equal parts in each cup. Put all the cups in a large, flat pan. Set the pan in the oven. By supporting on an oven rack above the custards insert a right-angled meat thermometer, so that the bulb of the thermometer is at the center of one custard. Place a second thermometer so that the temperature of the water can be read. Start heating the oven and then pour boiling water around the custard cups until it comes as high as the custard in the cups. If the oven has a regulator so that a low temperature, 125° to 150°C. (250° to 300°F.) is maintained, the custards can be cooked without adding the water to the pan. Record the time and the temperature of the custard every 3 minutes if the oven has a glass door, otherwise every 5 minutes. Remove one custard of each series at the following temperatures: 82°, 83°, 84°, 85°, and 87°C.
C. To determine the effect of varying the proportion of ingredients in baked custard.
Follow directions under B. If possible, bake all the custards under B and C in the same pan. Prepare 2 times the recipe.
2. Use 1 egg, 1 cup of milk.
3. Use 1 egg, 1 cup of milk, 4 tablespoons of sugar.
4. Use 1 1/2 eggs, 1 cup of milk, 2 tablespoons of sugar.
Are all the custards for the same experiment of the same thickness or consistency? How might you account for this? Are the custards removed at 83°C. all of the same consistency? Compare the time required for cooking. Does the increased egg result in a thicker custard than when 1 egg is used? Compare the stiffness of custards made with the whites and the yolks. What is the effect of increasing the sugar? Which proportion of sugar is desirable for serving? Are any of the custards curdled? What is the optimum temperature for serving each custard?
Time of cooking
Consistency of custard at
To reach 80°C.
From 80° to 87°C.
D. To determine the effect of substituting yolks or whites for the whole egg.
Follow directions under B. Prepare 2 times the amount given below.
1. Use 2 yolks (36 grams), 1 cup of milk, 2 tablespoons of sugar.
2. Use 2 whites (60 grams), 1 cup of milk, 2 tablespoons of sugar.
Beat the whites only slightly before adding the milk. If beaten stiff they float on top of the milk and do not blend well with it. Also fill the cups to the same height as those containing the egg-yolk custard. Otherwise the larger quantity of egg-white custard will heat more slowly than the egg-yolk custard.
When egg yolks are substituted for the whole egg in the custard, compare the stiffness of the custards with those made from the whole egg cooked to the same temperature. Compare the flavor. The color. Compare with custards made of egg white.
E. To determine the factors that affect coagulation. Prepare 1/2 the recipe, using only 1 custard cup.
1. Use 1 egg, 1 cup of distilled water, 2 tablespoons of sugar.
2. Use 1 egg, 1 cup of distilled water, 2 tablespoons of sugar. Dissolve 1/3 teaspoon of calcium lactate in the distilled water before adding the egg and sugar.
3. Use 1 egg, 1 cup of distilled water, 2 tablespoons of sugar. Bake until the temperature at which D2 sets is reached. Remove from the oven and add 1/3 teaspoon of calcium lactate that has been moistened in a tablespoon of distilled water. Stir. What happens?
4. To 1 egg, 1 cup of distilled water, 2 tablespoons of sugar, add about 1/16 teaspoon or less of aluminum or ferric chloride. Mix the ferric or aluminum chloride with the distilled water; then add the beaten egg and the sugar. What happens when the egg is stirred in the mixture? Continue stirring for a few seconds.
5. Repeat El, but add 1/3 teaspoon of aluminum or ferric chloride. Does the custard coagulate during cooking? Test the custards with litmus paper.
6. To 1 egg, 1 cup of distilled water, and 2 tablespoons of sugar, add 1/4 teaspoon of salt.
7. Repeat E6, but omit the salt and add 1/3 teaspoon of a milk-salt mixture used in feeding rats.
8. To 1 egg, 1 cup of distilled water, and 2 tablespoons of sugar, add 1/2 teaspoon of lemon juice.
9. To 1 egg, 1 cup of distilled water, and 2 tablespoons of sugar, add 1 teaspoon of lemon juice.
F. To determine the effect of beating on thickening power of the egg.
1. Use 2 1/2 eggs. Beat in a bowl either by hand or with an electric mixer until the yolks and whites are well blended. Weigh out 48 grams and combine with 1 cup of milk and 2 tablespoons of sugar.
2. Beat the egg remaining from part F1 until thoroughly beaten. The egg can be beaten as long a period as desired. Weigh 48 grams of the egg. Discard the remaining egg. Combine the 48 grams with 1 cup of milk and 2 tablespoons of sugar. If the egg was beaten with an electric mixer, put milk in the mixer bowl and combine with the mixer. Does the egg tend to float on top of the milk? Bake according to directions under B.
3. Beat 1 egg slightly, so that the yolk and white are not well blended. Add to 1 cup of milk and 2 tablespoons of sugar.
What is the effect of increasing the egg upon temperature of coagulation? Of varying the proportion of sugar? Does the distilled-water custard set? What is the effect of adding calcium lactate? Salt? What is the reaction of the custard containing the small proportion of aluminum or ferric chloride? The one with the larger proportion? Does either set? Unless the proportion of ferric or aluminum chloride is small enough, E4 may not set.
Time of cooking
Results and conclusions.
G. Soft custards.
The series under C and D may be repeated and cooked as soft custards, or the baked custards may be omitted and the soft custards prepared instead. Prepare once the recipe and follow directions under A for cooking.