This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
To determine the effect of the rate of turning on the texture of ice cream.
Directions for freezing experiments:
The freezers for the following experiments should be in good working order. The dashers should turn and scrape the crystals from the side of the can as they are formed.
To find the approximate swell of the ice cream the depth of the mixture should be measured in the can before and after freezing. If the depth is 2 inches before freezing and 3 inches after freezing the approximate swell is 50 per cent. The frozen mixture is not level across the top, so this method gives only an approximate measure of the swell.
Before the freezer is packed, the dasher, lid, and handle should be put in place. Otherwise in packing the can is often pushed to one side and it is difficult to get the handle in place. See that the handle turns properly.
Measure the approximate amount of ice and salt required for your particular experiment. For a freezer of 1-quart capacity, and using the proportions 1 part of salt to 8 parts of ice by measure, about 10 cups of ice are required for freezing. This will sometimes pack or partially pack the freezer also. Consult the instructor for the method to use for mixing ice and salt to place in the freezer. More uniform results are obtained with class work by mixing the salt and ice before placing in the freezer unless uniform methods of packing are employed. The better way of packing is to measure the ice required to pack the freezer half way to the top. Then add a layer of salt, using 1/8 of the measure of the ice. Add a layer of ice to 3/4 the distance from the top. Add a layer of salt, again using 1/8 the amount of the ice. Add ice nearly to the top of the can and the same proportions of salt. If the ice and salt are not measured, different amounts will be used for the different groups and the results will not be uniform, for the variables of the same experiments will increase.
Remove the handle and lid after the ice is packed and add the mixture to be frozen. If the freezer is the type that will freeze with the lid off, leave the lid off and adjust the handle. By freezing in this way the ice and brine will not come to the top of the can, but if not more than 1 cup of the mix is used in a quart freezer the frozen mixture will not come more than half way up the can, and the ice and salt will be sufficient for freezing.
Record the total time of turning the freezer and the time when the first crystals are formed; notice when the swell begins. Turn until the frozen mixture is the consistency of good thick gravy. Compare with your neighbors' so that all will be of the same consistency when the freezing period is stopped.
If the freezer will not turn with the lid removed, the end point of the freezing will need to be determined by removing the lid. Compare with your neighbors' so that as nearly as possible all will be of the same consistency when the creams are packed. If the lids of the freezers cannot be removed, neither the swell nor the time when the first crystals form can be observed. Nor can the time required for freezing be estimated very accurately. The results are less uniform with this type of freezer and sometimes are not worth while. Obviously, if some freezers are not in working condition the results from them should not be recorded. If the dashers do not work properly then the results can be used for slow-turning freezers.
Remove the dasher, put on the lid, plug the hole in the top of the lid and pack to harden. If the period of hardening can be only a short one, a larger proportion of salt to ice may be used for packing. Consult the instructor for the proportions.
Freezing mixtures that contain the same proportion of ingredients will have the same freezing point. Take the temperature while freezing in the can that is turned slowly. Since it is to be turned slowly the results for it will not be affected if the turning is stopped while the freezing temperature is taken.
Take the temperature of each of the frozen mixtures before tasting. During hardening some of the frozen mixtures may reach lower temperatures than others. Why? Because of this lower temperature they will be harder and colder. If possible they should be the same temperature before tasting. If they are not the same temperature in tasting do not confuse coldness and firmness of body with texture. The body should be firm and the texture smooth and velvety, that is, the crystals should be small and the cream should not be buttery.
An electrically operated freezer is preferable for many of the freezing experiments, as the rate of turning can be kept uniform. But unless it has different speeds, it cannot be used for determining the effect of rate of turning the freezer.
It is better for two girls to work together for each of the freezing experiments.
240 grams 37.5 grams
Use coffee cream containing 18 to 20 per cent fat. Dissolve the sugar in the cream. Add vanilla and freeze.
1. Turn slowly all the time: about 40 turns or less per minute.
2. Turn slowly at first, then rapidly while freezing; 40 turns or less per minute at first, then about 100 turns per minute.
3. Turn rapidly all the time: about 100 turns per minute.
The following headings are suggested for records of the freezing experiments. After all the experiments have been performed, write a summary of your conclusions and applications.
Time to freeze
Swell Per cent
Temperature of mix when tasted
To determine the effect of the richness of the cream used in making ice cream.
Use the same proportions given in Experiment 12. Use 1 part of salt to 8 of ice. Turn slowly at first, then rapidly during the freezing period, or use an electric freezer.
1. Use cream containing 18 per cent fat.
2. Use cream containing 24 per cent fat. If equal quantities of coffee cream (18 to 20 per cent) and whipping cream (30 to 32) are mixed, a cream with approximately 24 per cent of fat will be obtained.
3. Use a cream containing 30 per cent fat.
Does the amount of fat affect the freezing point? What would be the effect of a longer freezing period on the creams with a high fat content? Would it be advantageous to use a smaller proportion of salt for freezing these ice creams?