FoodNet

Experimental cookery

1932

Page 66

Presented as published in 1932. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
3. Make caramel or burnt-sugar icing by melting one-half the sugar to be used to a golden brown color. Then dissolve in water. Add the remainder of 82 SUGAR COOKERY the sugar, and the butter, and cook to the same temperatures used for choco- late fudge icing. Which temperature produces the best texture of icing? 4. Prepare boiled icing by pouring the cooked sirup over beaten egg white. Prepare an outline for making this type of icing, giving variations in tem- perature to which the sirup is cooked before adding to the egg white and the temperature to which the sirup is cooled before adding the sirup to the egg white. Vary the amount of sugar used for different proportions of egg. Consult any reference that you wish for making your outline and use the results of any of the sugar experiments. For a control use 1 cup sugar, 200 grams, ^ cup corn sirup, 82 grams, and y^ cup of water. Cook to 119° or 120°C. and pour slowly into 1 stiffly beaten egg white, beating as the sirup is added. For divinity beat until pieces dropped on wax paper will hold their shape. CHAPTER III FREEZING A pure liquid has a definite freezing point. In freezing the fluid changes from a liquid to a solid state. Water freezes at 0°C. or 32°F. Just as sugar solutions in cooling may give supersaturated solutions before crystallization starts, so water may be supercooled before it freezes. Furthermore, the conditions for supersaturation and supercooling are similar. For supersaturation the solution must not be agitated and no crystals must be added. If a test tube of water containing a thermometer is immersed in a mixture of ice and salt, the temperature of the water will drop to — 4°C. or lower. If the slightest movement is made or if a small crystal of ice is added the water will crystallize quickly, and the tempera- ture rises to 0°C., for water in freezing gives off heat. A gram of water changing from 0° to ice at 0°C. gives off 79.9 (or about 80) calories of heat. When the water has been supercooled, this heat of solidification elevates the temperature of the ice and liquid to 0°C. The heat of crystal- lization may be absorbed by the liquid or given off to the surroundings if the freezing liquid is not insulated. The Freezing Point of a Liquid The freezing point of a liquid cannot be defined as the temperature at which the liquid becomes a solid, for supercooled liquids are cooled below the freezing point. The freezing point and the melting point are identical, so that the freezing point may be defined as the temperature at which the solid melts. The freezing point of a liquid may also be defined as the temperature at which the solid and liquid are in equilibrium. Here equilib- rium means the temperature at which any proportion of solid and liquid can exist without change, that is, no solid melts and no liquid freezes. For water, this temperature is 0°C. Of course, equilibrium can exist for a long period of time only if the solid and liquid are completely insulated or if the temperature of the surroundings is at the freezing point of the liquid. If the temperature of the surroundings changes slightly above 0°C. so that heat is absorbed, some of the solid melts. If the temperature of the surroundings is below 0°C., so that heat is withdrawn from the mix- ture, the liquid freezes.