Final answer:
For the quick-mix method in ice cream making, both the liquid and fat components need to be sufficiently cold to freeze properly. Adding salt to water and ice reduces the mixture's freezing point, aiding in the ice cream's solidification. The exact freezing point can be calculated using the colligative properties of the solution.
Step-by-step explanation:
When using the quick-mix method to make homemade ice cream, the temperature of liquid and fat should be cold enough to ensure proper freezing and consistency of the ice cream. Typically, fat should be solid at room temperature to emulsify properly, but when making ice cream, both the fat and the liquid should start at a lower temperature. As explained in the quick-mix method, when ice and salt (NaCl) are combined, the salt lowers the freezing point of water, allowing the mixture to reach temperatures below 0°C, which is necessary for freezing the ice cream mixture. For the given instruction of adding one part salt to 11 parts water by mass, the exact freezing point of the solution can be calculated using the formula derived from the colligative properties of solutions. The dissociation of NaCl into ions in the solution will decrease the freezing point below the normal 0°C freezing point of water, ideal for making ice cream.