Refrigerator
Refrigerator

Ice cream maker

A domestic ice cream maker is a machine used to make small quantities of ice cream for personal consumption. Ice cream makers may prepare the mixture by employing the hand-cranking method or by employing an electric motor. The resulting preparation is often chilled through either pre-cooling the machine or by employing a machine that freezes the mixture.
Ice cream makers may prepare the mixture by employing the hand-cranking method or by employing an electric motor. The resulting preparation is often chilled through either pre-cooling the machine or by employing a machine that freezes the mixture. An ice cream maker has to simultaneously freeze the mixture while churning it so as to aerate the mixture and keep the ice crystals small (less than 50 m). As a result, most ice creams are ready to consume immediately. However, those containing alcohol must often be chilled further to attain a firm consistency. Some machinesīsuch as certain lower-priced countertop modelsīrequire the resulting mixture to be frozen for additional time after churning is complete.
Hand-cranked machines' ice and salt mixture must be replenished to make a new batch of ice cream. Usually, rock salt is used. The salt causes the ice to melt and lowers the temperature in the process, below fresh water freezing, but the water does not freeze due to the salt content. The sub-freezing temperature helps slowly freeze and make the ice cream. Some small manual units comprise a bowl with coolant-filled hollow walls. These have a volume of approximately one pint (500 ml). The paddle is often built into a plastic top. The mixture is poured into the frozen bowl and placed in a freezer. The paddles are hand-turned every ten minutes or so for a few hours until reaching the desired consistency and flavor.
Counter-top machines use a double-walled bowl with a solution between the walls (typically distilled water and urea) that freezes below 32 ĀF (0 ĀC). In a domestic freezer, this requires up to 24 hours before the machine is ready. Once frozen, the bowl is put into the machine, the mixture is added to the bowl, and the machine started. The paddles rotate, stirring the mixture as it gradually freezes through contact with the frozen bowl. After twenty to thirty minutes, the solution between the double walls thaws, and the ice cream freezes. This type of machine has the advantage of being relatively inexpensive; however, a pre-frozen bowl makes only one batch at a time. The bowl must be refrozen to make another batch. Multi-batches require extra bowls for the machine, which require extra freezer space.
The fourth type of electric ice cream maker uses an outer tub filled with ice and salt for chilling. An inner canister holds the ice cream mixture and churn and scraper assembly. A high-speed electric motor, geared at approximately 75RPM, drives a mechanism that simultaneously rotates the canister, counter-rotates the scraper, and holds the churn paddles stationary. As the canister turns, the ice cream mixture freezes against the inner wall of the canister. The counter-rotating scraper constantly removes the frozen product from the canister wall and returns it to the mixture. The continuing turning motion of the canister against the stationary churn paddles causes the mixture to become increasingly thick. Enough time, ice and salt produces a smooth "hard packed" ice cream.