How Do Ice Cream Makers Work?

The Ice Cream Dillema

In essence, ice cream is a simple creation: cream from cow's milk is sweetened, flavored, perhaps mixed with texture or color agents and add-ins (such as nuts or chocolate chips) and frozen. However, if you've ever tried to create ice cream by placing a container of sweetened cream in the freezer, you'll know that the results of this process are unsatisfactory: a hard, frozen lump, one that stays full of crunchy crystals even if it melts enough to be edible.
In order to create the smooth, soft dessert we know and enjoy, a different process must be implemented: the cream mixture must be constantly mixed even as it is being frozen. This keeps the ice particles from forming in any way large enough to be noticeable, creating a frozen liquid in the consistency of a custard. An ice-cream maker, therefore, is any kind of machine that both mixes and freezes cream.

Technology

Ice-cream makers that consist of cordless, battery-powered mixers designed to be used inside a conventional home freezer are available but they are, surprisingly, relatively advanced creations in the evolution of ice-cream makers. This is both because the technology required for a battery of this power is relatively new, and because the machine requires a motion sensor that will stop the maker from mixing once the cold freezer temperatures cause the ice cream to become so thick that it would break the mixing paddles.
For this reason, more traditional ice-cream makers are still the norm, including makers very similar to those used in the days before modern electricity.

Cooling

Early ice-cream makers consisted of hand cranks that operated mixing paddles inside sealed containers of cream mixture. These containers were sealed to keep the cream cold while it was mixed, because it had to be submerged in a bucket of ice combined with salt. In the days before electricity, ice was harvested during the winter and stored in well-insulated areas, while salt was added because it had the effect of melting the ice without warming it, keeping the liquid surrounding the cream cold for a longer period of time.
Many modern home ice-cream makers are little different from those used in the 1800s, except that the mixing of the cream is now handled with a powered motor. Makers that use powered cooling work in much the same way, but without the need for salt or ice water. These types of makers are usually the kind found in commercial settings.