edit] Electric machines

There are three types of electric ice cream machines. Each has an electric motor which drives either the bowl or the paddle to stir the mixture. The major difference between the three is in how the cooling is performed.

Counter-top machines use a double-walled bowl which contains between the two walls a solution that freezes below the freezing point of water. This is frozen in a domestic freezer for up to 24 hours before the machine is needed. Once frozen, the bowl is put into the machine, the mixture is added and the machine is switched on. The paddles rotate, stirring the mixture as it gradually freezes through contact with the frozen bowl. Twenty to thirty minutes later, the solution between the double walls of the bowl has thawed, and the ice cream has frozen. The advantage of this type of electric machine is low cost, typically under $100. The disadvantage of the pre-frozen bowl approach is that only one batch can be made at a time. To make another batch, the bowl must be frozen again. For this reason, it is usually possible to buy extra bowls for the machine, but of course these take up a lot of freezer space.

An ice cream maker that has to be placed inside the freezer.

Small freezer-unit machines sit inside the freezer (or the freezer part of the refrigerator), and operate similar to a food processor in slow-motion. The paddles turn every few seconds to stir the mixture enough to prevent large ice crystals from forming. When the ice cream has frozen sufficiently, the paddles automatically stop rotating and lift up. As the mixture is cooled simply through being in the freezer, it takes longer to freeze than other types of ice cream makers, which work by placing the ice cream bowl in direct contact with the cooling element. A disadvantage is that the freezer door has to be closed over the flat cord, which is plugged into the nearest power point outside, though some modern refrigerators have a built-in ice-cream maker as an accessory or a specialized electrical plug for use with certain freezer-unit machines. The advantage of this type of ice cream maker is that no pre-freezing of the appliance is necessary. However, some people feel that this type of machine produces a lower-quality ice cream because of its slow-motion method. It's also possible to get cordless, battery-operated ice-cream makers which can be placed directly in the freezer, though these tend to require expensive non-rechargeable potassium batteries (most rechargeable batteries or regular alkaline cells perform very poorly at low temperature).

More expensive, and much larger, machines have a freezing mechanism built in and do not require a bowl to be pre-chilled. The cooling system is switched on, and in a few minutes the mixture can be poured in and the paddle switched on. As with coolant-bowl machines, ice cream is ready in twenty to thirty minutes, depending on the quantity made. These machines can be used immediately with no preparation, and any number of batches of ice cream can be made without a delay between batches. Some of these machines cannot be moved without waiting twelve hours before use, as moving the unit upsets the coolant in its freezing system; they would normally be kept permanently positioned ready for use, impractical in a smaller kitchen.

Дата добавления: 2015-10-29