A domestic ice cream maker or ice cream freezer is a machine used to make small quantities of ice cream at home. Ice cream makers may stir the mixture by hand-cranking or with an electric motor, and may chill the ice cream either by using a freezing mixture, by pre-cooling the machine in a freezer or by the machine itself refrigerating the mixture.
An ice cream maker must not only chill the mixture but also simultaneously stir or churn it to prevent the formation of ice crystals and aerate it to produce smooth and creamy ice cream. Most ice creams are ready to eat immediately, but some, especially those containing alcohol, must be chilled further in a freezer to attain a sufficiently firm consistency. Ice cream stored in a freezer usually needs to be removed 20 to 30 minutes before serving to soften it, partly to make it easier to serve and eat and partly because when ice cream is very cold, the flavour is impaired.
Some machines, such as certain low-priced counter-top models, require that the resulting mixture be frozen an extra four hours or more (or overnight), depending on the recipe, in order for the ice cream to harden to the desired consistency.
These machines usually comprise an outer bowl and a smaller inner bowl with a hand-cranked mechanism which turns a paddle, sometimes called a dasher, to stir the mixture. The outer bowl is filled with a freezing mixture of salt and ice: the addition of salt to the ice causes freezing-point depression; as the salt melts the ice, its heat of fusion allows it to absorb heat from the ice cream mixture, thus freezing the ice cream.
This type of ice cream maker is inexpensive, but inconvenient and messy as the ice and salt mixture produces a lot of salty water as it melts which the user must dispose of, and the ice and salt mixture has to be replenished to make every new batch of ice cream.
Some small manual units comprise a bowl with a capacity of about one pint (500ml) and with hollow walls which are filled with a coolant. 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 then turned by hand every ten minutes or so for a few hours until the desired consistency and flavour is reached.
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 a solution between the two walls that freezes below the freezing point of water. This is first frozen (empty, before adding any ingredients) 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.
'Placed inside the freezer'
The second type are small freezer-unit machines that sit inside the freezer (or the freezer part of the refrigerator), and operate in a similar way to a food processor but 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 or fluid coolant. 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 specialised 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 lithium batteries (most rechargeable batteries or regular alkaline cells perform very poorly at low temperature).
More expensive, and therefore much larger machines have a freezing mechanism built in and do not require the 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 which is usually impractical in a smaller kitchen.
If you own and regularly - or even occasionally - use an ice cream maker, let us know what make/model it is, its advantages and disadvantages and maybe even write a short review on the 'Discuss here' page. Thanks.
How to prevent home made ice cream from freezing solid in the freezer
Home made ice cream is usually reasonably soft and 'scoopable' straight out of the ice cream maker, but once it is placed in the freezer for more than a few hours it becomes a solid block of ice, effectively.
Unfortunately without using artificial additives it is not generally possible to keep it soft once you freeze it. I have tried many suggestions and they all fail miserably, apart from this one!
Place the hard-frozen ice cream in your refrigerator for 2 to 3 hours before you want to use it and re-freeze it immediately you have scooped out what you need.
Admittedly this does require some planning ahead, but it does mean you'll have usable ice-cream.