Ice cream churns the ice cream mixture while cooled inside a household freezer. Some more expensive models have an inbuilt freezing element. A newer method is to add liquid nitrogen to the mixture while stirring it using a spoon or spatula for a few seconds; a similar technique, advocated by Heston Blumenthal as ideal for home cooks, is to add dry ice to the mixture while stirring for a few minutes. Some ice cream recipes call for making a custard, folding in whipped cream, and immediately freezing the mixture. Another method is to use a pre-frozen solution of salt and water, which
Freeze-dried ice cream Freeze-dried ice cream Freeze-dried ice cream is ice cream that has had most of the water removed from it by a freeze-drying process, sealed in a pouch, and requires no refrigeration. It is also known as astronaut ice cream or space ice cream, typically a slab of ready-to-eat dehydrated ice cream. Compared to regular ice cream, it can be kept at room temperature without melting and is more brittle and rigid but still soft when bitten into. It was developed by Whirlpool Corporation under contract to NASA for the Apollo missions. However, it was never used on any Apollo mission.