A nitrogen ice cream machine uses liquid nitrogen as its coolant. Because of the frigid temperatures involved, the ice forms only small crystals. Hypothetically, this should produce a creamier ice cream. Those who like nitrogen ice cream praise the smooth texture of the final product.
One stumbling block in the creation of nitrogen ice cream is the fact that the superchilled product tends to stick to a stainless steel mixing bowl, making lumps that definitely get in the way of that creamy texture. An important innovation in nitrogen ice cream machines is a part that stirs the product, keeping it from adhering to the metal.
Finding a way to stir the ice cream posed a challenge early in the days of nitrogen ice cream. One successful designer came up with the Brrr machine, which eventually came to use a pair of stirrers shaped like the twin helix of a DNA model. Because of the handcrafted design that went into this machine, though, ordering multiple machines incurs a considerable expense. Later innovations in nitrogen ice cream makes have "smart" stirrers that operate somewhat differently depending on the flavor, as some varieties are thicker than others, meaning that the stirrers have to work a little bit harder.