A citrus juicer is used for squeezing juice from soft-centered, citrus fruits (orange, lemon, lime, grapefruit). It has a conical ridged center. Centering the halves of fruit with their cut-side down over the juicer, a user presses the fruit down and turns the fruit back and forth to extract juice, discarding the fruit afterwards. Pulp and seeds are retained in the ends.
A hand-held kitchen utensil version is known as a "lemon reamer", "citrus reamer," or simply a "reamer." Electric versions exist.
Most juice extractors are electric, which requires less effort than their manual counterparts. A juicer differs from a blender: a juicer separates the juice from the pulp.
There are three main types of juicer: centrifugal juicers use blades and a sieve to separate juice from pulp; masticating juicers that 'chew' fruit to a pulp before squeezing out the juice; and, triturating juicers that have twin gears to first crush fruit and then press it.
The single auger masticating juicer uses a profiled screw style moulding to compact and crush fruit and vegetable matter against a static screen allowing juice to flow through the screen while pulp is expelled through a separate outlet.
Twin gear triturating machines are usually the most expensive juicers offering the best juice yield. Twin gear juicers employ two metal counter rotating gears to crush the juicing fodder. The precise tolerance of the gears allows the juice to flow through the gap between the gears while the large pulpy matter passes along the top of the gears and is discharged.