A vegetable juicer or fruit juicer is a conical-shaped kitchen utensil used for squeezing, or removing, liquid from various foods, specifically vegetables and fruits, for the purpose of drinking or adding flavor to other foods. The juicer is easy to use, although due to the possible risks involved, should be treated with care, caution, and expertise.
A couple of varieties of juicers exist - a manual, or hand-operated, type and an electrical version.
Manual/Hand-Held Juicer
Juicing consists of inserting fruit sections or vegetable slices cut side-down in the center of the juicer and then pressing down to squeeze the foodstuff and moving it back and forth so the fruit or veggie juice will run out of the rind and away from the pulp. The pulp and seeds are collected along the edges of the juicer, and the peel is then discarded.
Power Juicer
A power or electric juicer mechanically extracts juice from fruits, veggies, herbs, etc. A correct operation comprises of putting the article of food within and pushing the switch. The juicer then mechanically squeezes juice out of the fruit or vegetable. Because of its mechanical dynamics, electric juicers are much more dangerous than hand-operated types, and thus it is important that users be trained the way to correctly make use of them.
Two varieties of electric juicers are on the market:
Centrifugal juicers - these consist of a blade and sieve to separate juice and pulp from peels or outer shells or casings. Centrifugal juicers are unable to break fibres in food, so their use is somewhat limited.
Masticating juicers - these "chew up" the whole piece of food before, or so as to, squeeze juice from the inside. Once the food becomes mangled, the liquid naturally flows out. Masticating juicers can break fibres in food, so they really have a much broader use than centrifugal juicers.
By the way, electric powered juicers and blenders are very different in function and purpose. Electric (masticating) juicers can easily separate liquid from fibers, whereas blenders, like centrifugal and hand-operated juicers, cannot.
The principle is that because fast-moving mechanical components of a power juicer blow air into the food, triggering greater and speedier oxidation to important nutrients, electric powered juicers, especially those having variable speeds, are regarded as being of better quality than manual juicers. This has not been verified, nevertheless it's a popular belief.