Zest[1] is a food ingredient that is prepared by scraping or cutting from the rind of unwaxed citrus fruits such as lemon, orange, citron, and lime.
After any surface wax has been removed, a zester, grater, vegetable peeler, paring knife, or even a surform tool is used to scrape or cut zest from the fruit.
Fruit with peels that are almost all flavedo are generally mandarins; relatives of pomelos and citrons tend to have thicker mesocarp.
Zest also is added to certain dishes (including ossobuco alla milanese), marmalades, sauces, sorbets and salads.
Zest is a key ingredient in a variety of sweet and sour condiments, including lemon pickle, lime chutney, and marmalade.