Wikipedia Article About Lemon peel on Wikipedia Zest is the outer, colored shell of citrus fruit and is often used for baking. Zest has become a synonym for spice, strong flavor or interesting taste. To remove the zest a zester, vegetable/potato peeler, or paring knife should be used to scrape the colored part of the peel off. The white membrane or pericarp under the zest is bitter so it is important to be careful to not cut too deep.