Citrus oil is in the zest
The colored outer peel is packed with tiny oil glands. The oil is mostly limonene, which gives citrus its smell. Under the peel sits the white pith, which is bitter and has little aroma.
Rub zest into sugar or fat
Rubbing zest into sugar breaks open the oil glands and coats each crystal in lemon oil. Citrus oil also dissolves in fat, so zest stirred into butter or cream spreads evenly. Zest the whole fruit before juicing it, because a whole lemon is easier to grip.
Test yourself
Questions from the interactive lesson, with the answer and the why.
Where does most of a lemon's fragrance live?
In the colored outer peel. Tiny oil glands in the colored peel hold the citrus oil.
True or false: The white pith is the best part of a lemon to zest because it is the thickest layer.
False. Pith is bitter and has little aroma, so zest only the colored peel.
Fill the blank: The main aroma compound in citrus peel oil is ___.
The main aroma compound in citrus peel oil is limonene. Limonene is the main compound in citrus peel oil.
What went wrong? You grate a lemon right down to the white layer for a cake. The cake tastes bitter.
Grating into the white pith added bitterness. Pith is bitter, so grate only the thin colored layer.
Your lemon bars need more lemon fragrance without more sourness. What do you add?
Zest rubbed into the sugar before mixing. The sugar breaks open the oil glands and spreads lemon oil evenly.
True or false: Zesting a lemon before juicing it is easier than zesting after.
True. A firm whole fruit is easy to grip, while a squeezed half is slippery and soft.