On Food and Cooking

A special case of flavor extraction is the
making of flavor extracts themselves:
preparations that serve as instant sources of
flavor for other dishes. The most common
materials used for extraction are oils,
vinegars, sugar syrups (especially for
flowers), and alcohols (for example, a neutral
vodka for flavoring with citrus peel). The herb
and/or spice is usually bruised to damage the
cellular structure and make it easier for the
liquid to penetrate and aromas to escape. Oils,
vinegars, and syrups are often heated before
the herb or spice is added to kill bacteria and
facilitate their initial penetration into the
tissue, then are allowed to cool to avoid
changing the flavor. Delicate flowers may
require less than an hour to flavor a syrup,
while leaves and seeds are usually infused in
the extracting liquids for weeks at a cool room
temperature. When the extract has reached its
desired strength, the liquid is strained off and
then stored in a cool, dark place.