Hello Fkoe:

When I need lemon zest, I wash the lemon with a few drops of
dishwashing detergent and water, using a soft brush:

http://www.leevalley.com/garden/page...59&cat=2,42551

(If you buy the brushes, buy a dozen, you won't regret it.)

In theory, it's all but impossible to rinse off *all* the detergent.
In practice, one or two good rinses with rubbing seems to remove any
flavor and odor of detergent (well....of perfume, which is what's in
most detergents). So I rinse three times.

BTW I teach chemistry at university and do a lot of washing and rinsing
in the lab, where cleanliness is way ahead of godliness.... :-)

Best -- Terry