"Shaun Rimmer" <shaun@newtronic.co.uk> wrote in message news:<bja0si$gnuc7$1@ID-170198.news.uni-berlin.de>...[color=blue]
> Seville oranges are bitter oranges. I know they aren't too hard to find over
> here in the UK. Do a google on Seville oranges for more info![/color]
[...]

The trouble is, they have a very short season: I often miss the
end-of-January marmalade-making ritual by a whisker. I think it would
work to zest them and then freeze the zest in small packets. I freeze
the oranges whole without much detriment to the marmalade even months
later.

Kumquats, though, seem to be available for most of the year: their
peel might make a good, though less powerful, substitute. I'd even be
inclined to try an experimental brew with the peel minced without
separating the white pith: after all, it *is* the bitterness we're
looking for, and on kumquats the pith is very thin.

Mike.