On Food and Cooking

of microbes. There are also fish
fermentations that involve far less salt, so
that bacteria thrive and have a far more
powerful influence on flavor. One
notorious example is Swedish
Surstrømming. Herring are fermented in
barrels for one to two months, then sealed
in cans and allowed to continue for as
much as another year. The cans swell,
which is normally a warning sign for the
growth of botulism bacteria, but for
surstrømming a sign of promising flavor
development. The unusual bacteria
responsible for ripening in the can are
species of Haloanaerobium, which produce
hydrogen and carbon dioxide gases,
hydrogen sulfide, and butyric, propionic,
and acetic acids: in effect a combination of
rotten eggs, rancid Swiss cheese, and
vinegar, overlaid onto the basic fish flavor!
Fine smoked salmon may be treated with
salt and sometimes sugar for a few hours to a