On Food and Cooking

The Beany   Flavor  of  Soybeans

The strong aroma of simply cooked
soybeans results from two qualities: their
high content of polyunsaturated oil, which
is especially vulnerable to oxidation, and
their highly active oil-breaking enzymes.
When the cells of the bean are damaged
and their contents mixed together, the
enzymes and oxygen break the long carbon
chains of the oil into fragments five, six,
and eight carbon atoms long. These
fragments have aromas reminiscent of
grass, paint, cardboard, and rancid fat, and
the combination creates a smell usually
described as “beany.” Some bitter taste and
astringency also develop, probably due to
free fatty acids or to soy isoflavones that
are liberated from their storage form (p.
485).
The key to minimizing the development
of beany flavor is to inactivate the beans’
enzymes quickly, before they have a