On Food and Cooking

water, the more savory the shellfish. This fact
accounts for at least some of the flavor
differences among shellfish from different
waters, and it is part of the rationale for
“finishing” oysters for a few weeks or months
in particular locations. Because shellfish use
up their energy stores as they prepare for
spawning, they become noticeably less tasty
as spawning approaches.
When molluscs are cooked, their
savoriness is somewhat diminished because
heat traps some of the amino acids in the web
of coagulated protein and so withholds them
from the tongue. However, heating alters and
intensifies the aroma, which is generally
dominated by dimethyl sulfide, a compound
formed from an odd sulfur-containing
substance (dimethyl- -propiothetin) that
molluscs accumulate from the algae on which
they feed. DMS is also a prominent aroma in
canned corn and in heated milk: one reason
that oysters and clams go so well with these