On Food and Cooking

its temperature below the freezing point. This
effectively stops spoilage by bacteria, but it
doesn’t stop chemical changes in the fish
tissues that produce stale flavors. And the
proteins in fish muscle (especially cod and its
relatives) turn out to be unusually susceptible
to “freeze denaturation,” in which the loss of
their normal environment of liquid water
breaks some of the bonds holding the proteins
in their intricately folded structure. The
unfolded proteins are then free to bond to each
other. The result is tough, spongy network that
can’t hold onto its moisture when it’s cooked,
and in the mouth becomes a dry, fibrous wad
of protein.
So once you’ve brought frozen fish home,
it’s best to use it as soon as possible. In
general, the storage life of fish in ordinary
freezers, wrapped tightly and/or glazed with
water to prevent freezer burn (freeze the fish,
then dip in water, refreeze, and repeat to build
up a protective ice layer) is about four months