contamination by other foods. Because
parasitic worms are often found in otherwise
high-quality fish, the U.S. Food Code
specifies that fish sold for raw consumption
should be frozen throughout for a minimum of
15 hours at –31ºF/–35ºC, or for seven days at
–4ºF/–20ºC. The exceptions to this rule are the
tuna species commonly served in Japanese
sushi and sashimi (bluefin, yellowfin, bigeye,
albacore), which are rarely infected with
parasites. Despite this exception, most tuna
are blast-frozen at sea so that the boats can
stay out for several days at a time. Sushi
connoisseurs say that the texture of properly
frozen tuna is acceptable, but that the flavor
suffers.
Sushi and Sashimi
Probably the commonest form of raw fish is
sushi, whose popularity spread remarkably in
the late 20th century from its home in Japan.