Janani,
What species of tuna are you referring to as "red tuna". Do you mean yellowfin, bigeye, or bluefin?
These species of tuna are commonly eaten raw as sashimi. They do not contain parasites of public health concern in the edible muscle. Therefore freezing these fish prior to raw consumption is not necessary.
Freezing temperatures for tuna for other reasons such as transportation, storage, etc. depends on the intended end use. For canning raw material, freezer temperatures need not be very low. The raw frozen tuna oxidizes and turns brown. But after cooking and canning, the color of the raw muscle is not an issue.
To retain the natural red color and muscle clarity required for the sashimi market, freezing must be done at sea immediately and at ultra low temperatures (ULT). This requires specialized equipment. ULT frozen tuna is common in Japan because of the distance the fish must travel from the fishing grounds to the market and not because of a parasite food safety risk.
Frozen tuna treated with carbon monoxide does not need to be frozen or shipped at ultra low temperatures because the carbon monoxide prevents the natural oxidation that would otherwise result in the normal color change from red to brown. Carbon monoxide treated tuna retains its unnatural red color without requiring ULT freezer temperatures.
Aloha,
John Kaneko MS, DVM
PacMar Inc.
Honolulu, Hawaii
----- Original Message -----
From: Janani Tulasendrapuram
To: seafood@ucdavis.edu
Sent: Wednesday, January 10, 2007 6:09 AM
Subject: Parasites in Red Tuna
Good morning,
This is regarding parasites in Red Tuna. Is there a published lethality table that deals with temperatures above -20C? FDA says -35C for 15 hours is a good as -20C for 7 days. But what if you could only guarantee -10C in the transportation chain? How many days at -10C would you need?
I would appreciate it, if anyone can pass along any information regarding the above.
Thanks and have a nice day!
-Janani Tulasendrapuram
This archive was generated by hypermail 2b29 : Wed Jan 10 2007 - 10:45:52 PST