Jeb,
The vacuum application may facilitate blood removal (blood is a potent catalyst of oxidation) but I do not think that it would affect any lipids. Vacuum packaging is very effective against rancidity providing that the residual oxygen level is very low and the packaging material is of very low oxygen permeability characteristics. The ice glaze itself slows down a bit oxygen penetration into the product but its main function is to prevent the surface dehydration while keeping it smooth and consequently minimize the exchange area with the surrounding atmosphere.
Frozen products cook longer and therefore if they are thick the outer part of the product may be overcooked and de-hydrated vs the interior. Consequently, during practical commercial product design it is common to balance the product thickness vs its cook time to optimize the cook product quality and cook time while providing the convenience of cooking from frozen state.
Andrew Strak
-----Original Message-----
From: Jeb Wyman [mailto:jeb@pfmag.com]
Sent: Monday, March 18, 2002 11:54 AM
To: seafood@ucdavis.edu
Subject: extending salmon shelf life
Dear list:
I would be interested in knowing whether there is any validity to the claims of extended cold storage shelf life using the unusual process below and, if so, whether anyone can explain why it might work.
Troll-caught coho salmon are landed, bled, and put in 32-34 degree chill tank for about 24 hours. After removing head, guts, and tail, the fish are subjected to 30 inches of vacuum for about 1 minute. Although the fish may appear spotless, this process nonetheless extracts a significant amount of fluid from the fish. The fish are then carefully laid in a -50 degree "soaker freezer" (i.e., a freezer hold with -50 ambient temperature but without forced air circulation like a blast freezer, which allegely dessicates the product). They are glazed several times. After one or two months, the frozen carcasses are cut with a bandsaw into steaks, re-glazed twice, and double-wrapped in vacuum packaging. This process is supposed to greatly reduce oxidation. Apparently product as much as 36 month old is still palatable.
I am interested in learning whether vacuum extraction of fluids could remove lipids associated with rancification. Any science to support or de-bunk this process?
On a slightly different topic, I would like to know how food quality may or may not be compromised by directly cooking frozen product without a slacking-out period. Thawing food prior to cooking seems to be the norm. If there were no concerns that the food would cook unevenly or inadequately (i.e., a sanitation issue), does cooking frozen product otherwise damage the tissue and affect texture or taste?
Many thanks for any help you can lend me.
Jeb Wyman
Associate editor
Pacific Fishing/FIS
4209 21st Ave W
Seattle, WA 98199
206/216-0111 ext 215
FAX 206/216-0222
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