Extra precaution should be used when thawing fish that has been vacuum packed and frozen. The aquatic environment in which fish live can be a reservoir for the bacteria Clostridium botulinum. When harvested, fish may have these bacteria in their skin, gills, and intestines. Therefore, it is important that fish be carefully handled during harvest, storage, and when preparing for cooking.
The environment that allows for the spores of the Clostridium botulinum bacteria to germinate and produce the deadly botulism toxin is low acid, low oxygen, moist, and temperatures above 41 °F for a time of 2 hours or more. Fish are often stored in vacuum packaging to help maintain quality by creating a low oxygen environment. Fish are naturally a moist and low acid food. When being stored in vacuum packaging where a low oxygen environment is created, it is crucial to ensure that the fish is not left in the vacuum packaging at temperatures above 41 °F for an extended period of time. That means NO thawing, in the package, on a countertop.
Thawing under refrigeration is recommended for vacuum-packed fish, but sometimes, you may need to thaw more quickly. You can do that by thawing the fish under cool running water. If this method is used, the fish should be either removed from the packaging before being placed under running water or thawed in the package with cool running water (checking every 5 minutes) so that fish can be immediately removed from the packaging when thawed. A container that is large enough to allow plenty of space for the fish and water (i.e., a large bowl that is not packed tight with frozen fish) is needed for fast thawing. It should only take a few minutes to thaw the fish in cool running water. Never allow vacuum-packed fish to remain at temperatures above 41 °F for more than two hours. If the fish has not thawed in the packaging within 30 minutes, remove the packaging and continue to thaw in cool running water.
- Cortés-Sánchez, Alejandro De Jesús. Modern Applied Science; Vl. 15, No. 3; 2021