If food poisoning bacteria are present, they can multiply and cause illness when the seafood is eaten. Many different enzymes are present in living seafood species. They help build tissue, contract and relax muscles, and digest food. When seafood species die enzymes continue to work and start to digest or break down the flesh. This causes the flesh to soften and lowers the quality.
Enzymes also produce more food for bacteria to feed on, increasing the rate of spoilage.
This is especially important in fatty fish such as salmon and mackerel. All changes that cause seafood spoilage are affected by temperature. Sanitation is also important. Bacterial contamination of seafood from dirty ice, containers and surfaces can increase the number of bacteria on seafood and speed spoilage. Contamination with food- poisoning bacteria can cause illness when the seafood is eaten.