Newly bought dried shrimp are generally white and do not have a strong ammonia smell. However, after being stored at home for one or two months, the shrimp turn pink and develop a very strong ammonia odor. Besides dried shrimp, various types of dried seafood have similar problems, such as dried small shrimp, dried squid strips, and dried small fish, with only slight differences in the intensity of the smell. What's going on? Can this dried shrimp still be eaten? How should dried shrimp be stored?
Dried shrimp can be preserved for a long time, with the main antibacterial factors being low moisture and high salt. Both are essential. However, the dried shrimp people usually buy are not completely dry, mainly for two reasons: the air near the coast is humid, and undried shrimp are heavier, which means more profit. This not-fully-dried shrimp, with its high protein content, is particularly susceptible to bacterial growth.
When stored at room temperature, proteins are acted upon by microorganisms, first breaking down into peptides and amino acids, and then further decomposing into primary amines and ammonia gas. The primary amines are the source of the fishy, rotten smell, and the ammonia gas is the source of the pungent odor.
Primary amines are not only somewhat toxic themselves, but worse, they can easily combine with small amounts of nitrites in seafood to form strong carcinogens—nitrosamines. These substances are important chemical factors in promoting the development of esophageal and stomach cancer. The toxicity of nitrosamines is very high, exhibiting chronic toxicity, teratogenicity, and carcinogenicity. They are also volatile, and inhaling them from the air can also cause toxic reactions.
Various seafood and meat products are important sources of nitrosamines. Unpreserved or improperly preserved salted fish, cured meat, dried shrimp, dried small shrimp, dried squid strips, dried scallops, and dried fish can all exceed safe levels. Therefore, once your dried shrimp develops an off odor, don't hesitate to throw it away. Do not think that washing it with water will make it safe to eat.