1, shrimp blackening is mainly the role of enzymes, and microorganisms have little to do. Even in frozen or refrigerated conditions, tyrosinase is still active, so it will still occur black.

2, the shrimp head is also the shrimp viscera, if the shrimp in the catch before eating a lot of dark-colored algae, such as brown algae, may also appear shrimp hair black.

3, in addition, breeding shrimp undigested feed may also appear black.