Final answer:
Soaking seafood in acid causes the proteins to denature, changing their structure and 'cooking' them without heat. Acids also neutralize volatile amines in the fish, reducing odor and adding a sour taste. The addition of salt can precipitate proteins, contributing to the unique texture of ceviche.
Step-by-step explanation:
Ceviche is made by soaking seafood in large amounts of acid. This process affects the proteins in the seafood by causing a chemical reaction known as denaturation. When the seafood is exposed to the acid, such as lemon juice or vinegar, the proteins in the flesh unwind and unfold, changing their structure. This is because the acidic environment disrupts the hydrogen and ionic bonds holding the protein structure together. As a result, the proteins become 'cooked' without the use of heat.
In addition, when acids react with volatile amines present in fish, they neutralize them to form involatile ammonium salts. This reduces the fishy odor and gives the ceviche its distinctive sour taste. Moreover, the use of salt in the preparation of ceviche can lead to 'salting-out' of proteins, where increased protein-protein interactions cause proteins to precipitate. The overall chemical changes impart the unique texture and flavor that is characteristic of ceviche.