Re: Curdled milk in oyster stew

There are 2 main ways the milk in your stew would have curdled. First, by 
the addition of an acid, the isoelectric point of the proteins would have 
been lowered sufficiently to allow them to coalesce, i.e. curdle. This 
could have been a result of any one of the ingredients, perhaps a bit of 
lemon salt, or anything even slightly acid. Second, enzymes found in the 
fresh seafood could have caused chemical reactions in the stew allowing 
the proteins to coagulate with one another and thereby curdle. Typically, 
fresh meats and vegetables are blanched or somehow heated slightly to 
destroy or incapacitate these enzymes to prevent these reactions. 

A third theory but highly unlikely since you are well enough to submit the 
question is that oyster are susceptible to infection by strains of 
bacteria called Vibrio sp. These bacteria could possibly produce acidic & 
toxic metabolic by-products and release them into the stew causing the 
curdling. This is one reason, people are cautioned when eating fresh, raw 
oysters.