It's quite a common process. Most supermarkets use the same process to make processed meats such as mince meat look more appealing and fresh. Because it is a process and not an ingredient they do not have to disclose any chemical processes used. The fish in supermarkets such as salmon are fed dye pellets to make the meat look pink as they are farmed and fed artificial nutrients.
I always buy from my local butcher and fishmonger.
If you knew half the crap that was put in supermarket food you wouldn't buy from them.
