Having been in the seafood business for over 50 years, I have always had people tell me (most of them) that they just love seafood but don't know very much about it or why it is that they can have the same type of seafood at one restaurant and love it but have the same dish at another and it makes them sick. This usually can very easily be explained if you understand the principal of adulteration or substitution.
In the past, seafood was considered the most economical protein in our diet but as with everything the cost of production, market demand, competition, etc. has caused many of the so called "Luxury items" (primarily in the shellfish category) to almost become "cost prohibitive" to an increasingly larger segment of society.
As with almost everything in the marketplace, someone, somewhere, will find a way to sell an item cheaper than their competition can afford to sell it for. Keep in mind, there are 3 elements required for success in the "Vendor - Customer" relationship. They are; Quality, Service, Price...The customer gets to select 2 of those elements; the vendor may have which ever one is left in order to make a profit.
It is when the vendor compromises on quality that serious consequences can occur.
Take for example North Atlantic Sea Scallops. They are harvested, primarily by drag net, the meat is removed from the shell and they are packaged for market. Since scallops are all protein and no waste, even at a price of $10 per pound they are still more economical than most cuts of beef. Four ounces are considered a serving; therefore, even at $10 per pound, the serving cost is only $2.50!
All the vendors are paying $10 per pound, then someone realizes that by soaking 100 lbs of shucked scallops in ice water over night then adding a chemical called sodium tri-poly sulfate, they can pick up an additional 25% weight. Now instead of having 100 lbs of meat to sell, they have 125 lbs. If you do the math, we know that both the honest and the dis-honest vendors have $1,000 invested. The difference is that now the dis-honest vendor has 125 lbs at $1,000 invested which allows him to re-calculate his cost to $8.00 per pound ($1,000 invested divided by 125 lbs. = $8.00)
Let's go back to the scenario of the person that can't understand why the scallops they had at one restaurant were delicious and the scallops they had at another made them feel sick. The reason is simple, at the first restaurant; the scallops were "natural" with nothing added to alter the cost. At the other restaurant, the scallops served were "adulterated" with chemical.
In today’s "cost conscious" purchasing environment, un skilled purchasing agents purchase by price with little or no consideration given to quality.
Unfortunately, the word "QUALITY" has been so over used that it has become a "perception" rather than a "Fact".
The best advice I can give is to do the same thing I do when I go out to eat. I ask the server, "Does this menu item have any additives?" They will usually say, "No, we only have the very best". To which I reply "Great, because I will become violently sick if there are".
Nine times out of ten, they will tell me "Let me go back and ask the chef". It is not un-usual at all for the server to return and advise me to maybe go with another dish as they can't say for sure if the item I originally ask for is all natural.
Remember, you are paying good, hard earned money for your food, whether it is from a store or at a restaurant. Never, Never, Never feel guilty or shy about asking for as much information as possible.