Marinated meat from the butcher
For some time you can see the butcher - and in the supermarket - again and again marinated meat on offer. I'm not talking about the pickled Sauerbraten, but these oily marinades.
I can only guess, steer clear of it. This is where very often the very meat is used, which without these marinades already looks a bit "ugly" or even a little "smokey". the marinades mostly cover that!
So better buy the meat unmarinated and then marinate yourself at home. Then you know what you have!