@ felix:
Thank you very much for the informations regarding the TrimCheck tool, which has been offered by the user "Bad Machine" at "The SSD Review Forum."
I have just tested it with my Intel Z77 RAID0 array and this is what I got:

Just to verify the results, I executed the "Easy Trim Test" method by using a hex editor, which I had layed down >here<. Result: The sector, where the jpg file had been, zeroed out within a few seconds after the delition of the file.
So I am rather unsure, if "Bad Machine"s TrimCheck tool gives realistic results, if the SSD is part of a RAID array.