I have done many searches about Hermann Bemberg and nothing that I have found shows him to be of Jewish heritage. I found a site that gives a list of Jewish Composers, but I'm sure that cannot be comprehensive. It may be especially difficult to know for sure, because of the time period when he died. So many were doing everything they could to hide any evidence of Jewish ancestry (if they had any), that it may be impossible to know for sure.
Here is the list that I found.
I hope that helps.