Perhaps Steve is saying gristle when in fact he really means fat. If so, I think fat (or well marbled) may be indicative of a decent cut of brisket. Like Donna said, it may just be the connective tissue. It can appear rather gelatinous at times. I suppose it's possible that people who are not used to eating brisket, such as myself, may find it a bit fatty (rich) for their tastes. But it sure tastes good!