I read the book two months ago and, since it was borrowed, I returned it. I'm going to try to get at it again and reread the parts that mention this expression. At this moment I think that tobacco is the most likely answer. Here in Spain this kind of tobacco is virtually unknown and it was the last thing I would have thought.
However, as far as I can remember, the man who chewed that thing was european -french or italian- and I'm inclined to think that nobody chews tobacco out of America.

Juan Maria.