Here's an article that talks about the issues. Not the one I originally
saw, but pretty informative:

http://www.taunton.com/finecooking/pages/c00157.asp

That whole site seems to be an excellent resource.

Bob
===========================
In article >,
says...
> I know from experience that too much acidity will cause chicken to
> toughen up rather than tenderize. Some time back I did three different
> marinades on a "family-size" package of boneless/skinless chicken
> breasts. The ones that were soaked in a marinade based on apple cider
> vinegar were noticeably stringier than the other ones. One of the other
> two marinades only had a bit of lemon and lime juice for acid. The
> third marinade was yogurt-based, so probably not very acidic at all.
>
> Some time back I saw a good article and series of pictures that show
> what "meat tenderizers" do to meat over time. Suffice it to say that
> the results of the longest contact time were not pleasant to look at or
> contemplate. Basically meat mush. I can't find the link right now, but
> I'm sure the article is still out there somewhere on the web.
>
> Bob
> ===============================
> In article >,
> says...
> > In the case of the apple juice, I've found that an hour or so for
> > chicken or overnight for ribs gives an extremely moist meat with just a
> > little bit of a sweet taste that goes well with smoke. Maybe, since
> > apple juice is slightly acidic, a longer time would result in chemical
> > changes to the meat, but the shorter time just makes it juicy. I've
> > done no research into the changes in meat texture as a function of
> > acidity or papaya, so if anyone has more observations, I'd sure enjoy
> > reading about them.
> >
>