Stupid question, maybe, but in a pinch, could someone not simply press grapes, run the juice through a filter to remove matter (such as a coffee filter), and set it aside for a few days, long enough for fermentation to start (though it wouldn't get very far)?
It wouldn't be of high quality, but to my mind, it would indeed be wine. And it would have no preservatives.
I'll bet the Church has covered this, as far as the minimum # of days of fermentation and minimum % of alcohol content. But I don't know.
I doubt preservatives would invalidate wine, because it doesn't affect the grapes or essence of the alcohol but just keeps it "shelf safe", stops fermentation, and prevents the wine from turning into vinegar.
"In Kansas City, Naumann noted that many commercially available wines 'contain additives such as elderberry extract, sugars, alcohol, etc' -- all of which could render the wine invalid matter."
These additives affect the grape juice and the essence of the wine and I think that "mass wine" must be 100% (or very high) of grape juice.