Well, what do you mean by ripen?
Ripen, in the generic term, meaning basically, more palatable?
Or..
Ripen, as in text-book, meaning it continues to make sugars, change/reduce acids
Some fruits contain enzymes, like bananas, where they actually continue to text-book ripen, converting starches to sugars in significant amounts
Most fruits stop text-book ripening once picked from the plant. They'll convert some starches to sugars, which is why the fruit softens, but not in high enough amounts to be called ripening.
Peaches are best when tree-ripened.. Which is why, here in WA, i've never had a good "Georgia Peach"... Just WA ones
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