Unfortunately, all of the research that I've seen on dried papaya has been done on a very specialized type of dried papaya called papaya pomace (which is actually more like a waste product and used almost exclusively in animal feed). Papaya pomace is basically what's left after the juice has been extracted from the papaya fruit. I've seen studies on dried forms of these papaya "leftovers," but I assume they bear little resemblance to the dried whole fruit that we would purchase in a natural foods grocery.
Enzymes, including the papain enzyme found in papaya, are heat sensitive and become denatured upon exposure to too much heat. Therefore, the heat involved with the commercial drying of papaya will deactivate its enzymes. While enzymes from fresh, raw foods can sometimes be viable and aid digestive activity in our intestinal tract, deactivated enzymes cannot.
If you decide to buy dried papaya, it's important to remember that, like other dried fruits, it may be treated with sulfites. To avoid these sulfites, either look for dried papaya that notes that it contains no sulfites or buy organic dried papaya since sulfites are not added to organic food products. (Whether dried or fresh, I would always recommend purchasing organic papaya in order to avoid potential pesticide residues found on non-organic papaya and to take advantage of the greater nutrient benefits associated with organically-grown foods.)
It's important to remember, though, that papain is most concentrated in green unripe papaya and not ripe papaya, from which dried papaya is made. Green papaya is more readily found in stores that sell Asian foods. It makes the base for a great salad mixed with red onions and hot peppers in traditional Thai style. Cut up into small pieces or grated you can add it to cold salads or use it as a sandwich topping.
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