Fruits that prevent gelatin from setting
I recall when the only caution against fresh fruit on the jello package instructions was pineapple. But these days supermarkets routinely carry fruits grandma never heard of, and many of them can't be used fresh in jello. I would love to use kiwi and melon in jello molds but they'd lose their shape when cooked. Does anyone know at what temperature the problem enzymes are deactivated? I am wondering if using less heat - brief steaming or baking perhaps - would be enough.
Ok... I researched it. It appears that the papain enzyme in fruits like kiwi and pineapple die at 160°F or 71°C. A lot of recipes call for canned fruit because all canned fruit is cooked. I would think that temperature for 15 minutes would work fine and would cause a minimum of damage to the fruit.
Oh by the way this enzyme works very well as a tenderizer so a kiwi or papaya based marinade would be very effective. Ooh... pineapple on pork.. Can anyone say al pastor?
Two links from where I derived my info.
From "The Cook's Thesaurus" http://www.foodsubs.com/ThickenGelati...
"Like gelatin, agar will break down if exposed to the enzymes of certain raw fruits, like kiwi fruit, papayas, pineapple, peaches, mangos, guavas, and figs. Cooking these fruits, though, destroys the enzymes. If you plan to add any of these fruits to a gelatin salad, it's a good idea to buy them in cans, since all canned fruit is pre-cooked."
Sorry not sure what the lowest temperature that kills the enzymes is.
re: Hank Hanover
Most proteins denature above 42-44ºC and since the enzymes here are essentially proteases, I'd expect them to deactivate around this threshhold. Then again, we all know about the bacteria that can thrive around the boiling point.
Would be an interesting experiment with a circulator and a bunch of kiwi in separate bags.
From the world of raw food cuisine, I learned that dehydrators must operate at 120F or less in order to keep enzymes active. I don't know how much exposure to that minimum temperature is required to deactivate all the enzymes in food. In a dehydrator, foods dry anywhere from several hours to days.
I would guess though if you bring mashed fruit to a simmer, even briefly, that should be enough to gel. Or you could test by zapping small amounts in the microwave,