Kiwi and Pineapple contain an acit that will not set in gelatin
pineapple, kiwi, mango, gingerroot, figs and gauva are the fruits which will prevent gelatin from hardening.
It may have to do with the acidity of the fruit. I know that pineapple, kiwi, gingerroot, papaya, figs or guava will not work.
Pineapple kiwi papaya guava mango
Pineapple contains an enzyme which prevents gelatin from setting. Heat destroys (denatures) enzymes.
you could make it into juice and then add it to the jello.
Pineapples contain an enzyme called bromelain. THis enzyme stops the Jello from jelling because it breaks dowm the strands of protein that form Jello. Cooking the pineapple denatures this enzyme therefore preventing it from stopping the Jello.
Yes, as long as you do not use pineapple juice. this prevents the gelatin from setting.
Pineapples are actually reasonably solid. The question may mean, "Why can't you make fresh pineapple jello?" Enzymes in the pineapple prevent protein molecules from "setting up" into the (semi)solid gelatin.
Gelatin is a reversible colloid, so yes, if you melt a set jello, it should set again when chilled. However, other ingredients, such as pineapple, may alter the gelatin so that it does not set.
pineapple jam
Ingredients1 cn (8-1/2 oz.) crushedpineapple 1 c Boiling water1 pk (3 oz.) lemon-flavoredGelatin 1 c Chilled whipping creamDrain pineapple, reserving syrup. Pour boiling water over gelatin in bowl, stirring until gelatin is dis- solved. Add enough cold water to re- served syrup to measure 1 cup; stir into dissolved gelatin. Chill until al- most set. In chilled bowl, beat cream until stiff. Beat gelatin until foamy. Fold gelatin and pineapple into the whipped cream. Povr into 1-qt. mold or into indi- vidual molds. Chill 3 hr. or until frm. Unmold, serve with sweetened whipped cream, if you like, and gar- nish with other fruits. Serves 6 to 8