What Fruits Should I Not Put In Jell-o?

Made with the connective tissue and bones of animals, Jell-O, like all types of gelatin, consists of collagen, a type of protein. Corinne Marasco of “Chemical and Engineering News” explains that the structure of collagen resembles three twisted strands of spaghetti. These strands unwind when exposed to hot water and re-form as they cool. Some fruits contain a substance that interferes with the structure of this protein.

Proteases

Proteases are enzymes that break down proteins. When you add a substance containing protease to gelatin, the collagen strands cannot re-form -- or gel -- as they cool. The types of proteases that interfere with gelatin include papain, bromelain, ficin, actinidin and zingibain.

Fruits With Proteases

Papayas, pineapples, figs, kiwi, ginger, guava and mango contain proteases. If you add these fresh fruits to gelatin, the gelatin will not set. However, because of their proteases, these fruits make ideal meat tenderizer. The proteases break down some of the protein structure, making the meat more tender.

Using Protease-Containing Fruits

If you want to add any of the protease-containing fruits to gelatin, you can heat the fruit in the microwave or on the stove top. Heat denatures the enzymes, making them ineffective at breaking down the gelatin’s proteins. For example, zingibain, the protease found in ginger, becomes denatured at 158 degrees Fahrenheit. Unfortunately, some fruits, such as kiwi, become mushy when heated to these temperatures.

Canned Fruits

If you wish to make a gelatin dessert with papayas, pineapples, figs, kiwi, ginger, guava or mango, use canned versions of these fruits. During the canning process, the fruits are heated to a temperature that denatures the proteases. These canned fruits retain their shape better than if you heat the fruits yourself.