Soup or Salad? Investigating the Action of Enzymes in Fruit on Gelatin

Most enzymes are proteins that have evolved to function as catalysts for chemical reactions in living systems. Some fruits contain proteases, a group of enzymes that catalyze the cleavage of peptide linkages in proteins. This can have an undesired effect in a gelatin salad containing fruit, because proteases in the fruit can cleave the proteins that make up the structure of gelatin so that it will not set. This is the reason for the warning on many gelatin packages "Do not use with fresh or frozen pineapple." Other fruits may also be included in the warning. Fresh pinepple, papaya, kiwi, and figs contain the proteases bromelain, papain, actinidin, and ficin, respectively. When the enzymes are denatured, which can result from heating during the canning process, they lose their ability to cleave proteins.