gelatin concentration.
Both strongly acid ingredients and the
tannins in tea or red wine can cloud a jelly,
the acids by precipitating proteins in a meat or
fish stock into tiny particles, and the tannins
by binding to and precipitating the gelatin
molecules themselves. These ingredients are
best cooked briefly with the gelatin solution
so that it can be strained or clarified before
setting.
A number of fruits — papaya, pineapple,
melons, and kiwi among them — contain
protein-digesting enzymes that break gelatin
chains into short pieces and thus prevent them
from setting into a gel at all. They and their
juices can be made into a jelly only after a
brief cooking to inactivate the enzymes.
Cooling Temperatures The temperature at
which the gel forms and ages affects its
texture. When “snap-chilled” in the
refrigerator, the gelatin molecules are