In the U.S. and Canada, jelly refers to a clear or translucent fruit spread made from sweetened fruit juice and is set by using its naturally occurring pectin, whereas outside North America (read Europe and the rest of the world) jelly most of the time refers to a gelatin-based dessert. Unless you are talking to a marine biologist specialized in the non-polyp form of individuals of the Phylum Cnidaria.
The difference is subtle, yet important.
Jelly can be made from sweet, savory or hot ingredients. It is made by a process similar to that used for making jam, with the additional step of filtering out the fruit pulp after the initial heating. A stockinette “jelly bag” is traditionally used as a filter, suspended by string over a bowl to allow the straining to occur gently under gravity. It is important not to attempt to force the straining process, for example by squeezing the mass of fruit into the stockings or the clarity of the resulting jelly will be compromised.
Patience is a virtue when talking Jelly.
Jelly can come in a variety of flavors such as grape jelly, strawberry jelly, hot chile pepper and even jellyfish.
It is typically eaten with a variety of foods. This includes jelly with toast, or a peanut butter and jelly sandwich.
The Jellyfish variant is considered a delicacy in Japan and Korea.
Dried that is.
Pectin (from Ancient Greek: πηκτικός pēktikós, “congealed, curdled”) is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants and not found in Jellyfish.
It was first isolated and described in 1825 by Henri Braconnot.
It is produced commercially as a white powder, mainly extracted from citrus fruits, and is used in food as a gelling agent, particularly in jams and jellies.
Not to be confused with gels used in photography (that is another post).
“Good jelly is clear and sparkling and has a fresh flavor of the fruit from which it is made. It is tender enough to quiver when moved, but holds angles when cut.”
Now that is a definition I like.