The Jellying Point

This is the temperature to which such preserves as jellies, jams, and marmalades are cooked in order to be sure they will “jell.” For most preserves (there are exceptions, such as the No-Boil Grape Jelly), this is most easily determined by using a candy-jelly thermometer. The jellying point is 8 degrees above the boiling point of water at your altitude: the boiling point at sea level is 212 degrees, so the jellying point at that elevation is 220 degrees. If you don’t have a reliable thermometer, you can use the “sheet test” for jelly and for jams and marmalades that have a generous amount of syrup to “jell.” To make this test, you dip up some of the preserve in a cold metal mixing spoon and pour it back into the pot. So long as a stream, or individual droplets, falls, continue the cooking. Test often—as soon as two or three droplets join together on the edge of the spoon and shear off in a sheet, the jellying point has been reached. Stop the cooking at once—overcooked preserves tend to be rubbery and of poor color.