Grape or muscadine jelly can substitute for red currant jelly. Muscadine is a grape varietal. Three parts jelly mixed with one part lemon juice is also used as a substitute.
Fresh red currants are a type of berry that grows on flowering shrubs. They are either dark purple or deep red. Their flavor is sweet with an acidic kick. Both types become jelly, with the dark purple currants labeled as black. Red currant jelly is more common. Currants, as opposed to red or black currants, are dried seedless grapes, and they are also known as Corinthian raisins.
People use currant jelly the same way as any other jelly, to top toast or serve in a sandwich. However, a common use for the jelly is serving it with meat. Roast lamb or roast venison often has a side of red currant jelly as a complement to the flavor. Cold meats, strong cheeses and pork pie also pair well with red currant jelly.
Currants naturally feature pectin and acid, as do grapes, which is why grape jelly is a good substitute, though it may be overly sweet unless additional acid is added in the form of citrus juice, usually lemon. Some people might also find cranberry sauce an acceptable alternative for the same reasons.