Lime

Lime is citrus: sharp juice, aromatic zest, bitter pith. It is not Lemon, even when both make your mouth water.

Ohio State: marmalades are soft fruit jellies with small pieces of fruit or peel, and they often contain citrus ¹. Lime belongs in that citrus family next to lemon and Orange. The peel is pectin and aroma; the juice is acid. Details: Marmalade.

When a gel recipe calls for added acid, Ohio State names lemon juice or citric acid for gel formation ¹. That is the named acid in that fact sheet. Do not swap lime juice into a tested canning acidification (tomatoes, figs) because it tastes similarly sour. Acidity is pH; kitchen sourness is not a meter.

Jam. Conventional gel is still pectin, sugar, acid, and concentration. See Jam. Lime is not on Ohio State’s fruit pectin chart the way lemon is; do not invent a Group I claim for it.

What to notice. A good lime smells like zest before you squeeze it. Juice should be sharply sour, not flat. Brown, dry fruit is storage, not marmalade stock.