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Grapefruit Jelly
1/2 cup grapefruit Juice 1 1/4 cups water 1 cup sugar 2 tablespoons lemon juice 1/4 teaspoon salt 1/4 ounce vegetable gelatin 1 cup water in which to dissolve the gelatin While the gelatin is receiving its preliminary preparation of soaking and draining, mix together the grapefruit juice, water, sugar, lemon juice, and salt. Use a lemon drill to obtain the grapefruit juice. Both the grapefruit juice and the lemon juice should be strained before using. After draining the last time, boil the gelatin in the one cup of water till dissolved, then strain it into the remaining ingredients. Mix well, and pour into a mold or cups wet with cold water. When cold, unmold, and serve with cream, whipped cream, vanilla sauce, or lemon custard sauce.
A vegetarian jelly set with agar rather than animal gelatin, which changes almost everything about how it behaves. The measurements are workable as written, but the setting agent needs modern handling notes.
- Vegetable gelatin is agarThe 1/4 ounce called for is about 7 g of agar, sold as flakes, bars or powder. Weigh it rather than measuring by volume: flakes are many times bulkier than powder for the same weight.
- The soaking and drainingAgar bars and strips were soaked in cold water, squeezed and drained more than once to wash out marine odours and grit. Modern flakes and powder are clean enough that a 20-30 minute cold soak in the cup of water is sufficient, and you can boil them in the soaking water.
- It must actually boilThis is the hinge. Unlike gelatin, agar does not swell into a set at low temperature; it has to reach a full boil and dissolve completely, usually one to three minutes for powder, longer for flakes. Undissolved specks mean a weak or grainy jelly.
- Add acid after boiling, not beforeThe recipe boils the agar in plain water and only then strains it into the fruit juices. Prolonged boiling in acid degrades agar, so a jelly boiled up with the citrus juices may set weakly or not at all.
- Setting behaviourAgar gels as it cools below roughly 90-105F, so it sets and holds at ordinary room temperature without refrigeration. It gives a firm, cleanly sliceable jelly that does not melt on the tongue the way a gelatin dessert does. Chilling only speeds it up.
- Lemon drillA small handled tool with a ridged or spiralled point, worked into the fruit to draw out the juice; wooden and glass examples survive. Any hand reamer or citrus press will do the same work; straining is still worth doing, since pulp clouds the jelly.
- Proportions and yieldThe measured liquids come to about 2 7/8 cups, closer to 3 1/4 once the sugar has dissolved, giving roughly six half-cup molds. If you want a softer set, reduce the agar slightly rather than adding water, and test a spoonful on a cold plate before molding.
- UnmoldingWetting the molds is the whole trick with agar; it releases readily and does not need dipping in hot water, which would soften the surface.