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Rhubarb Mould
Cut into small lengths as much young rhubarb as will fill a quart measure. Boil this with a pound of loaf sugar, eight bitter almonds, blanched and chopped, and the strained juice and grated rind of half a lemon, and stir it over a brisk fire till it is thick and smooth. Dissolve half an ounce of isinglass or gelatine in two table-spoonfuls of boiling water, stir this into the fruit, and pour the whole into a mould which has been soaked in cold water for a time. Put it into a cool place, or upon ice, and when it is quite firm turn it out, and serve with Devonshire or other cream round it. Time to boil the rhubarb, about half an hour. Probable cost, 1s., if made with gelatine.
This is a gelatine-set rhubarb jelly, and it would be unremarkable except for the almonds. Eight bitter almonds is the reason the recipe cannot be followed.
- Bitter almonds are the problemBitter almonds (the kernels of Prunus dulcis var. amara and closely related stone-fruit kernels) contain amygdalin, which enzymes in the crushed nut convert to hydrogen cyanide. Chopping them, as the recipe directs, is exactly what starts that conversion.
- Cooking does not make them safeHalf an hour of boiling in a sugary fruit purée drives off some hydrogen cyanide but does not reliably remove it, and the amount remaining depends on the kernels, the pan and how tightly it is covered. There is no way to judge the dose in a home kitchen.
- The quantity is not trivialEstimates of a dangerous dose for an adult run to a few dozen bitter kernels, and for a small child to a mere handful; eight kernels divided into a chilled mould that a child may eat several servings of is not a comfortable margin. Sold raw for eating, bitter almonds are restricted or prohibited in the United States and tightly controlled elsewhere.
- Almond extract is not a substitute hereModern almond flavour comes from benzaldehyde, which is the aroma without the cyanogenic glycoside. That is why nineteenth-century recipes calling for bitter almonds read as ordinary and modern ones do not — but swapping it in does not make this particular set of instructions sound, and we are not offering a rewritten version. Use a current rhubarb jelly or rhubarb fool recipe instead.
- Isinglass, for the recordIsinglass is a setting agent made from the swim bladders of fish, offered as an alternative to gelatine in Victorian kitchens — as this recipe does — and now largely confined to brewing and conservation work. Half an ounce gives a firm set for this quantity of fruit.
- Rhubarb leavesOnly the stalks are food. The leaves are high in oxalic acid and other irritants and are never used; the recipe assumes a cook who already knows this, which is worth saying out loud.
Cassell's belongs to the later Victorian decades, when cheap commercial gelatine was displacing isinglass in domestic kitchens — note that the recipe prices itself at a shilling "if made with gelatine", the cheaper of the two options, though it still offers isinglass first — and cooks moulded a great range of sweet dishes. Rhubarb had moved from the physic garden to the fruit bowl over the previous century, forced under pots in market gardens around London and in Yorkshire and reaching the shops early enough in the year to fill the gap before the soft fruit. Bitter almonds appear here because they were a common Victorian source of almond flavour, sold alongside the sweet kind and used in small quantities in blancmanges, ratafias and macaroons; some contemporary books that call for them caution against using too many, which suggests the hazard was recognised, if not measured. Devonshire cream served round a turned-out mould was a conventional finish, and the instruction to soak the mould in cold water first is sound practice for releasing a set jelly cleanly.