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Nectarine Jam
Peel the nectarines, cut them in halves, crack the stones, then blanch and cut the kernels into small pieces. Put the pieces and broken stones into a saucepan with one-half pint of water for every pound of the fruit, and boil till reduced to one-half its quantity, then strain the liquor. Place the fruit in a preserving-pan, and add an equal weight of granulated sugar. Add the liquor from the stones and kernels with eight blanched and chopped bitter almonds for each one-fourth pound of kernels. Place the pan over a slow fire, and stir the contents with a wooden spoon until reduced to a stiff consistency. Turn the jam into jars, and leave for several hours until quite cold, then sift a small quantity of sugar over the top of each, cover with rounds of white paper that have been dipped in beaten egg, tie round the jars with twine, and pack them away for use.
This is a period preserve that deliberately extracts flavour from stone fruit kernels and adds bitter almonds on top of them. Both practices are the reason it cannot be recommended today, and the storage method compounds the problem.
- The kernels are the hazardNectarine, peach and apricot kernels contain amygdalin, which releases hydrogen cyanide when the crushed kernel meets moisture and the fruit's own enzymes. The recipe cracks the stones, chops the kernels, simmers them and then pours that liquor into the jam, which is an efficient way to concentrate exactly the compound you do not want.
- Bitter almonds on top of thatEight blanched bitter almonds per quarter pound of kernels is added flavouring from the same chemistry. Bitter almonds are not sold for food in the United States for this reason, and the quantity here is not trivial "a drop of extract" territory — it is whole nuts, chopped in.
- Boiling does not make it safeHeat drives off hydrogen cyanide, and open boiling removes a good deal of it, but the recipe reduces the kernel liquor and then adds it back, so an unknown quantity is retained. There is no home method for measuring what remains.
- The seal is not a sealA round of paper dipped in beaten egg and tied with twine gives a dust cover, not a hermetic one. Jam of this era relied on very high sugar and a hard set to keep; a modern reader should use a tested water-bath process with proper two-piece lids for any fruit preserve.
- If you want nectarine jamUse a current tested recipe. Nectarine flesh alone, with sugar and lemon, makes the same preserve; the almond note that this recipe is chasing is available from a few drops of pure almond extract, whose active aroma is benzaldehyde, either synthetic or from bitter almond oil with the cyanide removed.
- On the archaic terms, for readingA "preserving-pan" is a wide, shallow pan, usually of copper or heavy brass — a broad stainless or enamelled Dutch oven is the modern equivalent. Half a pint of water per pound of fruit is one cup per pound, and "a slow fire" means the lowest steady heat that keeps the sugar moving without scorching.
Cooking the cracked stones with the fruit was standard practice in nineteenth-century English and American preserving manuals; the bitter-almond note was prized as the "true" flavour of apricot, peach and nectarine, and confectioners called it noyau after the French for the fruit stone. The danger was not entirely unknown — people had been warned against eating kernels in quantity — but amygdalin was not something a household could measure, and the practice persisted because the flavour is genuinely distinctive. Commercial benzaldehyde-based almond flavouring, which delivers the aroma without the glycoside, is what displaced the kernel in twentieth-century kitchens. The paper-and-egg-white cover is older still: the beaten egg dries to a stiff varnish over the paper, a sealing trick recorded in English housekeeping books well before the screw-top jar.