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Cherry Jam
Choose sound, ripe Kentish cherries, remove the stones, and boil the kernels in a little water to draw out the flavour; this will impart a very agreeable taste to the jam. Weight the fruit, after stoning it, and allow one pound of sifted sugar to one pound of fruit. Put the sugar into a preserving-pan with a cupful of the water in which the kernels were boiled to each two pounds of fruit, making up the measure with water, or red currant juice. Boil to syrup, then add the fruit and boil it very quickly until it is on the point of jellying. Pour it into jars, cover it with brandied paper, and put over this paper dipped in gum. Time to boil the sugar and water or juice to a syrup, about ten minutes; the syrup and fruit to the point of jellying, about forty minutes. Probable cost, 8d. or 9d. per pound.
The jam itself is an ordinary equal-weights preserve, but the flavouring step at the head of the recipe puts a cyanogenic extract into the pan, and the sealing method belongs to a period before reliable jar closures. The notes below explain what the instructions mean and where they fail.
- The kernels are the problemCherry stones enclose a kernel containing amygdalin, which releases hydrogen cyanide when broken down. Simmering the cracked kernels in water and then pouring that water into the pan is precisely an extraction step, and the stones from several pounds of fruit are not a trace quantity. Modern food guidance is consistent in saying that cherry, apricot and peach kernels should not be eaten or infused; use a current cherry jam recipe, which will not ask for this.
- Not the same as almond flavouringThe "very agreeable taste" the book is after is the noyau or marzipan note, the same compound that gives bitter almonds their scent. Commercial almond extract and almond essence are made to a controlled specification and are a different proposition from an unmeasured home infusion of stones.
- Kentish cherriesThe name is generally taken to mean a sharp red cooking cherry of the Kentish Red type, closest today to a Morello or other sour cherry, though Kent grew sweet dessert varieties too. Sweet dessert cherries make a flatter, cloying jam at this sugar ratio because they lack the acid.
- Red currant juiceCherries are low in pectin and acid, which is likely why the recipe offers currant juice as an alternative to some of the water. Where it is used it will help the set; the recipe treats it as optional.
- Brandied paper and gum paperA round of paper soaked in brandy laid directly on the hot jam, then a second sheet brushed with gum stretched over the rim and left to shrink tight as it dried. It was a common British seal before screw-band jars, and it relies on evaporation and spirit rather than on a vacuum. It is not a reliable barrier against mould over months.
- Forty minutes at a rolling boilFar longer than a modern preserver would boil cherries. Setting point is a temperature, 220F at sea level, reached in a wide pan in a fraction of that time; three-quarters of an hour of hard boiling darkens the fruit and dulls the flavour.
- "Probable cost, 8d. or 9d. per pound"Eight or nine pence in pre-decimal money, the kind of costing Cassell's gave throughout so a housekeeper could judge whether making beat buying.
Cassell's belongs to a period when sugar had become cheap enough for ordinary households to preserve fruit on a large scale, and jam moved from a genteel still-room craft towards a staple of the bread-and-butter table. The insistence on Kentish cherries reflects a real supply chain: the Kent orchards sent cherries into London through the short summer glut. Infusing the cracked stones is an old confectioner's trick, the domestic cousin of noyau and ratafia, both of which were built on the almond-scented compounds in stone-fruit kernels and were used in eighteenth and nineteenth century kitchens before that chemistry was properly understood. The brandied paper and gummed cover are of their date, and were in time displaced by sealed jars.