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Magnum Bonum Plums, to Preserve
Take fine whole fruit, ripe and without bruise; peel and open them only just enough to extract the stones; handle them lightly, so that the juice may not be drawn and lost. Weigh the plums, and strew over each pound of fruit, placed on a flat dish, one pound of good powdered sugar, and cover them for twelve hours. Put them into a preserving-pan with the sugar; boil very gently (or the fruit will shrivel) for about half an hour. If the plums look clear, lift them out carefully with a spoon and put them into jars. Crush the stones, blanch and split the kernels, put some with the syrup (the quantity must depend on taste), but they are generally thought to impart a delicious flavour to the preserve; boil the syrup rapidly until a little put upon a plate will set, then pour it over the plums in the jars. This recipe will serve for large plums in general and for apricots.
MAGNUM BONUM PLUMS, TO PRESERVE (another way.) (See PLUMS, MAGNUM BONUM.)
An equal-weight sugar preserve of the old school, written for a coal range and an open larder. Two things in it fall outside current practice: the crushed stones and the unprocessed jars.
- The kernels are the problemPlum stones contain amygdalin, which can release hydrogen cyanide when the kernel is crushed and wetted — the same chemistry that makes bitter almonds a concern. The recipe adds them to taste with no limit given, and heating cannot be relied on to remove the compound entirely. This is the reason the page carries a caution.
- Filling and sealingFruit and syrup are ladled into jars with no sterilising, no headspace and no water-bath processing. High sugar and acidity do a great deal of preserving work, but an open-poured jar left in a modern warm kitchen is not shelf-stable. Follow a current tested preserving recipe if you want jars to keep.
- "Good powdered sugar"Not modern powdered/confectioners' sugar, which contains cornstarch. In Victorian usage it means loaf sugar crushed fine — the nearest thing now is ordinary granulated or caster sugar.
- Preserving-panA wide, shallow pan, typically copper or brass in this period, though tinned or enamelled iron was also used. Any wide heavy-bottomed stainless or enamelled pan gives the same fast evaporation; the width matters more than the metal.
- The maceration stepTwelve hours under an equal weight of sugar draws juice osmotically and firms the fruit walls, which is what keeps the plums whole rather than collapsing. It is not an optional soak.
- "Boil very gently"A bare simmer. Hard boiling with the fruit still in the pan shrivels and toughens the skins, which is why the plums are lifted out before the syrup is reduced fast.
- The plate testChilling a spoonful on a cold plate until it wrinkles and sets is still the standard set test; on a thermometer that corresponds to roughly 220F. The long rapid reduction of the syrup after the fruit is lifted out is doing much of the setting work.
- YieldThe original gives none. One pound of fruit plus one pound of sugar will fill roughly a pint to a pint and a half of jars.
Magnum Bonum — "great good" in Latin — is an old name for the large yellow egg plum grown in English gardens since at least the eighteenth century, prized for size and firmness rather than for eating raw, and long treated primarily as a preserving and bottling fruit. Cassell's was compiled as an alphabetical dictionary for the late-Victorian middle-class household, and gives varieties their own entries. The instruction to crack the stones and slip a few blanched kernels into the syrup reflects a widespread period habit of using kernels as a cheap substitute for bitter almond or ratafia flavouring in jams, custards and cakes — a practice that persisted for generations and is generally traced to the same taste for almond notes that made ratafia and noyau popular, and one that modern food safety has since ruled out.