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General Rule for Making Preserves
Weigh the prepared fruit and take an equal weight of sugar. If the fruit be soft, put a layer in a saucepan and sprinkle on sugar; add another layer of fruit and another layer of sugar.
Let heat gradually to the boiling-point, boil about ten minutes, skim, and store in small glasses.
If the fruits be firm, boil in barely enough water to cover until tender; skim out the fruit, add the sugar to the liquid, boil ten minutes, skim, add the fruit, and let cook from ten minutes to half an hour. If a thicker syrup be desired, cook twenty minutes before adding the fruit, or cook longer, after removing the fruit to the jars.
In the making of jams, marmalades, and butters, in which crushed fruit-pulp is cooked with its weight or nearly its weight in sugar, or other sweet such as honey, the best results, in general, are obtained when the addition of the sugar is delayed until the greater part of the water has been evaporated in cooking.
In the making of marmalade from citrus fruits, long cooking is essential to reduce the rind to tenderness. If sugar be added before the rind is exceedingly tender, no amount of cooking will render it soft and edible.
This is a method rather than a single recipe, and it holds up well — the chemistry of fruit and sugar has not changed. What has changed is how the finished jars are sealed and stored.
- The hinge: citrus rindThe last two sentences are the most important lines on the page. Sugar sets the pectin and toughens cell walls, so peel that is still firm when sugar goes in will stay leathery no matter how long it cooks. Simmer citrus rind in water until a strip crushes easily between finger and thumb before any sugar is added.
- Equal weight of sugarPound for pound is the historic preserving ratio and it is what makes these keep. Cutting the sugar substantially gives a looser, more perishable product that needs added pectin and refrigeration.
- "Small glasses"Jelly glasses, roughly half-pint. Small containers suited a household because an opened preserve spoiled quickly; the same logic applies now, so favour half-pints over quarts.
- Sealing is the missing stepThe original assumes an open-kettle fill, often finished with a paraffin cap. Neither is current practice. Use modern two-piece lids on hot, clean jars and process filled jars in a boiling-water bath — around 10 minutes for half-pints of high-acid fruit preserve — or treat the result as a refrigerator preserve and eat it within a month.
- Judging the setNo temperature is given. A full jam or marmalade sets at about 220F (8F above the boiling point of water where you live); the cold-saucer test does the same job.
- Delaying the sugarThe advice to evaporate most of the water before sweetening is sound and still taught. Sugar added early raises the boiling point and lengthens the cooking, which dulls fresh fruit flavour and darkens the colour.
- Boiling ten minutesFor soft fruit this is about right — longer turns raspberries and strawberries to mush. Firm fruit such as quince, pear or thick-skinned plum will want the upper end of the range given, and citrus marmalade routinely takes an hour or more before the sugar goes in.
- SkimmingThe foam is protein and trapped air, harmless but cloudy. A small knob of butter stirred in near the end reduces it; skim just before jarring rather than repeatedly.
- YieldAs a rough guide, 2 lb of prepared fruit with 2 lb of sugar gives about five half-pint jars.
The pound-for-pound rule that opens this page survived into the twentieth century because it works: at roughly 60 to 65 percent sugar, a preserve is too osmotically hostile for most spoilage organisms, which is why generations of cooks could seal jelly glasses with nothing but melted paraffin. Books of this kind proliferated in the decades after cheap beet and cane sugar put preserving within reach of ordinary households, and after the domestic-science movement began insisting that cooks be given principles rather than lists. The closing note on marmalade points back to Britain, where the word \em>marmelada, a quince paste — attached itself to bitter Seville orange preserves; the warning about rind toughening in sugar syrup is the kind of hard-won detail that separates a written-down household rule from one learned at someone's elbow.