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Blackberry Jam
Mash the berries, cook them in their own juice until they are thoroughly heated, then press them through a sieve to remove the seeds which are objectionably large if left in. Measure this liquid, and to every pint allow one-half pound of sugar. Return the sugar and the fruit to the fire, and boil rapidly twenty-five minutes, stirring constantly. Then set away as directed. Blackberries are not as often used for jam as the other varieties of berries, on account of the large seeds, but by pulping the fruit through a sieve as directed, this objection is overcome, and the jam is certainly all that can be desired. The medicinal properties of the blackberry are well known, and juice made of the berries is often medicine as well as food.
A seedless blackberry jam with an unusually restrained amount of sugar. The hinge is the sugar ratio, which is low by modern standards and changes both the set and the keeping.
- The sugar ratioHalf a pound of sugar to a pint of pulp is roughly 1 cup sugar to 2 cups puree — about half what most modern jam recipes use. Expect a soft, intensely fruity set that behaves more like a thick conserve, and plan to refrigerate the opened jar and use it within a few weeks.
- Pint means volumeThe measure is 2 cups of strained pulp, not a pound. Measure after sieving, since sieving removes a noticeable amount of seed and skin.
- Sieving the seedsA food mill with a fine plate does in two minutes what the original expects of a sieve and a wooden spoon. A conical sieve with a pestle also works; avoid a blender, which pulverizes the seeds back into the pulp.
- Judge by temperature, not the clockTwenty-five minutes at a rapid boil assumes a wide, shallow preserving pan. In a tall modern saucepan it will take considerably longer and scorch on the way. Use the widest heavy-bottomed pot you have and cook to 220F, or until a spoonful wrinkles on a chilled plate.
- Stirring constantly is not optionalSieved blackberry pulp is thick and catches on the bottom well before it sets. A flat-ended wooden spatula reaches the corners of the pan better than a spoon.
- "Set away as directed"Canning instructions of this period typically end in sealing wax or a paraffin cap over the jam. Neither is used now. Fill hot sterilized half-pint jars, leaving quarter-inch headspace, and process in a boiling water bath following current published times for berry jam, or simply keep the jars in the refrigerator.
- YieldTwo quarts of whole blackberries give roughly 4 cups of sieved pulp and, at this sugar level, about three half-pint jars.
Blackberry jam sits slightly apart from raspberry and strawberry in nineteenth-century preserving chapters, and the reason given here — the seeds — is a common one. Cooks who wanted blackberry without grit made jelly or, as here, pulped the fruit through a sieve. The closing remark about medicinal properties is not decorative: blackberry root, bark, and syrup were standard household remedies for diarrhea and summer complaint through the 1800s, listed in dispensatories and sold as blackberry cordial and blackberry brandy, so a jar of jam was understood to be partly a medicine chest item. The Butterick Publishing Company, better known for dress patterns, also issued a cook book, from a moment when home preserving was still governed by paraffin, sealing wax, and the cook's own judgment rather than by tested processing times.