Home › The Principles of Cookery › Blackberry Jam
Blackberry Jam
Proceed as above, leaving out the apples, and allow only half a pound of sugar for each pound of fruit.
A one-line variation that assumes you have just read the blackberry-and-apple entry above it. The omission it describes matters more than it looks: the apples were doing real work.
- Read it as a variation"Proceed as above" points back to the blackberry and apple jam entry immediately preceding, which is not reproduced here. Whatever method that entry gives stands, except for the apples and the sugar weight.
- The apples were the pectinThe apples were doing the setting work -- blackberries are low in pectin and, when fully ripe, low in acid as well, so the apples in the preceding recipe likely supplied both. Without them this version may set poorly; a proportion of underripe berries, the juice of a lemon per 2 lb of fruit, or a jam sugar with added pectin will help.
- The sugar ratioHalf a pound of sugar to a pound of fruit is roughly 50 per cent by weight, against the 3:4 or 1:1 usual in Victorian preserving. That is a fresher-tasting jam with a much shorter life; sugar is the preservative here, and at this level the jam is not shelf-stable in the way a full-sugar preserve is.
- Setting pointTest at 105C/220F on a sugar thermometer, or by the cold-saucer method: a spoonful on a chilled plate should wrinkle when pushed after a minute off the heat. With low sugar and no apple this can take longer than expected.
- SeedsThe original leaves them in. If you want them out, press half the cooked fruit through a nylon sieve before adding sugar and return it to the pan with the rest, accepting some loss of volume.
- StoragePot into hot sterilised jars and seal at once. Given the low sugar, treat it as a refrigerator jam, use within a few weeks, or process filled jars in a boiling water bath to a current tested method.
- Yield2 lb of blackberries with 1 lb of sugar gives roughly 2 lb of jam, so about two 1 lb jars, depending on how hard it is boiled and less again if you sieve out the seeds.
The pairing was not arbitrary. Blackberries ripen in late August and September alongside the first windfall cooking apples, and the apple supplied both pectin and acid, which is why so many British preserve books treat plain blackberry jam as the awkward exception rather than the norm. Blackberries were also the classic free fruit of the hedgerow, gathered rather than bought, which may explain the reduced sugar here: sugar cost money, the fruit did not, and a household making jam from a hedge-picking would stretch the expensive ingredient. The habit of hedgerow gathering was strong enough to carry a folk prohibition with it, generally traced to the belief that the Devil spoiled the fruit at Michaelmas, after which the berries should be left alone.