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Red Raspberry Jam
Red raspberry jam is made the same as strawberry, and is the choicest jam that is made. The quantity of fruit required in making jam is in the proportion of about six boxes of berries to six pint jars of jam, the boxes being of the size commonly known as quarts, although they do not hold that amount by any means.
This entry is really a proportion table with a cross-reference: the method comes from the book's strawberry jam, and what is given here is the fruit-to-jar ratio. A few of the period's assumptions need spelling out.
- What a "box" holdsThe berry boxes sold as quarts were shallow wooden baskets that, as the recipe itself complains, held well short of a quart; the book does not say how much. If they held nearer a dry pint (about 12 oz of raspberries), six boxes would come to roughly 4 1/2 lb of fruit rather than six quarts.
- YieldSix pint jars from that quantity, as stated. Expect somewhat less if you cook the jam hard and long, since evaporation is what thickens it.
- SugarPeriod strawberry jams generally worked on roughly equal weights of fruit and sugar, but the book's own strawberry recipe should be checked for the proportion it actually gives. Raspberries carry enough natural pectin and acid that no commercial pectin is needed at that ratio; much below about 3/4 lb sugar per pound of fruit the set becomes unreliable.
- Judging the setThe period test was a spoonful chilled on a cold saucer that wrinkles when pushed. A thermometer is faster: 220F at sea level, or 8F above the boiling point of water where you live.
- Pan and heatUse a wide, heavy pan filled no more than a third, and cook in a single batch of this size or smaller. Doubling the quantity extends the boil and cooks the fresh raspberry flavour out of it.
- SeedsRaspberry jam was expected to be seedy. If you want it smooth, press half the crushed fruit through a fine sieve before adding sugar and keep the rest whole for body.
- SealingThe book's era finished jars with melted paraffin over the surface, which is no longer considered a reliable seal. Fill clean hot jars, leave 1/4 inch headspace, fit two-piece lids and process in a boiling water bath for 10 minutes.
Raspberries are high in both pectin and acid, so they set firmly with nothing but sugar and heat, at a period before commercial pectin was on sale. Berry fruit was then retailed in flat wooden splint boxes, and the complaint that those boxes did not hold a quart "by any means" was a common one; short measure in berry baskets was later addressed by container-standardisation legislation.