Name: Jam
Ingredients: 1 pound ripe and slightly underripe berries; ¾ pound sugar

Jam

Ingredients

1 pound ripe and slightly underripe berries
¾ pound sugar

Directions

Weigh the berries and combine them in a pot.
Add ¾ pound of sugar for each pound of fruit.
Cook the mixture over medium heat, stirring gently with a wooden spoon.
Cook until the jam reaches 220°F (104°C).
To test, cool a small amount on a spoon; it should fall in a sheet or flake.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

What each ingredient does

Berries: Provide the fruit flavour, natural pectin and acids that help the jam thicken and set.
Sugar: Sweetens the jam and, with heat, helps it thicken and keep its set.

The step that matters

Cooking to the set point. Jam sets when enough water evaporates and sugar and pectin reach the right concentration. Cooking to 220°F (104°C), and checking the spoon test, shows when that point is reached. Stopping early leaves runny jam; cooking too long can make it stiff and dull in flavour.

“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.