- Use fresh or frozen fruit to make jam – or a mixture of the two. Make sure that fresh fruit is ripe, but not over-ripe.
- Use granulated or caster sugar – about three-quarters of the weight of the fruit
- Find jars that have well-fitting lids and prepare them by washing in hot, soapy water and rinsing well. Place them on a baking tray spread with a clean tea towel and dry in an oven heated to 120ºC. By the time the jam is ready they will be dry and sterilised.
- If you have a microwave oven put the rinsed jars into the microwave at high power (100%) for 45 seconds.
- Put two saucers into the freezer. You will use them to test the jam for setting.
Cooking the Jam
You will need a wide, heavy-based pan for jam making. It doesn’t have to be enormous and it should not be too deep. Low sides encourage rapid evaporation so that jams taste fresh and have a good, bright colour. A 12–15cm deep pan will allow space for the jam to bubble up, but not bubble over. Make jam in small batches so that the pan is only one-third full – no more than 2kg of fruit, and preferably a bit less.
- Cook the fruit with a little water or on its own until the fruit is soft. Once you add the sugar the fruit will not soften any more.
- Add the sugar slowly and stir until it dissolves.
- Bring the jam to a rapid boil and stir often with a wooden spoon. The stirring will help prevent the jam sticking to the bottom of the pan.
Testing for a Set
- Once the surface of the jam is covered with small bubbles, begin timing. After 5–6 minutes remove the pan from the heat while you test the jam. (If you have a sugar thermometer look for a temperature of 105ºC at which most jams will set.)
- Spoon a little jam onto one of the chilled saucers and leave it for 2 minutes. Then run your finger through the jam. If small wrinkles appear on the surface the jam has reached setting point.
- If not, return to the heat, bring back to a rolling boil and test again in another 5 minutes.
- Once the jam reaches setting point remove from the heat and drop in 1 teaspoon of butter. As it melts it will magically make any surface froth disappear.
Filling the Jars
When the jam has reached setting point, take the sterilised jars out of the oven. Ladle or pour the jam into the jars (a wide-mouthed funnel is useful here) and fill them as full as possible. Put on the lids firmly, or use cellophane covers. Leave undisturbed overnight or until completely cold.
Keep your jams in a cool, dark, dry place – not in a hot cupboard. Most jams will keep for at least one year with no deterioration. If you find a little mould on top of a jar, just spoon it off.
Pectin and Acid
You need both pectin and acid to make jam set. Some fruits are high in both and some are not. Increase the pectin in jam by adding some high-pectin fruit like sour apples, and increase the acid by adding lemon juice or tartaric acid.
Fruit Rich in Pectin and Acid
- Sour apples
- Red and black currants
- Grapes – under-ripe
- Sour oranges
Fruit with Pectin but Needing Acid
- Sweet oranges
- Sweet apples
Fruit with Acid but Needing Pectin
Fruit Low in Pectin and Acid
* These fruits may need pectin or acid depending on the variety and ripeness