To prepare for the Jam Plate Test
- Place 3 or 4 small plates into the freezer.
To prepare the orange peel
- Wash and pat dry the oranges.
- Use a vegetable peeler to carefully peel the oranges into long strips, taking care not to have too much pith (white part of the rind) on the rind.
- Finely slice each strip of orange peel as thinly as possible.
- Bring a large pot of water to the boil.
- Cook the thinly sliced orange peel for 1 minute.
- Drain and repeat once more.
- Set the cooked orange peel aside.
To prepare the orange flesh and juice
- Use a sharp knife to remove as much pith as possible from the oranges, as the pith will make the marmalade bitter.
- Remove segments of the oranges between the membranes. Do this over a large bowl to catch all of the juice.
- Squeeze the membranes to get as much juice as possible.
- Discard the membranes but keep all of the seeds for later.
To calculate how much sugar to add
- Weigh how much orange flesh and orange juice you have. I do this by measuring the orange flesh and juice directly in a saucepan on a set of digital scales.
- Calculate how much sugar you need. You will need 80 g (1/3 cup) sugar for every 100 g (3.5 oz) of orange flesh and juice.
- Add the sugar to the orange mixture.
To cook the orange marmalade
- Wrap the orange seeds in some muslin.
- Add the wrapped orange seeds to the orange mixture.
- Add the lemon juice.
- Add the cooked thinly sliced peel.
- Cook the mixture over high heat until it has thickened.
- Stir the mixture frequently so that it doesn’t stick to the bottom of the pan.
- If you are using a sugar thermometer, the temperature should reach 105°C (220°F).
- Once the marmalade is ready, fill your sterilised jars with the marmalade and seal while still warm.
The Jam Plate Test
- If you are not using a sugar thermometer (or even if you are), to test if the marmalade has reached setting point, put a tablespoon of marmalade onto the chilled plate.
- Run your finger through the marmalade.
- If the line remains, the marmalade is ready. If the marmalade fills the line, it is still too liquid and has not yet reached setting point.
- If the marmalade is not ready, continue boiling the mixture and testing the setting point every 5 minutes or so.
SETTING POINT TEMPERATURE
When making this orange marmalade, I frequently find that the mixture reaches setting point at about 110°C (230°F). But I would advise to start checking for the setting point once the temperature reaches 105°C (220°F).
IF YOUR JAM OR MARMALADE HAS NOT SET PROPERLY
If you end up bottling jam or marmalade which has not set – and you can tell if you tip the jar and the mixture sloshes around inside – simply empty the jars back into a large saucepan and reheat them until they have reached the desired thickness. You can try this a few hours after bottling when the jam has had time to cool, or even the next day. The jam should not suffer for this second cooking attempt, although you will have to rewash and sterilise all the jars again.
USING JAM SUGAR
If you are using jam sugar (sugar with added pectin), you should leave out the lemon juice and orange seeds.
HOW TO MAKE GINGER MARMALADE
To make ginger marmalade, grate in some fresh ginger to the finished marmalade while it is still hot. Add as much or as little ginger as you like. You can do this to the whole batch, or only some of the batch.