How to Make Marmalade: A UK Seville Orange Guide

What actually is marmalade, and how is it different from jam?

Marmalade is a preserve made from citrus fruit, and the thing that sets it apart is the peel. Jam is fruit pulp boiled with sugar until it sets. Marmalade does the same job but keeps the shredded rind suspended in a clear, glowing jelly, so every spoonful carries that slightly bitter, aromatic citrus note. That bitterness is the whole point. It's what makes marmalade grown-up, and what stops it being just orange jam.

By UK convention "marmalade" means a citrus preserve specifically. You'll see the odd jar of "onion marmalade" or similar, but the classic breakfast version is built on oranges, and the traditional orange for the job is the Seville.

Why are Seville oranges the classic choice?

Two reasons, and they're linked. First, flavour: Sevilles are bitter oranges, far too sharp to eat raw, but that bitterness is exactly what you want cooked down with sugar. Second, and this is the practical bit, they're naturally high in pectin, the substance that makes a preserve set. As British Frozen Fruits put it, Sevilles "naturally have a higher level of pectin, which is what makes the marmalade set so well."

That high pectin content is a real gift to a home cook. Sweet oranges are lovely but low in pectin, so marmalade made with them often struggles to set without help. With Sevilles, the fruit does most of the work for you.

The bitterness that stops you eating a Seville raw is the exact thing that makes it sing in a jar.

Why is January the time to make it?

Because that's the only time you can get the fruit. Seville oranges have a famously short UK season, roughly from the end of December through to mid-February. Blink and it's gone. That narrow window is why marmalade-making became a British January ritual, a cheerful bit of kitchen work to do when the garden's asleep and there's not much else going on outside.

What makes marmalade set? The pectin, acid and sugar science

A good set is not luck. It's three ingredients doing a specific job together, and understanding it makes troubleshooting much easier.

Pectin is a natural carbohydrate in the cell walls of fruit. When you heat it with sugar and acid, the pectin molecules link up into a loose mesh that traps liquid, and that mesh is what turns runny syrup into a soft, spoonable jelly as it cools.

Acid is what lets the pectin bond in the first place. Pectin molecules carry an electrical charge that makes them repel one another. Acid, from the oranges themselves and a squeeze of lemon, reduces that repulsion so the molecules can knit together. Too little acid and the set stays weak no matter how long you boil.

Sugar does two things. As the pan boils and water evaporates, the rising sugar concentration draws water away from the pectin, which pushes the molecules to bond rather than float about separately. Sugar is also the preservative: at marmalade strength it binds up the available water and stops most microbes growing, which is what gives you jars that keep for months.

Here's the useful part for a Seville. Most of the pectin isn't in the juice or the peel you can see. It's concentrated in the pith, the membranes and the pips. Which is exactly why the next bit of the method matters so much.

Why do I tie the pips and pith in a muslin bag?

Because that's how you get the pectin out of the bits you don't want to eat. You're not going to leave gritty pips and stringy membrane in the finished marmalade, but you do want their setting power. So you tie them into a square of muslin, simmer the bag right in the pan with the fruit, and let the heat draw the pectin out into the liquid. At the end you lift the bag out, let it cool enough to handle, and squeeze it hard over the pan. What comes out looks like clear jelly, and that's liquid pectin going straight into your batch.

Skip the squeeze and you're throwing away a good chunk of your set. It's the single most-missed step for first-timers.

How do I make it? Step by step

This follows a classic Seville method. Work through it in order and don't rush the peel-softening stage, because you can't fix hard peel later.

1. 1

   Wash and halve the fruit

   Scrub 1kg of Seville oranges and one lemon. Cut them in half and squeeze out all the juice into your preserving pan or a large heavy pan. Keep every pip and any stringy membrane that comes out.

2. 2

   Bag up the pips and pith

   Scrape the soft pith and membrane from inside the peel. Put that, plus all the pips, into a square of muslin and tie it into a bag with a long string. This is your pectin bag.

3. 3

   Shred the peel

   Slice the empty peel into shreds as thick or as fine as you like. Thin shreds give a delicate marmalade, chunky shreds a proper old-fashioned one. This is where you decide the character of the batch.

4. 4

   Simmer until soft

   Add the shredded peel, the juice, the muslin bag and about 2 to 2.5 litres of water to the pan. Bring to the boil, then simmer gently for around 1.5 to 2 hours, until the peel is soft enough to crush between your fingers and the liquid has reduced. Soft peel now means tender peel forever.

5. 5

   Squeeze the bag and add sugar

   Lift out the muslin bag, let it cool a little, then squeeze it hard over the pan to release the pectin. Add roughly 2kg of sugar and stir over a low heat until every grain has dissolved. Don't let it boil until the sugar is fully dissolved, or you risk a grainy set.

6. 6

   Boil hard to setting point

   Now turn it up to a proper rolling boil. This can take anywhere from 15 to 45 minutes. Start testing for setting point early so you don't overshoot.

7. 7

   Pot up

   Once it's set, take it off the heat and let it stand for about 15 minutes. This stops the peel floating to the top. Then ladle into hot sterilised jars and seal straight away.

How do I know when it's reached setting point?

Setting point is the moment enough water has boiled off for the pectin to gel once it cools. On a sugar thermometer that's around 104-105°C, or about 220°F. Kilner give the range as 104 to 105.5°C for jam and marmalade, so anywhere in that band is fine. You don't need pinpoint precision, just to be in the zone.

No thermometer? Use the wrinkle test, which is the traditional method and honestly just as reliable.

Taking the pan off the heat while you test matters. Marmalade can go from not-quite to over-boiled quickly, and a stiff, dark set is much harder to rescue than a slightly loose one.

How do I sterilise the jars, and why bother?

Sterilising is what keeps your marmalade safe and good for months rather than growing mould in a fortnight. Hot, clean jars mean there's nothing living in there to spoil the batch, and the high sugar and acid of the marmalade does the rest.

The easy method: wash your jars and lids in hot soapy water, rinse, then stand them upright on a baking tray and dry them in the oven at around 150°C (300°F) for 10 to 15 minutes. Time it so the jars come out hot just as your marmalade is ready. The golden rule is hot marmalade into hot jars. Pouring hot preserve into a cold jar can crack it, and filling a cool jar gives microbes a foothold. Seal the lids while everything's hot.

What ratio of fruit to sugar and water should I use?

Treat this as a reliable starting point rather than a rule carved in stone, because peels vary and so do tastes:

• 1kg Seville oranges
• Roughly 2kg sugar
• About 2 to 2.5 litres of water
• The juice of 1 lemon for extra acid and pectin

That's close to the ratio Jo's Kitchen Larder uses. You'll see leaner versions too, such as Borough Market's 1kg oranges to 1.75kg sugar, which gives a slightly less sweet, sharper result. The heavy sugar quantity isn't just for taste, remember: it's doing preserving work, so don't slash it dramatically. If you want a less sweet marmalade, drop it a little and lean on the bitterness of the fruit rather than cutting the sugar in half.

Why has mine gone wrong, and how do I fix it?

It won't set. Nine times out of ten it simply hasn't reached setting point, so get it back to a hard rolling boil and keep testing. If it still won't firm up, it's short on acid or pectin: stir in the juice of another lemon and boil again. And always, always squeeze that muslin bag, because that's where your pectin was hiding.

It's set like a brick. You've over-boiled it and driven off too much water, or pushed the temperature well past 105°C. There's no true fix once it's potted, but you can loosen a stiff batch by gently warming it with a splash of water. Next time, start the wrinkle test earlier.

The peel floats to the top (or sinks). This is a cooling issue, not a disaster. Peel drifts when you pot straightaway. Letting the marmalade stand for about 15 minutes before ladling lets it thicken slightly so the shreds stay evenly suspended, then give it a gentle stir as you fill.

What variations are worth trying?

Once you've got the basic method, it's yours to play with.

Thick cut or thin cut. This is just how you slice the peel. Chunky shreds for a rugged, traditional jar, fine shreds for something more elegant. Same method, different personality.

A splash of something. Stir a tablespoon or two of whisky in right at the end, off the heat, for a classic grown-up marmalade. A knob of finely chopped or grated fresh ginger added with the sugar gives warmth and bite.

Out of season. No Sevilles about and none in the freezer? Make a mixed-citrus marmalade with ordinary oranges, lemons and a grapefruit. It won't have the same bitter depth, and because sweet oranges are lower in pectin you'll want to be generous with the lemon juice to guarantee a set, but it's a good way to keep the marmalade jar full in July.

Marmalade is one of those kitchen jobs that looks fussier than it is. Get the peel properly soft, respect the muslin bag, and stop at setting point, and you'll have a shelf of glowing jars to see you through to next January.

Related guides

• Preserving: the full hub for the whole collection, from chutneys to bottling.
• How to make jam in the UK, the same setting science with soft fruit and a shorter afternoon.
• How to store apples over winter, for keeping the autumn harvest going long after the trees are bare.