This is a tested recipe for a thick, sweet-sour onion preserve in the marmalade style: red onions and sweet peppers boiled down in sugar and plenty of vinegar until the pan is half as full. It is sharper and looser than the butter-cooked onion marmalades in most cookbooks, and that extra vinegar is what lets it keep in the cupboard once processed. Follow the quantities exactly.
- Makes
- about 9 x 250 ml jars (full batch) or 4–5 jars (half batch)
- Cooking time
- about 30 minutes of gentle boiling
- Keeps
- up to a year sealed, if processed in boiling water; one month in the fridge if not
- Once opened
- in the fridge
- Processing
- 5 minutes in boiling water up to 305 m altitude, 10 minutes above
Ingredients
- 1.44 litres finely chopped red onions
- 720 ml finely chopped sweet red peppers
- 720 ml finely chopped green peppers
- about 300 g (360 ml) granulated sugar
- 1.44 litres vinegar labelled at least 5% acidity, preferably white distilled
- 2 tbsp canning or pickling salt
Measure the chopped vegetables by volume in a measuring jug; ordinary table salt is safe if you can't find pickling salt (it may cloud the liquid), but don't use flake salt.
Method
- Wash and finely chop the onions and peppers.
- Sterilise the jars by boiling: stand them upright on a rack in a deep pan, cover with hot water to 2.5 cm above the tops, boil for 10 minutes (add 1 minute for every 305 m above the first 305 m) and keep them hot until filling.
- Put all the ingredients in a large pan.
- Boil gently until the mixture thickens and the volume has dropped by half, about 30 minutes.
- Fill the hot jars with the hot mixture, leaving just over 1 cm of space at the top.
- Wipe the rims clean and put on new lids, sealing them tightly.
- Either process the jars in boiling water (see below) for cupboard keeping, or let them cool and put them straight in the fridge.
Why this recipe has so much vinegar
Onions are a low-acid vegetable. In a sealed jar, a low-acid food gives the bacteria that cause botulism the conditions they need. What stops them is acid: there must be a minimum, even level of it through the whole jar, and here the vinegar provides it. The vinegar is the safety margin, and the sugar and vegetables are part of the tested balance, so keep to the recipe:
- Use white distilled vinegar (first choice) or cider vinegar, labelled at least 5% acidity. Never use a vinegar whose strength isn't on the label.
- Never cut the vinegar or the sugar, add water, or add extra onion, pepper or anything else, such as fresh garlic, herbs or chilli.
- Don't add butter, oil or wine.
Recipes that soften the onions in butter or oil and add only a few spoonfuls of vinegar are a different product: nobody knows how acidic the finished jar is. A chutney or pickle that can't be relied on to reach pH 4.5 or lower should be kept in the fridge, even before it is opened. Oil adds its own risk: foods preserved in oil are among those linked to botulism. So treat any buttery or oily onion marmalade as a fridge preserve only, with no cupboard life.
Two ways to keep it
| Processed in boiling water | Hot-filled, no boiling-water step | |
|---|---|---|
| Jars | Sterilised, then processed after filling | Sterilised, filled hot and sealed |
| Unopened jars live | Cool, dark, dry cupboard | Fridge |
| Keeping time | Use within a year | Use within one month |
| Once opened | Fridge | Fridge |
A lid that seals as the jar cools doesn't change this: without the boiling-water step, the jars belong in the fridge.
The processing time is too short to sterilise the jars as well, which is why step 2 matters on both routes. Use jars of about 250 ml or 500 ml with new lids; for lid types that stand up to vinegar, see choosing jars for preserving.
Processing the jars
You need a deep pan with a rack in the bottom and a lid, and a jar lifter.
- Put the rack in the pan and heat the water until it is hot but not boiling (about 82°C) before the filled jars go in.
- Lower the jars in one at a time, upright.
- Top up with boiling water, poured around the jars, until it covers the lids by at least 2.5 cm.
- Bring to a vigorous boil, cover, and start timing only once it is boiling.
- If it stops boiling at any point, bring it back to the boil and start the full time again.
| Altitude of your kitchen | Processing time |
|---|---|
| Up to 305 m (1,000 ft) | 5 minutes |
| Above 305 m (1,000 ft) | 10 minutes |
Water boils at a lower temperature the higher you go, so upland homes need the longer time. If you are not sure of your height above sea level, check before you start.
When the time is up, turn off the heat, take off the lid and wait 5 minutes. Lift the jars out without tilting them onto a towel or rack, 2.5 cm apart and away from draughts, and leave them alone for 12–24 hours.
Checking and storing
Once cold, press the centre of each two-piece metal lid: if it springs back, the jar hasn't sealed. For other lid types, check as the maker directs. Put any unsealed jar in the fridge and use it first.
Label sealed jars with the date and store them somewhere clean, cool, dark and dry, ideally 10–21°C, away from the cooker, hot pipes and sunlight. Damp can corrode lids and break the seal, and freezing can soften the contents and risk a broken seal, so an unheated shed or garage is a poor store. For keeping times across all your preserves, see how long preserves keep.
Throw a jar out without tasting if the seal has gone, it smells wrong, liquid spurts out on opening, or there is any mould on the surface or under the lid.
Onions from the plot
Red onions from your own plot or store are ideal here, because the recipe uses a lot of them. Autumn-planted onions keep only until early winter, and any bulb whose neck never firmed up belongs on the use-first pile, so those are the ones to chop for a batch. For raising the crop, see growing onions; for curing and keeping the rest, see storing onions, garlic and shallots.
Half batch
Halve every ingredient together.
| Ingredient | Full batch | Half batch |
|---|---|---|
| Finely chopped red onions | 1.44 litres | 720 ml |
| Finely chopped sweet red peppers | 720 ml | 360 ml |
| Finely chopped green peppers | 720 ml | 360 ml |
| Granulated sugar | about 300 g (360 ml) | about 150 g (180 ml) |
| Vinegar, at least 5% acidity | 1.44 litres | 720 ml |
| Canning or pickling salt | 2 tbsp | 1 tbsp |
| Makes | about 9 x 250 ml jars | 4–5 x 250 ml jars |
Common questions
Why is it runnier and sharper than the onion marmalade I've bought?
It carries far more vinegar and no fat. It thickens as it boils down, but it will never set like a jam. Never cut the vinegar to change that.
Can I leave out the peppers and use only onions?
No. The recipe is tested with the peppers in, and swapping them for more onion changes the balance of vegetables to vinegar.
Can I use balsamic or red wine vinegar for a richer flavour?
Stick to white distilled or cider vinegar labelled at least 5% acidity, the vinegars recommended for tested pickles.
Do I have to process the jars in boiling water?
Only if you want to keep them in the cupboard. Without the boiling-water step, the jars go in the fridge and should be eaten within a month.
How long does an opened jar keep?
Keep it in the fridge and eat it within a few weeks. Check it for mould, bubbling or an off smell each time, and throw it out if you find any.
What else can I make with the onion glut?
Green tomato chutney uses onions too, pickled beetroot can take a few sliced onions in with the roots, and quick fridge pickles suit a single jar.
Sources
Show the 10 sources
- Pickled Pepper-Onion Relish (National Center for Home Food Preservation, University of Georgia): Recipe proportions based on: NCHFP tested recipe (adapted from USDA Complete Guide to Home Canning, 2015). Ingredients, 5% vinegar preferably white distilled, yield of 9 half-pints, method, cooking to half volume in about 30 minutes, sterile jars, 1/2-inch headspace, fridge storage and use within one month without processing, processing times by altitude for half-pints or pints
- Sterilization of Empty Jars (National Center for Home Food Preservation): Jars for pickled products processed less than 10 minutes must be sterilised first; boiling method (upright on a rack, water 1 inch above tops, boil 10 minutes, plus 1 minute per extra 1,000 ft)
- Using Boiling Water Canners (National Center for Home Food Preservation): Canner, rack and jar lifter; preheating water to 82°C for hot pack; water at least 2.5 cm over jars; timing from a vigorous boil and restarting if boiling stops; 5-minute wait, cooling 2.5 cm apart away from draughts for 12–24 hours; unsealed jars to the fridge and used first
- Storing Home Canned Foods (National Center for Home Food Preservation): Seal check on two-piece lids; storage clean, cool, dark, dry at 10–21°C, away from heat and sunlight; damp corroding lids; using within a year; spoilage signs and not tasting suspect jars
- Ensuring Safe Canned Foods (National Center for Home Food Preservation): Fresh vegetables other than most tomatoes are low-acid; mixtures stay above pH 4.6 unless enough vinegar is added
- General Information on Pickling (National Center for Home Food Preservation): White distilled and cider vinegars of 5% acidity; don't alter vinegar, food or water proportions or use vinegar of unknown acidity; minimum, uniform acid level to prevent botulinum growth
- Food Safety and Labelling Guidance for small scale home producers of chutneys, pickles, flavoured oils and jams (Scottish Borders Council): The amount of vinegar and/or sugar is essential for safety; chutneys and pickles that can't guarantee pH 4.5 or lower should be refrigerated even before opening; do not re-use lids
- Salts Used in Pickling (National Center for Home Food Preservation): Canning or pickling salt recommended; table salt safe but anti-caking agents may cloud the liquid; flake salt not recommended
- Botulism (Clostridium botulinum) (Food Standards Agency, via GOV.UK): Foods preserved in oil and home-preserved foods are linked to botulism
- Onions: grow your own (RHS): Autumn-planted onions store until early winter