An onion bed rarely comes up all one size, and the tiny bulbs are fiddly to peel for everyday cooking. Kept back and peeled in one sitting, they fill a batch of jars. This is a tested recipe for sweet pickled onions with mustard and celery seed, finished in a pan of boiling water so the sealed jars keep in the cupboard. Follow the quantities and times exactly.
- Makes
- about 3–4 x 473 ml (US pint) jars
- Keeps
- sealed, in a cool, dark, dry place; make only what you will eat within a year
- Once opened
- in the fridge
- Ready to eat
- after 3–5 days in the jar
- Processing
- 10 minutes in boiling water (up to 305 m altitude)
Ingredients
- 1.9 litres small whole white onions, pearl or pickling size, peeled (measured in a jug)
- 1.32 litres white distilled vinegar, 5% acidity
- 240 ml water
- 400 g granulated sugar
- 2 tsp canning or pickling salt
- 8 tsp mustard seed
- 4 tsp celery seed
The onions are measured by volume, not weight, and the vinegar and water stay at exactly 5½ parts to 1.
Method
- Wash and rinse the jars and keep them hot until you fill them. The 10 minutes or more in boiling water does the sterilising, so they don't need it first.
- Put a few onions at a time in a wire basket or sieve and dip them in boiling water for 30 seconds.
- Move them straight into cold water for 30 seconds.
- Cut a very thin slice (about 1.5 mm) from the root end, slip off the skin, then cut the same thin slice from the top.
- Measure the peeled onions in a jug until you have 1.9 litres.
- Put the vinegar, water, sugar and salt in a stainless steel or enamel pan and boil gently for 3 minutes.
- Add the onions, bring back to the boil, then lower the heat and simmer until half-cooked, about 5 minutes.
- Put 2 tsp mustard seed and 1 tsp celery seed in the bottom of each hot jar.
- Fill the jars with hot onions, stopping 2.5 cm below the rim.
- Pour in the hot pickling liquid to cover them, stopping just over 1 cm (½ inch) below the rim.
- Slide a clean spatula down the inside of each jar to release air bubbles, then top up with hot liquid if the level has dropped.
- Wipe the rims with a clean damp cloth and put on new two-piece metal lids.
- Process the jars in boiling water for the time in the table below.
- Leave the jars undisturbed for 12–24 hours, then check the seals.
- Wait 3–5 days before opening, so the flavour develops.
Why onions need the vinegar
Fresh onions, like almost every fresh vegetable, are a low-acid food, above pH 4.6. At that level the bacteria that cause botulism can grow in a sealed jar. The vinegar brings the whole jar down to pH 4.6 or below, where they can't, but only if there is enough acid spread evenly through every onion. So the rules are strict:
- Use vinegar of 5% acidity. Check the label, and never use a vinegar of unknown strength.
- Never cut the vinegar, add extra water or squeeze in more onions. The amount of vinegar is what makes the jar safe.
- Use vinegar labelled at least 5% acidity. White distilled keeps the onions pale; cider or malt vinegar works measure for measure but darkens them.
- Use small whole onions of pearl or pickling size only, never larger bulbs, whole or cut up.
- Use canning or pickling salt: pure salt with no iodine or anti-caking agent. Anti-caking agents can cloud the liquid, and iodised salt can darken the onions.
From the plot to the jar
Pick sound, firm bulbs of the best quality you have. Any onion that was bruised when lifted is better used in the kitchen straight away. Lift carefully with a fork and dry the crop for about two weeks on racks where air can get underneath: in a greenhouse or airy shed if the weather is damp, or in full sun if it's dry. The bigger bulbs can go into store for the winter: see storing onions, garlic and shallots. For sowing and growing, see growing onions.
Shallots haven't been tested in this recipe, so pickled shallots follow the fridge rule below. For winter use, dry them well instead: they store for at least six to eight months in a light, cool, airy place. See growing shallots.
Processing the jars
The jars go into a boiling-water canner: a deep pan with a rack in the bottom and a lid.
- Put the rack in the pan and heat the water until hot but not boiling (about 82°C) before the filled jars go in.
- Lower the jars in one at a time, upright, with a jar lifter.
- Top up with boiling water so it covers the lids by at least 2.5 cm.
- Bring to the boil, cover, and start timing only once it is boiling.
- Keep a gentle but steady boil. If it stops boiling at any point, bring it back to the boil and start the timing again from zero.
| Altitude of your kitchen | Processing time (473 ml jars) |
|---|---|
| Up to 305 m (1,000 ft) | 10 minutes |
| Above 305 m (1,000 ft) | 15 minutes |
Water boils at a lower temperature the higher you go, so upland kitchens need the longer time. If you live in a hill village, check your height above sea level before you start.
These times only apply to US pint jars (473 ml) closed with two-piece metal lids: a flat lid with a sealing ring, held on by a screw band. Don't use bigger jars. Jars with twist-on lids or clip-tops with rubber seals come under the fridge rule. For help telling lid types apart, see choosing jars for preserving.
When the time is up, turn off the heat, take the lid off and wait 5 minutes. Lift the jars out one at a time and set them on a towel or cooling rack, at least 2.5 cm apart. Leave them alone for 12–24 hours.
Checking the seal
Once cold, press the middle of each lid. If it springs back up when you let go, the jar hasn't sealed.
The fridge rule
Everything except a processed, sealed jar goes in the fridge. For anything on the fridge route, sterilise the jars first.
| Jar | Where | Eat within |
|---|---|---|
| Processed and sealed | Cool, dark cupboard | A year |
| Processed but didn't seal | Fridge, or reprocess within 24 hours with a new lid | A week |
| Not processed, other lids, shallots or traditional onions | Fridge | 10 days |
| Opened | Fridge | No set time; check before each use |
The 10-day limit comes from council food-safety guidance for pickles whose acidity can't be guaranteed.
The traditional British pickled onion
The old-style British pickled onion is made differently. The peeled onions are dry-salted overnight, rinsed, packed raw and covered with spiced malt vinegar that has been boiled and left to cool, then left for weeks to mature. The raw onions are never heated in the vinegar and the jars aren't processed, so nothing shows that the acid has reached the middle of every onion. No safe processing time or cupboard life has been worked out for that method, so it falls under the fridge rule, and a 10-day limit leaves no time for weeks of maturing.
When pickled onions go wrong
| Problem | Likely cause | Avoid it by |
|---|---|---|
| Soft or slippery | Vinegar weaker than 5%, jars not processed, or stale, mouldy spices | Using 5% vinegar, processing every batch and using fresh seeds. If there are signs of spoilage, don't eat them |
| Shrivelled | Overcooking or overprocessing | Keeping to the simmer and processing times |
| Dark or discoloured | Iodised salt, hard water, ground spices, or a brass, iron, copper or zinc pan | Pickling salt, soft water, whole seeds and a stainless steel or enamel pan. If a brass, copper or zinc pan was used, throw the pickles out |
| Faded or dull | Too much light in storage | Keeping jars somewhere dark |
| White sediment or cloudy liquid | Salt with an anti-caking agent | Canning or pickling salt |
Storing and using the jars
Label sealed jars with the date. Keep them somewhere clean, cool, dark and dry, ideally 10–21°C, away from hot pipes, the cooker and the boiler, and never above 35°C. An unheated shed or garage is a poor store over a Scottish winter: damp can corrode lids and break seals, and jars that freeze can soften, with spoilage getting in if a seal breaks. Pickles, jams and chutneys keep for different lengths of time: see how long preserves keep.
Before opening any jar, look at it. Throw it out without tasting if the lid has lifted or swollen, if there is any mould, if liquid spurts out when you open it, or if it smells wrong. Once opened, keep the jar in the fridge and check it for the same signs each time. For more vegetable pickles, try pickled beetroot or pickled red cabbage.
Common questions
Can I use malt vinegar?
Yes, if the label shows at least 5% acidity; that strength is what keeps the jar safe. White distilled vinegar keeps the onions pale, and cider or malt vinegar darkens them and changes the flavour. Onions pickled the traditional way, in cold malt vinegar with no boiling-water bath, still come under the fridge rule.
Can I cut the sugar to make them sharper?
Not in this recipe. Keep the sugar as written, and never change the vinegar or water. This is a sweet pickle by design, so for a sharper jar choose a different pickle rather than altering this one.
Can I pickle shallots this way?
Only as a fridge pickle, eaten within 10 days. Shallot jars can't go in the cupboard.
How long does an opened jar keep?
There's no set time. Keep it in the fridge, eat it steadily rather than keeping it for months, and throw it out without tasting if you see mould, bubbling or an unnatural colour, or it smells wrong.
Sources
Show the 13 sources
- Pickled Pearl Onions (National Center for Home Food Preservation, University of Georgia): Recipe proportions based on: NCHFP tested recipe (University of Georgia, October 2005). Yield, ingredients, peeling method, boil and simmer times, seeds per jar, headspace, hot jars, air bubbles, rims and lids, processing times by altitude for pint jars, cooling 12–24 hours, 3–5 days before eating
- General Information on Pickling (National Center for Home Food Preservation): White distilled and cider vinegars of 5% acidity recommended; white preferred for light colour; don't alter vinegar, food or water proportions or use vinegar of unknown acidity; uniform acid level to prevent botulinum growth; canning or pickling salt, non-caking agents clouding the brine
- Causes and Possible Solutions for Problems with Pickled Foods (National Center for Home Food Preservation): Troubleshooting table (soft, shrivelled, dark, faded, white sediment); pan materials; do not eat if spoilage is evident; discard pickles made with brass, copper or zinc utensils; produce of optimum quality
- Using Boiling Water Canners (National Center for Home Food Preservation): Rack and lid, preheating to 82°C (180°F) for hot pack, water at least 2.5 cm over jars, timing from the boil and restarting if boiling stops, 5-minute wait, jar lifter, spacing, cooling 12–24 hours, unsealed jars to the fridge, storing out of direct light
- Storing Home Canned Foods (National Center for Home Food Preservation): Seal check by pressing the lid; unsealed jars refrigerated and eaten within a week, or reprocessed within 24 hours; storage at 10–21°C, not above 35°C, away from hot pipes and cookers; damp corroding lids and breaking seals; freezing softening food and risking spoilage if seals break; 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 (pH above 4.6); vinegar lowers pH in pickled food; botulism risk
- Testing Jelly Without Added Pectin (National Center for Home Food Preservation): Boiling point of water falls with elevation
- Food Safety and Labelling Guidance for small scale home producers of chutneys, pickles, flavoured oils and jams (Scottish Borders Council): Amount of vinegar essential for safety; do not re-use lids; refrigerate pickles even before opening where pH 4.5 or lower can't be guaranteed
- Making Jam and Similar Products (Orkney Islands Council, Environmental Health): Pickles that can't guarantee pH 4.5 or lower refrigerated, with a maximum 10-day shelf life
- Sterilization of Empty Jars (National Center for Home Food Preservation): Pre-sterilising needed only for pickles processed for less than 10 minutes
- Homemade Pickled Onions (Kilner): What the traditional method involves only: overnight dry-salting, spiced malt vinegar boiled and cooled, weeks of maturing
- Onions: grow your own (RHS): Lifting with a fork without bruising; drying about two weeks on racks in sun, or greenhouse or shed if damp; using damaged bulbs straight away
- Shallots: grow your own (RHS): Shallots store at least six to eight months in a light, cool, dry, well-ventilated place