Pickling

How acid preserves

Most of the bacteria that spoil food, and most of the ones that make people ill, cannot grow in an acidic environment. Pour enough acid over food and you have made it uninhabitable — not sterile, but hostile, which for most purposes is the same thing.

That is why pickling is instant in a way fermenting is not. A ferment has to make its acid over days while the food sits in a vulnerable state; a pickle arrives acidic from the first second.

How acidic is acidic enough is the entire safety question, and it is not one to eyeball. It depends on the vegetable, on how much water the vegetable dilutes the vinegar with, and on whether the jar is going in the fridge or the cupboard. FoodHQ does not publish salt percentages, acidity figures, processing times, curing quantities or keeping windows. Those are safety numbers set by a food safety authority rather than by a cookery writer. In the UK the Food Standards Agency is the authority — take the figures from them or from a body of equivalent standing, and use this page to understand what those figures are doing.

The three kinds of pickle, and they are not interchangeable

Quick or refrigerator pickle

Hot or cold liquid over raw vegetables, cooled, refrigerated, eaten within days or weeks. Crisp, bright, fresh. Not a preserve — it relies on the fridge.

Keeping pickle, refrigerated

Stronger liquid, often hot-poured, kept cold. Weeks to months. The domestic default for onions, cucumbers and chillies.

Shelf-stable pickle

Acidified to a tested figure and heat-processed in sealed jars so it keeps in a cupboard. This is the one that must follow a validated recipe exactly, because nothing about the process is visible if it goes wrong.

What decides which you have made

The acidity, the processing and the storage — not the flavour. A cupboard pickle made to a fridge recipe is not a cupboard pickle.

Making a quick pickle

The technique that returns the most for the least effort in any kitchen.

1. Slice the vegetable thinly and evenly. Thin slices pickle through in minutes; chunks take days and are never as good in a quick pickle.
2. Make a liquid of vinegar, water, sugar and salt. A common domestic starting point is equal volumes of vinegar and water with sugar and salt to taste, and it is worth writing down what you liked.
3. Warm the liquid enough to dissolve the sugar and salt. It does not need to boil unless you want it to soften the vegetable.
4. Add whole spices — mustard seed, coriander, peppercorn, dill, fennel, chilli, bay. Whole rather than ground, which would cloud it.
5. Pour over the vegetables in a clean jar, making sure they are covered.
6. Cool, then refrigerate. Thin slices of onion, cucumber or radish are good within half an hour and better the next day.
7. Eat within a couple of weeks. This is a fridge pickle and is not a preserve.

Choosing the vinegar

The vinegar is most of the flavour, and the default choice is often the wrong one.

• Distilled or spirit vinegar tastes of acid and nothing else. Best when you want the vegetable and the spices to come through cleanly.
• Cider vinegar is softer and fruitier. Excellent with onion, apple, beetroot and anything going alongside pork.
• White wine vinegar is the all-rounder for European-style pickles and the least likely to fight anything.
• Rice vinegar is mild and slightly sweet, and is the right choice for East and Southeast Asian pickles. It is also much less acidic than the others, which matters if you are working to a figure.
• Malt vinegar is assertive and specifically British — onions, eggs, walnuts. It will dominate a delicate vegetable.
• Not balsamic, generally. It is sweet, dark, expensive and its character is wasted in a pickling liquid.
• Check the acidity on the label if the recipe specifies one. Vinegars vary, and rice vinegar in particular is often considerably weaker than the standard a recipe assumes.

What to pickle, and how

• Red onion, thinly sliced. The single most useful quick pickle. Half an hour and it transforms a taco, a salad or a sandwich.
• Cucumber, sliced thin with dill and mustard seed.
• Carrot and mooli in batons, with rice vinegar and sugar — the đồ chua of a bánh mì.
• Chillies, sliced, in a plain vinegar. They keep for months and the liquid becomes useful in its own right.
• Whole small onions or shallots, brined first to draw out water, then in malt vinegar. The traditional British keeping pickle.
• Beetroot, cooked first, in cider vinegar with allspice.
• Cabbage, cauliflower, green beans, radish, fennel, rhubarb, grapes and stone fruit all pickle well and are all underused.
• Brine hard vegetables first. Salting cucumbers or onions for a few hours and draining them draws out water that would otherwise dilute your liquid, and keeps them crunchy.

The pickles worth making first

Ranged from an hour of work to a month of waiting.

• A quick fridge pickle — thin slices in warm sweetened brine. Ready in an hour, keeps a week, and you will use all of it.
• Pickled onions, dry-salted overnight so they stay crunchy, then covered in vinegar and left for six weeks.
• Pickled cucumbers, with the blossom end cut off, which is the single most effective step against softening.
• Pickled beetroot, which has to be cooked first because raw beetroot is too dense for a brine to penetrate.
• Pickled red cabbage, salted overnight and covered in cool vinegar, and eaten within a couple of months rather than laid down.
• Pickled chillies, where the brine left behind becomes chilli vinegar and is worth as much as the chillies.
• Piccalilli, a mustard pickle with a thickened sauce and the vegetables kept deliberately crunchy.

Common questions