How do I preserve a glut of fruit or vegetables?

The four routes for a sudden surplus — freezing, pickling, jam and drying — and which is safe for what.

Difficulty: intermediate
Time: 1 hr 30 min
Read: 2 min
Safety: warning

Short answer

Freezing is the easiest and safest route for almost anything. Pickling and jam work because acid and sugar preserve; that is also why they are only safe for the right foods. Never bottle low-acid vegetables at home.

A glut arrives suddenly — a productive courgette plant, a neighbour's apple tree, a market bargain. The preserving method has to match the food's acidity, because that is what determines whether it is safe as well as whether it works.

Safety

Low-acid vegetables — beans, carrots, sweetcorn, most greens — cannot be safely bottled or canned at home without a pressure canner, because of the botulism risk. Water-bath preserving is only safe for high-acid foods: most fruit, jams, and anything properly pickled in vinegar. If you are unsure whether something is high-acid, freeze it instead.

Step by step

Freeze first, decide later.The safest and simplest option for nearly everything. Blanch vegetables first, and freeze fruit on a tray before bagging.
Pickle in a proper vinegar solution.Vinegar of at least 5% acidity makes the environment too acidic for harmful bacteria. Follow a tested ratio rather than improvising the vinegar-to-water balance.
Make jam for high-sugar fruit preserving.Sugar and the fruit's own acid do the preserving. Sterilise the jars, fill them hot, and seal immediately.
Dry herbs, chillies, apples and tomatoes.A very low oven, a dehydrator or a warm airy spot. Store completely dry in airtight jars — any residual moisture causes mould.
Never water-bath low-acid vegetables.Beans, carrots, sweetcorn, potatoes and most greens need a pressure canner to be safe. Botulism is odourless, tasteless and serious. Freeze them instead.
Sterilise jars properly.Wash in hot soapy water then dry in a 140°C oven for 15 minutes. Fill while both jar and contents are hot.
Check the seal and label everything.A sealed lid should not flex when pressed. Label with contents and date. Refrigerate anything that did not seal and eat it soon.
Cook and freeze as a fallback.Chutney, soup, sauce or a base, then frozen. It handles any quantity of anything and needs no special equipment.

Tips

Courgettes are the classic glut. Grated and frozen in portions, they disappear into soups, sauces and cakes.
Do not scale a jam recipe up too far. Large batches take much longer to reach setting point and the fruit overcooks.
Any jar with a bulging lid, a broken seal, an off smell or visible mould goes in the bin unopened. Never taste to check.

Common mistakes

Bottling low-acid vegetables in a water bath — It cannot reach a temperature that destroys botulism spores. This is a genuine and serious risk, not a quality issue.
Reusing jam jar lids — The sealing compound only works once. New lids are inexpensive and are the whole point of the process.

Questions people ask

Is home canning safe?

Water-bath preserving is safe for high-acid foods — most fruit, jams, and properly acidified pickles. Low-acid vegetables need a pressure canner; without one, freeze them.

What is the easiest way to deal with a glut?

Freezing. Blanch vegetables first, freeze fruit on a tray then bag it. It needs no equipment and carries no safety risk.