Is it safe to bottle vegetables, meat or soup in jars at home?

This is the one place in home cooking where the honest answer is genuinely 'do not do this'. The internet is full of confident jars of soup and green beans, and the reason UK preserving books do not include them is not caution for its own sake. Understanding the mechanism makes the boundary obvious rather than arbitrary.

Safety

Step by step

1. Understand what you are actually guarding against.Clostridium botulinum is a common soil bacterium. In its ordinary form it is harmless and easily killed, but it forms spores that survive hours of boiling. Those spores only germinate where there is no oxygen, low acidity and moisture — which is an exact description of the inside of a sealed jar of vegetables.
2. Understand why the toxin is different from other food poisoning.There is nothing to see, smell or taste. The jar looks normal, the food looks normal, and the toxin attacks the nerves, causing double vision, difficulty swallowing and progressive paralysis. It is rare, and it is a medical emergency when it happens. There is no sniff test.
3. Learn where the line is: pH 4.6.Below pH 4.6 — that is, more acidic — botulinum cannot grow at all. Above it, it can. Every safe domestic preserve is safe because it sits below that line, and the acid is doing the work that heat cannot.
4. Know which side each food is on.Below the line and safe to preserve at home: fruit, jam, jelly, marmalade, chutney with a full vinegar measure, pickles in vinegar of at least 5% acetic acid, bottled plums, gooseberries, rhubarb and apples. Above the line and not safe: green beans, carrots, potatoes, sweetcorn, peas, mushrooms, beetroot, pumpkin, all pulses, all meat and poultry, all fish, all stock and all soup.
5. Know why boiling the jar does not fix it.A water bath reaches 100°C. Botulinum spores need considerably more than that, held for a defined time, to be destroyed. Commercial canners and proper pressure canners reach around 116 to 121°C under pressure with a calibrated gauge, to schedules validated for each food and jar size. Boiling a jar in a pan does not come near.
6. Do not substitute a domestic pressure cooker.A pressure cooker is designed to cook food, not to process sealed jars. It is not tall enough, the pressure is not held or measured to a canning schedule, and there are no validated UK processing times to follow. An electric multicooker with a 'canning' preset is not a canner either. Nothing in a normal UK kitchen does this job.
7. Do not trust vacuum sealing or oil to preserve.A vacuum sealer removes oxygen, which removes the one thing that was holding botulinum back. Vacuum-packed low-acid food is a fridge or freezer item with a short life, never a cupboard item. Covering food with oil does the same thing for the same reason.
8. Use the routes that do work.Freeze it — freezing is the safe, easy answer for vegetables, meat, fish, stock and soup, and it is what almost every UK preserving book recommends for exactly these foods. Or move the food below the acid line properly, by making it into a chutney or a pickle with a tested vinegar quantity. Or dry it, if it is something that dries.
9. Follow a published, tested recipe for anything that goes in a jar.For jam, chutney and pickles, use a source that has been through editorial testing — a mainstream preserving book, the Women's Institute, or a manufacturer's tested recipe. The quantities of vinegar and sugar in those recipes are safety figures, not seasoning suggestions.

Tips

• If you find a jar of home-bottled vegetables, meat or soup of unknown origin, do not open it, do not taste it, and do not feed it to anyone. Bag it and bin it.
• The Food Standards Agency is the reference point for current UK domestic guidance — check there rather than following an American canning site, since US practice assumes equipment and tested schedules that are not part of UK home preserving.
• Pickled beetroot and pickled onions in a proper vinegar are fine. Beetroot boiled and bottled in its own water is not. The vinegar is the entire difference.
• 'It has always been done this way in my family' is not evidence. Botulism is rare precisely because most jars happen not to contain a spore, which is not the same as the method being safe.

Common mistakes

• Assuming a lid that has sealed means the food inside is safe — A vacuum seal proves the jar cooled and contracted. It says nothing about what survived inside, and in a low-acid food the airless space under that seal is exactly the environment botulinum needs.
• Adding a splash of vinegar or lemon to a low-acid recipe and calling it acidified — Acidifying to below pH 4.6 reliably, all the way through a jar of solid pieces, is a measured process with tested quantities. An unmeasured splash lowers the pH of the liquid a little and does nothing for the middle of a piece of carrot.
• Following an American canning video — US home canning assumes a proper pressure canner and USDA-tested processing schedules for each food, jar size and altitude. Watching the method without the equipment or the schedule reproduces the appearance of the process and none of its safety.

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