Make it at home

Four mechanisms, and everything else is detail

Sugar. A high enough sugar concentration binds water so tightly that very little is available for anything to grow in. That is what a jam or a marmalade relies on, which is why cutting the sugar in a jam recipe is not a matter of taste.

Acid, added. Vinegar makes the environment hostile to most spoilage organisms immediately. That is a pickle, and it is the most predictable of the four because the acid is there from the start.

Acid, made. Salt-tolerant bacteria already living on the food produce lactic acid over days, and the food becomes sour enough to preserve itself. That is a ferment — sauerkraut, kimchi, fermented cucumbers — and it is the one that needs the most care.

Cold, or nothing at all. A quick pickle, a cordial, a stock, a batch of butter or a fresh cheese preserves nothing much. They live in the fridge or the freezer and are eaten soon, which is precisely why they are the easiest place to start.

Which method suits what

High-pectin, high-acid fruit

Jam or jelly. Currants, gooseberries, damsons, quince, crab apples, Seville oranges. They set themselves.

Low-pectin fruit

Jam with help — added pectin, lemon, or a high-pectin partner. Strawberry, cherry, peach, fig, pear.

Firm fruit and vegetables with sugar and vinegar

Chutney. Apple, plum, green tomato, mango, onion, pear.

Firm vegetables and a vinegar brine

Pickle. Onions, cucumbers, beetroot, red cabbage, chillies, eggs.

Vegetables and salt alone

Ferment. Cabbage, cucumbers, chillies, radish.

Milk

Yoghurt, labneh, paneer, butter — none of which preserve much, and all of which are quick.

Bones and trimmings

Stock, which preserves nothing and improves everything.

Where to start

In roughly increasing order of how much can go wrong.

• A quick pickle. Ten minutes, lives in the fridge, and you will use it all week. Start here.
• A cordial. Elderflower in June, blackcurrant in July, rhubarb in spring. Nothing to set and nothing to judge.
• Butter, or labneh. Both are one ingredient and an hour, and both are visibly better than the bought version.
• A jam from an easy fruit — raspberry, blackcurrant, damson — which sets on its own and teaches you the setting test.
• Sauerkraut, which is the ferment to learn on: two ingredients and the whole process visible through the jar.
• A chutney, which is forgiving but needs a month of patience before you find out whether it worked.
• Marmalade, which is the most work and the most rewarding, and which has a six-week season.

The equipment that actually matters

Very little, and most kitchens have it.

1. A wide, heavy, non-reactive pan. Stainless steel or enamel — aluminium and unlined copper react with vinegar and acidic fruit. Width matters more than depth, because evaporation is most of the work.
2. A few small plates in the freezer, for testing a set.
3. Muslin, or a jelly bag, for straining and for holding spices and pips.
4. Jars with vinegar-proof lids. Bare metal corrodes over anything acidic.
5. Kitchen scales. Almost every recipe in this section is a proportion by weight, and a cabbage or a punnet of fruit can vary by half.
6. A funnel and a jam thermometer are both genuinely useful and neither is essential.
7. Somewhere cool and dark to keep what you make.

The line FoodHQ draws

FoodHQ does not publish salt percentages, pH figures, acidity thresholds, curing quantities or keeping times. 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 numbers from it, and take the explanation from here.

The reason is not caution for its own sake. Whether a jar is safe on a shelf in six months depends on numbers — how much salt, how acidic, how long, how hot — and those numbers change with what you are preserving and where you live. A cookery writer is not the right source for them and neither is a website.

What is on these pages is everything else: what the method is doing, why the recipe is shaped the way it is, what it should look like on day three, what has gone wrong when it does, and when to throw something away. Take the numbers from the authority and the understanding from here.

Common questions