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Garlic

Garlic keeps well, ferments beautifully and has one hard rule attached to it that every home cook should know: garlic in oil at room temperature is the best-documented botulism hazard in a domestic kitchen. Garlic is low-acid, it comes out of the soil carrying spores, and oil provides exactly the oxygen-free environment those spores need.

The season

Autumn-planted hardneck garlic — the type that survives a Baltic winter — is lifted in late July and August when the lower leaves have browned.

Acidity decides the method

Garlic is low-acid at roughly pH 5.8–6.5. It is the reason garlic in oil is a genuine hazard and not a scare story.

This is a reference guide, not a recipe authority and not medical advice. The one organism the safety rules here are written against is Clostridium botulinum, and the one way to be protected against it is a tested recipe followed exactly — substitutions of the acid, the sugar or the salt are not cosmetic. Where the national food authority publishes advice for a specific food (Baltic fish, wild mushrooms), that advice outranks this page.

Method by method

The classic preparation: Cured and braided hardneck garlic

Lift when the lower two or three leaves have browned but the upper ones are still green — leave it longer and the bulb splits its wrapper and will not store. Do not wash. Hang whole plants in bundles somewhere dry and airy, out of the sun, for two to three weeks until the necks are dry and papery. Then trim the roots, cut the stems or braid them, and store cold and dry. Hardneck varieties, which are the ones that reliably overwinter in Estonia and Finland, keep for four to six months; softneck types keep longer but rarely survive the winter in the ground here. Save the biggest bulbs for replanting in October, not for the kitchen.

Preparation that matters

Handle bulbs gently: garlic bruises and a bruised clove rots in store. Sort at curing time and use split, damaged or very small bulbs first. For freezing, peel the cloves whole or blitz them with a little oil into a paste and freeze it in a flat sheet — but keep that paste in the freezer, not the fridge, and never at room temperature. If a fermented garlic clove turns blue or green, that is a harmless pigment reaction between garlic sulphur compounds and trace copper, not spoilage.

What the preserve is worth

Garlic is used in gram quantities, so its contribution to a day's nutrition is essentially flavour. Its characteristic compound, allicin, is not present in the intact clove — it forms when the clove is crushed and an enzyme meets its substrate — and it degrades with heat and time, so a long-cooked or long-stored garlic is a milder one. That is a flavour fact, not a health claim.

The ways this goes wrong

• Garlic in oil kept on the counter. This is the hazard: low-acid food, no oxygen, room temperature. Homemade garlic oils and garlic-in-oil mixtures belong in the refrigerator and get used quickly.
• Washing bulbs before curing.
• Lifting too late, so the wrapper has already split.
• Storing in a sealed jar or a plastic bag, where it sweats and moulds.

Safety rules, temperatures, blanching times, headspace and the pH 4.6 line: USDA Complete Guide to Home Canning and the National Center for Home Food Preservation guidance (US Government / land-grant publications, public domain). Acidity classes: the FDA's published approximate-pH tables. Jam composition: Directive 2001/113/EC. Fish freezing before raw or lightly cured use: Regulation (EC) No 853/2004, Annex III. Checked 2026-09-06.

Sources for this food

• USDA and NCHFP guidance on garlic and flavoured oils (public domain)

Frequently asked questions

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