Sauerkraut

Ingredients

• 1 head cabbage
• 2-4 % sea salt

Method

Salt a finely shredded cabbage at 2–4 per cent by weight — this is your controlling principle. The salt triggers salt-curing by osmosis: it draws water from the cabbage cells, creating a brine that becomes the fermentation medium. Weigh your cabbage first, calculate the salt (a 1 kg head needs 20–40 g), and sprinkle it directly over the shreds. Massage firmly with your hands for 10 minutes. You're not being gentle — you're rupturing cell walls and accelerating the brine release. When enough liquid pools at the bottom to submerge the cabbage entirely, you're done. This brine is what prevents mould and aerobic spoilage.

Pack the cabbage and brine into a clean glass jar, pressing down hard so the shreds stay submerged. The anaerobic environment is essential: any cabbage that sits above the liquid will develop white film (fermentation can tolerate it, but flavour suffers). If the brine doesn't quite cover the top layer, add a small amount of extra salt water — roughly 2 per cent salt by weight — rather than plain water. Weight the cabbage down with a clean glass weight, a smaller jar filled with water, or a cabbage leaf folded tightly as a barrier.

Cover loosely — an airlock lid is ideal, but a coffee filter secured with a rubber band works fine. This lets carbon dioxide escape without allowing oxygen or contaminants back in. Keep the jar at 15–20°C. lactic-acid-bacteria in the raw cabbage will begin fermenting within 24 hours; you'll see bubbles rising and the brine turning cloudy within three to five days. This cloudiness is the bacteria multiplying.

Taste from day 7 onwards. At two weeks, most sauerkraut reaches a pleasant sharpness with soft texture. Continue to four weeks for deeper, funkier character — the acid level rises and the cabbage becomes increasingly tender. Once you're satisfied, seal with a tight lid and move to cold storage (4°C or below). The fermentation nearly stops in the cold, but flavour continues to deepen over months. A jar will keep for six months refrigerated, longer if the seal is airtight.