Lacto-fermentation

Lacto-fermentation is a way of preserving vegetables with salt alone. Lactic acid bacteria, which live naturally on vegetables, turn the sugars into lactic acid. The acid makes the food sour, keeps harmful microbes out and adds complex flavor. Sauerkraut, kimchi, sour dill pickles and fermented hot sauces are made this way. The "lacto" refers to lactic acid, not milk, so the process is dairy-free.

How to do it

For sauerkraut:

1. Weigh shredded cabbage on a kitchen scale.
2. Add 2% of its weight in salt, for example 20 g of salt per 1 kg of cabbage.
3. Massage and squeeze for 5 to 10 minutes until the cabbage is limp and sitting in its own juice.
4. Pack it tightly into a clean jar, pressing until the liquid covers it. Leave 3 to 5 cm (1 to 2 inches) of headspace.
5. Weigh the cabbage down below the liquid with a small weight or a bag of brine.
6. Cover loosely or use an airlock lid. Leave at 18 to 22°C (65 to 72°F) for 1 to 4 weeks, tasting from day 5.
7. Move it to the fridge when it tastes sour enough.

For whole vegetables such as cucumbers or carrots, cover them with a 2 to 5% salt brine instead.

How to tell it is done

It smells pleasantly sour, tastes tangy, and the liquid may turn cloudy. Bubbles appear in the first days, then slow down.

Why it works

Salt holds back spoilage microbes but lactic acid bacteria tolerate it. As they work, the acid builds up and the jar becomes too sour for most harmful bacteria. Keeping the vegetables under the liquid shuts out air and stops mold.

Common mistakes

• Too little salt, which can lead to soft, mushy or spoiled vegetables.
• Vegetables poking above the brine, where mold grows.
• Fermenting too warm, which gives a soft texture and a strong, yeasty taste.
• Mistaking spoilage for fermentation. A thin white film (kahm yeast) is common and can be skimmed. Fuzzy colored mold, slime or a rotten smell mean throw it out.

In recipes

Recipes often give salt as a percentage of the vegetable or water weight. Weigh it rather than measuring by spoon.