Method: Kimchi

Why this method

Kimchi (baechu kimchi) is a two-stage build: you first salt the napa cabbage to pull water out, expel air, and pre-season the leaves, then coat it in a spiced paste and let the same lactic bacteria as sauerkraut take over. The salting step is the safety and texture lever; the kimchi paste — gochugaru, garlic, ginger, a sweet element, and an umami source — is the flavor lever. Kimchi is fermented short and served young: it finishes around pH 4.2 and keeps drifting down toward 4.0 and below in cold storage. That is more acidic than the 4.6 botulism line, so a properly salted, submerged batch is safe; the sub-4.0 sourness of aged kimchi is a flavor choice, not a safety requirement.

Parameters

Parameter	Value
Brine for salting napa	5-10% salt solution, OR dry-salt 2.0-2.5% of cabbage weight
Salting time	2-6 h (brine) until leaves bend without snapping
Fermentation temperature	18-22°C / 64-72°F
Duration	3-14 days (shorter when warm)
Vessel	Wide-mouth jar or kimchi container, packed, low headspace
Finished pH	~4.2 trending to 4.0
Cold storage	2-4°C

Equipment

Large bowl for salting

Digital scale

Gloves for mixing paste

Packed jar or kimchi container

Workflow

Salt the napa

Quarter the napa lengthwise. Either submerge in a 5-10% brine (50-100 g salt per litre water) for 2-6 hours, turning once, or dry-salt 2.0-2.5% by cabbage weight between the leaves. The leaves are ready when a thick rib bends without cracking. Use the brine salinity or dry-salt calculator.

Rinse and drain

Rinse twice in cold water to wash off surface salt, then drain 20-30 minutes. Residual salt in the leaf tissue lands the whole dish near a working 2% — too little rinsing leaves it harsh, too much washes out the seasoning.

Make the paste

Build the reference kimchi paste: gochugaru, grated garlic and ginger, a sweet element (grated pear, apple, or a little sugar), and an umami source (fish sauce and/or salted shrimp — saeu-jeot). A flour-and-water porridge (juk) thickens it and feeds an even ferment. For vegan kimchi, swap in soy sauce, miso, or kelp stock.

Mix

Wearing gloves, coat every leaf with paste, working it into the layers. Fold in cut aromatics — scallion, Korean radish matchsticks, garlic chives.

Pack the jar

Press firmly into the vessel to drive out air; the surface should sit under its own liquid within a day. Leave only 2-3 cm headspace — kimchi ferments anaerobically and will fizz over if packed to the brim.

Ferment then chill

Hold at 18-22°C for 3-14 days, tasting daily and burping the jar. When it tastes pleasantly sour and reads about pH 4.2 (trending to 4.0), move to 2-4°C. Estimate timing with the ferment predictor.