Making Kimchi

The Encyclopedia of Korean Culture defines kimchi as vegetables such as napa cabbage, radish and cucumber that are salted, mixed with seasonings and left to ferment. Hundreds of variations exist, but nearly all follow the same three stages: salting, seasoning and fermentation. Late-autumn kimjang, when households make winter kimchi together, was inscribed on UNESCO's Representative List of the Intangible Cultural Heritage of Humanity in 2013.

Step 1: Salting

Salting is the step that makes kimchi possible. Salt draws water out of the vegetable so it softens and becomes pliable, seasons it throughout, and creates conditions that favor salt-tolerant lactic acid bacteria over many spoilage organisms.

• Napa cabbage is usually halved or quartered lengthwise, dipped in brine, and then sprinkled with coarse salt between the leaves, concentrating on the thick white ribs. A food-safety guideline from the BC Centre for Disease Control describes a brine of roughly 10–12% salt and a salting time of about 2 to 10 hours; a Colorado State University Extension recipe calls for 3 to 6 hours at room temperature.
• Rinse and drain. After salting, the cabbage is rinsed several times in cold water and drained well, often for 30 minutes or more. Rinsing removes surface salt and grit; draining keeps the finished kimchi from turning watery.
• Target saltiness. Colorado State notes that finished kimchi typically lands at about 2–5% salt. Too little salt risks soft, off-tasting kimchi; too much slows fermentation and makes it harsh.

Step 2: The seasoning paste

The classic paste for baechu-kimchi combines gochugaru, garlic, ginger, julienned Korean radish and green onion, usually bound with a thin porridge of glutinous rice flour that helps the seasoning cling. Fermented seafood such as saeujeot (salted shrimp) or myeolchi-aekjeot (anchovy sauce) adds depth; some cooks add grated Asian pear or a little sugar. The paste is spread between every leaf, and the cabbage is folded and packed tightly into a container with as little trapped air as possible.

Chili was a later addition. The encyclopedia explains that chili peppers reached Korea around the mid-Joseon period and that, by the 1760s, recipes describe chili powder mixed with vegetables and salted seafood; tightly headed napa cabbage of the modern kind became common only in about the last century.

Step 3: Fermentation

Kimchi ferments spontaneously, driven by lactic acid bacteria already present on the vegetables and seasonings. Research on napa cabbage kimchi describes a typical succession: Leuconostoc species dominate early, producing a fresh, lightly fizzy sourness, while Lactobacillus populations grow as the kimchi becomes more acidic. A 2025 study in Foods treated a pH between about 4.0 and 4.5 as optimally ripe and considered kimchi below pH 4.0 over-ripe.

Temperature controls the pace. The BC Centre for Disease Control summarizes modeling showing kimchi reaching pH 4.6 or lower in about 2 days at 20°C, 6 days at 10°C, 15 days at 5°C and 35 days at 0°C. Traditionally, kimjang kimchi was packed into earthenware jars and buried in the ground over winter, where steady near-freezing temperatures slowed fermentation for months. Since the 2000s, many Korean homes use dedicated kimchi refrigerators that can ferment at a set temperature and then hold the kimchi cold.

A common home approach is to leave freshly made kimchi at cool room temperature for a day or two, then refrigerate it. Colorado State suggests about 1 to 2 days at around 20°C (68°F).

Food safety

Kimchi is eaten raw, so the acid produced during fermentation is its main safeguard. Extension and public-health guidance agrees on a few points:

• Reach pH 4.6 or below. Colorado State advises that kimchi reach pH 4.6 or lower before eating and suggests inexpensive pH strips for home cooks. The BC guideline, written for food businesses, recommends discarding a batch that does not reach that level within about 3 days at room temperature or 7 days under refrigeration.
• Start clean. Wash produce thoroughly and use clean hands, tools and water. Outbreaks of pathogenic E. coli and norovirus linked to kimchi have been traced to contaminated raw ingredients or water and to insufficient fermentation.
• Treat fresh kimchi like salad. Unfermented geotjeori, eaten the day it is made, has not yet developed protective acidity. Keep it refrigerated and eat it within about three days.
• Choose the right container. Colorado State advises against metal containers and cracked or chipped earthenware; glass, food-grade plastic or sound glazed crocks work well.
• Know when to discard. Discard kimchi with surface mold. Oregon State University Extension adds that a soft, slimy texture signals spoilage, while a strongly sour taste on its own simply means over-fermentation.

Storage

Refrigerated kimchi keeps fermenting slowly and grows more sour over time. Colorado State suggests eating home kimchi within about two weeks for best quality, while Oregon State notes it can keep for months in the refrigerator. Well-aged, sour kimchi is prized for cooking, for example in kimchi-jeon.

Beyond napa cabbage

The same principles apply to cubed radish kkakdugi, stuffed cucumber oi-sobagi and green onion pa-kimchi. Water kimchi such as dongchimi and nabak-kimchi ferments in a mild brine and is usually made without heavy chili.