Pao cai (泡菜, “soaked vegetables”) is the everyday fermented pickle of Sichuan and Chongqing: firm vegetables – radish, cabbage, long beans, carrots, chilies, ginger – submerged in a salty brine flavored with Sichuan pepper, dried chilies and a splash of liquor, and left to sour for a few days. What sets it apart from sauerkraut is the brine: it isn’t thrown away but reused, batch after batch, in a jar with a water-sealed lid (pao cai tan), and an established brine sours new vegetables fast. Pao cai is eaten as a cold side dish and used in cooking – pickled chilies and ginger are part of Sichuan’s “fish-fragrant” (yu xiang) flavor. Northeast China sours halved napa cabbage heads instead, for weeks: see suan cai.
The Aged Brine and Its Microbes
Chinese homemade paocai is typically made by fermenting red radish or cabbage in aged brine with 6–8% salt; in a study that fermented six rounds of vegetables in the same brine, the vegetable itself shaped which bacteria thrived, with cabbage supporting a more diverse community than radish (Jiang et al., 2021). In spontaneously fermented radish paocai, Weissella and Lactobacillus were the main bacteria, and the salt level changed both the community and the flavor compounds (Mi et al., 2022).
Brines also go wrong. When researchers examined spoiled homemade paocai from seven Sichuan families, the culprits were mostly Bacillus bacteria plus film-forming yeasts and moulds (Candida, Kodamaea, Geotrichum) that softened the vegetables, changed their color and smell – and all of them produced nitrite (Ao et al., 2019). A white film on a pao cai jar is therefore not just cosmetic: skim it, top up salt and make sure everything stays submerged, and if it keeps coming back or the brine smells putrid, start a new brine.
Nitrite: Why to Wait Until It’s Sour
Vegetables contain nitrate, and in the first days of fermentation some of it is turned into nitrite before the acid builds up. In a study of Chinese fermented cabbage brine, nitrite peaked at 32 mg/kg while the pH was still 4.7, then fell to 0.04 mg/kg once the pH reached 3.6 (Xu et al., 2024). So eat pao cai once it’s clearly sour – after about 4–7 days in a new brine, sooner in an active old one – rather than in its first couple of days. A healthy, quickly souring brine is the best protection.
Salt and Serving
Pao cai is a salty food: the vegetables take up salt from the brine as they sit. Eat it as a condiment in small portions, and rinse it briefly before cooking if you want it milder. Raw pao cai contains live lactic acid bacteria; once it’s stir-fried, it doesn’t.
- Cold side dish: drained, with a drizzle of chili oil or sesame oil.
- Stir-fried: chopped pao cai with shredded pork or minced beef, or in fried rice.
- Pickled chilies and ginger: the base of yu xiang dishes such as yu xiang eggplant.
Related: kimchi, Sichuan’s fermented chili bean paste doubanjiang, quick fermented radishes, and our troubleshooting guide for films, mold and soft pickles. Sichuan’s other famous pickle is zha cai, the pressed mustard tuber of Fuling.