Making umeboshi is a simple and satisfying exercise and a lovely way to save the season.
Umeboshi are salted sour plums made from ume, a Japanese fruit related to the apricot family. Long regarded as a tonic, they are part of the traditional Japanese breakfast.
Ume ripen quickly, so look for them in early June and harvest before they turn yellow.
Here in the U.S., ume trees are abundant in areas settled by Japanese immigrants in the early 1900s, including California, Washington, and Oregon. A more common find at the farmers’ market, shiro plums can be substituted for ume. (Shiro are also well-suited for making plum wine.)
Umeboshi improve with age as they continue to ferment, and author Nancy Singleton Hachisu (Preserving the Japanese Way) says that she usually doesn’t start eating hers until at least one year has elapsed.
Her recipe, adapted below, results in umeboshi that can be enjoyed straight out of the jar with hot teas or rice dishes.
Yields 5 pounds
10 pounds sour plums — ume or shiro variety
13 ounces coarse sea salt (8% of the weight of the ume)
Salted red shiso leaves (optional)
Place the ume in a pail and run cold water over them to fill. Soak overnight in a cool spot.
Pour off the water the following day (be mindful- you can reserve and reuse the water). Using a large, wide-mouth wooden, ceramic, or glass jar, start with a layer of coarse salt, cover with a layer of ume plums, then add a bit of the shiso. Repeat the salt-ume-shiso layers, until the ume are used up.
Place a clean cotton towel across the surface of the salted ume and drape it down the sides of the tub. Place a lid that drops down into the jar on top of the sheet and weight with rocks or similar heavy items equaling the weight of the ume.
Store these salt-weighted ume in a cool dark spot, but check after 2 or 3 days to make sure the brine has surfaced. If it has not, massage any residual bottom salt up to the top fruit.
The ume should remain in the brine for several weeks, but check periodically to make sure no mold is forming (if it has, pick the mold off carefully).
After brining for at least 3 weeks (2 weeks for small ume), dry the ume for 3 days in the bright sunlight on bamboo or rattan mats (or the equivalent) stretched across a wooden frame for good air circulation.
On the last day of drying, strain the brine leftover in the bottom of the salting tub through a fine-mesh strainer and store in a clean jar or bottle to use for another application. It makes an excellent plum vinegar.
Pack the dried umeboshi in a re-sealable gallon-sized freezer bags or a glass jar or ceramic crock with a tight fitting lid. A dark, syrupy liquid will pool at the bottom of the container; don’t discard as it aids in the long-term preservation of umeboshi.
Umeboshi keep indefinitely at room temperature packed in an airtight container.