Umeshu is made from green, unripe whole fruit with the stone still inside. Total acid levels can be two to four times those found in plums. The fruit is steeped in alcohol (shochu) and sugar, releasing polyphenols (antioxidants) from the skins and flesh, acids, plus flavor and aroma compounds.
This results in a sweet and sour drink with an alcohol content of 10 to 15 percent by volume. Some brands are available with whole fruit in the bottle.
The Umeshu term is first documented in 1697. However it is likely that production dates back some time before this. References to ume go back another thousand years, and the fruit has long been prized in traditional medicine. Ume fruit is also used in juices, sauces, and pickles. A similar product, maesil-ju, is made in Korea.