Nankō (南高) and ko-ume (小梅) are the best plums for making umeboshi. And they are at their best when they take on a yellow color and become fragrant. When these plums are just starting to turn yellow, you can speed the process of ripening by wrapping them in newspaper or placing them in an open-top cardboard box for 1-2 days, but be careful not to let the fruit over-ripen. Immature plums should not be used for umeboshi because they will not produce enough umezu and their skins will be tough. They can, however, be used – indeed are suited – for plum pickles (梅漬け / umezuke), plum liqueur (梅酒 / umeshu), and plum syrup (梅シロップ / ume shiroppu).
Text by Kitchen Nippon