Ubiquitous throughout Japan, umeboshi are salt-pickled plums, though the variety of plum itself is closer in taste and appearance to an apricot. Salty, tangy, and with only the slightest hint of sweetness, umeboshi vinegar isn't technically a vinegar, but a brine. As the plums are weighed down during fermentation, the extracted juices are bottled up and used as a condiment, making it more akin to fish sauce, but with sweet-tangy plums instead of anchovies. Because of the plums, it does have a rich acidity, so it can be used anywhere you might use a mild vinegar, but be sure to adjust your other seasonings for the extra saltiness. Traditionally, purple shiso leaves are thrown into the pickling mix for a vibrant pink color, but some brands today use artificial dyes. Eden Foods sticks to the old-fashioned way, and keeps it free of chemicals and additives.