How long does miso keep before it spoils?
Unopened, miso can last up to a year past its expiration date, and once opened it can usually be kept for up to six months in the refrigerator.
Miso is an essential ingredient in Japanese cuisine. It's a paste made from various fermented ingredients and a high salt content, which keeps for a long time if stored properly. Even so, it can lose its freshness and even spoil, because while fermentation and the high sodium content help preserve it, they don't guarantee it.
The most obvious sign that miso has gone bad is mold. According to the USDA, even a little mold on the surface is cause for concern because it can contaminate the food underneath. It's best to discard the miso and buy new miso, rather than scraping off the mold. Changes in color and odor may also occur with spoilage, although smell isn't a reliable indicator because foodborne pathogens don't always have an odor. If the miso starts to darken, it's best to throw it away to avoid making anyone sick.
Although miso keeps for a long time, it's best to use it before it spoils. Besides classic miso soup and ramen, it can be used to make a marinade for meat and fish by mixing it with soy sauce and mirin. Creative cooks add it to unexpected dishes, such as peanut butter and jelly sandwiches or tuna salad.
If the miso has started to dry out, it hasn't spoiled; it has simply lost moisture. Just remove it from the packaging and mix it with a little water in a bowl until you achieve the moist texture of fresh miso paste.
