A Mysterious Fermented Food Known Only to Those in the Know! What is “Kobore-Ume”?

Maho Tanabe

February 13, 2023

Last October, American food professionals visited fermented food producers to deepen their knowledge of Japanese fermentation culture during the “Hakko Tourism in Japan” tour campaign. As part of the tour, organizers held a tasting session where guests gave candid advice from the perspective of the American market to food product manufacturers looking to enter the United States market.

Sake-kasu, or sake lees, is said to contain a treasure trove of nutrients. Amazake, meanwhile, is a sweet, non-alcoholic beverage made from fermented rice and rice malt. Both are widely known in Japan, but there’s another more elusive fermented item that many haven’t heard of: Kobore-ume.

Simply put, kobore-ume is the lees generated from the production of mirin – a staple Japanese cooking ingredient that’s beginning to catch on in the west.

Kobore-ume on palms
Korobore-ume is to mirin as sake-kasu is to, well, sake.

While related in this way, they’re also distinct for several reasons. Kobore-ume’s sweetness is derived from rice and it has a white, flakier consistency. Of course, sake-kasu comes from the production process of sake, while kobore-ume is derived from shochu – a type of high ABV spirit. Kobore-ume also retains some alcohol, sitting at about 7-8%.

The white, shredded shape looks like a plum (ume) flower in full bloom. This is the root of the word kobore-ume.

Because of its sweetness, it was a popular snack in Japan when sweets and candy were harder to get a hold of. In the past, it was sold at the gate towns that flourished near Japanese shrines and temples.

However, since the number of breweries that produce “hon-mirin” using the traditional method has decreased, Kobore-ume has become more difficult to find. Even in Japan, you’re not likely to find it at a standard supermarket.

It’s also a seasonal product, making it even more elusive. Mirin breweries usually only have it on sale during the brewing season.

Nowadays, kobore-ume is not as familiar as sake-kasu or amazake, but the gentle sweetness derived from rice and the deep flavor produced by aging make it a very appealing fermented food – if you can get your hands on it.

A bag of kobore-ume

The nutritional benefits of kobore-ume

Mirin lees is composed of carbohydrates, water, and alcohol, which make up about 90% of its mass, while the remaining 10% is made up of protein and fat. Mirin lees is made from glutinous rice, rice malt, and shochu, which are saccharified, fermented, and matured. The lees is said to help regulate the gut biome and detoxify the body. The process of aging the lees brings a wealth of nutrients such as glucose, amino acids, and B vitamins, which, it’s said, can also help relieve fatigue.

Mirin lees contains a kind protein called “resistant protein,” which works like dietary fiber. It isn’t digested in the stomach but reaches the intestines, absorbs excess sugars and fats in the intestines, and expels them from the body.

Mirin lees is also vegan and it can be used to make vegan-friendly sweets.

Cake made with kobore-ume
Sliced cakes made with kobore-ume
The health benefits don’t stop there! Mirin lees also contains vitamin B complex, which promotes metabolism, aids digestion and absorption, and could even help with weight loss.

Making use of kobore-ume

Kobore-ume is most typically used as a pickling agent. Moriguchi-zuke, one of Japan’s most popular pickles, has an elegant sweetness that can only be achieved with kobore-ume. For adventurous home cooks, it can be used to make a wide variety of Japanese style pickles.
Homemade karimori uri pickles on plates with chopsticks
Using room temperature, slightly more mature kobore-ume produces better, more flavorful pickles.

However, pickles are not the only way to use kobore-ume! It also comes in handy for daily cooking and baking.

For daily cooking

Like sake-kasu, kobore-ume can be used as a marinade for meat and seafood, making these ingredients more tender and flavorful. Combine with other seasonings for even better results!

Kobore-ume also works well in miso, yogurt-based dips, tandoori and alcohol-pickled items.

A bottle of hon mirin, a bag of kobore-ume, a bowl of dipping sauce made with kobore-ume and three crackers with dipping sauce on them placed on a wooden tray
Kobore-ume additionally goes well with ground meat and can be incorporated into hamburger and hamburg steak patties, meat sauces and other meat dishes. The sweetness of the kobore-ume works to boost and enhance flavor here.
Ground meat mixed with kobore-ume on a plate with a spoon and a pack of kobore-ume

For baking

Kobore-ume’s gentle sweetness and rich, mature flavor is perfect for baked goods. It can be used in cookies, pound cakes, scones, granola, crumble pies, and many other baked goods. It often adds a pleasant, natural yeasty flavor when incorporated, while the alcohol content helps produce a deeper flavor.

Cream-based products are also a perfect match, with kobore-ume bringing gentle sweetness and richness. Think cheesecakes, tiramisu and buttercream.

Two containers of tiramisu and a bag of kobore-ume
Four different sweets made with kobore-ume
Healthy, sweet, deep, rich and incredibly versatile — there’s a lot to like about kobore-ume! It’s hard to find in Japan, let alone other regions, but if you can get your hands on it, you’re in for a real treat!

Coming up next week: A recipe making use of kobore-ume!

*Note: Brewing mirin at home is illegal in Japan. Please check your local laws if you are attempting to make your own mirin lees.

Minamoto Shokudo | + posts

Maho Tanabe, the organizer of "Mirin Sweets and Fermented Foods" at Minamoto Shokudo, is an inner beauty planner and owner of Minamoto cafeteria. With expertise in fermented foods using koji and sake, she is a recognized authority in the fermented foods industry.