Kuromame Japanese Black Soybeans

Although it’s a simple dish with just a few ingredients, it can be very challenging to get the beans to turn out with piano black skin that looks like they’re about to burst. This makes Kuromame one of the more difficult New Year’s dishes to prepare. In this recipe, I’ve combined a few techniques to ensure you get plump beans with midnight black skin that melts away to reveal a rich and creamy center.

Why This Recipe Works?

Soaking the black soybeans in water overnight with baking soda and salt helps break down pectin in the skins. This makes it easier to achieve a velvety bean with skin that practically melts in your mouth. Adding a source of iron to the pot with the kuromame intensifies the black color of the beans while preventing the color from fading. As the iron dissolves, the ions form complexes with the anthocyanin in the beans, which results in a bathochromic shift and stabilizes the pigments. Traditionally, rusty iron nails were used, but these days you can buy food-safe pieces of iron that come in different shapes. Using a pressure cooker reduces the cooking time from 3-4 hours to around 30 minutes.

Ingredients for Kuromame

Black soybeans (Kuromame) - Also known as Japanese Black Beans, Kuromame are a type of soybean with black skin and a white interior. These are not to be confused with black turtle beans used in Latin American food, which have a different texture and taste and are not interchangeable. As for the type of black soybeans to use, the best ones come from Tanba in Hyogo prefecture. They can be very expensive, but they’re worth the extra money if you can find and afford them. Salt - Salt has two jobs here. Once dissolved in water, the sodium ions swap places with the calcium in pectin, which weakens the structure of the beans. Contrary to “common wisdom,” adding salt to beans not only speeds up the cooking process it also helps prevent the beans from splitting by making the skins more flexible. The second purpose of the salt is to season the beans. Baking soda - Baking soda not only adds sodium ions to the soaking liquid but also raises the pH of the water, which helps break down the pectin in the beans. This helps them soften much faster and allows the skins to virtually melt away in your mouth. Sugar - Sugar was an expensive ingredient historically, so foods cooked with sugar show the care and effort put into making it. This is why traditional celebratory foods often contain a lot of sugar. Within the context of Osechi Ryōri, many of the dishes are either salty or sour, so it’s a nice counterpoint to have a sweet contrast. I don’t like my kuromame to be overwhelmingly sweet, so I use a lot less sugar than most recipes call for, but you can add more if you want your beans to be sweeter. I also like the added flavor of using minimally processed sugar like evaporated cane sugar. Soy sauce - Soy sauce is added to balance out the sweetness of the other ingredients while imparting umami to the beans.

How to Make Kuromame in a Pressure Cooker

Rinse the black soybeans in cold water until the water runs clear. Drain them well and add them to a bowl with five cups of water, the baking soda, and the salt. Stir the mixture to dissolve the salt and cover the bowl to let the beans soak overnight. To cook the kuromame, dump the beans and soaking liquid into a pressure cooker and add one cup sugar and a tablespoon and a half of soy sauce. Next, add a food-safe piece of iron and seal the cooker’s lid. Set the pressure cooker to high pressure and quickly bring it up to pressure over high heat. Once you hear steam escaping, turn down the heat, so you still get a steady stream of steam, but it doesn’t sound like a jet taking off. Set a timer for twenty-five minutes. When the timer goes off, turn off the heat and let the pressure cooker cool to room temperature without opening it. You can eat the black beans at this point, but I prefer letting the kuromame rest overnight in the fridge with the iron and braising liquid. This allows the flavors to mature while making the beans an even deeper black. Kuromame skin will get wrinkles if exposed to air so keep the beans submerged until you’re ready to serve them and strain only the portion you want to eat.

How to Make Kuromame In a Pot

The process for preparing the beans is exactly the same, but instead of putting them in a pressure cooker, you just need to add the beans, seasonings, and iron to a saucepan or better yet a large cast iron pot. Bring this to a boil and skim off any scum that floats to the surface. Turn down the heat to maintain a gentle simmer, cover the beans with an otoshibuta (drop lid), and cook until the beans are very tender for 3-4 hours.