Japan — osechi ryori traditions documented from the Heian period; kuromame as a New Year preparation established through the Edo period
Kuromame (literally 'black beans' — specifically black soybeans, kuro daizu, Glycine max) are one of Japan's most important osechi ryori (New Year festive foods) components, prepared in a specific sweet, intensely soy-flavoured preparation that is eaten at New Year as a wish for health and hard work throughout the coming year — the word 'mame' means both 'bean' and 'health/diligence' in Japanese. The preparation is elaborate and takes 2–3 days: the beans are soaked, simmered with a specific combination of dark soy sauce, sugar (traditionally very sweet), and iron nails or a special iron simmering vessel (both to preserve the deep black colour — the iron reacts with the beans' anthocyanins to create a stable, vivid black rather than the purplish-blue that results from plain cooking). The cooking is exceptionally slow — the beans must be kept covered in their simmering liquid at all times during the 6–8 hour cook, topped up regularly, and cooked at the gentlest simmer to prevent the skins from breaking open. The finished kuromame should be glossy, very sweet, intensely soy-flavoured, tender throughout but unbroken — each bean a complete, intact sphere of glistening black. They are arranged in osechi boxes as a visual element as much as a culinary one — their glossy, perfect appearance is part of the New Year's aesthetic of abundance and good fortune.
Kuromame has an extraordinary sweet-savoury depth — the black soybeans absorb the intensely sweet soy cooking liquid until they are flavoured throughout, with the anthocyanin compounds contributing a slight astringency that prevents the sweetness from becoming cloying.
Iron element (nail or vessel) is traditional for colour stability — alternatively, adding a small amount of baking soda or using a vintage iron pot achieves a similar result through pH modification. Gentle heat is essential — the beans must never boil vigorously, only maintain the faintest simmer. Keeping the beans submerged throughout prevents the exposed beans from drying and splitting. The simmering liquid must be tasted and adjusted regularly — it concentrates as the long cook proceeds.
The traditional iron nail method: clean bright nails (not galvanised) are wrapped in cloth and added to the soaking water and then the cooking water — this is the historical method and produces excellent colour. Modern alternative: cook in a well-seasoned cast iron pot, which achieves a similar iron-anthocyanin reaction over the long cook. The beans improve significantly over 24 hours of soaking in their cooking liquid after the heat is off — the flavour integration is remarkable. For osechi assembly: arrange each bean individually with chopsticks for maximum visual impact — the glistening, perfectly round beans are the most visually striking element of many osechi boxes.
Vigorous boiling splits the bean skins — the entire preparation fails visually if the beans crack. Allowing beans to be uncovered at any point during the long simmer. Insufficient soaking before cooking — under-soaked beans require more aggressive cooking heat to become tender and are more prone to skin splitting. Under-sweetening — kuromame should be noticeably sweet; restraint misses the festive character.
The Japanese Kitchen — Hiroko Shimbo