Adzuki beans (red beans)

Pat is the adzuki bean, Vigna angularis, also called sodu in older Korean. It is an East Asian crop with a long history in China, Korea and Japan. In Korea it has turned up at a Bronze Age site at Odong in North Hamgyeong and, together with mung beans, in a Baekje granary. Traders still sort the beans by size and color — large red, small red, greenish, black — and Korean landraces such as those from Hongcheon, Jincheon and Yeongdong have been considered especially good.

Adzuki beans go into patbap (rice cooked with beans), sweetened paste for filled rice cakes, and gomul, the crumbly bean powder pressed onto gyeongdan or layered through steamed sirutteok. Red-bean sirutteok is the standard offering at gosa, household rites for good fortune, because the red color was thought to ward off evil.

The best-known adzuki dish is patjuk, porridge made by boiling the beans soft, sieving out the skins, and cooking rice in the bean liquid, often with small glutinous-rice balls called saealsim. It is the food of Dongji, the winter solstice. The custom probably came from China, where a red-bean gruel was used to chase away a disease spirit; Goryeo poems already mention eating it at the solstice, and Joseon seasonal almanacs record it too. Families flicked a little patjuk on gates and storage jars before eating, sometimes adding one rice ball for each year of a person's age, and the porridge was also made when moving into a new house, shared with neighbors, and sent to households in mourning.

• Plant protein and fiber: Dried adzuki beans are about one-fifth protein and rich in dietary fiber, per the Korean Food Composition Table.
• A source of potassium, folate and iron: The dried beans are notably high in all three.
• Sweet paste is a different food: Red-bean fillings for buns and rice cakes are cooked down with a lot of sugar, so they carry far more added sugar than savory patjuk or patbap.
• Traditional beliefs: Old herbal texts credited adzuki beans with easing swelling and helping milk flow after childbirth; these remain traditional ideas rather than established medical effects.