Adzuki Beans — Cups to Grams

Adzuki Beans by Preparation State: Weight Table

Adzuki beans (Vigna angularis) change significantly in weight and volume across their preparation states. Understanding these ratios prevents over- or under-purchasing and allows accurate recipe scaling.

Dry (197g/cup): Raw adzuki beans are small, uniform, oval-shaped legumes with a characteristic deep red color and a white ridge running along one side. They pack relatively efficiently into a cup due to their small, consistent size. The 197g/cup measurement is based on spooned-in, leveled beans — not shaken or packed.

Cooked (175g/cup): Fully cooked adzuki beans expand approximately 2.5× in volume from their dry state. Because each individual cooked bean is significantly larger than a dry bean but the same cup holds fewer of them by count, the weight per cup actually decreases relative to dry beans. Cooked adzuki are soft, slightly sweet, and hold their shape better than most legumes when properly cooked.

Anko paste (280g/cup): Sweet red bean paste is dense because the beans are cooked to complete softness, the skins are either kept (tsubuan) or removed (koshian), and sugar is cooked in until the mixture is tight and glossy. The 280g/cup figure reflects sweetened anko at the standard sugar ratio. Unsweetened cooked adzuki puree (without sugar reduction) would be approximately 240g/cup.

Canned drained (180g/cup): Commercial canned adzuki beans (Japanese brands such as Azuki, or Korean red bean cans) are already cooked. After draining, they measure approximately 180g/cup — slightly heavier than home-cooked due to the compact canning process.

Complete Adzuki Bean Cooking Guide: Soak, Simmer, and Test

Adzuki beans are among the more forgiving legumes to cook — they do not require soaking for safety (unlike kidney beans, which contain dangerous lectins in raw form), cook in a reasonable time, and hold their shape well. That said, proper technique produces a significantly better result.

Step 1 — Sort and rinse: Spread 1 cup (197g) dry adzuki beans on a light-colored surface and pick out any shriveled beans, debris, or small stones. Rinse under cold water in a fine-mesh strainer.

Step 2 — Cold soak (4 hours minimum): Cover the sorted beans with 3 cups (720ml) cold water. Soak at room temperature for 4 hours, or refrigerate overnight (up to 8 hours). After soaking, the beans will have absorbed approximately 60–80g of water and expanded noticeably. Drain the soaking water completely — it contains some of the flatulence-causing oligosaccharides.

Step 3 — Simmer: Transfer soaked beans to a pot and cover with fresh cold water by at least 3 inches. Bring to a boil over medium-high heat. Skim any foam that rises in the first 5 minutes. Reduce to a gentle simmer (small bubbles breaking the surface occasionally). Cook 45–60 minutes, checking every 15 minutes. Stir occasionally to prevent sticking. Add more water if the beans start to peek above the surface — they should always be submerged.

Step 4 — Test for doneness: Adzuki beans are fully cooked when a bean mashes easily between two fingers with no resistance, and the skin is tender without being falling apart. The interior should be smooth and creamy, not chalky or grainy. For anko, you want them extremely soft — cook an additional 10–15 minutes beyond the finger-mash stage.

Step 5 — Seasoning: Add salt only after the beans are fully cooked. 1 teaspoon (5–6g) kosher salt per 2.5 cups (435g) of cooked beans is standard for savory preparations. For sweet anko, no salt is added to the beans themselves — salt is added to the finished paste in trace amounts only, if at all.

Yield: 1 cup (197g) dry adzuki beans consistently yields 2.4–2.6 cups (approximately 435g) cooked beans in their natural cooking liquid, or approximately 2.2–2.4 cups if measured after draining.

Anko: Tsubuan vs Koshian, and the Recipe Ratios

Anko (餡こ or 小豆餡) is the sweet red bean paste central to Japanese confectionery. The two major types differ in texture and the presence or absence of bean skins:

Tsubuan (粒餡, "chunky paste"): Made by cooking whole adzuki beans, then sweetening them while leaving the bean structure largely intact. The result is a rustic, hearty paste with identifiable bean pieces and skins — the traditional form for ohagi/botamochi and some versions of dorayaki. Method: cook beans until very soft, drain most liquid, add sugar and cook over medium heat, stirring constantly until the paste thickens and begins to leave the pan sides.

Koshian (漉し餡, "smooth paste"): Made by cooking beans to complete softness, then pressing through a fine-mesh sieve or food mill to remove the skins and produce an ultra-smooth paste. The skins are discarded. The resulting strained paste is then sweetened and reduced. Koshian is used in mochi, nerikiri (traditional wagashi sculpted candies), and premium dorayaki where a refined texture is desired. More labor-intensive than tsubuan but produces an exquisitely smooth result.

Standard anko recipe (makes approximately 2 cups / 560g):

1 cup (197g) dry adzuki beans, soaked 4 hours, cooked until very soft → drained cooked beans (approximately 435g). In a medium saucepan, combine beans with 150–200g granulated sugar (the traditional Japanese ratio is nearly 1:1 weight sugar to dry beans; adjust from 150g for mild sweetness to 200g for standard sweetness). Cook over medium-low heat, stirring constantly with a wooden spoon in a figure-eight motion, scraping the pan bottom. As the mixture heats, the beans soften completely and integrate with the sugar syrup. Cook 15–20 minutes until the paste reaches the desired consistency: it should hold its shape when scooped with a spoon, pull away cleanly from the pan sides, and leave a trace when a spoon is dragged across it. Remove from heat and cool completely before using — anko firms up significantly as it cools.

Finished anko keeps refrigerated for up to 1 week, or frozen for 3 months. Freeze in tablespoon-sized portions for convenient single-use portions for mochi filling.

Adzuki Beans in Japanese Sweet Traditions

Adzuki beans occupy a position in Japanese sweets that has no real parallel in Western baking — they function as the primary flavoring agent and filling material across an enormous range of wagashi (traditional confections) and everyday treats. Understanding the quantities used in each application helps with recipe planning:

Dorayaki (per 3-piece serving): 60–90g anko (3–4.5 tablespoons tsubuan), sandwiched between two fluffy pancakes (approximately 30g each). The pancakes are made with honey-enriched batter; the anko should be mounded in the center and press to the edges when the halves are brought together.

Anpan (per bread roll): 40–50g anko (koshian preferred for smooth interior) enclosed in a soft milk-and-yeast roll. The dough is enriched with butter and sugar. Standard Japanese bakery anpan weighs 70–80g total, of which about 50g is anko filling.

Daifuku mochi (per piece): 20–30g koshian surrounded by approximately 30–35g sweetened mochi (glutinous rice cake). The mochi coating is stretched thinly around a ball of anko. Strawberry daifuku adds one whole strawberry (approximately 15–20g) to the anko filling.

Sekihan (per serving): Sticky rice (mochigome) cooked with 2–3 tablespoons dry adzuki beans per cup of rice. The beans are partially cooked first and their red cooking liquid is used to tint and flavor the rice. Traditional celebration dish served at weddings, birthdays, and coming-of-age ceremonies.

Commercial canned anko: Available in most East Asian grocery stores in 150g–500g cans. Commercially canned anko (both tsubuan and koshian) weighs approximately 280–300g per cup, consistent with homemade. Tsubu types are slightly denser than koshi types due to bean-skin inclusion.