Anko Red Bean Paste Two Types Tsubu Koshi

Japan (ancient use of adzuki in religious offerings; refined as wagashi filling through Buddhist temple and imperial court confectionery traditions)

Anko (餡子, sweet red bean paste) is the foundational filling and coating material of Japanese wagashi confectionery — made from adzuki beans (Vigna angularis) simmered with sugar until soft, then processed to either of two textures that define its use. Tsubuan (粒餡) retains the whole or partially intact bean grains, producing a rustic, textured paste with visible bean skin and grain — typically used in ohagi, imagawayaki, and less formal confections. Koshian (漉し餡) is strained through a fine sieve after cooking to remove all skins and fibre, producing a completely smooth, silky, uniform paste — used in nerikiri wagashi, mochi daifuku, and formal confections where complete textural refinement is required. A third form, sarashian (晒し餡), is koshian that has been further dried to a powder or dehydrated form for extended storage. The quality of anko depends fundamentally on adzuki bean quality — Tokachi (北海道十勝地方) in Hokkaido produces Japan's most prized adzuki, with high sugar content and delicate skin. Making anko requires the precise water-absorption and cooking management that prevents the beans from bursting (which releases starch and muddles the colour) while achieving complete tenderness. The final sugar content of quality anko is calibrated — typically 70–100g sugar per 100g dried beans — to balance sweetness without cloying.

Earthy, mildly sweet, subtly astringent from adzuki skins; calibrated sweetness; salt amplifies the bean's natural character; tsubuan has more grain presence, koshian is perfectly smooth