Anko: Tsubu-an, Koshi-an, and Shiro-an — The Three Pillars of Red Bean Paste

Japan — wagashi traditions centred in Kyoto, Kanazawa, and Tokyo; azuki cultivation in Hokkaido dominates production

Anko — sweetened bean paste — is the foundational filling ingredient in Japanese wagashi and a defining element of Japanese confectionery culture, appearing in everything from summer kakigori shaved ice to autumn manjū buns and winter oshiruko sweet soup. Understanding the three primary anko types — tsubu-an, koshi-an, and shiro-an — is essential for any pastry professional working with Japanese ingredients. Tsubu-an (粒あん) is whole-bean paste in which the azuki beans are simmered until tender but retain their shape, then crushed lightly and sweetened, leaving visible bean pieces and skins in the paste. Its texture is chunky and rustic, with a deeper, earthier flavour than refined pastes because the skins contribute tannins and colour. Tsubu-an is used in dorayaki, taiyaki, daifuku mochi, imagawayaki, and ohagi — popular confections where textural interest and robust flavour are valued. Koshi-an (こしあん) is the refined paste produced by cooking azuki beans until completely soft, then passing them through a fine sieve (uragoshi) to remove all skins, yielding a smooth, silky, burgundy paste of extraordinary refinement. Koshi-an has a more delicate, cleaner sweetness than tsubu-an — the removal of the bitter tannin-bearing skins eliminates astringency and creates the paste preferred for high-end wagashi such as nerikiri, higashi fillings, and tea ceremony confections. The sieving process is labour-intensive and reduces yield (skins are discarded), making koshi-an more expensive. Shiro-an (白あん) uses white beans (typically shiro ingen — Great Northern or other white navy beans, or tora mame — sometimes shiro azuki) rather than red azuki, producing an ivory-coloured paste with a milder, more neutral sweetness than either red bean variant. Shiro-an is valued as a base paste in nerikiri — the highly sculptable premium wagashi — where it is mixed with gyuhi (glutinous rice paste) and kneaded to a modelling consistency that holds intricate forms. Shiro-an's neutral colour also accepts natural food colourings — matcha, sakura, charcoal — allowing wagashi artisans to create the full seasonal colour palette seen in finest teahouse sweets. Each paste type requires distinct cooking techniques, sugar ratios, and moisture management to achieve optimal workability.

Tsubu-an: earthy, slightly tannic, robust sweetness with textural variation; Koshi-an: clean, refined, silky sweetness with zero astringency; Shiro-an: mild, creamy, neutral sweetness — a flavour canvas