Rice flour

Ssalgaru is simply rice flour, but in Korea it is above all tteok flour. An observation in the reference work Joseon sangsik, cited by the Encyclopedia of Korean Culture, contrasts the rice cakes of East Asia: Chinese cakes were based on baked wheat flour, Japanese on pounded glutinous rice, and Korean on steamed flour of ordinary non-glutinous rice. The plainest example is baekseolgi, a snow-white cake of moistened rice flour steamed in a siru. The Joseon-era Seongho saseol describes this method of dampening the flour before steaming. Two flours dominate: mepssalgaru from ordinary rice, for steamed layer cakes (siru-tteok) and the long white sticks of garaetteok; and chapssalgaru from glutinous rice, for boiled dumplings (danja and gyeongdan) and pan-fried flower cakes (hwajeon). See tteok and making tteok.

Food scientists distinguish two ways of making rice flour. In wet milling, the grain is soaked, drained and then ground, which produces very fine particles with little damaged starch. In dry milling, dry grain is ground directly. It is simpler and uses no water, but the flour tends to be coarser unless finely sieved, and grinding it finer raises the share of damaged starch. Those differences matter: a Korean study of baekseolgi found that flour particle size changed the cake's structure, with finer flour giving a looser, fluffier crumb and coarser flour a tighter, firmer one. Korean neighborhood mills (bangatgan) have traditionally ground rice that customers soaked at home, producing a damp flour that is steamed promptly.

Mills took over what was once home labor. The Encyclopedia of Korean Culture notes that as mills multiplied, tteok making moved out of the home, from grinding to steaming, until most families bought rice cakes ready-made. Until recently, it adds, people lined up at the mill from before dawn two or three days before Seollal to have garaetteok pressed for New Year's tteokguk.

• A gluten-free flour: NIDDK lists rice flour among flours that are safe for people with celiac disease, which makes plain rice cakes a useful option — though many tteok are filled, coated or seasoned with other ingredients, so check labels on packaged products.
• Low in fiber: Polished rice flour is almost all starch, with very little fiber, fat or sodium per the Korean Food Composition Table; brown-rice flour retains more of the grain.
• Added salt and sugar in tteok: Rice cakes are often seasoned with salt in the flour and sweetened fillings or syrups, so read labels on packaged versions.
• Sticky cakes need care: Dense glutinous-rice cakes should be cut small and eaten slowly, especially by young children and older adults.