Glutinous Rice Doughs.

Glutinous rice (糯米) has almost no amylose (XXI.2); its starch is almost all amylopectin, the large branched molecule that swells into a sticky, cohesive gel when cooked (V.3). Ground into flour (糯米粉) and mixed with water, it makes a dough that is plastic like clay — no gluten, no spring — and easy to wrap round a filling. Cooked, the gelatinised amylopectin becomes chewy, stretchy and sticky: the texture Chinese call Q or 糯, Japanese mochi-mochi. 汤圆 and 元宵 for the Lantern Festival, 麻糍, 驴打滚, Japanese daifuku and mochi pounded from steamed whole grains (餅つき) are all this starch.

Two other properties follow. Little amylose means slow retrogradation (VII.3): glutinous rice cakes stay soft far longer than ordinary rice, though they do harden over days in the fridge. Firmer cakes are made from ordinary rice: 宁波水磨年糕 uses japonica (粳米) with about 16 % amylose, so it holds its shape in stir-fries and soups but hardens fast; Cantonese 年糕 is glutinous and sweet. And stickiness is dangerous: a soft, elastic mass can block the throat, and every New Year Japanese emergency services report deaths from mochi among elderly people. Cut it small, chew well, and supervise children. The workshop chills a rice cake.

Below: how far a cooked rice cake has firmed after the hours in the fridge you choose, for glutinous rice (about 1 % amylose) and japonica rice (about 16 %), from the course retrogradation model at 4 °C scaled by amylose (teaching, as in XXI.2).