Calpico or Yakult). This flavor resemblance was recorded as early as 800AD, by the Tang Dynasty poet Bai Juyi in his Introduction to Lychee. Before the age of mass produced table sugar or modern transportation for fresh fruits, being able to get something this sweet and flavorful from the humble starchy grains was something to treasure.
fungi, which secretes the enzyme amylase that breaks down the starchy polysaccharide into shorter disaccharide (maltose) or monosaccharide (glucose) - which actually tastes sweet, and can be digested by the yeast to turn into alcohol. There are two main variant of rice fugus, Aspergillus oryzae, which is commonly found in the japanese koji, and Rhizopus oryzae, which is commonly found in chinese qu. Though pronounced differently, koji and qu share the same written character, 麹, as the two share a common root. To oversimplify the difference a little, Aspergillus oryzae secretes more α-amylase (which produces maltose) in addition to γ-amylase (which produce glucose), and is often used at a higher temperature (~60C), while Rhizopus oryzae relies more on glucoamylase, and is often used at a lower temperature (~30C).
The amylolytic process is faster with α-amylase at the higher temperature (6~8hrs vs 24~36hrs), but maintaining this higher warm-but-not-too-hot temperature requires precision cookers or more attendance. The lower maintenance temperature is easier to get hands-off, especially in the middle of summer. I stick mine in the garage and treat it like no-knead dough - sure it takes longer, but you don't need to do anything about it. The active time for this recipe is very, very short.
The traditional method calls for soaking short grain glutinous rice (also known as sweet rice or sticky rice) over night, steaming until thoroughly cooked, spreading the rice out to let it cool naturally, and adding water with rice wine yeast. It's not super complicated as is, but overnight soaking takes more planing ahead, and steaming properly is actually not so fool-proof. Depending on the steamer used, it is easy to get uneven heating, with mushy, overcooked rice in some places, and hard, undercooked rice in other places. I strongly recommend beginners to just use a rice cooker. The underlying reason for steaming is simply to cook through the rice kennels for starch gelatinization, which enables amylase to break down the polysaccharide into smaller sugar molecules (maltose or glucose). Obviously tradition can't call for electronic smart cookers. No reason for modern people to forgo the easier technology.amylopectin (branched starch) than amylose (single-chain starch), because its branched structure readily releases more glucose, allowing for more efficient fermentation, and higher potential alcohol content when aged. It also forms a more stable gel that doesn't retrograde as easily. So where selection is possible, try to pick a rice that's high in amylopectin.
- Cook rice to package instruction, or rice cooker/instant pot instruction.
- Rinse with cold water to break up the rinse and cool to room temperature. Drain thoroughly.
- Dissolve the yeast in water, and mix into the rice. (you can also mix in the dry yeast directly if the rice is very wet)
- Pack rice into sanitized container. Carve out a hole in the middle to observe alcohol secretion level.
- Drain over a nut milk bag if drinking straight. Sweet rice can also be eaten as is, or cooked with mochi for a dessert soup. It can also be steamed with milk to form a soft custard (2 part milk: 1 part drained rice wine).