Sweet Rice Wine for Newbies - Easy Variations from Traditions, & Chemistry Explained!
Sweet rice wine is a young, low-alcohol dessert wine
that is remarkably sweet and fruity in flavor, for something that's
derived purely from rice, with no added sugar or juice. Almost anyone
who tried sweet rice wine for the first time will tell you they would
not have imagined this is made from just rice. The flavor is akin to
lychee juice, or lightly fermented yogurt drinks (think 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.
The mechanism is simple - cooked rice is introduced to rice wine yeast, which contains strands of oryzae 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).
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.
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.
About the rice selection - tradition favors rice types higher in 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.
Amylopectin is the type of starch that makes cooked rice sticky. Glutinous rice are a special species of rice with extra high amylopectin content. The uncooked kernels are visibly more opaque than their more translucent regular rice counterpart. The cooked rice is noticeably much, much stickier than plain non-glutinous rice. If this type of rice isn't easily accessible to you, regular short grain will get closer results than long grain.
The rice difference will be more apparent in more aged wines. Nonetheless, since the sweet dessert wine is most often enjoyed in 1~3days, even plain long grain will suffice for this treat. Let it be your gateway rice wine! Once you get a hang of it, you can try the same method on sweet rice, black rice, or purple rice for an upgrade. You can even get creative with millet, barley, even quinoa. The chemistry is the same, any starchy grain will work! (with some proportion tweaking)
A few caveat -
1. My quickened method calls for rinsing cooked rice in cold water rather than waiting for it to naturally cool down. This generally does not cause a problem with short grain rice, but long grain rice has higher water absorption rate, and can soak up more water in the process, which could turn the wine sour early on. Make sure you move quickly with long grain, and drain it as soon as the kernels are broken up. Yeast should be mixed in when rice is not too hot to touch, ideally room temperature. If you have clean tap water or a faucet filter, it's best to rinse the rice over a mesh sieve in the sink to avoid too much water aborption. Otherwise, it's best to have a good amount of chilled purified water (boiled, filtered, or bottled) ready to rinse the rice down to room temperature quickly.
2. Containers should be thoroughly cleaned and dried before using. While the sanitation standard isn't as strict as more aged wine, it's still a fermentation vessel. At least put it through a high heat cycle in the dishwasher and let it heat-dry. Preferably boil, steam, or oven bake the containers to sterilize. If oven baking, I recommend preheating with the containers in oven, to ensure more even heating through out the container.
3. Yeast activity needs oxygen. Do not pack the container all the way to the top and seal it tight. You're better off with a half filled container if you're going to close it tightly. Loosely wrap the container in aluminum foil or saran wrap if the container is pretty full (leave at least an inch of room from the top so the yeast can breathe).
1~2 tbsp water (to dissolve yeast - option if rinsed rice is very wet) (~20g)
1 qt cold clean water for rinsing cooked rice
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.
Loosely wrap up the container and leave it somewhere warm and away from light (e.g. inside a cardboard box in the garage). Ideal fermentation temperature is ~30C; 25~35C are all acceptable.
Check the rice every ~24hrs. Once the alcohol shows through the hole, or pools around the bottom of class jar and rice is floating, move to the fridge. About 36~48 hrs. You can always refrigerate after a day and let cold fermentation continue in the fridge. Avoid leaving the rice out for more than 3 days, to prevent over-fermentation or spoilage.
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).
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