Fermented Rice Soup (Lao Zao)
醪糟汤
English: Fermented Rice Soup
Chinese: 醪糟汤
Pinyin: lao zao tang
Literal: fermented dregs/leftovers soup
The story of fermented grains stretches back over two millennia, with the earliest record of fermented rice within the Rites of Zhou, an ancient text from the Zhou Dynasty (1046-256 BCE). While the North historically favoured fermented millet, transforming it into low-alcohol drinks, the South embraced lao zao—a sweet and tangy rice soup sold as a pick-me-up.
Despite rice being less prominent in traditional Northern cuisine, lao zao carved out its own remarkable journey. Rice, transported northward from the southern provinces, became the star of fermented grains. These days its rare to see any other grains fermented.
The magic behind this dish is jiuqu (酒曲)—a miraculous starter that is the secret of China's fermented beverages. Jiuqu is a complex ecosystem of moulds, yeasts, and bacteria. When added to grains, it performs an alchemical transformation: converting starches into sugars, which yeasts then devour into alcohol, while the bacteria maintains a delicate fermentation environment.
You might find jiuqu sold as ‘Shanghai yeast balls’—ping-pong sized starters that look more like dusty pebbles than ingredients. In Beijing though, it’s more common to find packets of powdered jiuqu, next to the bread yeast. Use either one, whatever your local Chinese supermarket stocks.
My first encounter with lao zao was during Lantern Festival years ago when a colleague gave me a warm, slightly milky liquid, adorned with translucent glutinous rice balls. I had no idea what I was looking at, but I loved the contrast of flavours and textures: a sour soup with sweet, black-sesame-stuffed dumplings, the chewy skin alongside the soft beads of rice and warm liquid. It was comforting and delicate, like so many Chinese desserts.
While lao zao shines as a festive dish, for many, it’s a daily food. One friend of mine eats the same breakfast every day: a bowl of lao zao with raw egg poured in until it cooks into silken strands. Others might add soft cubes of silken tofu, turning it into a light, refreshing treat. In Gansu, they take lao zao even further, blending the fermented soup with dairy to create a milky rice soup —imagine a rice pudding, but with a sour kick.
Makes about 300ml - enough for 4 small bowls
Ingredients
250g glutinous rice
1g Chinese wine yeast (jiuqu 酒曲)
150-200ml bottled water or boiled and cooled water
Equipment
Sterilised bowl
Sterilised jar or Kilner jar
Steamer
Tea towel or cheesecloth
Pestle and mortar (optional)
Method
Prepare the Rice. Soak the glutinous rice in water overnight, or for at least 6 hours, until the grains are soft enough to easily crush between your forefinger and thumb. Rinse thoroughly and drain well.
Steam the Rice Line your steamer with a tea towel or cheesecloth. Spread the rice in an even layer, using your fingers to create a few small holes across the surface. Cover and steam for approximately 45 minutes. The rice should be cooked through but still retain its shape—avoid making it mushy.
Cool the Rice. Transfer the steamed rice to a large bowl or container. Allow it to cool completely. This step is crucial: adding wine yeast to hot rice will kill the active cultures.
Prepare the Wine Yeast. If using Shanghai yeast balls, crush them into a fine powder. You can use a pestle and mortar or place the ball in a tea towel and crush with a rolling pin. Sprinkle the powdered yeast evenly over the cooled rice, mixing thoroughly with a spoon to ensure even distribution.
Add Moisture. Gradually add water, 50ml at a time. Mix carefully, ensuring each rice grain becomes moist. Continue adding water until the mixture is wet but not waterlogged—there should be no standing water at the bottom of the bowl.
Prepare for Fermentation. Use your spoon to compress the rice slightly, then create a 3cm-deep hole in the centre of the rice, reaching to the bottom of the bowl.
Fermentation. Cover the bowl with cling film or a clean tea towel. Place in a warm location to ferment. In a warm room it might take 24 hours, in a cooler place, perhaps 3-4 days. If it’s too cool, it won’t ever kick-start the fermentation, so try to find somewhere warm in your house.
Check Fermentation Progress. The fermentation is ready when the central hole fills with a clear liquid. Taste carefully with a clean spoon—the liquid should be slightly sweet with a mild alcoholic flavour. If you ferment it for longer, the liquid (and rice) will become more sour and have a stronger alcoholic taste. If you leave it for too long, the flavour will turn extremely sour and almost inedible.
Store or Serve. When satisfied with the flavour, transfer to a sterilised Kilner jar, add 200-250ml of bottled or boiled (then cooled) water, seal and refrigerate.
If serving directly, still dilute with water, pour into a saucepan and heat over a low heat. If serving as a dessert, add a few glutinous rice balls (tangyuan | 汤圆) until they’re cooked through, or pour over silken tofu and drizzle over honey or brown sugar syrup and sesame seeds.
Long-Term Storage. If storing, taste periodically. The fermentation will continue in the fridge, so check weekly to ensure the flavour doesn't become too sour or strong.
Tips
Maintain clean equipment to prevent unwanted bacterial growth
Check the packet of your wine yeast, each brand and type is different and they may recommend more or less yeast for your amount of rice.
Trust your taste buds—the ideal flavour is a delicate balance of sweetness and mild alcohol.
