The Science of Makgeolli: How Rice Becomes Wine

Have you ever sipped a bowl of makgeolli and wondered how it actually got made? Most people shrug and figure you just add something to rice and it turns into booze. I thought the same thing. Then I started brewing it myself, and that vague assumption fell apart completely. The process of turning rice into rice wine is far more precise than it looks — a kind of coordinated teamwork between living organisms, each taking their turn. Once you understand what’s happening inside that crock, a cup of makgeolli will never taste quite the same again.

Two Stages of Fermentation

Makgeolli fermentation happens in two distinct stages: saccharification and alcoholic fermentation. What makes it remarkable is that both stages happen simultaneously, inside the same vessel.

First, saccharification. Rice is mostly starch — long chains of glucose molecules linked together. Yeast cannot eat starch directly. It can only consume simple sugars like glucose and fructose. So something has to break the starch down first. That something is nuruk.

Nuruk is a fermentation starter made from wheat or rice, packed with wild molds including Aspergillus species. These molds produce an enzyme called amylase. Amylase cuts through the starch chains and releases glucose. The yeast then consumes that glucose and produces alcohol and carbon dioxide. That gentle fizz you notice in a fresh cup of makgeolli? That’s the CO₂.

The fact that saccharification and alcoholic fermentation happen at the same time, in the same vessel, has a name: byeonghaeng bokbalhyo (竝行複醱酵), or parallel complex fermentation. It’s a defining feature of Korean traditional liquors, and Japanese sake uses a similar approach. Beer and wine, by contrast, handle saccharification and fermentation as separate steps. The parallel method keeps sugar concentrations from spiking all at once, which means less stress on the yeast — and a more layered, complex flavor in the finished drink.

Nuruk Is Everything

It’s not an exaggeration to say that nuruk determines 90% of makgeolli’s flavor. It’s a dense cake of grain inoculated with microorganisms — either wild ones drawn in from the air (traditional nuruk) or specific cultivated strains (commercial nuruk). Both work, but they produce very different results.

Here’s something worth knowing: more nuruk means faster fermentation and more sweetness. Beginners often think adding extra nuruk is a safety net. It’s half right. Too much nuruk drives saccharification into overdrive — you get a sweeter brew, but lower alcohol and a sourness that creeps in fast. The standard ratio is 10 to 15% nuruk by weight relative to rice. With commercial nuruk, you can go even lower.

One more thing beginners often skip: hydrating the nuruk before use. Soak it in water for 8 to 12 hours before you mix it into anything. This activates the microbes and enzymes inside. If you add dry nuruk directly to the rice, fermentation starts sluggishly. It seems like a minor step. It isn’t.

Temperature Controls Everything

Temperature might be the single most powerful variable in fermentation. Too cold and nothing happens. Too hot and unwanted bacteria take over.

The ideal range for makgeolli fermentation is 18 to 25°C (64 to 77°F). Yeast is most active in this window. Push past 30°C and the yeast gets stressed, producing off-flavors. Above 35°C, the yeast dies. Drop below 15°C and fermentation essentially stops.

This is exactly why makgeolli tastes different across seasons. Brewed in summer, fermentation wraps up quickly and the result tends to be sharper and more acidic. Brewed in winter, the slow pace allows aromatic compounds to build gradually, producing a more nuanced flavor. The old Korean tradition of brewing in winter wasn’t just custom — it was smart temperature management.

If you’re brewing in summer, the first 12 to 24 hours are critical. Keep the vessel somewhere cool, or use ice packs to stabilize the temperature. If the temperature spikes early on, lactic acid bacteria multiply too fast and the whole batch turns unpleasantly sour.

Basic Makgeolli Recipe

Now that the science makes sense, here’s how to actually brew it at home. It’s more straightforward than it sounds.

Ingredients

1 kg non-glutinous white rice (멥쌀, mepssal)
100 g commercial nuruk (or 150 g traditional nuruk)
1.2 L water (for fermentation)
200 ml water (for hydrating nuruk)
1 clean glass or ceramic vessel, 3 to 4 liters or larger

Steps

Step 1. Rinse the rice thoroughly and soak it in cold water for 6 to 8 hours. Drain well.
Step 2. Steam the soaked rice until fully cooked and translucent, about 30 to 40 minutes. This is called godubap — steamed rice firmer than table rice. If it’s too wet and sticky, the ferment will sour easily.
Step 3. Spread the steamed rice out and let it cool below 30°C. Adding nuruk to hot rice will kill the microbes.
Step 4. Soak the nuruk in 200 ml of water for at least 8 hours. Break up any clumps with your hands.
Step 5. Combine the cooled rice and the nuruk water. Mix thoroughly by hand or with a sanitized implement. Add the remaining 1.2 L of water.
Step 6. Transfer to the vessel. Cover the opening with a cotton cloth or muslin — do not seal it airtight. Carbon dioxide needs to escape, and a sealed lid can be dangerous.
Step 7. Store at 18 to 25°C. Stir once or twice daily with a clean, sanitized spoon or paddle.
Step 8. After 3 to 5 days, the bubbling will slow and a clearer layer will start to form near the top. That’s your sign that fermentation is winding down. Strain through a fine mesh or cheesecloth, pressing the solids to extract the liquid. That’s makgeolli.

You can drink it right away. Store it in the refrigerator — the residual yeast will keep slowly fermenting, so aim to finish it within two weeks.

Variables That Shape the Flavor

Brew makgeolli a few times and you’ll notice each batch tastes a little different. Understanding why helps you dial things in.

Water

Tap water contains chlorine, which can suppress yeast and lactic acid bacteria. If your fermentation is slower than expected or the flavor seems off, try using filtered water — or let tap water sit boiled and cooled overnight before using it.

Rice Type

Non-glutinous rice (mepssal) produces a cleaner, lighter makgeolli. Glutinous rice (chapssal) has more starch available for saccharification, which means more sweetness and a thicker, richer body. Commercial makgeolli labeled “chapssal” tends to be noticeably sweeter and heavier — now you know why.

Sanitation

Your hands carry all kinds of bacteria. Stirring directly with bare hands introduces contamination risk. Always use a spoon or paddle that’s been sanitized with boiling water. A large share of home-brew failures trace back to hygiene, not technique.

Temperature, nuruk, rice, water, sanitation. Get those five variables under control and you have a solid foundation. After that, it’s just practice. Brew enough batches and you’ll reach the point where a single sniff of the crock tells you exactly where the fermentation stands.

Disclaimer: This article is informational content introducing the science and process behind makgeolli fermentation. Alcoholic fermented foods, including makgeolli, are not recommended for the treatment or prevention of any disease. Alcohol consumption may be contraindicated depending on individual health conditions. Please consult a qualified healthcare professional before consuming alcohol. Quality of home-brewed makgeolli may vary depending on storage conditions and hygiene practices. This content is for informational purposes only and is not medical advice.

The Science of Makgeolli: How Rice Becomes Wine