Did you know that soju, despite being such a famous liquor and one of the most sold worldwide, is not the only alcoholic beverage that originated in Korea?. Rice wine known as Makgeolli is a traditional Korean alcoholic beverage that has been part of Korean cuisine since the Three Kingdoms period.
Makgeolli (막거리) is a traditional Korean alcoholic beverage prepared with grains of rice, barley, wheat, and malt as a source of fermentable sugars with an alcohol percentage between 6 to 8% vol. However, what makes it special, what chemical process is involved in its preparation, and what are its health benefits?
Figure 1. Bottled commercial Makgeolli 
The history of Korean rice wine (known as Makgeolli) dates back to the Koguryeo (고구려) dynasty period when Chinese literature recorded the ways and customs of drinking this beverage. .
Makgeolli is a beverage prepared from rice, wheat, and malt starch by fermentation using a natural starter known as Nuruk. (Aspergillus Rhizopus)  , which is a microscopic fungus that initiates the hydrolysis of the starch present in these cereals, converting them into fermentable monosaccharides. The flavor profile of this beverage depends mainly on the metabolic products of the cellular factories involved in the fermentation process, such as free sugars, amino acids, organic acids, and aromatic compounds produced by molds and yeasts. (mainly Saccharomyces Cerevisiae).
This drink is mainly composed of: 80% water, 2% protein, 0.8% carbohydrates, 0.1% fat, and 10% dietary fiber, in addition to vitamins B and C, as well as a significant amount of lactobacilli (giving it probiotic properties that help maintain the intestinal flora) and yeasts.
However, the making process of this beverage has a marked difference compared to the production of wines from fruits such as grapes or oranges and its process is more similar to the brewing process of beer.
The block flow diagram for Makgeolli production is shown as follows:
Figure 2. Block flow diagram for Makgeolli production 
The process begins with the selection of the starch source. The cereals used are medium or long grain sweet glutinous rice and barley. Once selected, a process known as maceration is carried out, which consists of converting the starch into fermentable sugar by the action of enzymes (known as amylases) present in this starch, which is activated by temperature.
During the maceration process by the action of enzymes, long chains of starch are converted into glucose, which is the substrate to be used by the microorganism that produces ethanol. This reaction is known as saccharification and is described in Figure 3.
Figure 3. Biochemical reactions involved in cereal grain fermentation using microorganisms 
After obtaining glucose from the malt and rice, the mixture known as wort undergoes a cooling process until the conditions necessary for the microorganisms (yeasts and fungi) to metabolize the substrate and convert it into ethanol.
It should be noted that before adding the yeast to the must source of glucose, it must be previously activated in water at a certain temperature (generally 20ºC) since the commercial yeast was subjected to an inactivation process to preserve it for a longer period of time; therefore, this microorganism requires a preparation process before being added to the wort.
Figure 4. Commercial dry yeast 
On the other hand, the Nuruk fungus is produced by aging wheat and rice flour cakes with humidities close to 20% and a specific thickness. This process is known as germination and results in the formation of Aspergillus Rhizopus fungi. This ingredient is commercially available in Korea to do maceration, boiling, and fermentation stages at home. The Nuruk production process is detailed in Figure 6.
Figure 5. Homemade Nuruk  and commercial Nuruk 
Figure 6. Block flow diagram for Nuruk production 
Having ready, the wortt and the microorganisms that will carry out the fermentation are shown in the second reaction of figure 3. At temperatures between 25-30ºC. It is very important to maintain these temperatures since they are optimal for the production of ethanol, which is a process that occurs in the absence of oxygen. Fermentation is carried out in two stages. First, nuruk, steamed starch, and/or water are combined and fermented at room temperature for 2 to 3 days. Second, nuruk, steamed starch, and/or water are added to the first fermentation base and incubated at the same temperature for 2 to 5 days to produce alcohol . The makgeolli is then filtered through a cloth to obtain the final product ready for consumption .
Makgeolli is a very nutritious drink, containing 80% water. 6-8% alcohol and a high content of lactic acid and Lactobacillus, aid digestion, improve immune function and retard the aging process. Lactic acid bacteria are known to retard harmful bacteria that can cause inflammation and cancer in the gut. Lactic acid bacteria also help strengthen the immune system.
In conclusion, Korean rice wine is an ancestral beverage with many beneficial health properties. Its fermentation process is very similar at the beginning to the beer process since sugars are not directly available for fermentation as in the case of sugar cane or fruits and therefore require the process of germination and maceration. On the other hand, Koreans have used a different way of germinating microorganisms than the one used in the West, which consists of cultivating fungi in rice and wheat cakes that will later become Nuruk, a key element as gives this beverage its characteristic organoleptic properties.
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Written by: Felipe Puentes
Reviewed by: Angie Salavarria