Jiuqu: The Ancient Probiotic Starter of China and East Asia

Jiuqu, often simply referred to as Qu, is a dried fermentation starter used in the production of traditional Chinese alcoholic beverages including Huangjiu (cereal wine), Baijiu (distilled spirits), and Jiuniang (fermented glutinous rice pudding). The word Jiuqu specifically combines Jiu meaning liquor and Qu referring to the fermentation agent. Jiuqu represents a foundational point of departure between Chinese and Western brewing cultures, as it is not employed in Western brewing traditions. The fabrication procedures of Jiuqu originated in China before the Shang Dynasty, approximately 1600 BCE, and were subsequently transmitted to South Korea, Japan, and Vietnam.

Unlike pure yeast cultures used in Western brewing, Jiuqu is a complex, solid state fermentation product that contains a symbiotic consortium of molds, yeasts, and bacteria. These microorganisms work in concert to simultaneously saccharify starches and ferment sugars into alcohol. This simultaneous saccharification and fermentation process is a unique characteristic that distinguishes Chinese Baijiu production from other distilled spirits, which employ sequential processes.

Cultural Roots and Historical Significance

Jiuqu is mentioned in the Book of Documents, one of the Five Classics of ancient Chinese literature. A book from the Shang Dynasty states that to make wine or sweet liquor one needs Qu Nieh. Most authorities concur that Qu refers to ferments while Nieh refers to sprouted grain. The Book of Documents predates 500 BCE, making the ancient predecessor of Qu potentially the world's oldest example of biotechnological manufacturing.

The approach of adding herbs during the fermentation process was first recorded in Nanfang Caomu Zhuang, a book on the flora of Lingnan dating to 304 CE. Studies suggest that adding herbs provides microorganisms, proteins, flavor components, and bacteriostatic ingredients from plants, which can inhibit harmful microorganisms and increase the taste, nutrition, and beneficial effects of alcoholic drinks.

The Three Main Categories of Jiuqu

Jiuqu can be divided into three primary categories based on raw materials and production conditions:

Daqu

Daqu primarily utilizes barley, wheat, and peas as raw materials, which are pressed into large blocks weighing between 1.5 and 4.5 kilograms. Its substantial size earns it the name Daqu, meaning large Qu. Daqu is further categorized by production temperature into high temperature Daqu for Maotai flavored Baijiu, medium temperature Daqu for strong flavored Baijiu, and low temperature Daqu for light flavored Baijiu. Approximately 70 percent of Chinese Baijiu is brewed with Daqu starter, including the most renowned varieties such as Maotai, Luzhou Laojiao, and Fenjiu. Daqu contains a diverse microbial community dominated by filamentous fungi including Rhizopus, Rhizomucor, and Aspergillus, yeasts including Saccharomyces and Candida, and bacteria including lactic acid bacteria and Bacillus species.

Xiaoqu

Xiaoqu is derived from rice flour and rice bran and is distinguished by its small size, typically weighing between 10 and 100 grams. It is suitable for the climatic conditions of southern China owing to its small size and reduced heat generation. The production process is relatively simple. Xiaoqu is made from rice, sorghum, or barley, often combined with several traditional Chinese medicines. In the brewing process, saccharification and fermentation occur simultaneously. Xiaoqu contains fewer types of microorganisms than Daqu, including Rhizopus, Mucor, Lactobacillus, and yeasts. Southern light flavored and rice flavored Baijiu often rely on Xiaoqu for production.

Fuqu

Fuqu is made from bran and undergoes inoculation with pure cultures of microbes, typically Aspergillus species including Aspergillus flavus, Aspergillus niger, and Aspergillus albus, followed by incubation under controlled temperatures and humidity. Fuqu primarily serves a saccharification role and typically requires the addition of yeast for alcoholic fermentation. Fuqu has been successfully used to produce Maotai flavored, light flavored, and sesame flavored Chinese Baijiu.

The Traditional Knowledge of Jiuqu Making

An ethnobotanical study of the Chuanqing people in Northwestern Guizhou, China, documented the unique traditional knowledge of Jiuqu production. The survey involved 225 informants, including 116 who provided information on making Chinese Baijiu Jiuqu and 139 who provided information on making fermented glutinous rice Jiuqu. The study found that older people have more abundant knowledge about Baijiu Jiuqu plants, with knowledge positively correlated with age. The informants were predominantly farmers with limited formal education.

Plant Diversity in Jiuqu Production

Numerous plants are used to make Jiuqu, with a total of 57 species belonging to 51 genera and 32 families documented. The families, plant parts, and life forms used differ between Baijiu Jiuqu and fermented glutinous rice Jiuqu:

For Baijiu Jiuqu, 27 families are used. The most frequently used family is Poaceae (grasses) with 7 species, followed by Liliaceae with 3 species. The whole plant is the most commonly used part at 19.5 percent, followed by the fruit at 19.5 percent and the root at 9.8 percent. Herbaceous plants comprise 75.6 percent of the plants used.

For fermented glutinous rice Jiuqu, 30 families are used. The most frequently used family is Poaceae with 7 species, followed by Polygonaceae with 5 species, and Liliaceae and Fabaceae with 3 species each. The whole plant is the most commonly used part at 22.6 percent, followed by the fruit at 15.1 percent and the root at 9.4 percent. Herbaceous plants comprise 69.8 percent of the plants used.

Some of the plants used are rare or protected species. Ephedra equisetina, Glycyrrhiza uralensis, Paris polyphylla, and Lilium sulphureum are all classified under China's national protection level II.

The Chuanqing people's Jiuqu is used not only for brewing but also as traditional medicine to treat dietary stagnation and indigestion, as it strengthens the spleen. The highest relative frequency of citation for Baijiu Jiuqu plants is Ficus tikoua Bureau, while for fermented glutinous rice Jiuqu, it is Buddleja macrostachya Benth.

The Microbiology of Jiuqu

Jiuqu is a rich microbial ecosystem. Metaproteomics analysis has revealed that the dominant community members include eight bacterial and seven fungal genera. Among these, Lactobacillus, Aspergillus, Pichia, Saccharomyces, and Rhizopus are the main contributors of proteins.

Key microorganisms identified in Jiuqu include:

Bacteria

The dominant bacterial species in Jiuqu include Gluconobacter japonicus and Pediococcus pentosaceus. Lactobacillus species are also prominent and play a crucial role in maintaining acidity through lactic acid production. Studies have documented that the abundance of Weissella, Lactobacillus, and Pichia changes during fermentation processes.

Fungi

The dominant fungal species in Jiuqu is Rhizopus oryzae. Additional key fungi include Aspergillus species, which are essential for saccharification, and various yeasts including Saccharomyces cerevisiae and non Saccharomyces yeasts such as Saccharomycopsis fibuligera.

Functional Roles of Microorganisms

The microorganisms in Jiuqu serve several essential functions during fermentation:

Enzyme Production

Jiuqu contains several functional enzymes including amylase, glucoamylase, and zymase. Rhizopus microsporus has been identified as the main producer of glucoamylase, the enzyme responsible for converting starches into fermentable sugars. The volumetric weight of Jiuqu has been identified as a major driving force for the key saccharifying microbiota. When Jiuqu is produced in a diffused shape with low volumetric weight, the key saccharifying genera significantly decrease and the key saccharifying enzymes are down expressed.

Acid Production

Acidity serves as a crucial indicator for Jiuqu quality assessment, reflecting the metabolic activity of acid producing microbes, particularly the lactic acid bacteria. These LAB play a vital role in the initial stages of brewing by rapidly proliferating and inhibiting harmful microbes, thereby ensuring fermentation safety. Acidity levels in Xiaoqu samples fluctuate, ranging from 0.24 mmol per 10 grams to 1.24 mmol per 10 grams.

Flavor Development

The microbial community directly impacts the flavor profile of the final beverage. Different Jiuqu types produce distinctly different flavor compounds. In light flavored Baijiu, alcohols and esters are the main contribution components. Daqu light flavored Baijiu exhibits higher sour taste and lower umami taste, with significantly higher relative content of esters. Xiaoqu light flavored Baijiu shows greater contributions from ethyl propionate, isoamyl alcohol, furfural, ethyl valerate, and isobutanol.

Probiotic Components and Functional Benefits

Jiuqu contains a diverse array of lactic acid bacteria that contribute to its probiotic potential:

Lactic Acid Bacteria Species Identified in Jiuqu

· Pediococcus pentosaceus

· Weissella cibaria

· Lactobacillus species (including Lactobacillus plantarum)

· Leuconostoc species

· Enterococcus species

These LAB contribute to the tangy flavor profile of beverages made with Jiuqu and may provide gut health benefits similar to those associated with other fermented foods. The lactic acid produced during fermentation creates an acidic environment that helps preserve the beverage and supports digestive health.

Yeast and Mold Species with Functional Properties

· Rhizopus oryzae and Rhizopus microsporus (molds, GRAS status for R. oryzae)

· Aspergillus species (molds, essential for saccharification)

· Saccharomyces cerevisiae (brewer's yeast)

· Saccharomycopsis fibuligera (non Saccharomyces yeast, flavor development)

· Pichia species (flavor development)

Traditional Medicinal Uses

The Chuanqing people's Jiuqu is used to treat dietary stagnation and indigestion. The herbs incorporated into the starter provide microorganisms, proteins, flavor components, and bacteriostatic ingredients. These herbal components can inhibit harmful microorganisms and increase the taste, nutrition, and beneficial effects of alcoholic drinks.

Preparation Guidelines for Traditional Jiuqu

The following represents the general principles of traditional Jiuqu production, based on practices documented in ethnographic studies.

Raw Materials for Approximately 5 Kilograms of Jiuqu

Primary grain or flour

Quantity: 5 kilograms. Wheat, barley, peas, or rice depending on the type of Jiuqu. For Daqu, wheat is the primary ingredient. For Xiaoqu, rice flour is used.

Water

Quantity: As needed to form a workable dough. The amount varies depending on the flour absorption.

Inoculum from a previous batch

Quantity: 200 to 400 grams (4 to 8 percent of the total weight). This traditional inoculum is known as seed Qu.

Herbs (for herbal Jiuqu)

Quantity: Varies by recipe. Traditional Jiuqu from the Chuanqing people uses a diverse array of herbs, with the whole plant being most commonly used. Over 57 species from 32 families have been documented for Jiuqu production. Commonly used herbs include those from the Poaceae family such as Avena sativa and various medicinal plants.

Rice husk or straw

Quantity: For wrapping and insulating during incubation.

Equipment

One large wooden or earthenware vessel for mixing, wooden molds or bamboo frames for shaping, bamboo mats for drying, straw or banana leaves for wrapping, and a warm, humid room for incubation.

Pre processing Guidelines

Grain preparation

Clean the selected grains thoroughly. For Daqu, the grains are typically coarsely crushed. For Xiaoqu, the rice is ground into a fine flour.

Herbal preparation

If using herbs, dry and grind them into a powder. The whole plant is most commonly used in traditional Jiuqu.

Inoculum preparation

Crush or grind the old Jiuqu into a fine powder. This serves as the seed culture for the new batch.

Water preparation

Use clean, filtered water free of chlorine.

Step by Step Recipe

1. Mix the dry ingredients

In a large, clean vessel, combine the crushed grains or flour with any ground herbs. Mix thoroughly to ensure even distribution.

2. Add the inoculum

Sprinkle the seed Qu powder over the dry mixture. Use approximately 4 to 8 percent by weight. Mix well to incorporate the inoculum.

3. Add water

Slowly add water while mixing with a wooden paddle or by hand. Add just enough water to form a cohesive dough. The dough should be moist but not excessively wet.

4. Shape the Jiuqu

For Daqu, press the dough into large brick shaped blocks using wooden molds. Each block weighs between 1.5 and 4.5 kilograms. For Xiaoqu, form small round cakes or balls weighing 10 to 100 grams.

5. Wrap the blocks

Wrap the shaped Jiuqu in straw, banana leaves, or rice husks. This wrapping helps maintain moisture and temperature while preventing contamination.

6. Incubate

Place the wrapped Jiuqu in a warm, humid room. Traditional production occurs during spring or autumn when ambient temperatures are favorable. The incubation period typically lasts several days to weeks, depending on the type of Jiuqu. During this time, the microbes grow and colonize the substrate. The temperature must be carefully controlled; high temperature Daqu requires temperatures above 60 degrees Celsius, medium temperature Daqu requires 50 to 60 degrees Celsius, and low temperature Daqu requires 40 to 50 degrees Celsius.

7. Monitor the fermentation

During incubation, the Jiuqu will undergo a visible transformation. A coating of mold mycelium will develop on the surface. The color may change to yellow, white, or black depending on the specific conditions. For Daqu, the process is divided into stages resulting in white Qu, yellow Qu, and black Qu. White Qu has the highest liquefaction and saccharification enzyme activity, while black Qu has the highest neutral protease and cellulase activity.

8. Dry the Jiuqu

After the incubation period, the Jiuqu must be dried to preserve it. Sun drying is traditional and effective. The final moisture content must be below 10 percent to maintain microbial and enzyme activities. Studies have shown that Xiaoqu samples from different regions maintain moisture content between 3.11 percent and 9.50 percent.

9. Store

Store the dried Jiuqu in a cool, dry place. Properly stored Jiuqu can be kept for up to three years without significant loss of viability.

Signs of Success

A properly made Jiuqu is a hard, dry cake with a uniform appearance. The color varies by type: Daqu may be yellow, white, or black; Xiaoqu is typically off white. The aroma should be pleasant and complex, with notes of grain, fermentation, and herbs. The Jiuqu should have a clean, non musty smell with no signs of insect infestation or mold contamination.

Troubleshooting Common Issues

Jiuqu fails to develop mold growth

Cause: Temperature too low, insufficient humidity, or weak inoculum. Solution: Ensure the incubation room maintains appropriate temperature and humidity. Verify that the seed Qu is viable.

Jiuqu develops black or green mold

Cause: Contamination with undesirable fungi due to poor sanitation or incorrect conditions. Solution: Discard the contaminated batch and thoroughly clean all equipment. Review the sanitation procedures.

Jiuqu smells rancid or putrid

Cause: Overgrowth of undesirable bacteria. Solution: Discard the batch. This often occurs if the incubation temperature is too high or if the Jiuqu is not turned or aerated properly.

Jiuqu crumbles easily

Cause: Insufficient binding from the flour or too little water during mixing. Solution: Use a finer grind of flour or increase the water content slightly in the next batch.

Jiuqu has low saccharification power

Cause: Weak inoculum, insufficient incubation time, or improper temperature for the specific microbial community. Solution: Use fresh, high quality seed Qu and ensure the incubation conditions match the requirements of the specific Jiuqu type.

Storage and Shelf Life

Properly dried Jiuqu stored in a cool, dry, dark place can remain viable for up to three years. The low moisture content, typically below 10 percent, preserves the microorganisms and enzymes in a dormant state. The Jiuqu must be protected from moisture, as rehydration can activate undesirable microbes and cause spoilage. For long term storage, traditional bamboo containers or modern airtight vessels are both suitable.

Fortified Jiuqu and Modern Innovations

Recent developments in Jiuqu production include the creation of fortified Jiuqu, which involves inoculation of Jiuqu with microorganisms that serve specific functions. This can change the microbial community structure of the original Jiuqu, enhance its fermentation performance, and improve the flavor quality of the Baijiu. Traditional Jiuqu is produced by natural fermentation without manually adding extra microbes.

When specific strains are inoculated into Jiuqu, measurable improvements occur. For instance, when Bacillus velezensis and Bacillus subtilis are inoculated into Daqu, the liquefaction power increases by 25.6 percent, the saccharification power increases by 9.0 percent, and the esterification power increases by 15.2 percent. The levels of flavor compounds such as tetramethylpyrazine and phenylethyl alcohol increase by 90.8 percent and 69.5 percent respectively.

Modern Jiuqu production is also moving toward mechanization, offering high stability, efficiency, and cost effectiveness. However, challenges remain, particularly regarding the poor production environment, difficulty avoiding harmful microorganisms and pest invasions, and safety concerns regarding the use of rice straw and other traditional materials.

Usage Note

Jiuqu is a starter culture and is not meant to be consumed raw. To use, crush or grind the dried Jiuqu and mix it into cooked, cooled grains. The microbes will reactivate and ferment the substrate into wine or a mash suitable for distillation.

Traditional Jiuqu may contain histamine and other biogenic amines due to the mixed microbial fermentation. Individuals with histamine intolerance should be cautious when consuming beverages produced with Jiuqu. The alcohol content of the final beverage varies depending on the specific brewing process, ranging from low alcohol fermented rice dishes to high proof distilled spirits.

The Jiuqu tradition represents a living heritage of microbial domestication that has been passed down through generations. The knowledge of Jiuqu making is a valuable cultural resource that deserves preservation and study. The use of online social media platforms and multimedia databases has been encouraged to spread Jiuqu culture and prevent the disappearance of traditional Jiuqu knowledge.

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