Jiuqu

''Jiuqu'', also simply known as ''qu'', is a type of dried fermentation starter used in the production of traditional Chinese alcoholic beverages. The word ''jiuqu'' specifically refers to a type of yeast () used to make alcohol () such as ''huangjiu'' (cereal wine), ''baijiu'' (distilled spirits) and '' jiuniang'' (alcoholic rice pudding).

Other forms of starters are used for different fermentations, such as soy sauce, rice vinegar, fermented bean curd, and paste. The starter culture for these foods are also known as ''qu''.''Jiuqu'' is similar to, but distinct from, the more widely known Japanese starter known as '' koji''. Science and Civilisation in China

The starter creation process in China traditionally took place in homes, villages, or small manufacturing facilities, later shifting to large-scale facilities.

History

In China, particular cultivars of ''jiuqu'' are known as , , or simply as ''qu''. Qū is known as nuruk in Korea, ''much'' or ''marcha'' in India and Nepal, ''banh men'' in Vietnam, ''pacing'' in Laos, ''loog pang'' in Thailand, ''mochi kouji'' in Myanmar, ''mae domba'' in Cambodia, ''ragi'' in Indonesia and Malaysia, and ''bubo'' in the Philippines. The tradition of making ''qū'' is believed to have originated in China 3000–4000 years ago, and introduced throughout East Asia, Southeast Asia, and South Asia.Shurtleff, William, and Akiko Aoyagi. ''History of Koji-Grains And/or Soybeans Enrobed with a Mold Culture (300 BCE To 2012): Extensively Annotated Bibliography and Sourcebook''. Soyinfo Center, 2012.

''Qu'' is mentioned in the ''Book of Documents'', one of the Five Classics of ancient Chinese literature and a foundational work in Confucianism. A book from the Shang dynasty () states that "to make wine or sweet liquor one needs ''qū'' ''nieh''". Most authorities concur that ''qū'' describes the preparation of ferments, while ''nieh'' refers to sprouted grain. They may have formed separate elements of liquor production (both ''qū'' and ''nieh'') or might refer to a single preparation made of fermenting sprouted grains (''qu nigh''). The ''Book of Documents'' predates 500 BC, so the ancient predecessor of ''qū'' may be the world's oldest example of biotechnological manufacturing.

''Qu'' is mentioned in the '' Zhouli'' (), a collection of texts from the Eastern Zhou dynasty. It is described in preparing fermented meat and a grain–meat paste. At Mawangdui (200 BC10 AD), bamboo strips in Han Tomb Number 1 documented an inventory of tomb contents that included two sacks of ''qu''. The '' Liji'' (100 AD), a collection of texts from the Eastern Han dynasty, mentions ''qū'' as one of six requisites to make good wine. Another almanac from the Eastern Han dynasty, the first-century AD ''Shuowen Jiezi'' records a character for ''qū'' modified to include the yellow chrysanthemum flower. This was interpreted as referring to the distinctive yellow color formed on ''qū'' by sporulating molds. The ''Shiming'' (151) mentions several types of ''qu'', which are interpreted as distinguished by the source of the starch and the form of the substrate. It claims that since the Han dynasty ''qū'' was produced in China from mostly wheat or barley and pressed into cakes or bricks for handling. The earliest reference to the actual preparation of ''qū'' appears in the ''Qimin yaoshu'' (544) of the Northern Wei dynasty. There the techniques employed for making nine separate kinds of ''qū'' ''nigh'' are described in detail, along with their usage in the manufacture of 37 wines. The usage of ''qū'' in making vinegar, soybean pastes, and soy sauces are documented. The ''Qing yilu'' (, 965) recorded the use of a special red starter for the first time.

The fourth-century ''Nanfang Caomu Zhuang'' has the earliest description of preparing a natural " herb ferment" with rice, used to make a special wine for marriage ceremonies. "In Nanhai, in Guangzhou">Nanhai_District.html" ;"title="nowiki/>Nanhai District">Nanhai, in Guangzhouthere are many fine wines, prepared not with yeast leaven but by pounding rice flour mixed with many kinds of herb leaves and soaked in the juice of ''Gelsemium, Gelsemium elegans'' (). The dough, the size of an egg, is left in dense bushes under the shade. After a month, it is done and is used to mix with glutinous rice to make wine. Therefore, when consumed in large quantities, occurs, hot and sweaty head even after the effects of intoxication have subsided, as the drink contains toxic herbs. The roots of ''yege'' are poisonous."

Production

Making ''qu'' involves cultivating microbes in starchy materials and is a separate process that precedes the fermentation of grains and legumes into food or alcoholic beverages. Traditional practices vary and diverge from the later processes used for industrially-produced ''qu''.Xiaoqing Mu et al "Solid-State Fermented Alcoholic Beverages", in Chen, Jian, and Yang Zhu, eds. ''Solid State Fermentation for Foods and Beverages''. CRC Press, 2013.

The major manufacturing principles are:

* Preparation of cereal grains, usually rice, or a dough made from them
* Inoculation with previously grown microbiota (generally 4–8% mass)
* Incubation in a warm, humid environment for a set duration to stimulate the growth and metabolism of the microbiota
* Dessication to preserve the functional properties

''Qu'' can be sold fresh or stored for up to three years, without significant loss of viability.

Substrate ingredients vary across China by regional preferences, availability, and the type of ''qu'' ultimately being produced. The most common flours used in ''daqu'' are wheat and barley/peas. The preparation of ''hong'' involves only whole rice grains. Herbs of many kinds are variously included in the rice dough of many ''xiao'' preparations.

Traditional methods have changed little since the publication of the ''Qimin Yaoshu'' (544 CE). Grains or flours are saturated with water (e.g., steaming rice or mixing flour with water to form a dough) and subsequently incubated in a warm, humid environment during a favorable season, typically spring or autumn. No inocula are used, but often herbs are added. To keep the grains or dough relatively moist and warm, they are housed in closed straw-roofed huts and typically kept in straw baskets, stacked on wooden shelves, or simply placed on the floor. Leaves of various plants, often straw, mulberry leaves or '' Artemisia'', are used to wrap or cover the ''qu'' to promote a beneficial condition. The presses and molds used to shape the dough are made of wood. All of these elements unknowingly provided access to the microbes. The cakes are deemed ready when a colored coating forms on the outside. They are then dried and stored until used. The control of moisture and temperature levels and a lack of atmospheric access was recognized as vital to making consistently good ''qu'' as early as the ''Qimin Yaoshu''.

One aspect that has changed is the method of re-culturing for later preparation. Traditionally, microbes indigenous to the raw material, the process, and the locale simply grew upon the grains or dough. At some stage in history, it was discovered that using small amounts (2–8% mass) of a previous successful batch to inoculate the current one gave more consistent results. The starter cultures are often handed down from generation to generation in a continuous cycle of serial re-culturing. The most important functional organisms in ''qu'' have been recognized as the filamentous molds ''Aspergillus'' and ''Rhizopus'', which reproduce only asexually through spores called conidia, so an important step in manufacturing is to allow some of the cultured substrate to mature and sporulate to inoculate the next batch. Most of the other microbes present are capable of vegetative budding (yeasts) or binary fission (bacteria) and propagate without intervention.

The incubation and maturation phase is a typical biomolecule manufacturing process using solid-state fermentation. Yeasts and bacteria are often used in industrial submerged fermentation because they thrive at high water activity and reduced oxygen levels. Molds, however, prefer the lower water content and increased oxygen found in solid-state fermentation. The steaming of grain or making of dough creates a solid substrate with reduced water activity. Thus, the actual technique passed down through history unknowingly favored the growth and reproduction of the mold genera, organisms capable of excreting large amounts of functional enzymes onto their substrate. The ''qu'' itself became a dried product carrying both microbes and their enzymes (the biomolecules). Most yeast and bacteria do not find the conditions of ''qu'' optimal, but still grow effectively in solid-state fermentation. Their relationships to ''qū'' are not well understood.

''Qu'' processing can be carried out synchronously in the factory or workplace that produces a fermented end-product (such as a brewery or soy sauce factory) or it can be produced independently for sale. Traditionally, breweries did not make ''qu,'' but later often specialized in the preparation. ''Qu'' manufacturing techniques still vary widely, with each brewery or factory using a slightly different process and locally indigenous microflora, which in turn have generated diverse strains across China.

The process of making industrialized ''qu'' is inherently more complex as the two end products are sought to be manufactured by the factory: ''qu'' for use in alcohol production and so-called 'seed' ''qu'' for continued culturing of the microbiota. Seed ''qu'' is a pre-production process tailored to suit the growth and subsequent reproductive cycle of select microbes.

As such, ''qu'' practices have evolved from:
* Non-inoculum, spontaneous growth of microbiota from the natural surroundings through to
* Inoculation with a previous batch to improve consistency, culminating in
* Industrial culturing in a special process

A fourth step was introduced in 21st century China, where aseptic laboratory conditions are used to mono-culture specific favorable strains of mold, yeast, and bacteria grown on independent, fortified substrates. Such isolates now find usage in biotechnology applications such as fuel ethanol or enzyme production. An important objective is continued research into the biotechnological domestication of such microbes and as such, standardization of ''qu'' preparation.

Functions

The advantage of using ''qū'' for alcohol production is its two-fold effect. The enzymes and microorganisms break down the starches and sugars, reducing the process of making grain spirits to one step. The use of microbial cultured starches for fermentation has a long history in East Asian countries, as evidenced by the diversity of foods and beverages produced. Brewing alcoholic beverages from grains typically involves the use of sprouted cereal grains that supply natural enzymes to break down carbohydrates, proteins, and lipids.

As the grains used for traditional East Asian alcoholic fermentations are raw and unsprouted ( unmalted), the enzymes responsible for the conversion of carbohydrates to fermentable sugars are absent and thus fermentation cannot proceed. Culturing microbes on cereal grains is a time-honored tradition in East Asia and the necessary way around this dilemma, as they exude the enzymes that allow liquefaction and saccharification to occur (up to fifty different enzymes have been isolated from ''Aspergillus oryzae'' starters). Their mutualistic symbiosis with fermentative yeast and bacteria initiates the complex saccharification-liquefaction-fermentation process to produce the sought-after alcoholic liquid.

''Qū'', in ground form, is directly applied to cooked grain at a temperature suitable for microbe growth. When rehydrated, any enzymes present become activated. However, due to the small amount of ''qū'' used (2–8%) in most cases, only a minor contribution of enzymes comes from the starter. As such, ''qū'' is used only to inoculate the mash with microbes. In the case of ''baijiu'' production, typical amounts of 15–25% ''qū'' are used, sometimes reaching as high as 50%, which consequently provides a major enzyme contribution to the mash to initiate catabolism. The exponential growth and reproduction of microbes after inoculation releases more enzymes in the process, inducing further catabolism, to produce poly- and mono-saccharides, amino acids, peptides, , alcohol and organic acids.

Although only one type of starter is required, many Chinese breweries use two or more types of starters for added flavor complexity. Modern Chinese brewing adopted many practices to optimize production and a 'seed mash' is now commonly prepared where the ''qū'' is added, often along with the yeast ( or simply ), to a small amount of the substrate. After incubation for 2–7 days, the seed mash is then added.

Microbiota

The environment exerts a significant influence on Xiu microbiology. Relevant microbe species and genera prefer different climatic conditions, and domestication in the ''qū'' making process favored the development of regional microbiota assemblages across China. By comparison, the industrial Japanese koji-making process favors a single monoculture species, ''Aspergillus oryzae''. One difficulty in identifying the species present in ''qū'' appears to be bias introduced by the analytical technique. Culture-dependent or DNA extraction methods often miss entire species or misrepresent their statistical importance. Studies have failed to establish any pattern in ''qū'' microbiology across China, reflecting regional diversity.

Molds

Molds are the most prevalent organisms found in ''qū'' and are considered to be the dominant enzymatic agents responsible for liberating glucose and other fermentable sugars from the source of carbohydrates used (along with the yeast ''Saccharomycopsis fibuligera''). Molds found in traditional Chinese fermentation starters include ''Aspergillus'', ''Rhizopus'', ''Amylomyces'', '' Monascus'', ''Absidia'', '' Rhizomucor'', and ''Mucor''. Species of ''Rhizopus'' are capable of producing fumaric acid, lactic acid and ethanol as they excrete zymases, but their production capabilities vary widely from strain to strain. ''Rhizopus oryzae'' and ''Aspergillus oryzae'' are the two most common molds isolated in ''qu''.Zhong Fangda, Hu Feng, and Tang Yunrong. "Investigation on Microecology of Shelf ''daqu'' for Xijiu Liquor". ''Liquor-Making Science & Technology'' 7 (2012): 008.

The mold species appears to be an important factor in determining the resulting type of ''qū''. In turn, the dominant mold species is dependent on the climate, the substrate, and the production techniques. Both substrate and incubation phases can be adjusted to favor the growth of desired species, e.g. ''Rhizopus'' and ''Mucor'' prefer higher water activities and temperatures to ''Aspergillus'', whilst ''Mucor'' and ''Actinomucor'' prefer substrates richer in protein. In some reported examples of ''qū'' microbiology, potentially harmful strains of mold were encountered such as ''Aspergillus flavus'' and '' Rhizopus microsporus'', but it is uncertain if they were identified correctly or if those specific strains were capable of toxin production.Lv, Xu-Cong, et al. "Identification and characterization of filamentous fungi isolated from fermentation starters for Hong Qu glutinous rice wine brewing". ''The Journal of General and Applied Microbiology'' 58.1 (2011): 33–42.

Yeast

Yeast species form part of the symbiotic nature of a ''qū'' starter and can be enzymatic (substrate-degrading) and/or fermentative. Yeast genera observed for ''qū'' in decreasing order of significance include '' Saccharomycopsis, Issatchenkia, Saccharomyces, Pichia, Candida'' and ''Rhodotorula''. The yeast species most frequently reported for ''qū'' starters is ''Saccharomycopsis fibuligera'', as is typical for traditional East Asian fermentation starters. A close relative, ''Issatchenkia orientalis'', is also reported frequently, and together they appear to be co-involved in starch breakdown with the mold genera. Both species have limited but capable (3–5% alcohol) fermentative capacities. ''Pichia anomala'' is almost ubiquitous and although incapable of elevated alcohol production, it appears to be vital in developing taste and aroma. ''Saccharomyces cerevisiae'' is the most common highly fermentative yeast present in Xiu.

Bacteria

Bacterial species are present in large numbers in ''qū'' and are partly responsible for the breakdown of proteins and carbohydrates and the conversion of fermentable sugars into organic acids. Lactic acid is the most common organic acid found in Chinese alcoholic beverages and plays a vital role in both the organoleptic qualities, as well as acting as a naturally occurring preservative. The bacterial species most commonly found (in decreasing significance) include ''Bacillus, Lactobacillus, Leuconostoc, Streptomyces, Acetobacter'' and ''Clostridium''. ''Bacillus'' species are the dominant bacterial genera in Xiu. ''Bacillus'' species are known to be large producers of enzymes and therefore contribute to the overall breakdown of the cereal grains.

Types

An exponential variety of ''qū'' can be produced by manipulating the ingredients and processes across the different environments. Some types are produced by exploiting natural temperature shifts, others by mechanical temperature adjustments. Some ''qū'' are wrapped in straw and sun-dried, while others are wrapped in straw and hung from the rafters to dry. Although ''qū'' contains its own distinctive, region-specific mix of microorganisms, the temperature schemes involved in preparation manipulates the microbial ecology, e.g., ''Aspergillus oryzae'' and species of ''Actinomucor'' and ''Mucor'' prefer lower temperatures than ''Rhizopus oryzae''. In turn, the starch ingredients used also alter the microbial ecology dictating both the type and the number of metabolites present, e.g., ''Aspergillus oryzae'' and ''Rhizopus oryzae'' both produce more starch degrading enzymes and are found commonly on 100% flour substrates, whilst ''Actinomucor'' and ''Mucor'' produce more proteolytic and lipolytic enzymes and are more abundant when pulse flours are added.

Each type of ''qū'' can be used individually or in conjunction with others. ''Huangjiu'', or cereal wines, can incorporate one or several of the starters with the combination of ''xiao'' and ''daqu'' being the most common. In contrast, ''baijiu'', a distilled beverage, generally uses only ''daqu''.

''Xiaoqu''

''Xiaoqu'' or are generally small () cubes or flattened or rounded balls made of rice dough incubated for usually only several days. Rice flour or bran and inoculum are used, with bentonite clay as a bulking agent. Traditionally various herbs (from one to fifteen varieties) are incorporated into the preparation as either ''you'' (herb ''xiao'') or bark (white or herbless ''xiao''). They are commonly referred to as Chinese or Shanghai yeast balls when available through Western Chinese suppliers.

Used mostly for the production of ''huangjiu'' and '' jiuniang'' and most popular in the southern provinces, ''xiao'' is added only to inoculate a fermentation and constitutes very little of the substrate in producing cereal wines (typically 3–8%). As such, xiao contributes very minor flavor, aroma, or enzymatic function when compared to ''daqu''. ''Xiaoqu'' is the Chinese equivalent of what most other East, South, and Southeast Asian countries use as a fermentation starter, e.g. banh men, bubo, Murcia, ragi, nuruk.

Incubation is relatively simple and done at ambient temperatures of for four to five days, before drying. ''Xiaoqu'' is almost always white because ''Rhizopus oryzae'' is the dominant mold species and saccharifying agent. Some types of ''xiao'' are now prepared by mixing yeast sediment with the normal inoculum to produce a more fermentative starter.

''Daqu''

''Daqu'' or are large () cakes or bricks of dough that have been incubated for long periods, typically 3–4 or 6–8 weeks, and then matured for an extended period of six months or more. They are rarely available outside of China. Wheat flour is the main ingredient, but some specific types call for the use of barley-wheat and barley-pea flour. The four most famous ''baijiu'', Maotai, Fenjiu, Luzhou Laojiao, and Xifengjiu, are all made with ''daqu'' only. Some huangjiu are often started with ''xiao'' and finished with ''daqu''. ''Daqu'' can come in three colors that mostly reflect the dominant mold species present: grey-white (''Rhizopus oryzae'' and/or ''R. chinensis)'', yellow to yellow-green (''Aspergillus oryzae''), and black (''A. niger'' and/or ''A. luchuensis'').

Both the larger size and the longer incubation ensure higher enzyme and microbial load than ''xiao''. They are the only starter used for most ''baijiu'' fermentations due to their greater starch degrading capacity, i.e., they contribute a high number of enzymes. The greater degree of microbial metabolism because of a longer, higher temperature conversion phase of incubation is also said to provide certain organoleptic qualities that would be otherwise unachievable in the final product. This directly relates to the greater use of data as an ingredient in making ''baijiu'' rather than simply as an inoculant. ''Daqu'' typically constitutes 15–25% of the overall fermentable, whereas ''xiao'' is used only to inoculate a fermentation (3–8%). The heavy use (50%) of large bricks of ''daqu'' incubated at high temperatures is responsible for the pungent aroma and umami-like the flavor of Maotai.

''Daqu'' is the most complex process of ''qū'' preparation and has undergone the most modernization. It involves the manipulation of specific time-temperature control schemes to achieve slightly different types, which in turn are used to generate several types of liquor. The four ''baijiu'' aromas most typical are considered to be sauce-aroma (e.g., Maotai), strong-aroma (e.g., Luzhou Laojiao), mixed-aroma (e.g., Xifengjiu) and light-aroma (e.g., Fenjiu). ''Daqu'' preparation is manipulated to help produce these different aromas.

''Daqu'' can be generally categorized into three kinds according to the highest temperature achieved during incubation: high-temperature (), medium-temperature () and low-temperature (), respectively. As an example of the differing usage schemes, Maotai uses high-temp ''daqu'' and Luzhou Laojiao uses medium-temp ''daqu'', and both are made from wheat flour. Fenjiu and Xifengjiu use low-temp ''daqu'' made from barley and pea flour but differ in the coarseness of the crushed grains.

High- and medium-temperature ''daqu'' generally undergo a four-step process:
# a low-temperature () incubation phase for 3–5 days to stimulate the initial growth of microbes,
# a higher temperature () conversion phase for 3–5 days to increase the metabolic activities of the microbes,
# a curing phase () for 9–12 days to create flavors and dehydrate the cake and
# maturation for up to six months or more at ambient temperatures.

Low-temperature ''daqu'' typically undergo a six-step process:
# a low temperature () incubation phase for 2–4 days
# a cooling phase () For 3–5 days to stabilize the growth of microbes.
# a heating phase () For 4–5 days to increase metabolic activities.
# a curing phase () for 7–8 days to create flavor and further dehydrate the cake.
# an equilibration phase (<) for 4–5 days to cool the cakes.
# maturation for up to six months or more at ambient temperatures.

The scientific basis for these processes need to be clarified, as standardizing production methods is a goal of the Chinese alcohol industry.

''Hongqu''

''Hongqu'' or , also called ''bangkok'' in Hokkien, is rice cultured primarily with ''Monascus purpureus'' or other red rice molds of the genus '' Monascus'', available as dried, mold-encrusted rice with a unique red color, and sold as "red yeast rice". Used mostly for ''huangjiu'' and rice vinegar, this starter gives the beverage a unique red or purple color due to pigments produced by members of ''Monascus''. ''Gutian'' ''hongqu'' is the name for this starter, inoculated with a "seed" culture called ''qumu'', containing only ''Monascus'' species. A popular alternative variety also used is ''Wuyi'' ''hongqu'', which involves seeding the rice with both ''Qū'' ''Mu'' as above and ''Qū'' ''Qing'', a "seed" culture that contains a black mold ('' A. niger'' or '' A. luchuensis'') to make the rice black on the outside and red inside. A rarer variety is called ''Huangyi Hong'' ''qū'' which involves ''Monascus'' with a yellow mold (''A. oryzae'' or ''A. flavus'') to make the rice yellow on the outside and red on the inside.

''Hongqu'' is prepared in a way similar to Japanese ''koji'': rice is steamed, cooled, and then mixed with the inoculum (1–2%). It is then transferred to an incubation room where the temperature is maintained at for four to five days and the rice is stirred frequently. Modern practice is to steep the rice in weak acetic acid solution for a short period to help create the optimum pH of 3–3.5 that favors ''Monascus'' growth. Afterward, the rice is removed and dried.

Often in the production of ''hongqu'' rice wine, both ''hong'' and ''xiao'' are utilized. Studies have revealed that '' Monascus'' species show strong gluco-amylase activity, but poor proteolytic and lipolytic enzyme production. Also, the fermentative yeast ''Saccharomyces cerevisiae'' was mostly absent from ''hong'' starters but present in ''xiao''. Thus, ''hong'' is used only to provide red pigmentation and saccharification and as such, should generally be used in conjunction with another starter with high fermentative capability.

Minor varieties

The following form the fourth category of ''qū'': is a starter for wheat only. It is used as a major component (15–25%) of the total starter for some ''huangjiu''. The manufacturing process and microbiota are similar to ''daqu'', but is made entirely from wheat.

*''Shenqu'' (from Shenzhen; ) uses raw, roasted, and steamed wheat,
*''Fuqu'' () uses wheat bran,
*''Shumaiqu'' () uses only steamed wheat,
*''Benqu'' () uses only roasted wheat,
*''Sengmaiqu'' () uses only raw wheat

See also

* Agkud
* Awamori
* Chinese wine

Notes

References

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Chinese alcoholic drinks
Rice wine
Fermentation in food processing