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| Jiuqu | |||||||
|---|---|---|---|---|---|---|---|
.jpg) Packets ofjiuqu | |||||||
| Traditional Chinese | 酒麴 | ||||||
| Simplified Chinese | 酒曲 | ||||||
| Literal meaning | liquor yeast | ||||||
| |||||||
| Qunie | |||||||
| Traditional Chinese | 麴櫱 | ||||||
| Simplified Chinese | 曲蘖 | ||||||
| Literal meaning | yeast and malt | ||||||
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| Jiumu | |||||||
| Chinese | 酒母 | ||||||
| Literal meaning | liquor origin | ||||||
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Jiuqu, also simply known asqu,[a] is a type of driedfermentation starter used in the production of traditionalChinese alcoholic beverages.[2] The wordjiuqu specifically refers to a type of yeast (曲;麴;qū) used to make alcohol (酒;jiǔ) such ashuangjiu (cereal wine),baijiu (distilled spirits) andjiuniang (alcoholic rice pudding).
Other forms of starters are used for differentfermentations, such assoy sauce,rice vinegar,fermented bean curd, andpaste. The starter culture for these foods are also known asqu.[3]Jiuqu is similar to, but distinct from, the more widely knownJapanese starter known askoji.[2][4][5][6][7]
The starter creation process in China traditionally took place in homes, villages, or small manufacturing facilities, later shifting to large-scale facilities.
In China, particular cultivars ofjiuqu are known as "starter cake" (曲饼;麴餅;qūbǐng), "liquor product" (酒药;酒藥;jiǔyào), or simply asqu.[4] Qū is known asnuruk inKorea,much ormarcha inIndia andNepal,banh men inVietnam,pacing inLaos,loog pang inThailand,mochi kouji inMyanmar,mae domba inCambodia,ragi inIndonesia andMalaysia, andbubo in thePhilippines.[8] The tradition of makingqū is believed to have originated in China 3000–4000 years ago, and introduced throughoutEast Asia,Southeast Asia, andSouth Asia.[4][6][9]
Qu is mentioned in theBook of Documents, one of theFive Classics ofancient Chinese literature and a foundational work inConfucianism. A book from theShang dynasty (c. 17th–11th centuries BC) states that "to makewine or sweet liquor one needsqūnieh". Most authorities concur thatqū describes the preparation of ferments, whilenieh refers to sproutedgrain. They may have formed separate elements ofliquor production (bothqū andnieh) or might refer to a single preparation made of fermenting sprouted grains (qu nigh). TheBook of Documents predates 500 BC, so the ancient predecessor ofqū may be the world's oldest example ofbiotechnological manufacturing.[4][6][9]
Qu is mentioned in theZhouli (c. 150 BC), a collection of texts from theEastern Zhou dynasty. It is described in preparingfermented meat and a grain–meat paste. AtMawangdui (200 BC – 10 AD),bamboo strips in Han Tomb Number 1 documented an inventory of tomb contents that included two sacks ofqu. TheLiji (100 AD), a collection of texts from theEastern Han dynasty, mentionsqū as one of six requisites to make good wine. Anotheralmanac from the Eastern Han dynasty, the first-century ADShuowen Jiezi records a character forqū modified to include the yellowchrysanthemum flower. This was interpreted as referring to the distinctive yellow color formed onqū bysporulating molds. TheShiming (151) mentions several types ofqu, which are interpreted as distinguished by the source of thestarch and the form of thesubstrate. It claims that since theHan dynastyqū was produced in China from mostlywheat orbarley and pressed into cakes or bricks for handling. The earliest reference to the actual preparation ofqū appears in theQimin yaoshu (544) of theNorthern Wei dynasty. There the techniques employed for making nine separate kinds ofqūnigh are described in detail, along with their usage in the manufacture of 37 wines. The usage ofqū in makingvinegar,soybean pastes, and soy sauces are documented. TheQing yilu (清异录, 965) recorded the use of a specialred starter for the first time.[4][6][9]
The fourth-centuryNanfang Caomu Zhuang has the earliest description of preparing a natural "herb ferment" with rice, used to make a special wine formarriage ceremonies. "In [Nanhai, in Guangzhou] there are many fine wines, prepared not with yeast leaven but by poundingrice flour mixed with many kinds of herb leaves and soaked in the juice ofGelsemium elegans (冶葛;yěgé). 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 withglutinous 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 ofyege are poisonous."[10]
Makingqū involves cultivatingmicrobes in starchy materials and is a separate process that precedes the fermentation of grains andlegumes into food oralcoholic beverages.[11] Traditional practices vary and diverge from the later processes used for industrially-producedqu.[2][4][6][7][12]
The major manufacturing principles are:
Qu can be sold fresh or stored for up to three years, without significant loss of viability.[2][4][6][7][12]
Substrate ingredients vary across China by regional preferences, availability, and the type ofqū ultimately being produced. The most common flours used indaqu are wheat and barley/peas. The preparation ofhong involves only whole rice grains. Herbs of many kinds are variously included in the rice dough of manyxiao preparations.[2][4][6][7][12]
Traditional methods have changed little since the publication of theQimin Yaoshu (544). Grains orflours 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. Noinocula 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 orartemisia, are used to wrap or cover theqū to promote a beneficial condition. The presses andmolds 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 goodqū as early as theQimin Yaoshu.[4][6][7][12]
One aspect that has changed is the method of re-culturing for later preparation. Traditionally, microbesindigenous 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% weight) 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 inqū have been recognized as the filamentous moldsAspergillus andRhizopus, whichreproduce only asexually through spores calledconidia, 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 ofvegetative budding (yeasts) orbinary fission (bacteria) and propagate without intervention.[4][6][7][12]
The incubation and maturation phase is a typicalbiomolecule 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.[12] 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 functionalenzymes onto their substrate. Theqū itself became a dried product carrying both microbes and theirenzymes (the biomolecules).[4][6][12] Most yeast and bacteria do not find the conditions ofqū optimal, but still grow effectively in solid-state fermentation. Their relationships toqū have been understudied.[7][13]
Qū processing can be carried out synchronously in the factory or workplace that produces a fermented end-product (such as abrewery or soy sauce factory) or it can be produced independently for sale. Traditionally, breweries did not makeqū, but later often specialized in the preparation.Qū manufacturing techniques still vary widely, with each brewery or factory using a slightly different process and locally indigenousmicroflora, which in turn have generated diverse strains across China.[4][6][7]
The process of making industrializedqū is inherently more complex as the two end products are sought to be manufactured by the factory:qū for use in alcohol production and so-called 'seed'qū for continued culturing of the microbiota. Seedqū is a pre-production process tailored to suit the growth and subsequent reproductive cycle of select microbes.[4][6][7][12]
As such,qū practices have evolved from:
A fourth step was introduced in 21st century China, whereaseptic laboratory conditions are used to mono-culture specific favorable strains of mold, yeast, and bacteria grown on independent, fortified substrates.[6] Such isolates now find usage inbiotechnology applications such asfuel ethanol or enzyme production.[14] An important objective is continued research into the biotechnological domestication of such microbes and as such, standardization ofqū preparation.[6][7]
The advantage of usingqū for alcohol production is its two-fold effect. The enzymes and microorganisms break down the starches and sugars, reducing the process of makinggrain 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 downcarbohydrates,proteins, andlipids.
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 allowliquefaction andsaccharification to occur (up to fifty different enzymes have been isolated fromAspergillus oryzae starters). Their mutualisticsymbiosis with fermentative yeast and bacteria initiates the complex saccharification-liquefaction-fermentation process to produce the sought-after alcoholic liquid.[2][4][5][6][7][15][16]
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 ofqū 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 ofbaijiu 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 initiatecatabolism. Theexponential growth and reproduction of microbes after inoculation releases more enzymes in the process, inducing further catabolism, to producepoly- andmono-saccharides,amino acids,peptides,CO2,alcohol andorganic acids.[4][6][7][15]
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 theqū is added, often along with the yeast (酵母;jiàomǔ or simply酵;jiào), to a small amount of the substrate. After incubation for 2–7 days, the seed mash is then added.[4][6][7][15]
The environment exerts a significant influence on Xiu microbiology. Relevant microbe species and genera prefer different climatic conditions, anddomestication in theqū making process favored the development of regional microbiota assemblages across China.[6][15] By comparison, the industrial Japanese koji-making process favors a single monoculture species,Aspergillus oryzae.[9] One difficulty in identifying the species present inqū appears to be bias introduced by the analytical technique. Culture-dependent orDNA extraction methods often miss entire species or misrepresent their statistical importance.[citation needed] Studies have failed to establish any pattern inqū microbiology across China, reflecting regional diversity.[7][17]
Molds are the most prevalent organisms found inqū and are considered to be the dominant enzymatic agents responsible for liberatingglucose and other fermentable sugars from the source of carbohydrates used (along with the yeastSaccharomycopsis fibuligera). Molds found in traditional Chinese fermentation starters includeAspergillus,Rhizopus,Amylomyces,Monascus,Absidia,Rhizomucor, andMucor. Species ofRhizopus are capable of producingfumaric acid,lactic acid and ethanol as they excretezymases, but their production capabilities vary widely from strain to strain.Rhizopus oryzae andAspergillus oryzae are the two most common molds isolated inqu.[18][13][17][19][20][21][22][23]
The mold species appears to be an important factor in determining the resulting type ofqū. 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 andMucor prefer higher water activities and temperatures toAspergillus, whilstMucor andActinomucor prefer substrates richer in protein.[18][22][23] In some reported examples ofqū microbiology, potentially harmful strains of mold were encountered such asAspergillus flavus andRhizopus microsporus, but it is uncertain if they were identified correctly or if those specific strains were capable oftoxin production.[24]
Yeast species form part of the symbiotic nature of aqū starter and can be enzymatic (substrate-degrading) and/or fermentative. Yeast genera observed forqū in decreasing order of significance includeSaccharomycopsis,Issatchenkia,Saccharomyces,Pichia,Candida andRhodotorula. The yeast species most frequently reported forqū starters isSaccharomycopsis 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.[18][19][25][26][27][28][29]
Bacterial species are present in large numbers inqū 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 theorganoleptic qualities, as well as acting as a naturally occurringpreservative. The bacterial species most commonly found (in decreasing significance) includeBacillus,Lactobacillus,Leuconostoc,Streptomyces,Acetobacter andClostridium.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.[18][26][30][31][32]
An exponential variety ofqū 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. Someqū are wrapped in straw andsun-dried, while others are wrapped in straw and hung from the rafters to dry.[4][5] Althoughqū 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 ofActinomucor andMucor prefer lower temperatures thanRhizopus 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 andRhizopus oryzae both produce more starch degrading enzymes and are found commonly on 100% flour substrates, whilstActinomucor andMucor produce more proteolytic and lipolytic enzymes and are more abundant when pulse flours are added.[7][18][12][13][17][19][33][26][22][24]
Each type ofqū can be used individually or in conjunction with others.Huangjiu, or cereal wines, can incorporate one or several of the starters with the combination ofxiao anddaqu being the most common. In contrast,baijiu, a distilled beverage, generally uses onlydaqu.[4][5][6][7]
Xiaoqu or "small starter" (小曲;小麴;xiǎoqū) are generally small (10–100 grams or 0.35–3.53 ounces) cubes or flattened or rounded balls made of rice dough incubated for usually only several days. Rice flour or bran and inoculum are used, withbentonite clay as a bulking agent. Traditionally various herbs (from one to fifteen varieties) are incorporated into the preparation as eitheryou (herbxiao) or bark (white or herblessxiao). They are commonly referred to as Chinese or Shanghai yeast balls when available through Western Chinese suppliers.[7][12][17][19][22]
Used mostly for the production ofhuangjiu andjiuniang 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 todaqu.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.[7][12][17][19][22]
Incubation is relatively simple and done at ambient temperatures of 25–35 °C (77–95 °F) for four to five days, before drying.Xiaoqu is almost always white becauseRhizopus oryzae is the dominant mold species and saccharifying agent. Some types ofxiao are now prepared by mixing yeast sediment with the normal inoculum to produce a more fermentative starter.[7][12][17][19][22]
Daqu or "large starter" (大曲;大麴;dàqū) are large (1–5 kg or 2.2–11.0 lb) 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 famousbaijiu,Maotai, Fenjiu,Luzhou Laojiao, andXifengjiu, are all made withdaqu only. Some huangjiu are often started withxiao and finished withdaqu.Daqu can come in three colors that mostly reflect the dominant mold species present: grey-white (Rhizopus oryzae and/orR. chinensis), yellow to yellow-green (Aspergillus oryzae), and black (A. niger and/orA. luchuensis).[7][18][12][33][26][22]
Both the larger size and the longer incubation ensure higher enzyme and microbial load thanxiao. They are the only starter used for mostbaijiu 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 makingbaijiu rather than simply as an inoculant.Daqu typically constitutes 15–25% of the overall fermentable, whereasxiao is used only to inoculate a fermentation (3–8%). The heavy use (50%) of large 5 kg (11 lb) bricks ofdaqu incubated at high temperatures is responsible for the pungent aroma andumami-like the flavor of Maotai.[7][18][12][33][26][22]
Daqu is the most complex process ofqū 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 fourbaijiu 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.[7][18][12][33][26][22]
Daqu can be generally categorized into three kinds according to the highest temperature achieved during incubation: high-temperature (60–70 °C or 140–158 °F), medium-temperature (50–60 °C or 122–140 °F) and low-temperature (40–50 °C or 104–122 °F), respectively. As an example of the differing usage schemes, Maotai uses high-tempdaqu and Luzhou Laojiao uses medium-tempdaqu, and both are made from wheat flour. Fenjiu and Xifengjiu use low-tempdaqu made from barley and pea flour but differ in the coarseness of the crushed grains.[7][18][12][33][26][22]
High- and medium-temperaturedaqu generally undergo a four-step process:
Low-temperaturedaqu typically undergo a six-step process:
The scientific basis for these processes need to be clarified, as standardizing production methods is a goal of the Chinese alcohol industry.[6]
Hongqu or "red starter" (红曲;紅麴;hóngqū), also calledbangkok inHokkien, is rice cultured primarily withMonascus purpureus or other red rice molds of the genusMonascus, available as dried, mold-encrusted rice with a unique red color, and sold as "red yeast rice". Used mostly forhuangjiu and rice vinegar, this starter gives the beverage a unique red or purple color due to pigments produced by members ofMonascus.Gutianhongqu is the name for this starter, inoculated with a "seed" culture calledqumu, containing onlyMonascus species. A popular alternative variety also used isWuyihongqu, which involves seeding the rice with bothQūMu as above andQūQing, a "seed" culture that contains a black mold (A. niger orA. luchuensis) to make the rice black on the outside and red inside. A rarer variety is calledHuangyi Hongqū which involvesMonascus with a yellow mold (A. oryzae orA. flavus) to make the rice yellow on the outside and red on the inside.[7][13][24][34]
Hongqu is prepared in a way similar to Japanesekoji: 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 35–40 °C (95–104 °F) for four to five days and the rice is stirred frequently. Modern practice is to steep the rice in weakacetic acid solution for a short period to help create the optimum pH of 3–3.5 that favorsMonascus growth. Afterward, the rice is removed and dried.[7][34]
Often in the production ofhongqu rice wine, bothhong andxiao are utilized. Studies have revealed thatMonascus species show stronggluco-amylase activity, but poor proteolytic and lipolytic enzyme production. Also, the fermentative yeastSaccharomyces cerevisiae was mostly absent fromhong starters but present inxiao. 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.[7][13][24][34]
The following form the fourth category ofqū:màiqū is a starter for wheat only. It is used as a major component (15–25%) of the total starter for somehuangjiu. The manufacturing process and microbiota are similar todaqu, but is made entirely from wheat.[7]
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