Jiuqu

Jiuqu, also simply known asqu,is a type of driedfermentation starterused in the production of traditionalChinese alcoholic beverages.The wordjiuquspecifically 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.Jiuquis similar to, but distinct from, the more widely knownJapanesestarter known askoji.
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 ofjiuquare known as "starter cake" (曲饼;麴餅;qūbǐng), "liquor product" (酒药;酒藥;jiǔyào), or simply asqu.Qū is known asnurukinKorea,muchormarchainIndiaandNepal,banh meninVietnam,pacinginLaos,loog panginThailand,mochi koujiinMyanmar,mae dombainCambodia,ragiinIndonesiaandMalaysia, andbuboin thePhilippines.The tradition of makingqūis believed to have originated in China 3000–4000 years ago, and introduced throughoutEast Asia,Southeast Asia, andSouth Asia.
Quis mentioned in theBook of Documents, one of theFive Classicsofancient Chinese literatureand a foundational work inConfucianism. A book from theShang dynasty(c.17th–11th centuries BC) states that "to makewineor sweet liquor one needsqūnieh". Most authorities concur thatqūdescribes the preparation of ferments, whileniehrefers to sproutedgrain. They may have formed separate elements ofliquorproduction (bothqūandnieh) or might refer to a single preparation made of fermenting sprouted grains (qu nigh). TheBook of Documentspredates 500 BC, so the ancient predecessor ofqūmay be the world's oldest example ofbiotechnologicalmanufacturing.
Quis mentioned in theZhouli(c.150 BC), a collection of texts from theEastern Zhou dynasty. It is described in preparingfermented meatand a grain–meat paste. AtMawangdui(200 BC – 10 AD),bamboo stripsin 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, mentionsqūas one of six requisites to make good wine. Anotheralmanacfrom the Eastern Han dynasty, the first-century ADShuowen Jiezirecords a character forqūmodified to include the yellowchrysanthemumflower. This was interpreted as referring to the distinctive yellow color formed onqūbysporulatingmolds. TheShiming(151) mentions several types ofqu, which are interpreted as distinguished by the source of thestarchand the form of thesubstrate. It claims that since theHan dynastyqūwas produced in China from mostlywheatorbarleyand pressed into cakes or bricks for handling. The earliest reference to the actual preparation ofqūappears in theQimin yaoshu(544) of theNorthern Wei dynasty. There the techniques employed for making nine separate kinds ofqūnighare described in detail, along with their usage in the manufacture of 37 wines. The usage ofqūin makingvinegar,soybean pastes, and soy sauces are documented. TheQing yilu(清异录, 965) recorded the use of a specialred starterfor the first time.
The fourth-centuryNanfang Caomu Zhuanghas 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 flourmixed 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 withglutinousrice 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 ofyegeare poisonous."
Makingqūinvolves cultivatingmicrobesin starchy materials and is a separate process that precedes the fermentation of grains andlegumesinto food oralcoholic beverages.Traditional practices vary and diverge from the later processes used for industrially-producedqu.
The major manufacturing principles are:
Qucan 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 ofqūultimately being produced. The most common flours used indaquare wheat and barley/peas. The preparation ofhonginvolves only whole rice grains. Herbs of many kinds are variously included in the rice dough of manyxiaopreparations.
Traditional methods have changed little since the publication of theQimin Yaoshu(544). Grains orfloursare 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. Noinoculaare 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 leavesorartemisia, are used to wrap or cover theqūto promote a beneficial condition. The presses andmoldsused 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 goodqūas early as theQimin Yaoshu.
One aspect that has changed is the method of re-culturing for later preparation. Traditionally, microbesindigenousto 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 inqūhave been recognized as the filamentous moldsAspergillusandRhizopus, whichreproduce only asexuallythrough 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.
The incubation and maturation phase is a typicalbiomoleculemanufacturing 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 functionalenzymesonto their substrate. Theqūitself became a dried product carrying both microbes and theirenzymes(the biomolecules).Most yeast and bacteria do not find the conditions ofqūoptimal, but still grow effectively in solid-state fermentation. Their relationships toqūhave been understudied.
Qūprocessing can be carried out synchronously in the factory or workplace that produces a fermented end-product (such as abreweryor soy sauce factory) or it can be produced independently for sale. Traditionally, breweries did not makeqū,but later often specialized in the preparation.Qūmanufacturing 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.
The process of making industrializedqūis inherently more complex as the two end products are sought to be manufactured by the factory:qūfor use in alcohol production and so-called 'seed'qūfor continued culturing of the microbiota. Seedqūis a pre-production process tailored to suit the growth and subsequent reproductive cycle of select microbes.
As such,qūpractices have evolved from:
A fourth step was introduced in 21st century China, whereasepticlaboratory conditions are used to mono-culture specific favorable strains of mold, yeast, and bacteria grown on independent, fortified substrates.Such isolates now find usage inbiotechnologyapplications such asfuel ethanolor enzyme production.An important objective is continued research into the biotechnological domestication of such microbes and as such, standardization ofqūpreparation.
The advantage of usingqūfor alcohol production is its two-fold effect. The enzymes and microorganisms break down the starches and sugars, reducing the process of makinggrain spiritsto 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 allowliquefactionandsaccharificationto occur (up to fifty different enzymes have been isolated fromAspergillus oryzaestarters). Their mutualisticsymbiosiswith 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 ofqūused (2–8%) in most cases, only a minor contribution of enzymes comes from the starter. As such,qūis used only to inoculate the mash with microbes. In the case ofbaijiuproduction, typical amounts of 15–25%qūare used, sometimes reaching as high as 50%, which consequently provides a major enzyme contribution to the mash to initiatecatabolism. Theexponential growthand reproduction of microbes after inoculation releases more enzymes in the process, inducing further catabolism, to producepoly-andmono-saccharides,amino acids,peptides,CO2,alcoholandorganic 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 theqūis added, often along with the yeast (酵母;jiàomǔor simply酵;jiào), to a small amount of the substrate. After incubation for 2–7 days, the seed mash is then added.
The environment exerts a significant influence on Xiu microbiology. Relevant microbe species and genera prefer different climatic conditions, anddomesticationin theqūmaking 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 inqūappears to be bias introduced by the analytical technique. Culture-dependent orDNAextraction methods often miss entire species or misrepresent their statistical importance.Studies have failed to establish any pattern inqūmicrobiology across China, reflecting regional diversity.
Molds are the most prevalent organisms found inqūand are considered to be the dominant enzymatic agents responsible for liberatingglucoseand 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 ofRhizopusare capable of producingfumaric acid,lactic acidand ethanol as they excretezymases, but their production capabilities vary widely from strain to strain.Rhizopus oryzaeandAspergillus oryzaeare the two most common molds isolated inqu.
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.RhizopusandMucorprefer higher water activities and temperatures toAspergillus, whilstMucorandActinomucorprefer substrates richer in protein.In some reported examples ofqūmicrobiology, potentially harmful strains of mold were encountered such asAspergillus flavusandRhizopus microsporus, but it is uncertain if they were identified correctly or if those specific strains were capable oftoxinproduction.
Yeast species form part of the symbiotic nature of aqūstarter and can be enzymatic (substrate-degrading) and/or fermentative. Yeast genera observed forqūin decreasing order of significance includeSaccharomycopsis,Issatchenkia,Saccharomyces,Pichia,CandidaandRhodotorula. The yeast species most frequently reported forqūstarters 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 anomalais almost ubiquitous and although incapable of elevated alcohol production, it appears to be vital in developing taste and aroma.Saccharomyces cerevisiaeis the most common highly fermentative yeast present in Xiu.
Bacterial species are present in large numbers inqūand 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 theorganolepticqualities, as well as acting as a naturally occurringpreservative. The bacterial species most commonly found (in decreasing significance) includeBacillus,Lactobacillus,Leuconostoc,Streptomyces,AcetobacterandClostridium.Bacillusspecies are the dominant bacterial genera in Xiu.Bacillusspecies are known to be large producers of enzymes and therefore contribute to the overall breakdown of the cereal grains.
An exponential variety ofqūcan 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. Someqūare wrapped in straw andsun-dried, while others are wrapped in straw and hung from the rafters to dry.Althoughqūcontains its own distinctive, region-specific mix of microorganisms, the temperature schemes involved in preparation manipulates the microbial ecology, e.g.,Aspergillus oryzaeand species ofActinomucorandMucorprefer 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 oryzaeandRhizopus oryzaeboth produce more starch degrading enzymes and are found commonly on 100% flour substrates, whilstActinomucorandMucorproduce more proteolytic and lipolytic enzymes and are more abundant when pulse flours are added.
Each type ofqūcan be used individually or in conjunction with others.Huangjiu, or cereal wines, can incorporate one or several of the starters with the combination ofxiaoanddaqubeing the most common. In contrast,baijiu, a distilled beverage, generally uses onlydaqu.
Xiaoquor "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 clayas 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.
Used mostly for the production ofhuangjiuandjiuniangand most popular in the southern provinces,xiaois 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.Xiaoquis 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 25–35 °C (77–95 °F) for four to five days, before drying.Xiaoquis almost always white becauseRhizopus oryzaeis the dominant mold species and saccharifying agent. Some types ofxiaoare now prepared by mixing yeast sediment with the normal inoculum to produce a more fermentative starter.
Daquor "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 withdaquonly. Some huangjiu are often started withxiaoand finished withdaqu.Daqucan come in three colors that mostly reflect the dominant mold species present: grey-white (Rhizopus oryzaeand/orR. chinensis), yellow to yellow-green (Aspergillus oryzae), and black (A. nigerand/orA. luchuensis).
Both the larger size and the longer incubation ensure higher enzyme and microbial load thanxiao. They are the only starter used for mostbaijiufermentations 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 makingbaijiurather than simply as an inoculant.Daqutypically constitutes 15–25% of the overall fermentable, whereasxiaois used only to inoculate a fermentation (3–8%). The heavy use (50%) of large 5 kg (11 lb) bricks ofdaquincubated at high temperatures is responsible for the pungent aroma andumami-like the flavor of Maotai.
Daquis the most complex process ofqūpreparation 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 fourbaijiuaromas 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).Daqupreparation is manipulated to help produce these different aromas.
Daqucan 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-tempdaquand Luzhou Laojiao uses medium-tempdaqu, and both are made from wheat flour. Fenjiu and Xifengjiu use low-tempdaqumade from barley and pea flour but differ in the coarseness of the crushed grains.
High- and medium-temperaturedaqugenerally undergo a four-step process:
Low-temperaturedaqutypically 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.
Hongquor "red starter" (红曲;紅麴;hóngqū), also calledbangkokinHokkien, is rice cultured primarily withMonascus purpureusor 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 forhuangjiuand rice vinegar, this starter gives the beverage a unique red or purple color due to pigments produced by members ofMonascus.Gutianhongquis the name for this starter, inoculated with a "seed" culture calledqumu, containing onlyMonascusspecies. A popular alternative variety also used isWuyihongqu, which involves seeding the rice with bothQūMuas above andQūQing, a "seed" culture that contains a black mold (A. nigerorA. luchuensis) to make the rice black on the outside and red inside. A rarer variety is calledHuangyi HongQūwhich involvesMonascuswith a yellow mold (A. oryzaeorA. flavus) to make the rice yellow on the outside and red on the inside.
Hongquis 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 acidsolution for a short period to help create the optimum pH of 3–3.5 that favorsMonascusgrowth. Afterward, the rice is removed and dried.
Often in the production ofHongqurice wine, bothhongandxiaoare utilized. Studies have revealed thatMonascusspecies show stronggluco-amylaseactivity, but poor proteolytic and lipolytic enzyme production. Also, the fermentative yeastSaccharomyces cerevisiaewas mostly absent fromhongstarters but present inxiao. Thus,hongis used only to provide red pigmentation and saccharification and as such, should generally be used in conjunction with another starter with high fermentative capability.
The following form the fourth category ofqū:màiqūis 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.