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Past, present, and future of Chinese fermented foodproductsTaosheng Chen a & Chi‐Tang Ho Translator b

a Department of Biotechnology , Shanghai University of Science and Technology , Shanghai,People's Republic of Chinab Department of Food Science , Rutgers University , New Brunswick, New Jersey, U.S.A.Published online: 03 Nov 2009.

To cite this article: Taosheng Chen & Chi‐Tang Ho Translator (1989) Past, present, and future of Chinese fermented foodproducts, Food Reviews International, 5:2, 177-208, DOI: 10.1080/87559128909540849

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Food Reviews International, 5(2), 177-208 (1989)

PAST, PRESENT, AND FUTURE OFCHINESE FERMENTED FOOD PRODUCTS

TAOSHENG CHENDepartment of BiotechnologyShanghai University of Science and TechnologyShanghai, People's Republic of China

CHI-TANG HO, TranslatorDepartment of Food ScienceRutgers UniversityNew Brunswick, New Jersey U.S.A.

ABSTRACT

In China there are many kinds of traditional fermented food products,which have a centuries-long history. The main products are alcoholicbeverages, Chiang, Chi, soy sauce, vinegar, red rice, and fermented beancurd. These products play a very important role in Chinese cuisine. Theancient methods of making fermented foods are changing graduallythrough modern microbiology and technology. This paper discusses thehistorical aspects, the manufacturing technology, and the future outlookon fermented food products in China.

177

Copyright © 1989 by Marcel Dekker, Inc.

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178 CHEN AND HO

Traditional Chinese fermented products-such as White-jiu (or Shaojiu, a distilledspirits), Yellow-jiu (a natural yellow alcoholic beverage fermented from rice),soy sauce, vinegar, Red-qu (red fermented rice; "qu" is a fermentation starter,called "Koji" in Japan), and Doufuru (fermented bean curd)—are noted for theirlong histories and established qualities.

For thousands of years, Big-qu (big Koji) and Small-qu (small Koji) (culturesused for fermentations to an extensive and a lesser extent, respectively) havebeen prepared by traditional methods in which various kinds of naturally occur-ring microorganisms were skillfully selected and used. Fermented products playa very important role in the Chinese cuisine which has been so popular aroundthe world. For example, condiments such as soy sauce, cooking wine, vinegar,and Zao (a variety of fermented cereals) contribute greatly to the unique palat-abilities of Chinese foods. Doufuru, like cheese in Western countries, is used asboth a cooking condiment and a side dish. Red-qu is widely used as a naturalfood colorant.

The purpose of this review is to introduce the background, achievements anddevelopment of fermented foods in China.

JIU

The word Jiu means "alcoholic beverage" in Chinese. Jiu includes distilled andnondistilled spirits, wine, and beer. Jiu making has-a very long history in Chinaand is still a very important industry today. Many varieties of Jiu are manufac-tured, with an annual production of 4-5 million metric tons. Some famous brands,such as "Maotai" from Guizhou Province and "Shaoxing" from Zhejiang Prov-ince, are very well known.

The Origin of Jiu

According to ancient books entitled Huangdi Neijing, Zhan Guo Ce, and Mengzi,Sweet-jiu (a kind of sweet alcoholic drink) originated before White-jiu. Accord-ing to the records of Tiangong Kaiwu, one of the earliest encyclopedias on sci-ence and technology in China, by Song Yingxing and published during the SungDynasty, Sweet-jiu was produced by extracting a soluble substance from ger-minated grain seeds, followed by the natural fermentation of the extract so ob-tained. People have known for a long time that malt could be obtained fromgerminated barley grain during the rainy season. The similarity in the produc-tion of malt and Sweet-jiu should explain the sweet flavor in Sweet-jiu. How-ever, Sweet-jiu, due to its low alcoholic strength, was not well liked, and theproduction of Sweet-jiu from malt extract gradually disappeared and remainsa mystery today.

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CHINESE FERMENTED FOOD PRODUCTS 179

Jiu making originated during the Huangdi period, which was about 4000 B.C.,and it is known that Sweet-jiu originated at that time.

The Origin of Qu

Official documentation of Qu and Qu making can be traced back to the ZhouDynasty (about 1100-777 B.C.). Shijing, the earliest collection of ancient Chi-nese poems, says that "Without Qu or germinated cereals, one cannot make Jiu."Liji: Yue-Ling Pian also has it that "Timing is important in Qu making." It isalways cold in the north and hot in southern China. Due to the difference inweather, Big-qu was used in the north and Small-qu in the south. In addition,Big-qu and Small-qu were made from different materials and in different shapes.Generally, Big-qu was brick-like in shape, and Small-qu varied in spheric, plate-circular, or rectangular shapes, and was much smaller than Big-qu. Other dif-ferences existed: (1) Big-qu was made from barley (or wheat) and beans whileSmall-qu was made from rice or rice bran with various herbs; (2)Aspergillus wasthe major microorganism in Big-qu while Mucor and Rhizopus were the majormicroorganisms in Small-qu; (3) for a certain amount of substrate, much moreBig-qu was needed than Small-qu.

Small-qu

Small-qu includes Yaoqu, Kanggu, White-qu, Qu-cake, and Qu-powder. All canbe produced in several different ways. Sichuan Yaoqu, for instance, is preparedfrom rice with 72 different kinds of herbs added to a Qu starter. The functionof these medicinal herbs in this Qu making is still unclear. It is reported thatsome medicinal herbs such as dried orange peel, licorice root, and the rhizomeof nutgrass flatsedge {Cyperus rotundus) promote the growth of yeast and hencethe production of alcohol. Contrary to this, some other herbal substances, suchas the root of Chinese thorowax (Bupleurum Chinese) and Fuling {Poris cocos),were reported to inhibit the growth of yeast and the production of alcohol. Itremains unknown whether the use of the medicinal herbs favors the growth ofRhizopus although it has been shown that they are inactive and inhibit any othermicroorganisms that may exist.

Actually, Sichuan Kangqu is produced from a mixture of rice bran (87-92%),ground rice (5-10%), and £?«-starter (3%) without the addition of medicinal herbs,and the quality is as good as the one with medicinal herbs added. Xiamen White-qu is prepared from the fermentation of rice bran and rice flour using the pureculture of Rhizopus and yeast, and Guizhou Qw-powder is prepared from thepure culture of Rhizopus and yeast using wheat bran as the raw material. Figure1 is a diagram of the production of Small-qu.

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180 CHEN AND HO

Soaked

"Qu" Starter

Inoculated •> Shaped •

MedicinalHerbs

Milled

Qu-houseIncubation

-> Mixed

• Dried Small-Qu

Figure 1. Flow chart of Small-qu making.

Materials Ground •Mixed ShapedQu-house

Molding

• Dried • Powdered Big-Qu

Figure 2. Flow chart of Big-qu making.

Big-qu

Big-qu has a history of several thousand years, and it was used originally to makeYellow-jiu. It was then used to make White-jiu. Many well-known types of White-jiu are made using Big-qu. Steps for Big-qu making are shown in Figure 2.

Yellow-jiu Making and Its Well-Known Products

Jiu making started around 4000 B.C. However, Qu was not used to replace ger-minated cereal seeds in Yellow-jiu manufacture until the Zhou Dynasty (1100-771 B.C.), when the techniques of Qu application became established.

Six detailed essentials for Jiu making can be found in Yue-Ling-Pian of Liji,another ancient historical classic. It was noted that (1) the raw materials shouldbe of good quality; (2) the Qu should be made in the right seasons; (3) the waterused to make Jiu should be of good quality; (4) utensils and operating environ-ment should be clean; (5) the earthen jars or china used as the containers shouldbe of the best quality; and (6) fermentation should be carried out under suitabletemperatures. It is very important for Jiu makers to meet those requirements.It was mentioned in Qiyue of Yuofeng that the rice harvested in the autumn was

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CHINESE FERMENTED FOOD PRODUCTS 181

used to make Jiu the following spring. Therefore, the Yellow-jiu made duringthe Zhou Dynasty was produced by using Qu and rice.

Yellow-jiu is made from the fermentation of rice. It is called "Yellow-jiu"(yellow wine) because of the yellowish color of the finished product. Yellow-jiu making is popular along the southern part of the Yangtze River, such as inZhejiang, Ziangxi, and Fujian Provinces. Rice is used in these areas. However,fragrant rice is used in the northern provinces such as Shandong, Liaoning, Jilin,and Heilongjiang.

Well-known products of Yellow-jiu are as follows:

Shaoxing Jiafan Jiu (Shaoxing Wine)

This is one of the oldest Yellow-jiu in China, and it is known worldwide. Theancient six-element essentials mentioned previously are the backbone of its pro-cessing procedures, and fresh harvested waxy rice is used as the raw material.The water used is fetched from the center of Qingtianjian Lake, which is formedby the water descending from Huiji Mountain. Specific processing, includingfermentation, is done in the severe winter to ward off microbial contamination.The finished product contains 7-10% alcohol. It is traditionally stored in a carvedand painted jar, and therefore is also known as "Color-carved China Jiu."

Chengang Jiu

This wine is produced in the beautiful mountain villages in Longyan County ofFujian Province and is a highly praised wine in China. A wonderful combinationof sweetness, hotness, freshness, and pleasant bitterness affords the distinctiveflavors to this wine. It is also appreciated for its rich nutrients. The fermentationmaterial (waxy rice) sinks and rises three times in the medium during the fermen-tation process. It is therefore called Chengang Jiu ("Jar-bottom-sunken wine").

To produce Chengang Jiu, several kinds of Qu are needed, including Yaoquand Red-qu, which are prepared from some rare medicinal herbs. This specialvariety of Qu dates back to the Jin Dynasty, about 1500 years ago.

Modification of Yellow-jiu Making

The traditional methods are still followed in making Yellow-jiu. Some manpowerinvolved in the processing, however, has been replaced by machines.

White-jiu Making and Its Well-Known Products

It was noted that Sweet-jiu appeared before Yellow-jiu, and that White-jiu wasdistilled from Yellow-jiu after the invention of the distillation process.

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182 CHEN AND HO

Table 1. Differences Between Big-qu-jiu and Small-qu-jiu

Big-qu-jiu Small-qu-jiu

Qu dosage Large Small

Material treatment Ground Intact

Fermentation Solid culture Solid or liquid culture

White-jiu is recorded in Bencao Gangmu, a Chinese encyclopedia of medicinalherbs compiled by Li Shizhen during the Yuan Dynasty (1578 A.D.). The pro-cessing of White-jiu was invented during the Yuan Dynasty (1279-1368 A.D.).However, it was also noted that White-jiu appeared even before the Tang Dyn-asty (618-906 A.D.), as witnessed in some Tang poetry. This viewpoint was re-cently cited in a Japanese book, Chinese Wine, written by Sosuke Dai.

Varieties of White-jiu are produced with different materials and methods.White-jiu can be classified as Big-qu-jiu and Small-qu-jiu. The amount of Qu used,the treatment of the raw material, and the procedure of fermentation make thedifference, as summarized in Table 1.

Five types of aromas differentiate various kinds of White-jiu. They are the fer-mented-sauce type, the strong-scented type, the delicate-scented type, the mixed-aroma type, and the fermented-rice type. Maotai, Luzhou Tequ, Fen, Xifeng,and Guilin Sanhua Jiu represent each type, respectively.

Small-qu-jui

Slightly modified methods are adopted, depending upon the raw material used,to produce different kinds of Xiaoqujiu. Examples are as follows:

Guilin Sanhua Jiu: The reputation of Small-qu rice wine produced in Guilincan be traced back to the Tang and Sung Dynasties. An ancient method to de-termine the quality of wines was by measuring the amount and stability of thefoaming of the liquor after it was shaken. Guilin Sanhua Jiu assumed its namefrom its ability to generate three layers of colorful foams when shaken.

Fermentation of rice and Small-qu mixed with some special local medicinalherbs were used for Sanhua Jiu. Water used for fermentation was obtained fromthe Lijiang River. The area is warm in winter and cool in summer, providingideal conditions for the growth of microorganisms. The product is aged in na-tural caves for special results. Its taste and aroma are of the typical rice-aromatype.

Dongjiu: Dongjiu is produced by the Dong Brewery in Zunyi County of Guiz-hou Province. It is distinguished for its special process. Waxy sorghum is used as

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CHINESE FERMENTED FOOD PRODUCTS 183

the raw material, and both Big-qu and Small-qu, with the addition of medicinalherbs, are used to obtain the distinctive flavor during fermentation.

Small-qu is added to the raw material to produce Small-qu-jiu, which has adelicate,- elegant, but not strong flavor. The remaining Jiuzao (remainder of rawmaterial after fermentation) is mixed with Dongjiu Pei (unfiltered crude liquor)and fermented with Big-qu for another 6 months. Small-qu-jiu is then added af-ter the fermentation and the resultant liquor is distilled to obtain Dongjiu, whichis aged for another 6 months to become the final product.

Dongjiu possess both Big-qu and Small-qu flavors, with a pleasant medicinalaroma and a refreshing sour taste. It cannot be grouped into the five aroma typesthat have been mentioned, however, and stands as a typical example of the mis-cellaneous aroma type.

Big-qu-jiu

Big-qu-jiu is much appreciated in China. The following are some selected exam-ples.

Maotai: Built during the Ming Dynasty (1529 A.D.), and known as Dahe Shao-fang (Dahe Brewery), the Maotai brewery is located in Maotai Village, RenhuaiCounty, Guizhou Province.

Meotai is one of the best White-jiu in China. It is made with sorghum and in-volves repeated distillation and Qu addition amounting to eight times each. Big-qu used to produce Maotai is prepared with wheat, barley, or peas. Great quan-tities of Big-qu are needed in Maotai making, and are almost equal to the amountof the starting material.

Big-qu-jiu has a strong yet elegant flavor which is believed to be generatedfrom Big-qu during fermentation. Maotai is a typical example of Big-qu-jiu witha soy sauce aroma. The climate of Maotai Village is mild and humid. It providesideal conditions for the growth of microorganisms and may contribute to thespecific quality of the product.

Luzhou Laojiao Tequ: Located at the confluence of the upper reaches of theYangtze and Tuojiang Rivers, Luzhou County has a long history of wine mak-ing. Shujuyuan is one of the most famous breweries, dating back 400 years. Wa-ter from a special well named Longquan has been used by Shujuyuan for Jiumaing. It is recorded that the well was rebuilt in 1807.

The ancient cellars for wine fermentation and aging have been used contin-uously by Shujuyuan Brewery for more than 200 years. The soil within theseold cellars, which is black mixed with a reddish green color, emits very strongwine aromas. Many interesting and useful microorganisms have been found inthe soil. These old cellars are called the "Thousand Year Old Cellars," whichnaturally lend the named "Laojiao Tequ," meaning wine produced from oldcellars, to the Jiu manufactured from those cellars.

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184 CHEN AND HO

The fermented mash from the previous fermentation is used in the fermenta-tion of the new raw material so that the microorganisms continue to grow andfunction constantly. Some of the fermentation mash could be several hundredyears old and is called "ten-thousand-year" mash.

Luzhou Laojiao Tequ wine has won national prizes several times and it is atypical example of the strong-scented type.

Fenjiu: Fenjiu got its name from the place of its origin, Xinghua Village, Fen-yang County, Shanxi Province. It is an example of the delicate-scented type. Thehigh quality of the water used may contribute to the flavor of the wine. Zhuye-qing, a blended wine based on Fenjiu, is also one of the most famous wines inChina.

The success of Fenjiu making has been attributed to the following seven rea-sons: (1) highly experienced brewers; (2) good water; (3) Qu made at the righttime (March, July, and August); (4) plump and healthy seeds of sorghum; (5)clean and sanitary equipment; (6) earthen jars conditioned at suitable humidityfor fermentation, and (7) good temperature control (high temperatures for steam-ing of the raw materials and mild temperatures for wine distillation). The Quused for fermentation is made from barley (60%) and peas (40%). A two-cycleprocess of fermentation and distillation is employed. The raw material, sorghum,is mixed with Qu and first fermented for 21 days in a large-diameter but small-mouthed earthen jar, which is planted in the earth but open to air through themouth. The mash so obtained is then distilled and the residue is again mixedwith Qu and fermented in the same manner for another 21 days. The mash isdistilled and the distillate mixed with the one obtained the first time to makeFenjiu.

Years of practice suggest that four additional elements are also essential inaddition to the original seven points for making Fenjiu. They are: (1) carefulprocessing; (2) accurate formulation; (3) strict quality control; and (4) appro-priate blending and maturation. An example of formulation and output of Fen-jiu is given in Table 2.

Table 2. Formulation and Output for Fenjiu Fermentation

Component

Sorghum (raw material)

Big-qu

Auxiliary material

Output (65% alcohol)

Quantity(kg)

1100

220

275

484

Percentage, comparedto raw material

-

20

25

44

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CHINESE FERMENTED FOOD PRODUCTS 185

Zhuyeqing, also a product of the Xinghua Village Brewery, is based on Fenjiuand mixed with 10% table sugar and extracts of 12 different medicinal herbs,such as bamboo leaves, cape jasmine, chrysanthemum, sandalwood,dried orangepeel, cloves, Chinese angelica, costusroot (Saussurea lappd), and Chinese torreya{Torreye grandis). It contains 45% alcohol and has some medical functions.

Xifengjht: Xifengjiu is produced in the western plains along the Wei River,where according to local legend, a phoenix was seen. The Xifeng Brewery is lo-cated at the foot of Lingshan Mountain. Contrary to the method used to makeFenjiu, the cellar used for Xifengjiu fermentation is renewed after each batchof fermentation. A layer of soil on the cellar floor and walls is removed and re-placed by some fresh earth. The total fermentation period lasts only 14 days,considerably shorter than required by other procedures. Maturation of the Jiu,however, takes 3 years in a special aging pool before the product is put on themarket. It is said that the Kings of the Qin Kingdom (770-476 B.C.) used Xi-fengjiu to counteract food toxicity. Xifengjiu is now still widely used to soakand extract medicinal herbs for medical use.

Wuliangye: This wine is the product from the Big-qu fermentation of five dif-ferent cereals: sorghum, waxy rice, corn, rice, and wheat, and hence is named"Wuliangye" (five-cereal wine). The product has a very strong aroma with hom-ogeneously mixed and appealing flavor characteristics. It belongs to the strong-scented type.

Located at the confluence of the Jingsha and Minjiang Rivers, the startingpoint of the Yangtze River, the Wuliangye brewery is in Yibin City, SichuanProvince, where, according to history, the brewery dates back to more than1200 years. A famous poem by Du Fu of the Tang Dynasty highly praises thequality of the wine produced here.

Five-hundred-year-old cellars are still used for fermentation. Aged putty isalso used to seal the cellars during fermentation, which takes about 70 to 90days. Distillation followed by maturing, blending, packing, and so on result inthe celebrated Wuliangye.

Gujing Gongjiu: It is well known that the quality of water is a key factor inwine making. In Bo County, Anhui Province, there is a Gujing (old well) whichis about 1400 years old and is probably the oldest well still in use in China. Thewell water is slightly sweet, with a fresh egg-white taste. It is neutral and rich inminerals. During the Ming and Qing Dynasties several breweries were built onthis site because the wine made from this water was of distinguished quality.One of them, known as the Gongxing Brewery then, survived through the agesand is called Gujing Gongjiu Brewery today.

The wine made from the Gujing water is crystal-clear and the aroma, whichis pure and strong with a floral note, belongs to the strong-scented type. In an-cient times, the product was used as "tribute" to emperors in the Ming and QingDynasties, and it is still called Gongjiu ("wine for tribute").

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186 CHEN AND HO

Yanghe Daqu: The brewery is located in Siyanghe Village, in JiangsuProvince.There is a spring in the village known as "Spring of Beauties." Legend has it thatduring the Ming Dynasty, the spring was a gift from a goddess to two angels whopretended to be sisters-in-law living in the village. The angels made a very finewine using this spring water and in doing so brought fame to the village. Thespring was later named "Spring of Beauties" in honor of the two angels, whowere said to be very beautiful.

Since 1915, Yanghe Big-qu has won several prizes both nationally and inter-nationally. It is another example of the strong-scented type, with its character-istic color, aroma, and taste. Its production tops those of its kind manufacturedin China.

Baofengjiu: Baofeng Brewery has a very long wine-making history and is lo-cated between the Shahe River and the Ruhe River in Henan Province. It is saidthat the wine aroma from Baofeng Brewery can be smelled about 20 km to thesouth, beyond the Ruhe River.

The aroma of Baofengjiu belongs to the delicately scented type and has a spe-cial fruity flavor. It is produced according to the traditional fermentation pro-cess. The total fermentation period is about 25 days and the maturation periodis from 6 to 12 months. Recently, microwave heating has been employed toshorten the maturation period, which has shown some beneficial results.

Shuanggou Daqu: The Shuanggou Brewery in Shuanggou Village, Jiangsu Prov-ince, is located beside the Huaihe River and to the west of the famous HongzeLake. The 240-year-old cellars are still in use. A modern factory, equipped withan automatic production line, has been developed. The product has a strong-scented-type flavor and is popular in many countries around the world.

Scientific Research on Brewing Technology

Microbiological Studies on Qu

In 1932, when studying in the United States, the author conducted microbio-logical research on different Qu. A. total of 15 different yeast microorganismsand several species of Aspergillus were isolated from some wine starters such asNanjing Jiuyao. Some morphological and physiological studies were conductedaccordingly. In 1934 a yeast with high fermentation activity was isolated fromHunan Jiuyao. and in 1935 a high saccharifying activity Rhizopus was isolatedfrom Yanzhou Jiuyao. Other organisms, such as Absidia, Torula, and My coder-ma, were isolated and reported as well.

During the last few years, some research on microorganisms used for makingthe strongly scented type Big-qu-jiu was done at the Chengdou Biological Re-search Institute of the Chinese Science Academy.

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CHINESE FERMENTED FOOD PRODUCTS 187

Research on Yellow-jiu Manufacturing

The alcohol content of Yellow-jiu is usually higher than 20%. It was reportedthat the oryzenin contained in the raw material, or fermented rice, could pro-tect the yeast from the high alcoholic content present in the fermentation broth.

Research on White-jiu Manufacturing

The transformation rate, and hence the efficiency of utilization, of starch usedto produce White-jiu is relatively low (approximately 42-52%) in traditionalprocessing. In 1965, in order to increase productivity and conserve cereal grains,the Yantai Brewery combined the pure culture of Aspergillus oryzae and Sac-charomyces for fermentation. Starch utilization efficiency increased to 70-80%and the Qu dosage was reduced to below 15%. Recently, wheat bran Qu wasused to replace Big-qu, and a submerged liquid culture was used in the fermen-tation process to increase the alcohol output. Although the product rate was in-creased, the aroma of the finished product was not as good as the one producedby the traditional methods.

Two new techniques are now being used to improve the flavor of wine prod-ucts.

Aroma Stripping: A traditional process is used to produce Xiang Pei (fermentedmash used as an aroma source), which is placed near the vapor outlet of the dis-tillation apparatus. When the alcohol vapor passes the aroma source, it stripssome of the flavors and lets them co-condense in the product. This method stillrequires some traditional operations and loses some alcoholic content when pass-ing through the aroma source.

Aroma Blending: The alcohol used for blending is deodorized with active car-bon before artificial flavorants are added. The ingredients of the artificial flavorsused by the Jiangxi Institute of Fermented Foods consist of acetic acid, butyricacid, lactic acid, citric acids, ethyl acetate, isopentyl acetate, isopentyl butyrate,ethyl isovalerate, acetaldehyde, isopentyl alcohol, glycerol, etc. Usually, 10% ofthe traditional White-jiu is added. However, the quality of the product is not asgood as that of the traditional product.

Revealing the Mystery of the Aroma of Established Chinese Wine Products

In 1975 the Mongolian Institute of Light Industry and Chemical Engineeringisolated a caproic acid-producing bacterium (CAPB) from the black soil of oldwine-making cellars. Through microbiological studies it was found that the bac-terium belongs to Bacillus and is strictly anaerobic. Therefore it is very impor-tant to control the oxygen level during cultivation of this bacterium. Alcoholand sodium acetate are required as the major carbon source. In industry, the

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188 CHEN AND HO

Submerged LiquidFermentation

Distillation • White-jiu

Figure 3. Manufacturing process for White-jiu and its aroma enhancement by CAPB (caproicacid-producing bacteria).

caproic acid-producing bacteria is incubated separately until a certain amountof acid is obtained. The culture broth (5% by volume) is then transferred into afermentation mash and fermented for another 24 hours. The finished productcontains up to 158 mg/100 L of hexyl acetate. The sensory evaluation resultsfor this product are fairly close to those of the strong-scented type of Big-qu-jiu.

This discovery raised much interest in the field of fermentation all over China.Aroma-enhancing techniques utilizing caproic acid-producing bacteria wereworked out and applied to White-jiu making by one-step liquid culture fermen-tation at the Zhigu Brewery, Tianjin City. The procedures are shown in Figure 3.

The main parameters are:

1. Raw materiahwater = 1:4.2. Composition of raw material = sorghum, 83.5%; barley, 15%; bean, 1.5%.3. 11% saccharifying Qu was added when the temperature of gelatinized liquid

was brought down to 70° C. The mixture was further cooled down to 28° Cand pumped into the fermentation pool with 6% yeast added as the starter.A total of 5% CAPB broth (containing 15-20% caproic acid) was added whenthe fermentation reached 48 hours. Distillation followed after 72 hours ofmixed fermentation.

The finished product contains a high content of total acids and total esterswhich contribute to an excellent taste and a crystal-clear appearance of the wine.In addition, the production line is free from a series of traditional, tedious op-erations and the equipment they require. Further studies on this process aretherefore highly recommended.

At the Sichuan Biological Research Institute of the Chinese Science Academy,a microbiological study was conducted on the flavor simulation of certain estab-

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CHINESE FERMENTED FOOD PRODUCTS 189

lished strong-scented wines. It was reported that by using the mixed fermenta-tion of methane-producing bacteria (MPB) and CAPB, the output of the totalalcohol was raised from 38.95% to 40.42%, and high-quality wine output in-creased from 31.45% to 38.65%, as compared to those proportions when CAPBwas used alone.

Future Research Trends

The future goals for microbiological research on Qu are to screen the new strainsof microorganisms and their metabolites related to brewing. Direct fermentationof uncooked rice in Yellow-jiu making is yet to be developed in order to con-serve energy. As for White-jiu, a good understanding of the chemical composi-tions of different aroma types and their specific compounds can be achieved byusng advanced instruments and techniques. The biosynthesis of flavor compon-ents and manipulations should be extensively studied.

JIANG AND CHI

Jiang

The ancient book Zhou-Li: Qu-li-pian states that cooking with the use of Jiang,a fermented sauce, results in appealing and appetizing food. According to Wu-yan, a classic record of the science and technology in ancient China, Lord Zhou,the Emperor during Zhou Dynasty, learned to make Jiang himself. It is there-fore apparent that Jiang was invented during the Zhou Dynasty. However, Jiangis a term used in ancient times and seems to refer to either meat Jiang, fish Jiang,or shrimp Jaing. It is possible that .the Jiang mentioned in the ancient documentis meat, shrimp, or fish Jiang instead of soybean Jiang. On the other hand, liter-ature also shows that Qu, the precursor of Jiang, was produced during the ZhouDynasty. This suggests that soybean Jiang also can have originated during theZhou Dynasty.

The Traditional Method for Making Jiang

Natural molding is the traditional method for making Jiang. The process is sim-ilar to soy sause making, except that the ripened Jiangpei (fermented mash) isconsumed directly without brine treatment and drip-washing, which are neces-sary in soy sauce making.

New Method for Jiang Making

Unlike the processing in natural molding, a pure culture of Aspergillus oryzae isused in the fermentation of the raw material simulating Qu making. Salt is added

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190 CHEN AND HO

[Wheat Flour

| Soybean |- •> Soaked • Steamed •Cooled

|Zhongqu|

Mixed • >Thick-layer Ventilated

Incubation• Soybean-Qu

Fermentor

Brine (14.5 Be')

WarmedNaturally

(40C)

-> Fermented -(45 C. 10 Days)

Stirred

Soybean JiangRipened —

(4-5 Days)

Figure 4. Manufacturing process for soybean Jiang.

upon completion of the fermentation, followed by naturization, which is a slowcooling process.

The accompanying flow chart (Fig. 4) shows the typical procedures for soy-bean Jiang making.

Improvement of Manufacturing Techniques

Jiang making shares the same principles as soy sauce making. They both dependupon the function of enzymatic saccharification and proteolizataion by microor-ganisms. Therefore, Qu is prepared and added in certain proportions to the cookedraw materials for fermentation. As a result, a higher productivity is achieved byconserving the raw materials, equipment, and manpower used in larger scale Qumaking, as compared to when the whole raw materials are to be made into Qu.

Qu making can be accomplished by using both solid cultures and liquid cul-tures. Both are known as the "enzymatic method."

Solid Culture Method: The pure culture of Aspergillus oryzae is introduced intopowdered Qu, which is then used as a starter for Jiang making. For example, inmaking Flour Jiang (wheat sauce), the wheat flour is hydrated and steamed, thenmixed thoroughly with powdered Qu and fermented at 45-50° C for a period of10 days. The temperature could reach as high as 65° C during the 8th day. About200 kg of Flour Jiang is obtained from 100 kg of wheat flour. Figure 5 showsthe flow chart of Jiang making by solid culture.

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CHINESE FERMENTED FOOD PRODUCTS 191

| Wheat Bran |

Pressed Filtration |

| Enzyme Extract |

Wheat Flour

Steamed

' Mixed

JFermented(45-50 C)

VPasterized

Figure 5. Flow chart of Jiang making by solid culture.

Liquid Culture Method: The culture broth from the submerged liquid cultureof Aspergillus oryzae is concentrated and used in place of the solid culture toproduce Jiang. This method was developed by the Shanghai Institute of Brew-ing Science.

Chi

Chi is a traditionally fermented food in China and is widely distributed in mostsouthern provinces such as Zhejiang, Fujian, Sichuan, Hunan, Hubei, Jiangsu,and Jiangxi, as well as some areas in northern China.

It is uncertain whether Chi originated at the same time as Jiang. However, theliterature indicates that Chi making existed before the Qin Dynasty.

"Chi making method No. 72" in Qimin Yaoshu (a classic record of ancientagriculture and technologies by Jia Sixie, published in about 533-544 A.D.) statesthat Chi is made from soybeans. April and May are the best months for Chi mak-ing, followed by late July and August. It is difficult to control the temperaturesduring hot summer days, which therefore are not appropriate times for Chi mak-ing. The soybeans are sorted and steamed until they feel soft to the touch. Theyare then cooled and spread on mats on house floors. The thickness of the ma-terial and frequency of agitation depend upon the temperature of the material.When a yellow color appears on the surface of the soybeans, they are brought

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192 CHEN AND HO

outside the house. The yellow color is removed by winnowing. The material isthen washed in earthen jars half filled with water. The soybeans are placed in abasket and rinsed thoroughly in order to remove the bitter taste. The cleanedsoybeans are then moved into a "fermentation" cellar, on the top of a layer ofrice bran about 2 feet thick. Covering the top of the soybeans are straw mats,upon which another layer of rice bran (about 1 meter thick) is placed. The ma-terials are pressed firm and fermented for a period varying with the seasons. Tendays are needed in summer, 12-13 in spring or fall, and 15 days in winter.

The Chi produced in this way is, in fact, fermented by naturally occurring ,4 s-pergillus (as evidenced by the yellow color generated). It has a flavor similar tothat of soybean Jiang.

Today, Chi is produced by fermentation with pure cultures, which can beeither Apsergillus, Mucor, or bacteria, with Aspergillus predominating. A bittertaste has been detected in Chi produced by a pure culture of Huniang 3.042, aspecies of Aspergillus. This motivated a research study for the mutant of Asper-gillus. In 1983 a mutated species of Huniang 3.042, Aspergillus 3798, was ob-tained by artificial mutation. Its use produces a highly flavored and savory Chiwithout an off-flavor (Zhongguo Niangzao 2:23-25, 1987).

SOY SAUCE

Soy sauce has been regarded as one of the most popular condiments in the longhistory of China. It is estimated that at present more than 2 million tons are pro-duced yearly in China.

No document provides enough information indicating when Chinese peoplestarted making soy sauce. However, Dou Jiang Qing (filtrate of Jiang) is believedto be the soy sauce mentioned in Qimin Yaoshu. "Jiang" appeared in Chinaaround 500 B.C.

The skill of making soy sauce was first introduced to Japan and the PacificIslands, and then to the Western countries.

The traditional method for making soy sauce involves many complicated prin-ciples and secret methods, some of which are still far from being understood.This section discusses the traditional method and its improvement in China.

The Traditional Method for Making Soy Sauce

There are three essential steps involved:

1. Cooked soybeans are mixed with wheat flour and put in a warm-house to un-dergo natural molding. The resulting product is called Yellow-zi (yellow seeds).

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CHINESE FERMENTED FOOD PRODUCTS 193

2. The Yellow-zi are soaked in a brine solution in earthen jars, which are exposedto sunlight and open air.

3. Fermentation is usually completed after many hot summer days.

The details are as follows: Soybeans and wheat flour are chosen as startingmaterials. The rinsed soybeans are cooked in a pan for approximately 5 hours,usually starting at about 10 o'clock in the morning. Heating is stopped at about2-3 in the afternoon, but the contents are kept warm in the pan until the nextmorning. The cooked soybeans, now dark brown in color, are taken out andspread out on bamboo mats to cool. An equal amount of wheat flour is thenadded and mixed well.

The mixture is then placed in bamboo baskets and brought into the "warm-house" to make the Yellow-zi. The warm-houses of simple construction usuallyface south. The bamboo baskets containing the mixture of cooked soybeans andwheat flour are kept warm by straw mats and stored on shelves. The Yellow-zimaking usually begins every February 18 according to the lunar calendar, which'corresponds approximately to mid-January. At that time, the weather is cold.It is therefore necessary to close all doors and windows to keep the materialwarm. Molding occurs after 8-9 days and the temperature and atmosphere shouldbe adjusted, by opening or closing the windows and doors, to compensate forboth the weather and the heat generated during the molding. In another 7-8days, the Huangzi is ready. During the rainy season (from April to May), ripen-ing of the Yellow-zi is accelerated, taking only half of the usual time needed.Colder weather is not conducive to producing the Yellow-zi. The quality of theproduct depends totally on the experience of the workers. The majority of theYellow-zi produced in this way results in yellowish-green molds, sometimes mixedwith white hypha molds as well. It is said by experienced makers that the longerthe white hypha, the better the quality. This is an interesting observation.

An appropriate amount of brine solution (25% salt) is added to the Yellow-zito make it into semicircular cakes, which are then put into earthen jars with bam-boo lids. Usually, there are 200-2000 earthen jars in a factory. The volume ofthe jar is about 1500 L. The Yellow-zi is usually packed into the jars in the spring.The jars are placed in the open air. The lids are removed when the sun shinesand put back when it rains. The soy mash ripens during the summer.

The ripened soy mash, called Jiangpei, with the added brine solution, is thenpiped into cloth bags. The bags are pressed by an old-fashioned wooden squeezer.The resulting exudate is the soy sauce, and the residue is used as animal feed.

Modification of Traditional Manufacturing of Soy Sauce

For a long time, no one attempted to research the traditional methods for soysauce making. The author, in 1930, began to conduct some scientific researchin this area at the Nanjing Industrial Experiment Institute.

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194 CHEN AND HO

Isolation of Molds from Yellow-zi

The molds in Yellow-zi consist of green, white, gray and dark, and other variousspecies, with the predominance of the green ones. One mold (Aspergillus ory-zae) which contains the highest protease activities was isolated. It was then cul-tivated and made into Qu (a fermentation starter, called "Koji" in Japan). TheQu was distributed to manufacturers all over the country with user's instruc-tions.

The advantages of using the pure culture, Qu, in making soy sauce are:

1. Qu can be produced all year long, regardless of the season.2. Due to the strong protease activity of the Qu, the protein can be efficiently

utilized and, in addition, a shortened ripening time of Jiangpei (soy mash)can be. achieved.

3. Compared to the traditional Yellow-zi making, it takes only 2 days, or onefifth of the time required to make Qu.

4. Risk of contamination by other bacteria in making the Qu is relatively re-duced.

Modification of Manufacturing Process

Soybean and wheat flour are used together in traditional soy sauce making. Atleast 1 year is needed to complete on batch. It was found at Guantou, FujianProvince, that Chi sauce, which uses soybean as the sole raw material, needs only100-120 days for production, about one third of time compared to the tradi-tional method. In addition, the quality of the Chi sauce was found superior tothe ordinary soy sauce. This raised the attention of researchers. At the same time,it was reported in Japan that sugars resulting from the degradation of starch in-hibited the enzymatic hydrolysis of protein. This led to the invention of the"Y-shaped" fermentation process, in which soybeans and wheat flour are fer-mented separately.

To adopt the method of making Chi sauce using soybeans as the sole materialfor producing Qu was the primary attempt. However, it failed because the soy-bean grains contained too much moisture for the yeast to grow. A small amountof heated wheat flour was therefore used to absorb the moisture during the Qumaking. The Qu, after removal of the wheat flour and addition of the brine, wasincubated at 50-55° C for 1 month. The soybean mash was then ready, but shorton flavor. Therefore, one tenth of the 1-month-old fermented wheat exudatewas added to the soybean mash. The mixture was further fermented for anoth-er month. The quality of this product was as good as the one that took 1 fullyear to produce. This detailed method has been published in Niangzao Yanjiu[Fermentation Research] by Jing Pei-Song.

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CHINESE FERMENTED FOOD PRODUCTS 195

New Methods of Soy Sauce Making

In China the demand for soy sauce started to increase during the 1950s, andconsiderable progress has been made in soy sauce manufacturing.

Experiment on Salt-Free Fermentation in Soy Sauce Manufacturing

Since salt is known to inhibit the hydrolysis of protein, fermentation of soysauce without salt was studied in 1957. The Qu was made following the tradi-tional process with defatted soybean cake and wheat bran. Water was added tothe Qu in the proportion 100-130% by weight. The mixture was placed in abucket, and the temperature inside was kept around 60° C with a constant am-bient temperature of 45° C. The fermentation took about 48 to 60 hours to com-plete. The process of pressing out the soy sauce was unchanged.

The advantage of this method is to bring the protein utilization efficiency upto 75% in a short time. Unfortunately, because less flavor is generated and be-cause of spoilage often resulting from difficulty in controlling temperatures, thisprocedure calls for further study.

The Method of Low Salt Concentration and Heat Preservation

This method is currently being widely used in China. A salt concentration of 13°Be (usually 20° Be), 62-65% by weight of Qu, is used in the fermentation. Thetemperature is kept at 44-46° C. Though it will take 10 or more days to completethe fermentation of the soy mash, no risk of spoilage is involved. Details are asfollows.

Qu Making: The traditional method of using shallow wooden trays, requiringextensive use of labor, has been replaced with aerating deep tanks for Qu mak-ing. The whole process begins with the cooking of soybeans in a retort (or high-pressure cooker), followed by cooling and mixing with roasted wheat bran. Themixture is then pumped into the aerating deep coment tanks. There are someaerating holes at the bottom of the tank. An optimum temperature is maintainedby intermittently blowing cool or hot air through the aerating holes. Manpoweris much reduced by employing vacuum pipelines to feed the tanks, although thefinished product is still discharged manually.

Fermentation: The soy sauce Qu is placed on the bottom of the fermentationcement tanks and mixed with brine. The perforated bottom is replaceable. Steamcomes from underneath and around the tank wall to keep the temperature about42-48° C during fermentation. The fermentation is usually completed in 8 daysbut could be prolonged to 10 or 15 days, if necessary.

Drip-Washing: Brine is pured into the Jiangpei in the fermentation tank andallowed to soak the soy mash for a certain period. The soy sauce thus resulting

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196 CHEN AND HO

Wheat Bran | |Zhongq

Soybean Cake • Steamed -•Mixed •

Qu-making Fermentor

(Ventilated Thick-layer)| Soy Sauce Qu | -Milled

•|Brine(13Be')

Fermented(42-48 C)

->\ Ripe Jiangpei | '—>-Drip Washing

Pasterized Soy Sauce

Figure 6. Manufacturing process for soy sauce by the method of low salt concentration andheat preservation.

will drip to the bottom of the tank, where it is then drawn off. Compared to thetraditional expression process, the drip-washing method saves a considerableamount of energy. Figure 6 is a flow chart of the process of low salt concentra-tion and heat preservation soy sauce making.

Experiment on Submerged Liquid Culture Making

The solid Qu making requires large amount of raw material and labor. Since thesubmerged liquid culture has been used in alcohol manufacturing, attempts havebeen made to adopt some of its procedures in soy sauce making. Highly activeproteases (neutral and acidic), glutaminase, and other enzymes are required insoy sauce making, besides those mentioned in wine making. In 1972 an investi-gation was carried out by the Sanxia Mill in Yichang City, Hebei Province, toutilize blanched water in soy sauce making. A submerged culture of Aspergillusoryzae was used to produce protease. The aqueous enzyme extract was mixedwith the raw materials (the blanched water in which the rice sticks had beencooked, and defatted soy flour) at a ratio of 0.3:1, and incubated at 45°C for24 to 48 hours. The efficiency of protein hydrolysis was up to 45% or higher;however, the quality of the soy sauce was inferior to that produced by solid Qu.

Around 1979 the Shanghai Institute of Fermentation Science made consid-erable progress on applying the technique of submerged liquid culture in soysauce making. Following are some of their achievements.

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CHINESE FERMENTED FOOD PRODUCTS 197

1. Preparation of two different submerged liquid cultures:a. Aspergillus oryzae Huliang UE 328, a neutral protease, produced with a

2.8 ton fermentor, which has an activity range of 1566 to 3255 units/mL,with an average of 2,207 units/mL.

b. Apsergillus oryzae AS 3.4310 (#537), an acidic protease, which has anactivity range of 3500 to 5447 units/mL, with an average of 3920 units/mL.

2. Manufacturing red soy sauce by the submerged liquid culture:a. Raw material: defatted soy flour (550 kg) mixed with wheat bran (120

kg) and wheat flour (75%).b. Treatment of raw material: addition of 105% of water and cooking under

pressure.c. The ratio of total raw material to water is 1:1.6.d. Quantity of salt: 9% of the initial fermentation mash.e. Enzyme dosage: 5,000 units of neutral protease per gram of total raw ma-

terial or 600 units of acidic protease per gram of total raw material.f. Prefermentation: The whole fermentation cycle takes 30 days, of which

the first 18 days are for prefermentation. During the prefermentation pe-riod the temperature is maintained at 45-53° C.

g. Ripening: following the prefermentation, the temperature is brought downto 35° C, liquid yeast culture added, and ripening allowed to take place foranother 12 days.

h. Drip-washing: performed as usual.i. Protein utilization efficiency: 80.74%.j . Rate at which amino acids are produced: 50.54%.

Figure 7 is a flow chart for the process of manufacturing soy sauce by sub-merged liquid culture method.

Employment of submerged liquid culture to replace solid culture results ineasier processing, simpler fermentation techniques, and lower labor requirements.The addition of "Huniang 214" yeast culture during ripening improves the fla-vor of the finished product. It suggests a prosperous future for soy sauce manu-facturing.

Suggestions for the Improvement of the Technology of Soy SauceManufacturing

For thousands of years, Chinese soy sauce was produced by using natural fer-mentation method to make Yellow-zi, the precursor of soy sauce. In 1930 a Qufermentation method was introduced to soy sauce manufacturing, using the cul-ture of pure Aspergillus isolated from Yellow-zi. Pure culture fermentation shor-tened the ripening time for soy sauce from 1 year to 2 months. The invention

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198 CHEN AND HO

Wheat BranWheat FlourSoybean Cake

ISteamed

Submerged LiquidCulture

Alkaline EnzymeSolution

Mixed

11 Fermentation 1

Postfermentation |

i

Yeast CultureBroth

I Drip Washing

Pasterized

Soy Sauce

Figure 7. Manufacturing process for soy sauce by the submerged liquid culture method.

of a no-salt soy sauce making process made it possible to reduce the fermenta-tion time to 1 or 2 days, but the problem of temperature control has yet to beresolved. A low salt concentration and heat preservation method was then used,and the manufacturing time was 10 days. This has become the soy sauce manu-facturing method in present use throughout the country. Recently, the sub-merged liquid culture method has shown some success and a promising futurein soy sauce making.

The techniques for soy sauce manufacturing have advanced a great deal overrecent decades. However, the quality still needs to be improved. The followingtopics are suggested for future research.

Culture Screening

Though some good soy sauce microorganisms such as "Huniang" Aspergillus3.042 have been in use, better species are still desired, especially in terms ofhigher protease activity. The cytoplasm fusion and in vitro gene recombinationand,other advanced techniques could be used to screen and obtain a microor-ganism which possesses multifunctional enzymic activity, such as high activitiesof protease, glucoamylase, glutaminase and cellulase.

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CHINESE FERMENTED FOOD PRODUCTS 199

Research on Mixed Fermentation

Traditional Chinese soy sauce was made by natural fermentation with variousmicroorganisms which work coordinately to give the final product a superiorand specific flavor. Fermentation with pure culture of Aspergillus was provento decrease the quality of soy sauce. However, with the addition of yeast andlactobacter, the quality was improved. This indicates that the key to soy saucemaking is mixed fermentation. Further research is necessary to better under-stand and employ this technology.

Another means recently employed to improve the quality of soy sauce is theuse of immobilized yeast and lactobacter cells as posttreatment agent, whichneeds further research.

Research on Savory Nucleotides

Nucleotides such as 5'-inosine monophosphate (IMP) and 5'-guanosine mono-phosphate (GMP) are flavor enhancers. The commercial production of 5'-nu-cleotides from enzymatic hydrolysis of polynucleotides has been successfullyachieved. Addition of these nucleotides to soy sauce has created a product withsuperior flavor, which enjoys a good market. The conversion of 5*-xanthosinemonophosphate to 5'-inosine monophosphate, and phosphorylation of inosineto 5-inosinephosphate and the production of savory nucleotides directly byfermentation, are among the efforts to optimize soy sauce processing.

VINEGAR

The word "vinegar" was first mentioned in Zhouli: Tiangwn, which was pub-lished more than 2000 years ago.

The Traditional Method for Making Vinegar

A very detailed description of vinegar making was found in Qimin Yaoshu. OnJuly 7th of the lunar calendar, clear well water is fetched for vinegar making.About 10 L of wheat bran is poured into an earthen jar, followed by 1.5 L ofwater and 30 L of cooked and cooled millet. The filled vessel is then coveredwith cotton mats which are held in place with a chefs knife. About a 0.5 L ofwater is added to the vessel on the 7th day and yet another 0.5 L on the 21stday. At this time, the vinegar is ready. The vinegar is usually ladled from thevessel using a dry half calabash, which is a gourd whose hard shell is used as autensil. It should not be ladled with a wet or salty utensil because this would

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200 CHEN AND HO

spoil its flavor. This kind of practice suggests that some basic principles of mi-crobiology were instinctively used by the ancient Chinese people.

Manufacture of Some Well-Known Vinegars. Shanxi aged vinegar and Zheng-jiang scented vinegar are considered the best among the traditional Chinese vin-egars. Both of them were fermented using a mixed solid culture.

Like wine making, the solid culture fermentation of vinegar employs Big-qufermentation and Small-qu fermentation. Shanxi-aged vinegar is a typical exam-ple of Big-qu fermentation. Big-qu is a fermentation starter, brick-shaped andmade of wheat, barley, or green peas. The characteristics of Big-qu fermentationare: (1) a large amount of Qu is used (62.5 kg of Big-qu for 100 kg of sorghum);(2) a longer fermentation time (about 8 days) is needed; (3) saccharification andalcoholic fermentation proceed at low temperatures; and (4) the aging time islong. The freshly obtained vinegar is placed outdoors, heated in summer by thesun and frozen in the winter. The ice formed in winter is removed. After agingthrough a hot summer and a severe winter, the final product of Shanxi aged vine-gar is ready, which is viscous, dark purple in color, and sweet in taste, and has along shelf-life.

On the other hand, Zhenjiang scented vinegar presents a typical example ofSmall-qu fermentation. In the past, the distilled Yellow-jiu mash was used asthe raw material. Regular rice or waxy rice is now used. The whole procedureincludes alcoholic fermentation, Pei (unfiltered mash) making, Pei discharging,and drip-washing of the vinegar. It involves more than 40 individual operationsand takes about 60 days. The finished product is famous for its delicate com-bination of color, fragrance, sourness, mellowness, and richness.

As mentioned before, like wine making, both Big-qu and Small-qu fermenta-tion are a result of naturally mixed culture fermentations. They also suffer thesimilar disadvantage of low production rate because of a long, labor-intensivefermentation time.

New Methods of Vinegar Making

Some improvements have been made to speed up the fermentation cycle, replacethe manpower with machines, and increase the utilization efficiency of the rawmaterials.

Enzymatic Vinegar Making by Aerating Fluid Recycling

The benefits of this process are: (1) the use of pure culture for acetic acid fer-mentation; and (2) labor can be reduced by replacing the manual discharging offermented mash with natural aerating fluid recycling. The details are as follows:

1. Ground rice is used as the raw material for regular alcoholic fermentation.2. Acidic acid fermentation: The fermented alcoholic mash, wheat bran, and

acetobactal culture broth are mixed and piped into the fermentation tank,

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Rice Ground • • Soaked

Yeast Culture

Saccharified AlcoholicFermentation

Wheat Bran Ou-Amylase

- > Milled

Wheat Bran, Rice Bran

AcetobacterAcetic Acid

Fermentation

-> Drip Washing Pasterized Vinegar

Figure 8. Manufacturing process for vinegar by the enzymatic method.

the optimum loading temperature being 35-36°C. After 1 day the fluid re-cycling is ready to start when the material temperature reaches 40° C. To re-cycle the fermentation liquid, part of the exudate is drained off and pumpedback at a rate of 6 cycles per day. It is ready for the next step after about 30days.

3. Addition of salt: Sodium chloride is added to prevent the loss of acetic aciddue to excessive oxidation by acetic acid bacteria.

4. Drip-washing: In a fermentation tank, a removable perforated bottom is in-stalled to facilitate the drip-washing. The liquid washed off from the fermen-tation tank is the final product of vinegar, which contains 5% acetic acid,1.32% total sugar, and 0.52% total nitrogen. The product has a density of 5Be with a reddish brown color and a sweet/sour taste. The quality of it is com-parable to Zhengiiang scented vinegar.

In comparison with the traditional process, this method carries the advantagesof: (1) 10% or higher increased production rate of vinegar; (2) reduced energyconsumption; and (3) less labor.

Figure 8 shows the manufacturing process of vinegar by enzymatic method.

Submerged Liquid Fermentation

Submerged liquid fermentation was developed to reduce the fermentation timeand simplify the complicated operations of both traditional and aerating fluidrecycling methods. The alcoholic fermentation using ground rice as the raw ma-terial remains the same. The fermented alcoholic mash is then piped into a stain-less steel fermentor (rising air current type), and the acidic acid fermentationstarts with the addition of 10% acetobacter culture broth (contains Acetobacterlavaniensis). The temperature is maintained at 32-35° C and the aerating rate in-

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202 CHEN AND HO

creases gradually from 1:0.07 to 1:0.1. It takes 65 to 72 hours for the wholeacetic acid fermentation process. The final product is obtained after the addi-tion of salt followed by filtration, sterilization, and blending. A total of 3.5 kgof vinegar, with an acetic acid concentration of 5%, is obtained from 1 kg ofrice.

Suggestions for Research on Vinegar Fermentation Techniques

Established vinegars, such as the Shanxi aged vinegar and the Zhenjian scentedvinegar, are natural fermentation products. Though the Shanghai scented vine-gar, produced by an enzymatic aerating fluid recycling process and a pure cul-ture fermentation, has a quality close to that of Zhenjiang scented vinegar, fur-ther improvement of its quality is possible. The submerged liquid fermentationmethod is praised for its high extent of automation and short production cycle.However, it produces vinegars of lower quality, especially when flavor is con-cerned.

Culture Screening

New technology, such as protoplasmic fusion and genetic engineering, shouldmake possible the production of a hybrid which can resist high acetic acid con-centrations up to 12% (now 9%), and which can produce good flavor compar-able to that of established vinegars.

Application of Immobilized Acetobacters

An economic and reliable support for acetobacter immobilization is needed forhigh productivity and high vinegar yield.

Yield Efficiency

It is possible to ferment the rice bran discharged residue again in an aerating fluidrecycling process to improve the efficiency. *•

HONGQU

Red-qu, or "red rice," is a fermentation product of rice with various strains ofMonascus purpureus. It was first noted in the book Qingyi Lu, written by TaoGou of the Sung Dynasty (1000 A.D.). More detailed information on Red-quwas found in Tiarigong Kaiwu by Song Yingxing of the Ming Dynasty (1637A.D.).

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Traditional Red-qu Making

Natural fermentation is used for traditional Red-qu making. Rice is washed andsoaked in water for 5-7 hours. It is then drained, steamed, and cooled on bam-boo mats. The next day, the same procedure of steaming and cooling is repeated.It is then well mixed with Quzhong Zao, or starter, at a ratio of 100:1.9 by vol-ume at 35-37° C, and moved to a Qu-making room for fermentation. Ambientconditions within the room are quite critical. Ideally, the temperature of thematerial is 35° C, moisture content 45%, and room temperature 30° C. The mix-ture is turned over four to five times daily and the thickness of the layer is gradu-ally reduced to 10-13 cm to compensate for the heat generated during fermen-tation. Little vent holes on the walls are used to adjust the temperature in thewindowless Qu-making room. On the third day, the material is taken out of theQu-making room to a riverside or a pondside, immersed in water for 10 to 15minutes and then brought back to the room to continue the natural fermenta-tion. On the fifth day, it is immersed in water again for 2-3 minutes. The nextday, after being sprayed with water, it is transferred to an ordinary room, wherethe natural fermentation continues for 3 more days. It is dried in the sun on theninth day.

Details of the process are:

1. Quzhong Zao (Qu starter), a milled and cream-like mash, is prepared from thefermentation of the mixture of Quzhong (0.6 kg), nonglutinous rice (1.5 kg),and water (3 kg). The fermentation is carried out in a 15-L earthen jar for 5-6days.

2. Quzhong is prepared from the fermentation of nonglutinous rice (100 kg) andQuyao Zao, using the same procedures as in Red-qu making.

3. Quyao Zao (Quyao mash), a red liquid with a bitter and astringent taste, isprepared from the fermentation of a mixture of Quyao, glutinous rice, Quz-hong, and Rice-jiu (contains 25% of alcohol) for 12-15 days.

4. Quyao, originating in southern China, is a Qu product with a deep-red coloron the surface and a reddish-white color inside, with a garlic-like smell. Itcontains Monascus and can be stored for years without deterioration. Oneportion of Quyao can produce 50,000 portions of Red-qu.

New Methods of Red-qu Making

The traditional method depends on the natural fermentation of Quyao. The iso-lation of pure Monascus culture from Quyao simplifies the whole process forthe modern method. The pure Monascus culture is scaled up to produce Zhong-qu by incubating the culture with unglutinous rice. Zhongqu is then used toproduce Red-qu. Red-qu making is illustrated in Figure 9.

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204 CHEN AND HO

Xianmi(Nonglutinous Rice)

•Washed •Steamed • Cooled

Monascus||Aceticacid | | Spraying Water

- > Mixed >• Incubation • > Stirred

• Dried >\ Red-Qu |

Figure 9. Manufacturing process for Red-qu.

The nonglutinous rice is washed, steamed, and cooled to 42-44°C. The cookedrice is mixed well with ZHongqu powder and the proper amount of glacial ace-tic acid and powdered Zhongqu. The mixture is then placed in a gunnysack andbrought into a (2«-making room. After about 24 hours, the temperature of therice rises to 50-51° C. The sack is then unpacked and the rice is spread on woodentrays. The temperature of the rice is about 36-38°C at this time. The materialshould be kept below 42° C by turning and stirring when necessary. After about10 days, the rice becomes pink and extremely dry. The material is soaked inwater of 25° C and turned over several times during a total of 4 days of fermen-tation. At the end, about 7-12 kg of water is absorbed per 100 kg of rice.

Application of Hongqu

A wide range of application of Red-qu is found in alcoholic fermentation, cook-ing, and medicine. Red-qu is used in wine making in Fujian and Taiwan prov-inces, and the products are noted for their red color and mellow taste. Red-zao,the residue of the Red-qu alcoholic fermentation, is an ideal condiment in Chi-nese cuisine. The established Fujian dishes such as Red-zao chicken, Red-zaofish, and Red-zao pork are widely loved. It is a tradition to prepare Red-zaomeat, Red-zao fish and, Red-zao chicken for Chinese New Year Holidays. Thefresh taste can be preserved for several months. Red-qu is also used as a color-ing agent for Doufuru (fermented bean curd).

The preservation effect of Red-qu has been well described in Tiangong Kaiwu."The role of Red-qu is mystical and wonderful. As perishable as fish and meatare, a small amount of Red-qu can preserve them for weeks in hot summer, keep-ing flies and worms out of the food. The color and taste of the food also wouldbe well preserved." Recently, it was reported that an antibiotic, called Hongqu-

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mycin, was found in Red-qu. The antibiotic is not only a good preservative butalso a drug which can be used to cure chronic enteritis and dysentery. Red-quis also claimed to help digestion and blood circulation, and to benefit the spleenand stomach functions.

Scientific Research on Red-qu

Some research has been done on the colorants and carbohydrate hydrolases ob-tained from Monascus V. Tiegh, which was isolated from Red-qu.

Red Food Color

Red colorants obtained from Monascus are natural products and safe to be usedas food color, an advantage not possessed by some synthetic colorants.

Recently, a mutated species of Monascus capable of producing high concen-trations of red pigments has been isolated from the induced parent microorgan-ism. This considerably decreases the dosage level of Red-qu used in food andenables the production of Monascus red colorants on a commercial scale.

Carbohydrate Hydrolases in Monascus

The extract of carbohydrate hydrolases from Monascus is characterized by lackof transglucasidase activity. The culture broth of Monascus could be used directlyfor the hydrolysis of starch. The dextrose equivalent (DE) of the product canbe as high as 99%.

Antibiotics in Monascus

The nature of the preservation and medical functions of Red-qu suggests theproduction of antibiotics by Monascus. This area of research should be furtherexplored.

DOUFURU

Doufuru, or Furu (fermented bean curd) is one of the most famous Chinese fer-mentation food products. It is flavorful, tasteful, and nutritious and has beenconsumed for more than 1000 years in China. It is produced all over the coun-try and many provinces have their own characteristic Furu. Among them, theproducts from Jiangsu, Zhejiang, Guangdong, Guangxi, Sichuan, and Hunanprovinces are most famous.

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Traditional Doufuru Making

Traditionally, Doufuru is made by natural fermentation. The process is still usedin many places such as Suzhou and Wuxi.

Preparation of Doufu (Soybean Curd)

The soybeans are washed and soaked in water, and then milled into slurries. Theslurries are diluted with warm water and pressed to obtain soybean milk. Thesoybean milk is boiled and immediately placed on wooden trays which containa solution of brine stock or bypsum to precipitate the proteins. The aggregatedsubstance is put in cloth bags. Stones or wooden planks are used to squeeze offthe water. After the curd is formed, it is sliced into different-sized pieces.

Preparation of Furupei

Furupei, or prefermented bean curd, is prepared by means of natural fermenta-tion. Small pieces of soybean curd are placed in a square wooden tray with aboundary of 60 cm and a depth of 10 cm. The bottom of the tray is made ofbamboo strips loosely woven together. The pieces of curd are placed 3 cm apart.The loaded wooden trays are brought into a building for natural fermentation.This structure is very simple, and the ground is covered with a layer of straw15 cm thick. Twelve trays are piled up, and the top one, which is left empty, iscovered with straw. Stoves are used to keep the room warm. In spring, gray my-celium of the mold appears in 4-5 days and can grow to several millimeters thickin 8-9 days. In winter, this step takes as long as 20 days.

Salt Treatment

The prefermented Furupei is transferred to a big earthen jar and salt is spreadbetween layers of Furupei as they pile up in the jar. After 12-13 days, the Furu-pei is transferred to earthen jars that can hold about 100 pieces each.

Postfermentation

Red-qu, the exudate of alcoholic fermentation mash and salt, is added to theearthen jar. It is then fermented for another 2 months to complete the wholeprocess.

This method of natural fermentation is far from being reliable since it dependson the microorganisms prevailing in the air and in the utensils within the fer-mentation house, and is affected greatly by the weather and the experience ofworkers. A new method has been developed.

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New Method for Doufuru Making

Culture Screening

A microorganism, Mucorwutungchiao, was isolated from traditionally fermentedbean curd in the 1950s. However, the optimum temperature for the growth ofthis Mucor is low, therefore limiting the production of Doufuru to the cold sea-son. A culture of Rhizopus was later isolated and used by the Nanjing VegetableSupply Cooperation. This microorganism has a high protease activity and cangrow in a wide range of temperatures with an optimum temperature of 28-30° C.This culture not only takes a shorter growing time on Furupei (2 days as com-pared to 7 days) but also makes it possible to produce Doufuru regardless ofthe weather and the season. In addition, use of this microorganism during thehot season inhibits, to a certain extent, the contaminating organisms. However,the identity of this species is still not known.

Scale-up Cultivation of Pure Culture

The pure culture is kept in Agar Slant in test tubes. Wheat bran is mixed withwater and sterilized in a bottle. The pure culture is then inoculated in the bot-tle and incubated at 28-30° C. After 2 days, it is then diluted with water, shaken,and filtered. The spores in the filtrate are ready for the fermentation of Furupei.

Making of Furupei

The utensils used and the way of loading the bean curds are similar to the tradi-tional method. However, the bean curds are sprayed with the filtrate of the sporesfor fermentation. The fermentation period is shortened (about 2 days) and thesuccess of fermentation is almost guaranteed.

Postfermentation

Postfermentation is the same as in the traditional method.

CONCLUSION

The fermentation technology passed down by ancient Chinese is a priceless trea-sure. However, some of the principles behind the technology remain a mystery.Considerable progress has been made in the area of microbiology; however, someof the microorganisms involved in fermentation are yet to be defined and classi-fied. Despite the sophisticated analytical techniques and equipment we have to-day, the functions and identities of certain trace flavor constituents in the fer-

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mented foods remain unknown. Biochemical and biological interrelationshipsbetween different microorganisms are still beyond our present knowledge.

In light of all these facts, it is not surprising to find that although the use ofpure culture fermentations has greatly reduced the time for fermentation andincreased the yield of the products, their qualities are not up to the standardsof the traditional products. For instance, the fermentation of distilled spiritsis shortened from several months to 2 days and that of soy sauce from over 1year to 15 days. Fermentation efficiency, as indicated by product yields of dis-tilled spirits, increased 50% to 80%; vinegar from 40% to 80%. In addition, therate of protein utilization increased from 60% to 80% for soy sauce. However,the quality decreased for all these pure culture fermented products, as comparedto their counterparts produced by the traditional fermentation method. There-fore, even today, the best-quality spirits, such as Maotai, Fenjiu, Wuliangye, andLuzhou Tequ, are still produced by the traditional process.

The traditional process is a natural mixed fermentation in which some compli-cated biochemical and biological changes exerted by multicultures are involved.The superior quality thus produced must be a joint result of different metabolicand physiological processes by various microorganisms involved in the naturalfermentation. To surpass the traditional processes in speed, efficiency, and qual-ity remains a great task. The area is still wide open for further research.

BIBLIOGRAPHY

Central Industrial Experimental Station, "Brewing Research," Shangwu Yingshuguan, 1935.Chen, T. S., "Advanced Brewing Science," Vols. 1-2, Shangwu Yingshuguan, 1953.Chen, T. S., "History of Chinese Microbial Industry," Qinggong Chubanshe, 1979.Chen, T. S., Industrial Fermentation in China, J. Chem. Tech. Biotechnol., 32, 669-673 (1982).Fong, L. Z., "Questions and Answers for Soy Sauce Production," Light Industry Publication

Agency, 1987.Huang, Z. A., "Vinegar Production," Chemical Industry Publication Agency, 1988.Shanghai Technical School of Cereal and Oils, Shanghai Institute of Fermentation, "Produc-

tion Technology of Fermented Condiments," Vol. 2, Light Industry Publication Agency,1979.D

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