CHAPTER 4.
CEREAL FERMENTATIONS IN LATIN AMERICAN COUNTRIES 

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Argelia Lorence-Quiñones , Carmen Wacher-Rodarte* and Rodolfo Quintero-Ramírez
Research Center of Biotechnology
State University of Morelos, Mexico,
* Faculty of Chemistry, National University of Mexico

Cereal crops, in particular maize which has its origins in Mexico, are very important in Latin America and have been consumed in the fermented form for hundred of years. According to FAO statistical data, cereal production in Latin America and the Caribbean Region during 1996 was as follows:

The relative proportion of cereals fermented for human consumption in the Latin American Region is unknown. A number of traditional products based on maize were developed by the indigenous populations of Mexico and Peru in the Pre-colombian era. These fermented products are utilised as stimulants, in traditional medicine, as well as in religious ceremonies. Over the past twenty years consumption of many of these fermented cereals has declined due to urbanization.

This Chapter reviews fermented cereal products in Latin American countries.

Among the cereals grown in Latin America, maize is most widely utilized, probably because Mexico is the center of the origin of maize, and over hundreds of years indigenous populations developed and established processes for transforming maize into different types of products. Although the Latin-American region is currently a net importer of maize (International Food Policy Research Institute, 1992), the situation differs from country to country: Brazil and Mexico are very important maize producers while most other countries are net importers of it. Fermented beverages and porridges consumed in the Latin American Region are presented in Table 1. Of the products listed, chicha (maize beer) is the most important traditional fermented beverage in the region and also the most widely studied.

Chicha is a clear, yellowish, effervescent, alcoholic beverage prepared from maize. It has a flavor similar to that of cider. Chicha has been consumed by the Andean Indians for centuries. When prepared from pigmented maize varieties, its color varies from red to purple. The alcoholic content of chica varies between 2 and 12 per cent (v/v).

The traditional production of chicha is a somewhat unique fermentation process in which saliva serves as the source of amylase for converting starch to fermentable sugars. Malting (germination) of maize kernels to produce the amylase required for starch conversion is an alternative procedure which is widely used in modern day processing. Frequently, salivation is combined with malting to yield chicha (Steinkraus, 1996).

Adapted from: Wacher-Rodarte, C. (1995). "Alimentos y bebidas fermentados tradicionales". In "Biotecnología Alimentaria". García-Garibay, M., Quintero, R. and A. López-Munguía (coord.). Limusa, Mexico. pp. 313-349. 

Production and Consumption Patterns-Chicha is produced in the Andean regions and sometimes in the lower altitude regions of countries such as Argentina, Bolivia, Brazil, Colombia, Ecuador and Peru.

In the Andean region, maize has always been of profound religious and magical significance, and chicha has played a role in fertility rites. Chica was used to induce the "thunder god" to send rain, and was also used in sun and harvest festivals. Even today, chicha manufacture is a significant household or communal activity and the beverage is consumed mainly by the Indians during religious and agricultural festivities and during important family and social events. A special annual festival designated the Kayova (Cayua) is dedicated to chicha production in Peru. This festival takes place in January at the beginning of the maize harvest (Cavero, 1986).

Substrates Used in Chica Production- The principal substrate used in chica production is maize. Although any available maize may be used, certain types are considered to yield a high quality chicha. Alazan maize contains kernels which are light to dark red in color, are early maturing, and highly drought resistant. Viru maize is yellow, requires a relatively long growing season, and is somewhat less drought resistant. Maize Negro is a purple-black variety used for preparing chicha in the Arequipa region of Peru. Other starchy materials such as manioc (yuca; cassava), sweet potatoes, or ripe plantains are used in chica production. Quinoa, a grain (Chenopodium quinoa) is also used as a substrate in chica production (Steinkraus, 1996).

Pre-Fermentation Processing- Starch hydrolysis is an essential step in the production of chicha. It is accomplished either through the salivation process which utilises salivary amylase (diastase), or through amylases generated during the malting (germination) of maize kernels.

In order to introduce salivary amylase into maize, it is first desirable to dry-grind the maize kernels. Dry-grinding is performed by Indian chicha makers using either a primitive half-moon-shaped rocker stone mill or a mortar and pestle. The maize flour thus obtained is slightly moistened with water, rolled into a ball of appropiate size, popped into the mouth and thoroughly mixed with saliva using the tongue. The gob thus obtained is then flattened against the roof of the mouth with the tongue and placed in the sun to dry. The salivated gobs referred to as muko resemble the upper plate of a set of false teeth. They are sun-dried and ground in a stone mill. Muko production is generally carried out as a social event by groups of older women, sometimes with the help of young girls, who all sit in a circle.

During the malting/germination process, the kernels are soaked for 12 to 18 h, generally overnight, then drained and kept in the dark usually about three days, under moist conditions until the plumules range between 0.25 and 0.5 cm in length. The kernels are then heaped and covered with burlap for 1 to 2 days, during which time the temperature rises until it is uncomfortable to place the hand in the mass of kernels. The kernels become white, parched, and covered with a thin layer of ash. Germinated grains are sun-dried, following which they are finely ground in a stone mill.

Chicha Production From Maize Flour- Chicha is produced using a variety of methodologies. Methods of extracting the maize flour vary rather widely. In one method, an earthenware pot about 75 cm high and 85 cm in diameter is filled to one-third of its capacity with maize flour. When muko is used, additional nonsalivated flour may be added along with crude sugar or squash pulp. The pot is then filled with water and heated to approximately 75 ^oC. Boiling water is not used since it produces an undesirable pasty consistency. The flour and hot water are thoroughly mixed for 1 h and then allowed to settle and cool, following which three layers are formed: a top liquid layer called upi; a middle jelly-like layer, and a bottom layer which contains coarse particles (hanchi). The upi is scooped out with a gourd and is transferred to another earthenware pot. The middle layer is placed in a shallow pan, heated, and concentrated to a sugar-like product. The hanchi is pressed and filtered and the filtrate thus obtained is added to the upi. The upi is simmered for several hours until it becomes caramelized. This caramelized product, referred to as misqui kheta, is allowed to cool. Additional upi may be boiled for as long as 3 h and then combined with the misqui kheta. After an incubation period of four days, the mixture of upi and misqui kheta begins to ferment and bubble violently. In the highlands, fermentation is complete and bubbling ceases in approximately 6 days, while in the hot lowlands, fermentation may be complete within 2 days. When bubbling ceases, the chicha is transferred to narrow-mouth pots and is ready for consumption. Froth is removed from the chicha with a cupped hand prior to consumption. This froth is used either as a furniture polish or as a starter for new batches.

An inoculum is not required, since the fermentation pots are never cleaned. After the chicha has been consumed, a layer of sediment remaining in the pot is filtered to obtain sutu, which resembles chicha in color but lacks carbonation and the typical tangy flavor associated with cider. Sutu is reportedly of a higher alcohol content than chicha. Forty litres of chicha yield about 1 litre of sutu. Chica production has not changed very much over the centuries (Steinkraus, 1996).

Chicha Production From Germinated Grains- Germinated dried maize referred to as jora is ground in a stone mill, or by a village miller. The ground jora is referred to as pachucho. Pachucho is mixed with water and boiled in an earthenware pot for 3.5 h. Water is added to replace moisture lost by evaporation. The mixture may then be slowly cooked for a further 24 h. After cooling, handfuls of the mixture are rubbed in order to separate hulls and starch, and the pachucho is boiled for a further 4 h. It is then cooled and filtered through a cloth or wire screen. The filtrate is collected in pots which are used exclusively for fermentation and are therefore already inoculated with the necessary organisms. Fermentation proceeds for 1 day. The chicha is ready for consumption when the sweetness disappears and the flavor becomes semisharp. If not immediately consumed, it becomes increasingly sour and over time, turns to vinegar. Brown sugar or molasses may be added at the time of the second boiling in order to increase the alcoholic content of the chicha. Fourty pounds of pachucho yield approximately 7 gallons of chicha; and 100 pounds of shelled maize yields between 14 and 15 gallons of chica (Steinkraus, 1996).

Microbiology of Chicha- Yeasts, particularly Saccharomyces cerevisiae, and bacteria of the genus Lactobacillus, are the primary fermenting organisms in chicha produced in northern Argentina. Various yeasts (S. cerevisiae, S. pastorianus and Mycoderna vivi, Oidium lactis and Monilia candida), bacteria of the genera Leuconostoc, Lactobacillus, Acetobacter, and various molds including Aspergillus and Penicillium are present and presumably active in Colombian chicha (Steinkraus, 1996).

Biochemical Changes During Chica Production- It has been reported that the natural mixture of organisms found in chicha has a greater ability to utilize starches, dextrins, and sugars than do pure culture s of S. cerevisiae. According to Steinkraus (1996) chicha organisms produced a total alcohol content of 13.4 % (v/v) when fermenting a 30 per cent solution consisting of 15 % starch and dextrin and 15 % fermentable sugars. Ninety percent of the total solids were fermented within 10 days, and the total acid produced was 0.8 per cent (Steinkraus, 1996).

Nutritive Value of Chica- The nutritive value of chicha would be expected to be relatively high. The alcohol content of chica supplies a caloric source. Chica is also rich in the B vitamins. The riboflavine concentration is doubled, while thiamine and niacin remain fairly constant during the fermentation of chica (Steinkraus, 1996).

Toxicology- There are no reports describing toxic reactions resulting from the consumption of chicha. If the starting maize were contamined with mycotoxin-producing moulds such as Aspergillu flavus however, the chicha produced would likely contain aflatoxin.

Pozol (from the Aztec pozolli, foamy) is a fermented maize dough formed into balls of various shapes and sizes ranging from 10 to 12 cm in length, 5 to 8 cm in width and 70 to 170 g in weight. Some unusually large pozol balls weigh 1 kg or more. Pozol is consumed by Indian and mestizo populations, mainly in the Southeastern states of Mexico, such as Chiapas, Tabasco, Campeche, Yucatan, and on a smaller scale in Veracruz, Oaxaca and Guatemala (Ulloa et al., 1987).

Consumption Patterns-Balls of freshly prepared pozol, or pozol at various stages of the fermentation process are diluted with water to produce a whitish porridge which is consumed in the uncooked state as a basic food in the daily diet of large communities. The ratio of pozol dough to water varies between 1:2 and 1:3. Salt, toasted ground chili pods, sugar, or honey may be added.

The beverage prepared from pozol is consumed particularly by low-income individuals during working hours, at meals, or as a refreshment at any hour of the day. Balls of fermented and mouldy pozol are carried by some Indians, such as the Lacandones and Chamulas, as a provision for their journeys through the jungle. Pozol consumption varies between 80 and 1000 g of undiluted pozol dough per person per day.

There are descriptions indicating the alimentary and ceremonial usage of this food by the Maya culture for several centuries prior to the Spanish conquest. Since then, pozol has been and continues to be consumed by ethnic groups such as the Chontales, Mayas, Lacandones, Tzeltales, Tzotziles, Tojolabales, Chamulas, Mames, Zoques and Zapotecos in mexico. It is consumed by all social classes. Two basic types of pozol are distinguishable: a traditional-type prepared by the indigenous Indians and a mestizo-type, characterized by additional cooking of the dehulled grains (Cañas-Urbina et al., 1993).

The Lacandones utilize pozol mixed with water and honey to reduce, according to them, the fever of the sick. Present-day Mayas offer pozol at ceremonies performed at immature, mature, and ready-to-harvest stages during the cultivation of maize.

Pozol is also consumed for the control of diarrhea. Moldy balls of pozol are said to have been used since ancient times as cataplasms in curing superficial infections and wounds. An in vitro antagonistic effect of pozol on several species of bacteria, yeasts, and molds, many of which are pathogenic or potentially pathogenic to man, has been reported.

Production- Pozol is prepared either domestically for consumption or on a small commercial scale according to traditional procedures handed down from generation to generation. In the production of pozol, 1 to 1 1/2 kg of kernels obtained by shelling cobs of maize (preferably white Zea mays L.), are boiled for 1 h in a pot containing 1 to 2 liters of an approximately 10 per cent (w/v) calcium hydroxide solution. During boiling, swelling of the kernels takes place, thus allowing the pericarp to be relatively easily peeled off the kernels. The kernels are cooled, rinsed with water, and drained resulting in what may be described as nixtamal. The nixtamal is ground in a manual metal mill to obtain a coarse dough which is manually shaped into balls. The balls are then wrapped in banana leaves to prevent desiccation, and fermented for 1 to 14 days or more depending on consumer preference and prevailing circumstances, Figure 1.

In the state of Tabasco, ground cacao beans are added to the dough prior to fermentation, to yield a fermented product called chorote. Ground coconut is also be added to pozol (Cañas-Urbina et al., 1993) in the state of Yucatan.

Microbiology of Pozol- During the initial 24 h of pozol fermentation, bacteria outnumber yeasts and molds and are probably responsible for the majority of acid produced. It has been reported that at the start of fermentation, traditional pozol contains lactic acid bacteria (10⁴-10⁶/g), aerobic mesophiles (10⁴-10⁵/g), Enterobacteriacea (10²-10³/g), yeast (10²-10⁴/g) and molds (less than 10³/g) at a pH of 7.3. After incubation for 30 h at 28⁰C, bacterial counts increase to: 10¹⁰/g lactic acid bacteria, 7x10⁶/g aerobic mesophiles, 5x10⁵/g Enterobacteriaceae, 10⁶/g yeast and 10⁴/g mold while the pH decreases to 4.6 (Wacher et al., 1993). Lactic acid bacteria, the predominant microbial flora of pozol include strains of Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus confusus, Lactococcus lactis and Lactococcus raffinolactis (Nuraida et al., 1995). 

The majority of microorganisms associated with maize kernels used in pozol preparation are destroyed by heat treatment during nixtamal production. Inoculation of the maize dough takes place during processing of the nixtamal, since sanitary measures are not taken by the people who prepare pozol. Lactic acid bacteria, Enterobacteriaceae, and aerobic mesophiles are introduced at the grinding step (Wacher et al., 1993) .

Geotrichum candidum, Trichosporon cutaneum and various species of Candida are always associated with pozol during the first few hours of fermentation. Yeasts associated with pozol include Candida krusei, Trichosporon cutaneum, Hansenula fabiani, Kluveromyces fragilis, Candida guillermondii, C. parapsilosis, C. tropicalis and S. cerevisiae (Ulloa et al., 1987). Molds such as Cladosporium clados-porioides or C. herbarum, Monilia sitophola, and Mucor rouxianus or M. recemosis are also common in pozol balls as their surface progressively dries and their pH in lowered. Other species of molds isolated from pozol include Alternaria tenuis, Aspergillus flavus, Aureobasidium pullulans, Cladosporium herbarum, Epicoccum sp., Fusarium sp., Paecilomyces fumosoroseus, Rhizopus stolonifer, Trichoderma viride, Penicillium claviforme, P. cyclopium, P. expansum, P. italicum, P. lanoso-viridae and Phialophora richardsiae (Ulloa et al., 1987).

Bacteria isolated from pozol include Bacillus cereus, Paracolobactrum aerogenoides, Agrobacterium azotophilum and Alkaligenes pozolis, Escherichia coli var. napolitana, Pseudomonas mexicana and Klebsiella pneumoniae (Ulloa et al., 1987). Two newly identified bacterial species: Agrobacterium azotophilum and Alkaligenes pozolis have also been isolated from pozol.

A.azotophilum, originally isolated from pozol fixes atmospheric nitrogen both aerobically and anaerobically, in maize dough. It also exhibits nitrogen-fixing capability in several culture media, soil by-products, wastes of the sugar industry, and other substrates. K. pneumoniae has also been observed to act as a nitrogen fixer in some pozol samples. In vitro studies on A. azotophilum revealed that it exhibited different degrees of antagonism toward many microorganisms. The chemical nature of the substance or substances which are antagonistic towards the growth of these microorganisms is not yet known. It is however believed that antifungal substances produced by A. azotophilum and/or other micro-organisms growing in pozol may prevent mould growth on pozol during the first few days of storage. Other factors such as the pH, moisture content, and temperature are presumably also important.

Flavor, Biochemical and Nutritional Changes During Pozol Fermentation- Two essential changes that occur in maize dough during pozol fermentation are the development of an acidic flavor and a characteristic aroma which impart the refreshing properties of the product on ingestion. The acidic pH (pH 5.7) of the maize kernels is elevated to 7.5 by treatment with lime water. The maize dough, which has an initial pH of 6.8, attains a pH of 3.9 on the eighth day of fermentation. Its moisture content remains around 30 percent.

Improvement in the nutritive value of pozol over that of maize kernels is important to pozol consumers. Pozol is richer in protein, niacin, riboflavin, lysine, tryptophane, and some other nutrients than maize; however, maize contains more thiamine and phosphorous than pozol. In addition, on the basis of its essential amino acid composition and growth-promoting efficiency in albino rats, the protein quality of pozol was found to be better than that of maize. The nitrogen content of pozol was determined to be higher than that of unfermented maize dough.

Crude and soluble protein were significantly higher in nixtamal than in cooked maize and protein/ash ratios increased in nixtimal but not always in cooked maize. These findings suggest that fermentation is influenced by modifications in the dough caused by nixtamalization. Further investigations are required to ascertain the precise reasons for these changes (Loaeza-Chávez and Wacher-Rodarte, 1993).

Pathogenic or potentially pathogenic species of fungi, such as Candida parapsilosis, C. tropicalis, and Phialophora richardsiae, have been isolated from pozol. It has been shown that if the maize kernels used in the preparation of pozol are contaminated with the aflatoxins produced by Aspergillus flavus, most of these aflatoxins are destroyed by treatment with lime water and heat. Remaining toxins however persist throughout dough fermentation. One advantage of fermenting maize dough is that it can be preserved without refrigeration under the tropical conditions in which it is routinely eaten, owing to its low pH. A primary advantage however is the improvement of the nutritional qualities of this maize product due to the development of certain bacteria, yeasts, and moulds.

Tesgüino is a slurry-like, alcoholic beverage prepared by fermentation of germinated maize or maize stalk juice. The term tesgüino or tejuino comes from the Aztec tecuin, meaning heartbeat (Robelo, 1948). Tarahumaras refer to tesgüino prepared from maize stalk juice as paciki and tesgüino prepared with the incorporation of the bark of certain species of Rubiaceae, as batari. The beverage is also referred to as sugiki. Tepehuanos in Mexico refer to tesgüino prepared from germinated maize as navaitai and that prepared from the juice of maize stalks as vougadi navaitai. Navaitai is generally preferred over vougadi navaitai.

Tesgüino is consumed by several ethnic groups of northern and northwestern Mexico. Yaquis and Pimas in Sonora, Tarahumaras in Chihuahua, Guarijíos in Chihuahua and Sonora, Tepehuanos in Durango, Huicholes in Jalisco and Nayarit and Zapotecos in Oaxaca all consume tesgüino. It is also consumed by the mestizo populations of the states of Sonora, Chihuahua, Sinaloa, Durango, Nayarit, Jalisco, and Oaxaca.

The beverage plays an important role in the everyday life of indigenous groups. It is the preferred beverage at any celebration, religious ritual, funeral, sporting game, or in the so-called tesgüinadas, which are some of the most important events in Tarahumara´s life. Tesgüino when diluted with water, is commonly drunk by babies and infants, and is also drunk at meals during family reunions. Tarahumaras, during their ball games, take a provision of tesgüino along with them and even drink it for strength prior to the games.

Tesgüino is consumed primarily as a refreshing beverage during hot weather by Mestizo populations. Tesgüino prepared by the Mestizos is of a relatively low alcoholic content and is not a basic dietary ingredient. The quantity of Tesgüino consumed and frequency of its consumption varies with the age and type of consumer, season, and occasion of consumption. Usual consumption ranges between 250 ml and several litres per day.

Tesgüino is generally prepared by the fermentation of germinated maize, maize stalk juice or prepared juice obtained from mashed leaves of Agave sp.

Methodologies used in the preparation of tesgüino vary among ethnic groups. The most common method for preparing tesgüino is summarised in Figure 2. About 10 kg of dry maize kernels are soaked in water for several days, drained, and placed either in baskets in the dark or in a hole in the gound in order to allow them to germinate. The germinating kernels are protected from light, in order to prevent the formation of green and bitter sprouts. The germinated kernels are ground in a manual metal or stone mill and then boiled in water until the mixture turns yellow (about 8 h). The liquid portion is then transferred to a clay pot, and catalysts are added. The most common catalysts in the vicinity of Cannon Urique in Chihuahua are bark (batari) or kakwara (Randia echinocarpa, R. watsoni, and R. laevigata) and kaya (Coutarea pterosperma), which are chopped, ground, and boiled for many hours prior to being added to the tesgüino.

At higher altitudes where pine trees grow, the catalysts used are leaves of roninowa (Stevia serrata), rojisuwi (Chimaphila maculata), and ubitakuwari (Datura meteloides); stems of basiawi (Bromus arizonicus), roots of gotoko, otoko, or goto (Phaseolus metcalfei and Plumbago scandens); rawici kitakame or "mouse´s ear" (Hieracium fendleri); and two unidentified plants, one of the Graminea species, and the other a legume, gotoborisi. The mixture is allowed to ferment for several days prior to consumption (Taboada et al., 1977 in Steinkraus, 1996). 

In order to prepare tesgüino from maize stalks, the raw material either fresh or dry is macerated by pounding with a club, in the depression of a rock. The macerated material is then placed on a sieve made out of awaka (Salix bonplandiana) or baka (Arundo donax or Phragmites communis). Water is slowly poured over the macerated stems and juice is collected in a hollow pumpkin. The juice is mixed with water and boiled for several hours prior to the addition of catalysts. The mixture is allowed to ferment in a dark place for 2 to 3 days, until it develops a pleasant appearance and flavor before it is consumed.

The juice obtained from Laphophora williamsii (the hallucinogenic peyote), known as jukuri, or from Ariocarpus fissuratus, is sometimes added to the tesgüino in the Conchos river region of Mexico. The juice of peyote is not considered a catalyst but an additive that makes the ingestion of tesgüino more pleasant to consumers.

Several bacteria, yeasts and molds have been isolated from tesgüino. These include Lactobacillus, Streptococcus, Leuconostoc, Pediococcus, Saccharomyces, Candida, Cryptococcus, Hansenula, Brettanomyces, Pichia, Geotrichum and Penicillium (Ulloa et al., 1987).

S. cerevisiae is an important microorganism in the alcoholic fermentation of tesgüino. It has been isolated from samples of tesgüino obtained from different localities. The yeast inoculum is maintained on surfaces of the utensils and clay pots, which are used exclusively for the preparation of tesgüino. Bacillus megaterium has also been isolated from several samples of maize tesgüino and appears to be constant in the microflora of tesgüino. Since there are no standards for the preparation of tesgüino, the microflora of tesgüino varies according to the manufacturer, and the substrates and catalysts utilized in its preparation.

Microorganisms initially detected in the gruel after cooking, filtering, and cooling are of homo- and hetero-lactic bacteria genera (Lactobacillus, Leuconostoc, Pediococcus, and Streptococcus) and increase throughout the fermentation. These organisms produce the lactic and acetic acids which give tesgüino some of its distinctively refreshing, acidic, slightly, acrid, flavor. Abundant yeast species consistently identified at various stages of the fermentation are alcohol producers, and include: Candida guilliermondii, Hansenula anomala, S. cerevisiae, and S. kluyveri. S. cerevisiae, and S. kluyveri. Other yeasts produce oxidative esters which contribute to turbidity, aroma, and flavor. Thus tesgüino production is a lactic-alcoholic fermentation followed by an alcoholic-acetic acid fermentation. Of the yeasts isolated from tesgüino, Brettanomyces intermedius, H. anomala, and S. cerevisiae were also identified in the clay pots used for fermentation and these serve as an inoculum.

Acetylene reduction detected in samples of tesgüino from the Tarahumara region, indicates the presence of nitrogen-fixing microorganisms. Such organisms have not however been isolated from tesgüino.

Fermentation catalysts may serve as sources of vitamins, enzymes or other growth factors. Basiawi (Bromus arizonicus), for example, supplied survival factors to a gram-negative strain isolated from tesgüino, significantly favoured the stationary phase of the organism, and accounted for the increment of the specific growth rate of a Lactobacillus strain, being a source of minerals or non-thermosensitive growth factors. It did not have any effect on a yeast strain (Escamilla-Hurtado et al., 1993). Florets of this catalyst were also identified as a source of Candida guilliermondii.

Compositionally, tesgüino contains 73.9 % moisture, 2 % protein, 0.21 % crude fiber, 2.5 mg/100 g iron, 0.03 mg/100 g thiamine, 0.03 mg/100 g riboflavin, and 0.29 mg/100 g niacin.

During tesgüino fermentation, protein content increased by 58% and lactic acid, acetic acid, and ethanol concentrations were 0.41, 0.11, and 3.73%, respectively. At the end of the process total protein concentration approached 13.2 per cent (Wacher-Rodarte, 1995).

Atole is a sour porridge-type product prepared from maize by members of the Tzotzil ethnic group in Southern Mexico. It is produced by steeping maize grains in water for 4 days, milling and allowing to stand for 1 day.

During atole production, lactic acid fermentation commences during steeping and continues in the milled product (Escamilla-Hurtado et al., 1993). Lactic acid bacteria present in the atole form diacetyl, which contributes to the characteristic sensory properties of the product. 

This review was begun with the expectation of finding several references to research projects and results obtained in Latin American laboratories working on traditional cereal fermentations. It was however surprising to find that over the past 15 years relatively little experimental work has been conducted in this field. Furthermore, over the past five years, there has been practically no published data on the subject. There is however a need to study in greater detail, the physicochemical and functional changes that occur during the fermentation of cereals in order to improve the methodologies used in their production.

The reasons for the loss of interest in the development of cereal fermentations in Latin America are unclear, since cereal products are still produced and consumed by several million people living the region. 

References

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Cavero, R. (1986). "Maiz, chicha y religiosidad andina". Universidad Nacional de San Cristobal de Humanga, Ayacucho, Peru, 195 p.

Christen, P., Villegas, E. and S. Revah (1994). Growth and aroma production by Ceratocystis fimbriata in various fermentation media. Biotechnol. Lett. 16, 1183-1188.

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Escamilla-Hurtado, M.L., Prado-Barragán, L.A., López-Baca, A. and J.R. Velázquez-Corona (1993). "The effect of basiawi (Bromus arizonicus) on axenic cultures of strains isolated from tesguino". In "Alimentos Fermentados Indígenas de México". M.C. Wacher and P. Lappe (comp.). Universidad Nacional Autónoma de México, Mexico City, pp. 87-91.

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Nuraida, L., Wacher, M.C. and J.D. Owens (1995). Microbiology of pozol, a Mexican fermented maize dough. World J. Microbiol. Biotechnol. 11, 567-571.

Sobrinho, I.L., García, J.A., Coelho da Silva, J.F., Campos, J. and A.C.G. Castro (1981). The effect of heating, fermentation and grinding of sorghum and maize on in vitro protein digestibility. Revista da Sociedade Brasileira de Zootecnia 10, 275-294.

Steinkraus, K.H. (1996). "Handbook of Indigenous Fermented Foods". 2nd edition, Marcel Dekker, New York.

Ulloa, M., Herrera, T. and P. Lappe (1987). Fermentaciones tradicionales indígenas de México. Serie de Investigaciones Sociales, No. 16. Instituto Nacional Indigenista, Mexico City, pp. 13-20.

Van Veen, A.G., Graham, D.C:W. and K.H. Steinkraus (1968). Fermented rice, a food from Ecuador. Arh. Latinoamer. Nutr. 18, 363.

Wacher, C., Cañas, A., Cook, P.E., Bárzana, E. and J.D. Owens (1993). Sources of microorganisms in pozol, a traditional Mexican fermented maize dough. World Journal of Microbiology and Biotechnology 9, 269-274.

Wacher-Rodarte, C. (1995). "Alimentos y bebidas fermentados tradicionales". In "Biotecnología Alimentaria". García-Garibay, M., Quintero, R.and A. López-Munguía (coord.). Limusa, Mexico. pp. 313-349. 

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