A

SEMINAR REPORT

ON

“FERMENTED CEREAL PRODUCTS”

DEPARTMENT OF FOOD TECHNOLOGY

INSTITUTE OF ENGINEERING & TECHNOLOGY Bundelkhand University, Jhansi

Submitted to: Submitted By :

Dr. Shubhangi Nigam Pratyush Maurya

Co-ordinator 08237033

Dept. of Food Technology (6th Semester)

I.E.T., B.U. , Jhansi

Certificate

This is to certify that the Seminar entitled “Fermented Cereal Products” has been submitted by Pratyush maurya for the partial fulfillment of the degree of Bachelor of Technology in Food Technology / Institute of Engineering & Technology, Bundelkhand University, Jhansi. during the academic year 2010-2011 (6th Semester) .

Date:-16/05/2011 Dr. Shubhangi Nigam

Co-ordinator Department of Food Technology I.E.T. B.U. JHANSI 284128

ACKNOWLEDGEMENT

Whenever a module of work is completed successfully, a source of inspiration and guidance is always there for the students. I hereby take

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the opportunity to thank Dr. Shubhangi Nigam and all Food Technology. Dept. faculty members who helped us in developing this seminar report.

First and foremost, I am grateful to the management of Instt. Of Engg. & Tech. Bundelkhand University, Jhansi for providing me the opportunity to undertake 6th semester semester seminar report in the organization.

After completion of this report, it gives me great pleasure to express my gratitude and heartfelt to all went along the way in completing this report. There are several people who deserve more than a written acknowledgment of exemplary help.

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Table of Contents

Topics Page no. 

1. Introduction--------------------------------------------------------------042. Introduction of Cereals------------------------------------------------053. Introduction of Fermentation-----------------------------------------104. Fermented Cereals------------------------------------------------------115. Importance and Benefits of Fermented Cereals--------------------146. Fermentation Starter----------------------------------------------------157. Fermented Cereals Products in the Various Countries------------17

Pozol-------------------------------------------------------------17Mawe-------------------------------------------------------------18 Injera-------------------------------------------------------------20

8. Fermented Cereal Products In The Asia Pacific Region----------22 Alcoholic Food and Beverages---------------------------------------------22

Vinegar---------------------------------------------------------------------------24 Bread-----------------------------------------------------------------------------28

9. Conclusion---------------------------------------------------------------3110. References------------------------------------------------------------32

            

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INTRODUCTION

Cereal grains are the fruit of plants belonging to the grass family (Gramineae). Cereal crops are energy dense, containing 10 000-15 000 kJ/Kg, about 10-20 times more energy than most succulent fruits and vegetables. Nutritionally, they are important sources of dietary protein, carbohydrates, the B complex of vitamins, vitamin E, iron, trace minerals, and fiber. It has been estimated that global cereal consumption directly provides about 50 percent of protein and energy necessary for the human diet, with cereals providing an additional 25 percent of protein and energy via livestock intermediaries. Some cereals, notably wheat, contain proteins that form gluten, which is essential for making leavened bread. Although dried cereal grains constitute living cells that respire, when kept in an appropriate environment, whole grains can be stored for many years. In 1996, world cereal production amounted to more than two billion metric tons. Major cereal crops produced worldwide include wheat, rice, maize and barley. Other major cereal crops produced include sorghum, oats, millet and rye. Asia, America, and Europe produce more than 80 percent of the world’s cereal grains. Wheat, rice, sorghum, and millet are produced in large quantities in Asia; corn and sorghum are principal crops in America, and barley, oats and rye are major crops in the former USSR and Europe.

Cereals have a variety of uses as food. Only two cereals, wheat and rye, are suited to the preparation of leavened bread. The most general usage of cereals is in cooking, either directly in the form of grain, flour, starch, or as semolina, etc. Another common usage of cereals is in the preparation of alcoholic drinks such as whiskey and beer (barley; sorghum), vodka (wheat), American bourbon (rye), Japanese sake (rice), etc. A variety of unique, indigenous fermented foods, other than leavened breads and alcoholic beverages, are also produced in regions of the

world that rely mainly on plant sources of protein and calories. In developed countries, that obtain most of their protein from animal products, cereals are increasingly used as animal feed. More than 70 percent of the cereal crop produced in developed countries is fed to livestock; whereas, in developing countries, 68-98 percent of the cereal crop is used for human consumption.

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INTRODUCTION OF CEREALS

Cereals, grains, or cereal grains are grasses (members of the monocot families Gramineae) cultivated for the edible components of their fruit seeds (botanically, a type of fruit called a caryopsis): the endosperm, germ, and bran. Cereal grains are grown in greater quantities and provide more food energy worldwide than any other type of crop; they are therefore staple crops. In their natural form (as in whole grain), they are a rich source of vitamins, minerals, carbohydrates, fats, oils, and protein. However, when refined by the removal of the bran and germ, the remaining endosperm is mostly carbohydrate and lacks the majority of the other nutrients. In some developing nations, grain in the form of rice, wheat, millet, or maize constitutes a majority of daily sustenance. In developed nations, cereal consumption is moderate and varied but still substantial.

Wheat

One of the oldest of all cultivated plants. Today, there are more than 50000 cultivars of wheat in existence and as a result wheat can be grown in a relatively wide range of climatic conditions. Growing best in temperate climates, it is susceptible to disease in warm, humid regions and cannot be grown as far from the equator as can rye and oats. Different types of wheat are classified based on planting season and endosperm composition. Wheat holds a special place amongst the cereals because upon mixing wheat flour with water, an elastic matrix called "gluten" required for the production of leavened breads is formed. "Hard wheats" tend to contain relatively high levels of starch and relatively low levels of protein, while the reverse is true for "soft wheats". High protein flours are best suited for pastas and breads, while flour from soft wheats is excellent for cakes and pastries, etc.

Rice

The second most abundant cereal crop originated in the Indian subcontinent and Africa. Today, 90 percent of the world rice crop is grown in Asia. Growing rice requires more water than other cereal crops, although rice is a highly productive crop. There are several thousand rice cultivars which may differ in color, aroma and grain size. The main commercial distinction between rice types is the grain size, i.e. long, medium and short. Long grain rice, also called "Indian", tends to separate relatively easily on cooking and is dry and flakey. Unlike wheat, rice is most often consumed as grain rather than as a flour. Different grades of milling include brown rice (hull removed), unpolished rice (hull, bran and most of germ removed), and

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polished rice (aleurone layer removed from unpolished rice). Since polishing removes most of the lipid, the latter product is relatively stable during storage. The discovery that rice bran can alleviate beriberi led to the discovery of the vitamin thiamine. The traditional technique of parboiling rice in India and Pakistan (also called "converted rice") prior to milling improves the nutritional quality of the grain by allowing the B vitamins in the bran and germ to diffuse into the endosperm.

Maize

Corn was originally cultivated in Central America and became the staple of many countries. Different types of maize are classified on the basis of their protein content and the hardness of the kernel. These include pop, flint, flour, Indian and sweet corns. Much of the niacin in corn is in a bound form and this led to pellagra in areas where corn became the food staple.

Millet and Sorghum

Millet and sorghum are often grouped together because their growing conditions, processing and uses are similar. Millets are native to Africa or Asia and have been cultivated for more than 6 000 years. Millets grow well in arid regions with poor soils and are valued for their relatively high protein content among the cereals. Sorghum originated in East Africa and today is an important food crop in Africa, Asia, India and China where it is made into porridge, unleavened bread ("roti" in India) and beer.

Barley

In the United States, barley is mostly used for feed, brewing and alcohol production with only about 2 percent used for human food. Barley flour is produced by abrasion dehulling, followed by milling of the "pearled" barley.

Rye

Rye appears to have originated in central Asia around 4000 BC. Rye flour has a relatively low gluten content compared to wheat flour, but contains a unique class of carbohydrates that facilitate bread making. The milling of rye yields a flour that is classified based on color or ash content.

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RICE WHEAT

RYE MAIIZE

Figure 1

MAJOR CHEMICAL COMPONENTS OF CEREAL GRAINS

Compositionally, cereals consist of 12-14 percent water, 65-75 percent carbohydrates, 2-6 percent lipids and 7-12 percent protein. Cereals are quite similar in gross composition being low in protein and high in carbohydrates. Oats and maize however contain relatively large amounts of lipids. The lipid content of maize ranges between 0.4 percent and 17 percent, most of which are triacylglycerides. The chemical components of cereals are not uniformly distributed in the grain. Hulls and bran are high in cellulose, and ash. The aleurone layer of wheat contains 25 times more minerals than the endosperm; whereas the lipids are generally concentrated in the aleurone and germ. The endosperm, which contains mostly starch, has a lower protein content than the germ and the bran, and is low in fat and ash.

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NUTRITIONAL QUALITY OF CEREALS

Cereals, together with oil seeds and legumes, supply a majority of the dietary protein, calories, vitamins, and minerals to the bulk of populations in developing nations. Some components of cereal nutritive value are summarized in Table 1. Cereal grains are low in total protein compared to legumes and oilseeds. Lysine is the first limiting essential amino acid for man; although rice, oats and barley contain more lysine than other cereals. Corn protein is also limiting in the essential amino acid tryptophan.

Table 1. Comparative nutritive value of cereal grains

FACTOR Wheat Maize Brownrice

Barley Sorghum Oat Pearl millet

Rye

Available CHO (%) 69.7 63.6 64.3 55.8 62.9 62.9 63.4 71.8

Energy (kJ/100 g) 1570 1660 1610 1630 1610 1640 1650 1570

Digestible energy (%) 86.4 87.2 96.3 81.0 79.9 70.6 87.2 85.0

Vitamins (mg/100 g)

Thiamin 0.45 0.32 0.29 0.10 0.33 0.60 0.63 0.66

Riboflavin 0.10 0.10 0.04 0.04 0.13 0.14 0.33 0.25

Niacin 3.7 1.9 4.0 2.7 3.4 1.3 2.0 1.3

Amino acids (g/16 g N)

Lysine 2.3 2.5 3.8 3.2 2.7 4.0 2.7 3.7

Threonine 2.8 3.2 3.6 2.9 3.3 3.6 3.2 3.3

Tryptophan 1.0 0.6 1.1 1.7 1.0 0.9 1.3 1.0

Protein quality (%)

True digestibility 96.0 95.0 99.7 88.0 84.8 84.1 93.0 77.0

Biological value 55.0 61.0 74.0 70.0 59.2 70.4 60.0 77.7

Net protein utilil. 53.0 58.0 73.8 62.0 50.0 59.1 56.0 59.0

ANTINUTRIENTS AND TOXIC COMPONENTS IN CEREALS

Cereals and other plant foods may contain significant amounts of toxic or antinutritional substances. In this regard, legumes are a particularly rich source of natural toxicants including protease inhibitors, amylase inhibitors, metal chelates, tannins. Most cereals contain appreciable amounts of phytates, enzyme inhibitors, and some cereals like sorghum and millet contain large amounts of polyphenols and

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tannins. Some of these substances reduce the nutritional value of foods by interfering with mineral bioavailability, and digestibility of proteins and carbohydrates.

Enzyme Inhibitors

Protease and amylase inhibitors are widely occurent in seed tissues including cereal grains. Trypsin-, chymotrypsin-, and cysteine-protease inhibitors are present in rice. Although these inhibitors tend to be heat stable, there are numerous reports that trypsin inhibitor, chymotrypsin inhibitor, and amylase inhibitor levels are reduced during fermentation.

INTRODUCTION OF FERMENTATION

Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. A more restricted definition of fermentation is the chemical conversion of sugars into ethanol.

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Fermentation has been used for several thousand years as an effective and low cost means to preserve the quality and safety of foods. Fermentation is the oldest known form of food biotechnology. Food fermentations involve mixed cultures of microorganisms that grow simultaneously or in succession. According to Steinkraus (1995), the traditional fermented foods contain high nutritive value and developed a diversity of flavours, aromas, and textures in food substrates. Food fermentations is important in developing countries where the lack of resources limits the use of techniques such as vitamin enrichment of foods, and the use of energy and capital intensive processes for food preservation. Some important indigenous fermented foods of India are Bhallae (Black gram Product), Bhatura ( White wheat flour Product), Dhokla (Bengal gram Product), Dosa (Rice and Black gram product), Idli ( Rice and Black gram product), Jalebie ( White wheat flour Product). India and Bangladesh are known for its own traditional fermented foods like Dadhi (Yoghurt).

Uses

The primary benefit of fermentation is the conversion of sugars and other carbohydrates, e.g., converting juice into wine, grains into beer, carbohydrates into carbon dioxide to leaven bread, and sugars in vegetables into preservative organic acids.

Enrichment of the diet through development of a diversity of flavors, aromas, and textures in food substrates

Preservation of substantial amounts of food through lactic acid, alcohol, acetic acid and alkaline fermentations

Biological enrichment of food substrates with protein, essential amino acids, essential fatty acids, and vitamins.

FERMENTED CEREALS

Animal or plant tissues subjected to the action of microorganisms and/or enzymes to give desirable biochemical changes and significant modification of food quality are referred to as fermented foods. Aside from alcoholic fermentations and the production of yogurt and leavened bread, food fermentations continue to be important primarily in developing countries where the lack of resources limits the

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use of techniques such as vitamin enrichment of foods, and the use of energy and capital intensive processes for food preservation. The technology of producing many indigenous fermented foods from cereals remains a household art in these countries. Prospects for applying advanced technologies to indigenous fermented foods and for the production of value-added additive products, such as colors, flavors, enzymes, antimicrobials, and health products during food fermentations have been reviewed.

Indigenous Fermented Cereal Foods

Most bacterial fermentations produce lactic acids; while yeast fermentation results in alcohol production. Many of the indigenous fermentation products of cereals are valued for the taste and aroma active components produced and are used as seasonings and condiments. A number of fermented products utilize cereals in combination with legumes, thus improving the overall protein quality of the fermented product. Cereals are deficient in lysine, but are rich in cystine and methionine. Legumes on the other hand are rich in lysine but deficient in sulfur containing amino acids. Thus, by combining cereals with legumes, the overall protein quality is improved. The Chinese concept of "fan" (rice) and "tsai"(other vegetables) for a balanced and interesting diet is seen throughout the world.

Among cereal-based foods, beer and bread are the main fermented products. In making beer and bread, alcoholic fermentation by yeast is the main type of fermentation; the yeast as live organisms are removed or killed in the final process. Lactic acid fermentation also occurs in many bread-making processes and in some beers, and the fermentation may result in beneficial modification of the cereal substrate. In some other cereal processes, the lactic acid bacteria survive and live lactic acid bacteria are ingested with the cereal food. Currently it is not known if the various and undefined lactic acid bacteria present in traditional fermented cereal products have any probiotic effects, although this question could be raised on the basis of some reports available on fermented maize, sorghum, and millet. The particular nutritional properties of oats as a potential functional food have created an interest in finding new food uses for oats, including fermented products. Work done in Finland and Sweden, the two major oat-producing and -exporting countries in Europe, has resulted in a new generation of oat products in the nondairy yogurt and beverage category. Defined probiotic strains have been used in the fermentation of oat-based cereal foods. Oat-based products also offer an alternative to soy-based fermented nondairy yogurts.

CEREAL AS A SUBSTRATE

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Cereals are, in general, a good medium for microbial fermentations. They contain a high level of carbohydrates, which can be used as a source of carbon and energy by microbes in fermentation. Most of the carbohydrate in cereals is present as starch and only available for microbes after amylolytic hydrolysis. The level of free sugars in fully matured sound grains is relatively low, but the 2–5% free sugars supports the initiation of the fermentation process. The content of free sugars in rye is higher than in other cereals, whereas in oats there are only 1–2% free sugars. Endogenous cereal enzymes, added malt, or selected enzymes can be used to break down the starch to simple fermentable sugars (i.e., maltose and glucose). There are also strains of amylolytic microbes, molds in particular, which produce amylases efficiently and can be used for the liquefaction and hydrolysis of starch, such as Aspergillus strains in the sake process. Lactic acid bacteria that are capable of breaking down and utilizing starch are also known. Besides carbohydrates, cereals also contain relatively high levels of minerals, vitamins, sterols, and other growth factors, which support growth of microbes, including the fastidious lactic acid bacteria.

TECHNOLOGIES AND EXAMPLES OF CEREAL-BASED FUNCTIONAL FOODS

Several technologies are available for manufacturing functional foods. The ILSI definition refers to elimination or replacement of constituents with a negative contribution to nutritional value, or addition of positive components, or balancing the nutritional composition of the product. Table 2 lists some available techniques for making cereal based functional foods. The nutritionally valuable components present in various cereal grains and their suitability for fermentation raise expectations about fermented cereal-based functional foods. However, only few such products have appeared on the market so far. Many possibilities for future development exist, some examples of which are listed below. Folate content of bread is increased by fermentation of bread dough by yeast. Developing this technique might be of great importance because today a substantial part of the population does not meet the average recommended folate intake. Phytate (myo-inositol hexaphosphate) constitutes 1–2%of cereal grains. It acts as the mineral and phosphor reserve of the seedling but is not hydrolyzed by the human digestive system. Although some recent studies suggest phytate to be a beneficial component, an improved bioavailability of minerals like zinc and magnesium would be desirable in strict vegetarian diets that are low in protein. Lactic acid fermentation in sourdough systems and indigenous fermented cereal foods will help in degradation of phytate. Glycemia and insulinemia can be reduced by the lactic acid formed in wheat sourdough, according to a recent finding. The mechanism is not fully clarified but it is anticipated that the rate of starch digestion is reduced because of increased gluten–starch interactions.

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Table 2 Examples of Cereal-Based and Cereal-Related Foods Containing Live Probiotic Bacteria

Product Preparation method and type of product

Bacteria used

Togwa Sorghum or maize cooked in water, cooled, addition of starter, fermentation. Traditional weaning food, beverage after dilution

Dominated by Lactobacillus plantarum, also L. brevis, Strains from local starters.

Fermented oatmeal soup for enteral feeding

Oatmeal cooked with malted barley flour, cooled, addition of starter, fermentation. Designed for enteral feeding

Probiotic Lactobacillus strains.

Fermented fruit drink with oatmeal

Oatmeal and water-heated, cooled, fermented, cooled and mixed with flavored fruit drink. Snack-type nondairy beverage

Lactobacillus plantarum

Oat bran vellie Oat bran and water cooked, cooled, fermented, cooled and flavored with fruit, berries. Yogurt-type nondairy snack

Lactobacillus acidophilus

Importance and Benefits of Fermented Cereals

Fermented foods contribute to about one-third of the diet worldwide. Cereals are particularly important substrates for fermented foods in all parts of the world and are staples in the Indian subcontinent, in Asia, and in Africa. Fermentation causes changes in food quality indices including texture, flavor, appearance, nutrition and safety. The benefits of fermentation may include improvement in palatability and acceptability by developing improved flavours and textures;

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preservation through formation of acidulants, alcohol, and antibacterial compounds; enrichment of nutritive content by microbial synthesis of essential nutrients and improving digestibility of protein and carbohydrates; removal of antinutrients, natural toxicants and mycotoxins; and decreased cooking times.

The content and quality of cereal proteins may be improved by fermentation. Natural fermentation of cereals increases their relative nutritive value and available lysine. Bacterial fermentations involving proteolytic activity are expected to increase the biological availability of essential amino acids more so than yeast fermentations which mainly degrade carbohydrates. Starch and fiber tend to decrease during fermentation of cereals. Although it would not be expected that fermentation would alter the mineral content of the product, the hydrolysis of chelating agents such as phytic acid during fermentation, improves the bioavailability of minerals. Changes in the vitamin content of cereals with fermentation vary according to the fermentation process, and the raw material used in the fermentation. B group vitamins generally show an increase on fermentation. During the fermentation of maize or kaffircorn in the preparation of kaffir beer, thiamine levels are virtually unchanged, but riboflavin and niacin contents almost double.

Reddy and Pierson (1994), reviewed the effect of fermentation on antinutritional and toxic components in plant foods. Fermentation of corn meal and soybean-corn meal blends lowers flatus producing carbohydrates, trypsin inhibitor and phytates. Fungal and lactic acid fermentations have also been reported to reduce aflatoxin B1, sometimes by opening of the lactone ring which results in complete detoxification.

Another benefit of fermentation of cereals is that frequently the product does not require cooking or the heating time required for preparation is greatly reduced.

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Fermentation starter

Fermentation starters (called simply starters within the corresponding context) are preparations to assist the beginning of the fermentation process in preparation of various foods and fermented drinks. A starter culture is a microbiological culture which actually performs fermentation. These starters usually consist of a cultivation medium, such as grains, seeds, or nutrient liquids that have been well colonized by the microorganisms used for the fermentation.

Table 3. Fermentation starters used in different Asian countries

Country Name Ingredients

China Chu Wheat, barley, millet, rice (whole grain, grits or flour)

Korea Nuruk Wheat,rice, barley(whole grain, grits or flour)

Japan Koji wheat, rice(whole grain, grits or flour)

India Marchaa rice

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Flowchart of traditional method of Nuruk (Korea) production

Whole wheat flour

Add water to 30-40 %

Wrap in a cloth and press in a molder

to make cakes (5 cm thick, 10-30 cm dia)

Incubate 10 days at 30-45 0C

Incubate 7 days at 35-40 0C

Dry 2 weeks at 30 0C

Age 1-2 months at room temperature

Nuruk (Korea)

Figure 2

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FERMENTED CEREAL PRODUCTS IN THE VARIOUS COUNTRIES

1. Pozol

Pozol 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 Latin Americans. 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. People utilize pozol mixed with water and honey to reduce, according to them, the fever of the sick. Pozol is also consumed for the control of diarrhea.

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 , are boiled for 1 h in a pot containing 1 to 2 liters of an approximately 10 per cent 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.

Microbiology

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

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mesophiles, 5x105/g Enterobacteriaceae, 106/g yeast and 104/g mold while the pH decreases to 4.6.

Flow chart for the preparation of Pozol

Corn

Boil in water containing calcium hydroxide (this process is known as nixtimalization)

Grind to obtain a dough

Shape dough into balls and envelope with banana leaves

Allow to ferment for 1-14 days

POZOL

Figure 3

2. Mawe

Mawe is a sour dough prepared from partially dehulled maize meal which has undergone natural fermentation for a one to three-day period. Mawe is prepared in African counties.

Production

Mawe is produced using both a traditional (home) process and a commercial process. In the commercial process which takes place entirely in a milling shop, the grits are washed by rubbing in water, following which the germ and remaining hulls

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are floated off and discarded along with the water. The sedimented endosperm grits are subsequently blended with the fine endosperm fraction.

Microbiology

Dominant microorganisms in mawe preparation include lactic acid bacteria (mainly Lactobacillus fermentum and its biotype L. cellobiosis, L. brevis) and yeasts.

Flow chart for the production of mawe

Maize grains

Clean and wash

Crush

Screen and dehull

Soak and wash; discard hull, and germ

Drain

Add water and allow to stand for 2-4 h

Grind

Add water and knead to form a dough

Ferment for 1-3 days

MAWE

Figure 4

3. Injera19

Injera is the most popular baked product in Ethiopia and other African countries. It is a fermented sorghum bread with a very sour taste and is the undisputed national bread of Ethiopia. According to a report, over 8% of total sorghum production in Ethiopia is used for ‘injera production.

Production

The sorghum grains are dehulled manually or mechanically and milled to flour which is subsequently used in the preparation of injera. On the basis of production procedures three types of injera are distiguishable: (i) thin injera which results from mixing a portion of fermented sorghum paste with three parts of water and boiling to yield a product known as ‘absit’’ which is, in turn, mixed with a portion of the original fermented flour (ii) thick injera, which is reddish in color with a sweet taste, is a ‘tef’ paste that has undergone only minimal fermentation for 12-24 hours; (iii) komtata-type injera, which is produced from over-fermented paste, and has a sour taste. The paste is baked or grilled to give a bread-like product.

Microbiology

Yeasts are the major microorganisms involved in the fermentation of the sweet type of injera.

Flow chart for the preparation of injera

Sorghum flour

Mix with water, 4:1 w/v

Knead to form a dough

Mix with starter(Fermented yellowish liquid saved from previously fermented dough)

Knead

Add water

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Ferment for 48 h

Add water and allow to stand for 1 h

Bake on hotgreased clay griddle metal till holes begin to form on top

INJERA

Figure 5

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FERMENTD CEREAL PRODUCTS IN THE ASIA-PACIFIC REGION

Indigenous fermented foods may be classified according to a number of different criteria. They may be classified in accordance with the raw materials used, the major type of fermentation taking place, the usage of the product, and the district of production. In general, fermented products are classified according to usage of the products and the major fermentation process taking place; e.g. alcoholic foods and beverages, vinegars, breads. The type of cereals used in the fermentation process and the regional variation of the fermentation form the sub-classes of each category.

Alcoholic Food and Beverages

The most important fermentation products of cereals in the Asia-Pacific region are acids and alcohols, which are both flavor compounds and food preservatives. Alcohol fermentation is more important than acid fermentation in this region in terms of the relative amounts of cereals used for fermentation and the varieties of the products produced. Alcoholic fermentation of cereals also involves acid fermentation, which prevents the growth of spoilage and pathogenic microorganisms at the initial stage of the fermentation, but causes quality deterioration during storage.

The process of cereal alcohol fermentation using mould starters was well established in the year of 1000 BC, and 43 different types of cereal wines and beers were described with detailed processing procedures in Chi-Min -Yao-Su. Millet appeared to be the main ingredient for alcohol fermentation. Among the 43 product types described, 16 were prepared from millet, 11 from rice and 12 from Indian millet. The dried and powdered starter was mixed with water and steamed grains, and fermented for 2-3 weeks or up to 5-7 months depending on the brewing method. Multiple brews prepared by adding newly cooked grains to the fermenting mash for 2, 3, 4 and up to nine times were described.

The incubation period for each step of the brewing process varies from 2 days to one month depending on the fermentation temperature. Low temperatures (ca. 10oC) are better for improving taste and keeping quality of the wine. Wines are traditionally prepared in late autumn or early spring, when ambient temperatures

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are below 10oC in the Far Eastern region. The volume of wine produced is approximately the same as that of raw grain used.

Flow chart for the production of rice-wine in Korea

Polished rice powder (4 parts)

Wheat flour (1/2 parts)

Water (8 parts)

Boil to make gruel and cool

Add nuruk powder (1 part)

Ferment for 12 days (mother brew)

Add 12 parts of cooked rice cake

Ferment for 12 days (2nd brew)

Add 16 parts of steamed rice

Ferment for 12 days (3rd brew)

Put into a sack and press

Remove clear liquid and discard filter

cake

Sam-hai-ju (Korean Rice Wine)

Figure 6

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Beer is the world's most widely consumed and probably oldest of alcoholic beverages; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from cereal grains—most commonly malted barley, although wheat, maize (corn), and rice are widely used. Most beer is flavoured with hops, which add bitterness and act as a natural preservative, though other flavourings such as herbs or fruit may occasionally be included.

Cereal beers are produced at a higher fermentation temperature, (ca. 20oC) than are cereal wine, and are usually prepared by either single or double brewing. The fermentation starter powder is mixed with cooked cereals incubated at approximately 20oC for 2-3 days, following which it is filtered through a fine mesh, sieve or cloth. Cereal-beers are abundant in micro-nutrients, such as the B vitamins which are formed during the fermentation. Takju contains 7% alcohol.

Flow chart for the processing of takju

Polished Rice ( 4 parts)

Wash and steep

Steam

Mix with 1 part powdered nuruk

and 10 parts water in an earthen jar

Ferment for 2-3 days

Sieve

Takju ( Korean Rice Beer)

Figure 7

Vinegar

Vinegar is an acidic liquid produced from the fermentation of ethanol in a process that yields its key ingredient, acetic acid (ethanoic acid). It also may come in a diluted form. The pH of table vinegar ranges from 2.4 to 3.4 (higher if diluted). The

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acetic acid concentration typically ranges from 4% to 8% by volume for table vinegar and up to 18% for pickling vinegar. Natural vinegars also contain small amounts of tartaric acid, citric acid, and other acids. Vinegar production is as ancient as is alcoholic fermentation, since acetic acid is produced in any natural alcoholic fermentation upon exposure to the air. In the Asia-Pacific region, vinegar prepared from cereal alcoholic fermentations is widely used in Northeastern Regions, while vinegars from tropical fruits, such as coconut, sugar cane and pineapple, are prepared in Southeastern countries. Cereal vinegars may be divided into three classes: rice vinegar, rice-wine filtercake vinegar and malt vinegar. Indigenous processes for the preparation of vinegars are natural or spontaneous fermentations brought about by the growth of Acetobacter on alcoholic substrates under aerobic conditions. Traditionally, degraded or poor quality rice-wines were used for the production of low-grade vinegars at the household level. Today, vinegars of high quality standards are produced by industry.

Rice vinegar is prepared from polished, unpolished or broken rice. The fermentation starter, chu, nuruk or koji prepared from rice, is used for saccharification and alcohol fermentation as in the preparation of rice-wine. Slightly greater amounts of nuruk (ca. 30% of steamed rice) than are used in the preparation of rice wine are added to steamed rice, following which water is added (2-3 parts water : 1 part raw rice). Fresh vinegar containing the appropriate organism is added to the fermented mash at a level of 8-20% of the weight of raw rice, and incubated at 30-35oC for 1-3 months. An additional storage period of 2-3 months is required for production of a high quality aged product.

Commercial vinegar is prepared from rice-wine filtercake in the Far-eastern countries. Filter cakes from rice-wine factories are collected and tightly packed into a storage tank for a 1-2 year period. The filtercake contains large amount of unused carbohydrates and proteins, which are further hydrolyzed by inherent microorganisms and enzymes during storage, converting them into alcohol and other nutrients and flavor substances. The cake is slurried in two to three volumes of water prior to filtration. The filtrate is fermented with Acetobacter to produce filtercake vinegar. Figure 11 shows the industrial process for the preparation of rice-wine filtercake vinegar.

Malt vinegar is made by malting barley, causing the starch in the grain to turn to maltose. Then an ale is brewed from the maltose and allowed to turn into vinegar, which is then aged. It is typically light brown in color.

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Flow chart for the processing of Rice Vinegar

Ricealted Rice Yeast

Saccharification

Alcoholic Fermentation

Vinegar Seed

Acetic Fermentation

Aging

Filtration

Pasteurisation

Bottling

Figure 8

Idli and other Cereal Based Fermented Product

Idli is a small, white acid-leavened and steamed cake prepared by bacterial fermentation of a thick batter prepared from carefully washed rice and dehulled black gram dhal. The rice is coarsely ground and the black gram is finely ground. Dosa batter is very similar to idli batter, except that the rice and black gram are finely ground. Following fermentation, the dosa is quickly fried as a thin, fairly crisp pancake and eaten directly. Dhokla is similar to idli except that dehulled Bengal gram dhal is used instead of black gram dhal in its preparation. The fermented batter is poured into a greased pie pan, and steamed in the open rather than in a covered idli steamer. Fig 9 shows the flow chart for idli production:

Flow chart for traditional Indian idli production 26

Black gram dahl White polished rice

Wash and soak for 5-10 hrs Wash and soak for 5-10 hrs

Grind finely in a mortar Grind coarsely in a mortar

Combine slurries into a thick batter an mix well

Add salt for seasoning (approximately 1 %)

Incubate overnight in a warm place (30-32 °C)

Pour batter into small cups in idli cooker

Steam for 10 minutes

Ready for consumption

Figure 9

Bread

Bread is a staple food prepared by cooking a dough of flour and water and often, additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed, fried, or baked on an unoiled skillet. It may be leavened or

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unleavened. Salt, fat and leavening agents such as yeast and baking soda are common ingredients, though bread may contain other ingredients, such as milk, egg, sugar, spice, fruit.

Bread Flour

The amount of flour is the most significant measurement in a bread recipe, as it affects texture and crumb the most. Professional bakers use a system of percentages known as Bakers' Percentage in their recipe formulations, and measure ingredients by weight instead of by volume. Measurement by weight is much more accurate and consistent than measurement by volume, especially for the dry ingredients.

The flour in the sourdough is the substrate for the fermenting microorganisms. Wheat and rye flour are mostly used for sourdough making, but maize flour can also be used. Flour is a product made from grain that has been ground into a powdery consistency. Flour provides the primary structure to the final baked bread. Commonly available flours are made from rye, barley, maize, and other grains, but wheat flour is most commonly used for breads. Each of these grains provides the starch and protein needed to form bread.

The quantity of the proteins contained in the flour serve as the best indicator of the quality of the bread dough and the finished bread. While bread can be made from all-purpose wheat flour, for quality bread a specialty bread flour, containing more protein, is recommended. If one uses a flour with a lower (9-11%) protein content to produce bread, a longer mixing time will be required to develop gluten strength properly. This extended mixing time leads to oxidization of the dough,which gives the finished product a whiter crumb, instead of the cream color preferred by most artisan bakers.

Wheat flour, in addition to its starch, contains three water-soluble protein groups, albumin, globulin, proteoses, and two water insoluble protein groups, glutenin and gliadin. When flour is mixed with water, the water-soluble proteins dissolve, leaving the glutenin and gliadin to form the structure of the resulting dough. When worked by kneading, the glutenin forms strands of long, thin, chainlike molecules, while the shorter gliadin forms bridges between the strands of glutenin. The resulting networks of strands produced by these two proteins are known as gluten. Gluten development improves if the dough is allowed to autolyse.

Fermentation In Bread Making

Many breads are leavened by yeast. The yeast used for leavening bread is Saccharomyces cerevisiae, the same species used for brewing alcoholic beverages. This yeast ferments carbohydrates in the flour, including any sugar, producing

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carbon dioxide. Most bakers in the U.S. leaven their dough with commercially produced baker's yeast. Baker's yeast has the advantage of producing uniform, quick, and reliable results, because it is obtained from a pure culture. Many artisan bakers produce their own yeast by preparing a 'growth culture' which they then use in the making of bread. When this culture is kept in the right conditions, it will continue to grow and provide leavening for many years. Both the baker's yeast and the sourdough method of baking bread follow the same pattern. Water is mixed with flour, salt and the leavening agent (baker's yeast or sourdough starter). Many breads are made from a straight dough, which means that all of the ingredients are combined in one step, and the dough is baked after the rising time. Alternatively, dough can be made using a pre-ferment, when some of the flour, water, and the leavening are combined a day or so ahead of baking, and allowed to ferment overnight. On the day of the baking, the rest of the ingredients are added, and the rest of the process is the same as that for straight dough. This produces a more flavorful bread with better texture.

Sourdough

The sour taste of sourdoughs actually comes not from the yeast, but from a Lactobacillus, with which the yeast lives in symbiosis. The Lactobacillus feeds on the byproducts of the yeast fermentation, and in turn makes the culture go sour by excreting lactic acid, which protects it from spoiling (since most microbes are unable to survive in an acid environment). All yeast-leavened breads used to be sourdoughs. Sourdough breads are most often made with a sourdough starter (not to be confused with the starter method discussed above). A sourdough starter is a culture of yeast and lactobacillus. It is essentially a dough-like or pancake batter-like flour/water mixture in which the yeast and lactobacilli live.

Figure 10. Flow chart for bread production from fermented dough

Ingredients

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Mixing/Kneading

Dough

Fermentation

Pre-ripened dough

Dividing/Forming

Activities of microorganisms

Dough pieces and enzymes

Fermentation

Mature dough pieces

Baking

Bread

CONCLUSION

Fermented cereal-based foods have a long tradition, although some of the processes may almost be forgotten. However, the new information on the benefits of probiotic strains has also spurred an interest in the research and development of

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cereal-based probiotic carrier foods. Fermentation also provides possibilities for physicochemical (solubility) and enzymatic modifications of the cereal substrate, and therefore further development of the processes and products may also lead to enhancement of the health-promoting functional properties of the food.

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 many countries are unclear, since cereal products are still produced and consumed by several million people living in the world.

REFERANCES1. N. Shakuntala Manay and M. Shadaksharaswamy. 2010 . ‘Foods: Facts and

Principles’.

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2. William C Frazier and Dennis C Westhoff. 2008. ‘Food Microbiology’.3. Martin R Adams and Maurice O Moss. 2008 . ‘Food Microbiology’.4. Prescott and Dunn. 1999. ‘Industrial Microbiology’.5. Norman N. Potter and Joseph H. Hotchkiss. 2007.’Food Science’6. ‘Food Science’ Fourth Edition by B. Srilakshmi.7. Y. H. Hui.‘Handbook of Food and Beverage Fermentation Technology’. 8. http://en.wikipedia.org/wiki/Fermentation_(food)9. http://en.wikipedia.org/wiki/Beer10.http://en.wikipedia.org/wiki/Vinegar11.http://en.wikipedia.org/wiki/Bread12.http://www.mizkan.co.uk/background/production.asp13.http://www.fao.org/docrep/x2184e/x2184e09.html14.http://www.fao.org/docrep/x2184e/x2184e04.html15.http://www.fao.org/docrep/x2184e/x2184e05.htm16.http://www.fao.org/docrep/x2184e/x2184e06.htm17.http://www.fao.org/docrep/x2184e/x2184e10.html18.www.pjbs.org/pjnonline/fin143.pdf19.www.after-fp7.eu/en/products/cereal_based_products

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