SECTION II REVIEW OF LITERATURE

SECTION II REVIEW OF LITERATURE Review of Literature CHAPTER – I MILLETS Millet is a general category for several species of small grained cereal ...
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SECTION II

REVIEW OF LITERATURE

Review of Literature

CHAPTER – I MILLETS Millet is a general category for several species of small grained cereal crops and is a food staple in parts of India, Africa, China and elsewhere. Millet has been cultivated since prehistoric times in regions of North Africa and Central Asia, though its origin is ambiguous. Most millet is produced in Asia and Africa. In Europe and the United States, millet is grown mainly as forage for poultry and as bird feed. Millet contains an average of 10 - 12% protein. While its protein is superior to that of wheat or corn in terms of content of essential amino acids, it nonetheless contain less than half the amount of the essential amino acid lysine that is found in high quality protein sources such as meat. Millet lacks gluten, the wheat protein that makes dough prepared from wheat flour elastic; hence millet flour is not suitable for leavened breads. Millet flour is used in making flat cakes and breads. The whole grain is used in soups, stews or as a cooked cereal. Millet is also popped; roasted or sprouted (Robert Ronzio 2004) The term millet is employed for several related genera, some used to produce grain, or forage or both. Millets are cereal species growing in an equally broad range of environments. The most widely cultivated millets are finger millet (Eleusine coracona), foxtail millet (Setaria itallica), pearl millet (Pennisetum typhoideum), proso millet (Panicum miliaceum), barnyard millet (Echinochooa colona) etc. Millets are considered the least important of cereals, with annual production less than 2% of the world’s grain. However they are of great local importance as staples and as reserve crops in marginal areas.

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The use of millets not only provides farmers with a market for their products but also saves foreign exchange, which would otherwise be required to import cereals. Particularly in the developed countries, there is a growing demand for gluten-free foods and beverages from people with celiac disease and other intolerances to wheat who cannot eat products from wheat, barley, or rye.

Geographical Distribution and Production of Millets Table 2.1 presents the millet area and production across the globe in 2002 and 2009. According to FAO statistics (2009), the world production of millets was 26702000 metric tons from an area of 33692000 Hectare. Nearly a decade earlier (2002), the world production of millets was down to 23338000 metric tons from an area of 33396000 Hectare. Africa was the largest producer of millet in 2009 (20626000 metic tonne), followed by Asia (12492000 metric tons) and India (10500000 metric tons). Relative to wheat, rice, maize and barley, sorghum ranks fifth in importance, in terms of both production and area planted, accounting for 5% of the world cereal production (Obilana 2004)

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Table.2.1 Millet Area and Production Across the Globe Region

Production

Area Harvested

(‘000 tons)

(‘000 ha)

2002 1

2009 2

20021

20092

World

23338

26702

33396*

33692*

Africa

13633

14908

20626*

20631*

Asia

9123

1142

11359*

12492*

India

6150

8810

12527

10500**

* May include official, semi official or estimate data ** Unofficial data No symbol – Official data, Source – FAO (2002); http://www.fao.org

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Table 2.2. Top Ten Producers of Millet in the World Country

Production (‘000 tons) 2000

2009

India

10078

8810

Nigeria

6105

4885

China

2126

1226

Niger

1679

2678

Burkina Faso

726

971

Mali

759

1390

Sudan

496

630

Uganda

534

841

Chad

259

709 Im

Ethiopia

320

560

No symbol – Official data Im – FAO data based on imputation methodology Source: (http://www.fao.org).

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Distribution of Millets in India

India is the top most producers of millets followed by Nigeria for the year 2000 and 2009 (Table 2.2). In India, eight millets species (sorghum, finger millet, pearl millet, foxtail millet, barnyard millet, proso millet, kodo millet and little millet) are commonly cultivated under rain fed conditions. Further, in each of the millet growing areas at least 4 to 5 species are cultivated either as primary or allied crop in combination with the pulses, oilseeds, spices and condiments. For instance, while pearl millet and sorghum are primary crop and allied crops respectively in the desert regions of Rajasthan, in the eastern parts of Rajasthan and Gujarat it is the opposite. Similarly, sorghum is sown as major crop in the Telangana (Andhra Pradesh), Maharashtra and parts of Central India, while it is considered as fodder crop in some of the Southern regions. Likewise, Finger millet is a primary crop in Tamil Nadu and Gharwal, while the same is a minor crop in Telangana. Hence, the spatial distribution of millets either as a primary crop or as allied crops largely depends on the growing habitat and the amount of rainfall the region receives. While sorghum predominates in areas receiving annual rainfall beyond 400 mm, pearl millet rivals it in areas with annual rainfall of 350 mm. Further, the small millets like finger millet, foxtail millet, barnyard millet, little millet and proso millet are found in most of the southern and central states in India especially wherever annual rainfall is below 350 mm, perhaps where no other cereal crop can grow under such moisture stress. However, in spite of a rich inter/intra-species diversity and wider climatic adaptability cultivation of diverse millet species/varieties is gradually narrowing in the recent past. In a way, a lack of institutional support for millet crops in contrast to the institutional promotion of rice and wheat continue to shrink the millet-growing region. Over the last 50 years, Page 10

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the share of ‘Coarse grains’, which include pearl millet, sorghum, maize, finger millet, barley and 5 other millet species known as ‘Small Millets’, in terms of total area has registered 25.3% decline from 38.83 Mha. (1949-50) to 29.03 Mha. (200405). In spite of this, several communities in the dry/rain fed regions having known the food-qualities of millets over generations continue to include a range of millets in the traditional cropping patterns, which recognize millets as an essential part of the local diet.

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Table 2.3 – Common Names of Millets

English

Sorghum/ Great Millet

Bengali

Jowar

Pearl/ Spiked Millet Bajra

Guajarati

Jowari, Juar

Bajri

Hindi

Jowari, Juar

Bajra

Kannada

Jola

Sajje

Ragi

Navane

Marathi

Jowari, Jondhala

Bajri

Nagli, Nachni

Kang, Rala

Oriya

Juara

Bajra

Mandia

Kanghu, Kangam, Kora

Punjabi

Jowar

Bajra

Tamil

Cholam

Kambu

Telugu

Jonna

Sajja

Finger Millet Marwa Nagli, Bavto Ragi, Mandika Marwah

Mandhuka, Mandha Keppai, Ragi, Kelvaragu Ragi Chodi

Foxtail/ Italian Millet Kaon

Little Millet

Kodo Millet

Sama Gajro, Kuri

Kodo

Proso/ Common Millet Cheena

Kodra

Cheno

--

Kodon

Chena, Barri

Sanwa

Harka

Baragu

Oodalu

Kodra

Vari

--

Suan

Kodua

China Bachari bagmu

Khira

Kangni

Swank

Kodra

Cheena

Swank

Tenai

Samai

Varagu

Pani varagu

Kuthiraivolly

Korra

Samalu

Arikelu, Arika

Variga

Udalu, Kodisama

Kang Kakum

Kutki, Shavan Same, Save Sava, Halvi, var

Barnyard Millet Shyama

Source: (http://www.swaraj.org)

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Table 2.4 – Nutrient Content of Major Millets (per 100g of edible portion)

Protein

Fat

Ash

Iron

Calcium

(g)

(g)

(g)

(mg)

(mg)

Pearl millet

11.6

5.0

2.3

8.0

42.0

Finger millet

7.3

1.3

2.7

3.9

344.0

Foxtail millet

12.3

4.3

3.3

2.8

26.0

Sorghum millet

10.4

1.9

1.6

4.1

25.0

Proso millet

12.3

4.9

3.1

2.9

8.0

Kodo millet

9.8

3.6

3.3

1.7

35.0

Little millet

9.6

5.2

5.4

9.3

17.0

Barnyard millet

11.0

3.9

4.5

18.6

22.0

Rice, raw, milled

6.8

0.5

0.6

0.7

10.0

Wheat

11.8

1.5

1.5

5.3

41.0

Millets

Source: NIN, Hyderabad; Jones et al, 1970; www.egerbil.com/millet

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Sorghum

Pearl Millet

Barnyard Millet

Ragi

Kodo Millet

Proso Millet

Foxtail Millet

Little Millet

Figure 2.1. Pictures of Commonly Used Millets

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Chemical Composition of Millets Nutrient composition of millets: a. Finger millet (Eleusine corucana): Finger millet also known as ‘ragi’ in India is an important staple food for people belonging to the low socio-economic group. It is also known as African millet, and is an important staple food in Africa and India. Finger millet, a chief dry land crop has the ability to withstand adverse weather conditions when grown in soils having poor water holding capacity. It is grown in arid regions of Eastern and Southern Africa, India and Nepal. The small millet seeds can be stored safely for many years without insect damage, which is invaluable in farmers risk avoidance strategies in drought prone areas. Finger millet is the third most important millet in India, next to sorghum and pearl millet, covering an area of 2 million hectares with annual production of 2.15 million tones. In Karnataka, it is grown in an area of 0.8 Mha with an annual production of 1.34 mt. Finger millet grown on marginal land provides a valuable resource in times of famine. Its grain tastes good and is nutritionally rich (compared to cassava, plantain, polished rice and maize meal) as it contains high levels of calcium, iron and manganese. It has a carbohydrate content of 81.5%, protein 7.3%, crude fiber 4.3% and mineral 2.7% that is comparable to other cereals and millets (Table 2.4). Its crude fiber and mineral content is markedly higher than wheat (1.2% fiber, 1.5% minerals) and rice (0.2% fiber, 0.6% minerals); its protein is relatively better balanced; it contains more lysine, threonine and valine than other millets. The millet straw is also an important livestock feed, building material and fuel. Finger millet contains methionine, an essential amino acid

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lacking in the diets of hundreds of millions of the poor who rely mostly on starchy staples (Apoorva et al 2010; Ravindran 1991). b. Sorghum: Sorghum contains 10.4 % protein, 1.9% fat (Table 2.4) and around 8.3% total dietary fiber. Most of the fiber is present in the pericarp and cell walls. Sorghum contains 6.5 – 7.9% insoluble fiber and 1.1 – 1.2% soluble fiber. Insoluble dietary fiber increased during food processing due to increased levels of bound protein mainly kafirins, and enzymes-resistant starch. Kafirins (the sorghum prolamin proteins) and glutelins comprise the major protein fractions in sorghum. These fractions are primarily located within the protein bodies and protein matrix of the endosperm, respectively. The germ and aleurone are rich in fat-soluble and B-vitamin. Sorghum contains 0.3 – 0.8 µg/g of α – tocopherols and 9 – 11.5 µg/g of τ– tocopherols. Precursors of vitamin A (carotenes) are found in yellow and heteroyellow endosperm sorghums. Sorghum is an important source of minerals that are located in the pericarp, aleurone, and germ. Phosphorus is the mineral found in greatest amounts, its availability is negatively related to the amount bound by phytates. Phytase activity during malting and fermentation significantly increases availability of phosphorus and other minerals as well. The sorghum aleurone layer is not a major source of endosperm-degrading enzymes. The scutellum of sorghum is where α – amylase is formed and diffuses into the endosperm. Sorghum does not respond to gibberellins to enhance production of amylases during malting. α – amylase activity in sorghum starts 24–36 h after germination. Limit dextrinases and proteases are found mainly in the endosperm, whereas, carboxypeptidases are located primarily in the germ. Sorghum malt has high levels of α – amylase activities but it has reduced β – amylase activities. Page 16

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Condensed tannins (proanthocyanidins) are not present in all sorghums; however, all sorghums contain phenolic acids, and most contain flavonoids. Kernels that contain condensed tannins have a thick, highly pigmented testa. These sorghums were referred to as brown sorghums but are not classified as tannin sorghums. Tannins protect the kernel against pre-harvest germination and attack by insects, birds and molds. Birds consume brown sorghum when other food is unavailable. Animals fed tannin sorghum rations eat more feed and produce about same amount of gain, so feed efficiency is reduced. There is no toxicity problem but feed efficiency is reduced by the condensed tannins. The condensed tannins have a high affinity for prolamins proteins and decrease feed efficiency by 5 – 15% depending upon the livestock species and processing of the rations. The tannin sorghums are potent sources of antioxidants. Bran fractions and extracts from them have significantly higher oxygen radical absorbance capacity (ORAC) levels, a measure of antioxidant strength, than most fruits and vegetables. Bakery products containing this bran have increased fiber content, higher antioxidant potential, and attractive natural brown or chocolate color. Tannin sorghums can also be transformed into excellent whole grain snacks by extrusion. The extrusion process significantly reduced the degree of polymerixation of tannins, which may be beneficial in human foods (Waniska et al 2004). Sorghum and millet have considerable further potential to be used as a human food and beverage source. In developing countries the commercial processing of these locally grown grains into value-added food and beverage products is an important driver for economic development (Taylor 2004). Sorghum, in particular, could also play an important role in the production of ethanol and other bio-industrial products such as

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bioplastics, especially in dry areas where other crops are not as easily grown (McLaren et al 2003). Millets are good sources of phytochemicals such as phenolic acids, lignans and phytoestrogens. Phenolic acids like p – coumaric acid and vanillic acids are present in the bran layer of the grains and are mainly present as gently bound form with insoluble polymers. Generally grains contain low to moderate levels of tocopherol due, but to the large amount consumed in Korean diet, they provide a significant and consistent source of tocopherols. Tocopherols are regarded as intracellular antioxidants due to their activity of inhibiting the peroxidation of polyunsatureated fatty acids in biological membranes (Qureshi et al 2000). The methanolic extracts of highly pigmented red sorghum and black rice have showed significantly higher antioxidant activities and contained higher polyphenolic contents. Polyphenolic compounds are the major naturally occurring antioxidants in millets. Although carotenoids and vitamin E contents are relatively low than polyphenolics, grains may contribute to a significant supply of antioxidant to prevent oxidative stress due to the fact that grains are used as a staple food and consumed large amounts in our diets (Youngmin et al 2007). c. Foxtail Millet (Setaria italica): Foxtail millet is commonly known as Italian millet, German millet, Chinese millet, Hungarian millet, Dwarf setaria, giant setaria, liberty millet, and Siberian millet. The seeds are small and measure around 2mm in diameter. They are encased in a thin, papery hull which is easily removed upon threshing. Seed color can vary greatly between varieties grown and range from a pale yellow, through to orange, red, brown and black. A thousand of these seeds weighs approx. 2 grams. The protein in Foxtail millet is known to be Page 18

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deficient in Lysine, and its amino acid scores are comparable to that of Maize. In different grain varieties, higher the protein content, lower is the Lysine content in the protein. It is relatively high in leucine and methionine. The starch in some foxtail millet varieties contain 100% amylopectin, and the starches contained in foxtail, proso and barnyard millets are more digestible than maize starch. The total ash content of foxtail millet is good and is much higher than the more commonly consumed cereal grains including sorghum, however de-hulling of the grain, like in other millets, causes considerable nutrient losses. d. Barley (Hordeum vulgare): Barley is one of the major millet crops of the world, characterized for its small seeds. It is of major importance in the west but a stable in diets of African and Asian people. Barley is important millet used for malting and brewing because of its high diastatic power (Pawar et al 2006) e. Little Millet: Little millet is a relative of Proso millet and is grown throughout India but is of little importance elsewhere and has received very little attention from plant breeders as a crop source. The plant varies in size between 30-90cm and its oblong panicles ranged from 14 to 40cm long. The seeds of little millet are much smaller than proso millet. It has reasonably good levels of protein, but very poor amino acid values. It also has the highest fat content of all the millets. f. Browntop Millet: Browntop millet is another native of India but was introduced to the U.S.A. in 1915. It is grown in the south eastern states mainly for hay and pasture, and often for bird and quail feed plantings on game preserves. It has a short growing season and finer stems that allow for easier curing for hay

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production. Seed and forage yields of this plant are low in tests and it has been found that it doesn't compete well with weeds. g. Barnyard: Barnyard or Japanese millet is a domesticated relative of barnyard grass and there exists several varieties. It is the fastest growing of all the millets and produces a crop in six weeks. In India, Japan and China it is often used as a substitute for rice when the paddy crop fails. In the U.S.A. it is grown primarily for forage, and can produce up to eight harvests a year. It is comparable to proso millet in protein and fat content, but the actual quality of the protein, like that of little millet have the poorest amino acid values of all the millets. It is very high in fiber. h. Kodo Millet: Kodo millet is a minor grain crop in India but is of much greater importance in the Deccan Plateau. It is an annual grass species that grows to around 90cm high. Some varieties of Kodo millet are prone to attacks from mycotoxins. The grain varies in color from light red to dark grey and is enclosed in a tough husk that is difficult to remove. It has high protein content, being around 11% and the nutritional value of the protein is regarded as being slightly better than that of foxtail millet, but comparable to the other millets. It is however deficient in the amino acid tryptophan. It is also reasonably low in fat with high fiber content. Due to high antioxidant content, it is beneficial in protecting against oxidative stress and maintaining glucose levels in type-2 diabetes (Taylor 2004).

Antinutrient Composition Millets are nutritionally comparable and even superior to major cereals in terms of energy value, proteins, fat and minerals (Anu et al 2006; Malik et al 2002). Page 20

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However, due to the presence of antinutrients like phytate, polyphenols, oxalates and tannins, mineral bioavailability is affected. These antinutrients form complexes with dietary minerals, such as calcium, zinc and iron leading to a marked reduction in its bioavailability and make them biologically unavailable to human organism (Arora et al 2003). In human and animal nutrition, oxalic acid, denoted as ‘oxalate’ is considered as an ‘undesired compound’. Oxalate is removed by excretion through the urinary system where it can precipitate calcium and form renal stones. As oxalate is an undesirable compound, the level of oxalate can be reduced by blanching where water soluble oxalates can be leached out. In the human diet, the bulk of oxalic acid intake comes from vegetables. Oxalate content should be low in foods, especially in infant formulas or in dietary foods for consumers metabolically prone to oxalate renal stone formation, the development of low – oxalate products is considered to be reasonable (Thomas et al 2005). All cultivars of setaria contain oxalates and vary between the varieties. In many animal species high oxalate levels can cause a range of problems. Foxtail millet has been reported to have a diuretic effect in horses that may lead to kidney and joint problems although no reports to actually document this have been found. When severely stressed during growth, foxtail millet can accumulate high nitrate levels which are toxic to livestock when grazing it. The red seed varieties of proso millet tend to have smaller seeds and are considerably higher in tannins, which makes them less acceptable as a feed. Bird seed manufacturers tend to use small amounts of this seed in mixtures to approve eye appeal of the final product. Tannin however is objectionable for two reasons; it competes for available protein and carbohydrates and also has a bitter taste. In rat, Page 21

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chicks and livestock studies it has been shown that high tannins in the diet adversely affect digestibility of proteins and carbohydrates, which in turn reduces feeding efficiency and growth. It is known to contain a saponin called as diosgenin which is known to cause hepatogenous photosensitization in animals throughout the world. Other problems when grazing the plants are also known as it is a nitrate accumulator. The seeds should never be offered sprouted as the growing shoots contain amounts of hordenine which is a phenylethylamine alkaloid. Hordenine is an indirectly acting adrenergic drug. It liberates norepinephrine in higher animals. Experiments in animals (rats, dogs, horses, mice) show that hordenine has a positive inotropic effect (increasing the heart's beating strength) upon the heart, increases systolic and diastolic blood pressure, peripheral blood flow volume, inhibits gut movements but has no effect upon the psychomotorical behaviour of mice. Although its effects are only short lasting it could seriously disorientate the affected animal (Taylor 2004).

Effect of Processing on the Nutrient Composition of Millets Cereals and millets are the primary sources of minerals in most vegetarian diets, secondary sources being legumes. Besides inherent factors such as phytate, tannin, and fiber negatively influencing the bioavailability of zinc and iron from these food grains, the same may also be influenced by processing, such as cooking, boiling, roasting or germination which these food grains undergo. Food processing by heat generally alters the bioavailability of nutrients – both macro and micro. The digestibility and consequently absorption of micronutrients such as iron is believed to be improved upon heat processing by softening the food matrix, releasing of proteinbound iron and thus facilitating its absorption. In addition, heat processing of food is Page 22

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also likely to alter the inherent factors that inhibit mineral absorption, such as phytate and dietary fiber, especially the insoluble fraction (Amparo et al 2003; Abdalla et al 1998). A study carried out to evaluate the influence of heat processing (pressurecooking and microwave heating) on the bioaccessibility of zinc and iron from food grains consumed in India such as Cereals – rice (Oryza sativa), finger millet (Eleusine coracana), sorghum (Sorghum vulgare), wheat (Triticum aestivum), and maize (Zea mays), and pulses – chickpea (Cicer arietinum) – whole and decorticated, green gram (Phaseolus aureus) – whole and decorticated, decorticated black gram (Phaseolus mungo), decorticated red gram (Cajanus cajan), cowpea (Vigna catjang), and French bean (Phaseolus vulgaris) demonstrated that zinc bioaccessibility considerably reduced upon pressure-cooking, especially in pulses. Among cereals, pressurecooking decreased zinc bioaccessibility by 63% and 57% in finger millet and rice, respectively. All the pressure-cooked cereals showed similar percent zinc bioaccessibility with the exception of finger millet. Bioaccessibility of zinc from pulses was generally lower as a result of pressure-cooking or microwave heating. The decrease in bioaccessibility of zinc caused by microwave heating ranged from 11.4% in chickpea (whole) to 63% in cowpea. Decrease in zinc bioaccessibility was 48% in pressure-cooked whole chickpea, 45% and 55% in pressure-cooked or microwaveheated whole green gram, 32% and 22% in pressure cooked or microwave-heated decorticated green gram, and 45% in microwave-heated black gram. Iron bioaccessibility, on the other hand, was significantly enhanced generally from all the food grains studied upon heat treatment (Sreeramaiah et al 2007).

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Processing techniques traditionally used such as soaking, milling, sieving, germination, fermentation, boiling and frying to produce four maize foods commonly consumed in Africa were investigated for the nutritional composition, with special focus on iron and zinc and factors affecting their bioavailability of the products. The impact of the processes on lipid, fiber, phytate, iron and zinc contents varied with these processing methods. The lowest IP6/Fe (myo-inositol hexaphosphate) and IP6/Zn molar ratios, the indices used to assess Fe and Zn bioavailability were obtained in mawe, fermented dough. Analysis of maize products highlighted a noteworthy increase in iron content after milling, as a result of contamination by the equipment used. Evaluation of iron bioaccessibility by enzymatic digestion (in-vitro) followed by dialysis revealed that the iron contamination, followed by lactic acid fermentation, led to a considerable increase in bioaccessible iron content. Extrinsic iron supplied to food products by the milling equipment could play a role in iron intake in developing countries. The investigation of iron bioaccessibility in mawe and owo products showed that only a small part of the contaminant iron originating from the mill was available for absorption. However, it appeared that fermentation can greatly increase the amount of bioaccessible iron; most of it was due to the acidification. Thus, the combined effect of contamination and fermentation resulted in enhanced levels of iron potentially accessible for absorption. Consequently, the use of mills equipped with iron-containing grindstones could be useful to enhance iron dietary intake in the poorest consumers, as has already been proven for iron pots (Valerie et al 2011). Soaking, boiling and germination resulted in a significant reduction of phytate phosphorus. The concentrations of calcium, magnesium, iron and zinc increased upon soaking and germination, while boiling decreased calcium, Page 24

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magnesium and iron concentration. Solubility of minerals was higher in soaking and germination than in boiling (Sushma et al 2008). Major biochemical changes occurred during fermentation (48 h) of finger millet compared to its germination (24 h). The processing decreased the pH from 5.8 to 3.8 and increased the total sugars, reducing sugars and free amino acids. The phytate content decreased by 60% while the phytate Ca/Zn molar ratio decreased from 163 to 66.2, indicative of an increased Zn bioavailability. The study revealed that a combination of germination and fermentation is a potential process for decreasing the antinutrient levels and enhancing mineral availability (Sripriya et al 1997) Barley (Hordeum vulgare) is used for malting and brewing because of its high diastatic power. Barley grains after dehulling and malting resulted in reduction of phytate phosphorus content which significantly improved ionizable iron content (Pawar et al 2006). Refining of the whole maize by fine milling and complete removal of husk and germ led to a slight increase of diffusible iron. However the iron content was reduced by the milling process. The diffusibility increased by the partial loss of phytic acid and fibers. Maize corn flour displayed even higher iron diffusibility because it contains virtually no phytic acid or fibers (Hazel et al 1989)

Food Uses of Millets Millets have considerable potential in foods and beverages. As they are glutenfree they are suitable for celiacs. The major categories of traditional foods where millets can be effectively used are fermented and unfermented flat breads, fermented and unfermented thin and thick porridges, steamed and boiled products, snack foods, alcoholic and nonalcoholic beverages. As millets are less expensive compared to Page 25

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cereals and is a staple for the poorer sections of population, studies have been carried out to explore the possibility of the millet as a vehicle for fortification. Millets have been successfully utilized in food products, beverages, convalescent and weaning foods. Food Products: Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and millets. Unlike composite breads, wheat-free sorghum breads are suitable for coeliacs and might possibly replace wheat breads in developing countries, reducing expensive wheat imports (Schober et al 2005). Millet bread remains the main challenge as they are gluten free. Limited number of studies has addressed the issue of wheat-free loaf breads from sorghum. Additives such as native and pre-gelatinized starches, hydrocolloids, fat, egg and rye pentosans are known to improve the bread quality. However, specific volumes of gluten free breads are lower than wheat bread and these breads tend to stale faster. Sorghum is useful in food products because it does not impart unusual colors or strong flavors and it could be desired over maize flour for these reasons (Waniska et al 2002). Dark colors from black or tannin-containing sorghum varieties might be advantageous in products for the health market (Rooney et al 2005) or in countries where dark, rye-based bread is common (e.g. Germany or Eastern Europe). In such communities, usually ‘‘dark’’ is associated with ‘‘healthy’’. Brownish colors might also be acceptable in chocolate cakes, cookies and muffins, or molasses cookies. For example, a sorghum line with red pericarp produced interesting, pinkish-brown bread that might be promoted as specialty bread (Schober et al 2005). It was found that consumers did accept the color and appearance of a lighter-colored sorghum muffin, resembling a plain or maize muffin as well as a dark brown one, resembling a Page 26

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chocolate, pumpernickel or dark bran muffin. The resulting color of sorghum products, however, cannot be predicted based on the color of the whole grain. It depends on pericarp and endosperm colors, pigmented or non-pigmented testa, degree of milling and pH of the food (Brannan et al 2001; Rooney, 1996). Traditional flatbreads from sorghum and millets might be regarded as leavened if they are fermented like injera (Ethiopia) or puffed like chapatti/roti (India). Another wellestablished use of sorghum in leavened baked goods is in wheat–sorghum composite breads (Munck 1995). Worldwide, the most popular unfermented flat breads from sorghum are ‘roti’, a portion of the flour is gelatinized, mixed with more flour and warm water and kneaded into dough, which is shaped into a circle, and baked on a hot griddle. For tortilla production, whole sorghum is lime cooked steeped over night, washed; stone ground into ‘masa’ shaped into thin circles and baked on a hot griddle. The most popular fermented breads are ‘injera’, ‘kisra’ and ‘dosa’ consumed in Ethiopia, Sudan and India. The sorghum flour is mixed with water and a yeast starter from a previous batch of injera. After fermentation for 24 – 48h, the batter is poured onto a greased pan for baking. The resulting product is a flexible, large diameter pancake like breads containing uniformly distributed air bubbles. It is moist and retains its flexibility for 2 – 3 days. Dosa consumed in India and produced from a mixture of black gram, sorghum and rice flour. It is used as wrap for vegetables, sauces and other foods. Porridges are popular foods from sorghum. ‘To’ is an unfermented stiff porridge cooked in alkali in mali, cooked in acid in Burkina Faso, or fermented and cooked. Popular fermented porridges are ‘ogi’ and ‘nasha’ widely consumed in West and East Africa, respectively (Waniska et al 1999) Page 27

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Finger millet is still an important cereal in Africa, despite the fact that the area under production of the crop has not increased in recent times. The crop serves special food and traditional needs and earns cash for households. With increased research input in production, processing and utilization, the crop holds a lot of potential in productivity, commerce and industry in Africa (National Research Council 1996). The traditional methods like popping and flaking as well as contemporary methods like roller drying and extrusion cooking of cereal processing could be successfully applied to foxtail millet to prepare ready – to – eat products (Singh et al 2004). Baby corn/mini corn/vegetable corn is an innovation in maize research. The term baby corn (Zea mays L) refers to young tender flowering maize ears harvested within 2 – 4 days after while silk emergency before fertilization. Baby corn is cultivated and consumed on a large scale especially in Thailand, Taiwan, Europe, Japan and China. Baby corn being low in fat, carbohydrate and rich in fiber is highly preferred from nutritional point of view. Dehusked baby corn is used in making snacks and savories like vada, kofta, finger fry, roti and raita. Sweet products like burfi, kheer, kesari and halwa are also prepared. These products can bring dietary diversity and value addition to products of specific dietary importance (Anitha et al 2005). Beverages: Malted sorghum is used to produce alcoholic beverages. The high – solids beer is sour, alcoholic, pinkish and effervescent. The fermentation time is short and the beer is drunk while actively fermenting. The beers vary from sweet to very sour, alcohol and their solids content vary. The most common type in southern Africa, called opaque beer, undergoes souring and yeast fermentation. Non-alcoholic beverages and extracts are produced from malted sorghum. In southern eastern and Page 28

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western Africa sorghum malt is used for alcoholic and non alcoholic beverages, weaning foods and breakfast foods while sour-opaque are produces commercially in southern Africa. Traditionally opaque beer is produced by malting sorghum, converting cooked sorghum and maize grits into fermentable sugars, souring the mash and finally fermenting the sugars into alcohol (Waniska et al 1999). Larger and stout beers with sorghum are brewed commercially. Sorghum’s high-starch gelatinization temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt. The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bio-ethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable byproducts such as the kafirin prolamine proteins and the pericarp wax have potential as bio-plastic films and coatings for foods, primarily due to their hydrophobicity (John et al 2006). Convalescent / Medicinal / Weaning foods: Millets are potentially important sources of nutraceuticals such as antioxidant phenolics and cholesterol-lowering waxes. Finger millet is eaten to satisfy traditional requirements as well as nutritional supplements. As nutritional supplement, the food products are fed to expectant and lactating mothers, babies and the sick. The grain's protein content (7.4 %) is comparable to that of rice (7.5 %). The main protein fraction (eleusinin) has high biological value, with good amounts of tryptophan, cystine, methionine, and total aromatic amino acids, which are all crucial to human health and growth and are Page 29

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deficient in most cereals. For this reason alone, finger millet is an important preventative against malnutrition. The uses of finger millet in Africa include porridge and “Ugali or Sima or Saza which are relished for their flavor and aroma. Malted finger millet (sprouted seeds) is a nutritious food which is easily digested and recommended particularly for infants and the elderly. In terms of malting qualities, finger millet could be the key to providing cheap and nutritious foods for solving the malnutrition that kills millions of infants throughout the tropics. Malting is the process of germinating finger millet to activate enzymes that break down the complex structures of starches into sugars and other simple carbohydrates that are easy to digest. Because of its nutritive properties, the crop has medicinal value and it is used in management of measles, anemia, and diabetes diseases (Chrispus 2005; Taylor, 2004b). By virtue of its nutritive value, finger millet has industrial potential in the manufacture of baby and sick person’s food formulations and breakfast cereals. Other than brewing, the malting process can be used in making cheap, digestible, liquid foods for children. The germinated grain can be used to liquefy any starchy foods: wheat, rice, maize, sorghum, millet, potatoes, cassava (manioc), yams etc (National Research Council 1996). As a consequence of the diversity of the roles of finger millet in society, there is growing market demand for the grain. Commercialization of finger millet is already in place in some countries, especially in the brewing industry. In Zimbabwe and Malawi finger millet malt is used in brewing commercial chibuku (Mushonga et al 1993; Mnyenyembe 1999) Studies on Fortification of Millets Fortification is a cost-effective method that can be used to combat the deficiencies of micronutrients such as zinc and iron without changing the existing Page 30

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dietary patterns. As millets are less expensive compared to cereals and is a staple for the poorer sections of population, studies were carried out to explore the possibility of the millet as a vehicle for fortification. Finger millet flour was fortified with either zinc oxide or zinc stearate so as to provide 50 mg zinc per kg flour, and was examined for the bioaccessibility of the fortified mineral, as measured by in-vitro simulated gastro intestinal digestion procedure and storage ability. Finger millet flour was cofortified with EDTA to increase the amount of bioaccessible zinc from the zincfortified flour. EDTA enhanced the bioaccessible zinc content nearly 3 times over that provided by the millet flour alone, and 1.5 – 3 times from the fortified flour. Inclusion of citric along with the zinc salt and EDTA during fortification did not have any additional beneficial effect on zinc bioaccessibility. Moisture and free fatty acid contents of the stored fortified flours indicated the keeping quality of the same, for up to 2 months. Both zinc oxide and zinc stearate were equally effective as fortificants when used in combination with EDTA as a co-fortificant. The preparation of either roti or dumpling from the fortified flours stored up to 60 days did not result any significant compromise in the bioaccessible zinc. Therefore, it was concluded that finger millet flour could be effectively used as a vehicle for zinc fortification to derive additional amounts of bioaccessible zinc, with reasonable good storage stability, to combat zinc deficiency (Bhumika et al 2010a). Similarly in another study, flours of pearl millet and sorghum were evaluated as vehicles for fortification with zinc. Zinc stearate was used as the fortificant, and added at a level that provided 5mg Zn/100 g flour. The metal chelator EDTA was used as a co-fortificant, the molar ratio of exogenous Zn: EDTA being 1:1. The results of the study revealed that there were differences among these two flours with respect to the feasibility of fortification with Page 31

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zinc. Although fortified pearl millet flour provided a higher amount of bioaccessible zinc, this was attributed to the presence of EDTA, rather than to the fortified zinc. The benefit of fortification with zinc was more evident in sorghum flour, compared to that in pearl millet flour, the increase in bioaccessible zinc content being more than 1.5 times higher as a result of fortification. Fortified sorghum and pearl millet flours were stable during storage for a period of up to 60 days. Thus, millet flours seem to be satisfactory candidates for fortification with zinc, and can be exploited to address zinc deficiency. (Bhumika et al 2010b).

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Chapter – II PEARL MILLET

Pearl millet (Pennisetum typhoideum) is the most widely grown type of millet. Because of its tolerance to difficult growing conditions such as drought, low soil fertility and high temperature, it can be grown in areas where other cereal crops, such as maize (Zea mays) or wheat (Triticum aestivum), would not survive. Pearl millet production is concentrated in the developing countries which account for over 95% of the production and acreage. India continues to be the single largest producer of pearl millet in the world, although the area has been declining in the traditional growing states of Gujarat, Rajasthan and Haryana. Pearl millet is usually grown as a dry land dual purpose grain and fodder crop although it is sometimes irrigated in India, particularly the summer crop grown mainly as a forage crop. Pearl millet is one of the most extensively cultivated cereals in the world, after rice, wheat, and sorghum, and particularly in arid to semi-arid regions. Pearl millet is so important that it is planted on around 14 million hectares in Africa and 14 million hectares in Asia. Global production of its grain probably exceeds 10 million tons a year, to which India contributes nearly half. At least 500 million people depend on pearl millet for their lives. Pearl millet has been historically grown for forage production and cattle grazing in the US. It is widely grown as a multi-purpose cereal grain crop principally for food, and also for feed, fodder, fuel, and mulch on more than 26 million hectares, primarily in arid and semi-arid regions of India and Africa (FAO 2000). It is a staple grain for about 90 million people living in the semi-arid tropical regions of Africa and the Indian sub-continent. Besides its importance as food and feed crop, pearl millet is Page 33

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potentially an ideal species for genetic studies because of its small diploid genome with large chromosomes, abundant phenotypic variation, and protogynous flowering habit. As a new-use grain crop, it currently occupies relatively small acreage in the US, but has high potential because of its ability to tolerate drought and low fertility, better nutritive properties and diverse use over other cereals. Pearl millet has significant potential as feed and food grain in addition to its current use as forage. The agro-tourism and recreational wildlife industries are finding superior results from using pearl millet in rations for bobwhite quail production and for supplemental feeding. It is also an excellent feed for other birds, including dove, turkey, song-birds, ducks, and swine. The large immigrant population from Africa and the Indian subcontinent where pearl millet is a staple food ensures a steady demand in the US in the foreseeable future. Being gluten-free, marketing opportunities for this grain also exists in the health-food outlets.

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Table – 2.5. Taxonomic Classification of Pearl Millet. Family -

Gramineae

Sub-family -

Panicoideae

Tribe -

Panciceae

Genus -

Pennisetum

Species -

Americanum

Synonimia -

Pennisetum typhoideum (Burm) Staph & Hubbard Pennisetum typhoiidium Rich Pennisetum glaucum (L) R. Br. Pennisetum spicatum (L) Koern Pearl millet, Bulrush millet, Bajra (India), Mwele (East Africa), Kalasat (Burma)

Source: http://www.aicpmip.res.in

Each dot represents 20,000 hectares (http://www.aicpmip.res.in)

Figure – 2.2. Pearl Millet – Growing Areas in the Subcontinent.

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Table 2.6. Area and Production of Pearl Millet in Karnataka, India

Area

Production

Yield

(Lakh ha)

(Lakh tonnes)

(Kg/ha)

2007 - 08

4.300

3.540

823

2008 - 09

2.650

1.850

698

2009 - 10

3.040

1.500

493

2010 –11 (Advance)

3.110

2.400

772

Year

Source: http://www.aicpmip.res.in

Table – 2.7. Area and Production of Pearl Millet in Major Growing States of India

Rajasthan Year

Area (‘000 ha)

Production

Gujarat Area

(‘000 tons) (‘000 ha)

Haryana

Production

Area

Production

(‘000 tons)

(‘000 ha)

(‘000 tons)

1972–73

5355

1471

1842

1330

914

594

1977–78

4070

1092

1464

1279

901

405

1982–83

4916

1548

1421

1419

825

518

1987–88

4732

1662

1202

1053

626

500

1993–94

4767

2135

1228

1231

575

603

1999–2000

4571

2389

952

979

593

690

2004–05

5128

4140

971

1252

596

811

Source: Basavaraj et al (2010); www.ejournal.icrisat.org

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Production and Geographical Distribution Pearl millet belongs to the family Gramineae. It was classified by Linnarus (1753) into 2 sub species Panicum glaucum and Panicum ameicanium. The two names that were commonly used in the past: Pannisetum typoidus (Burm) and Pennisetum glaucum (L) R.Br. The first name is used today as a synonym for the crop (Table 2.5). Pearl millet in India is grown as a single season crop. Cultivation predominantly takes place on marginal lands and un-irrigated lands. Karnataka is one of the major pearl millet growing states in India. However, the area for production of pearl millet in Karnataka has declined over the years. Similar trend was observed in its production and yield from the year 2007 – 2011. The major decrease in the yield of the millet was seen in the year 2009 – 10 which improved in the year 2010 – 11 (Table 2.6). It is also grown in a small area as summer crop under irrigation particularly in the northwestern states of India mainly as a fodder crop. Area trends of pearl millet in India are constantly declining. Between 1972–73 and 2004–05, nearly 3 million ha has been diverted from pearl millet cultivation to other crops, such as wheat, rapeseed, mustard, cotton, chickpea and groundnut. Reduction in area under cultivation of pearl millet is highest in Gujarat with 48% decline from 1971–72 to 2004–05 (Table 2.7). The shift in area is also most prominent in Haryana where increased irrigation facilities have made the cultivation of fine cereals like rice (Oryza sativa) and wheat a more profitable venture. Pearl millet production is concentrated in Gujarat, Maharashtra and Rajasthan which account for 70% of production in India. These states also have the highest concentration of pearl millet consumers since bulk of the consumption for food use takes place in the growing areas. Haryana used to be an important growing state, but since the 1980s, rice and wheat have replaced pearl millet, and now it Page 37

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accounts for only 9% of pearl millet production in the country. On the whole, production levels have remained relatively stable and with the introduction of highyielding hybrids in the late 1980s, production has started increasing steadily. Pearl millet is very thinly traded in the world market. In the early 1970s and into the 1980s, pearl millet cultivation in India was primarily subsistence in nature with very little being marketed. A combination of low yields and fluctuating production in those years made trade infeasible. In 1987–88 close to 60,000 tons of pearl millet were exported to compensate shortfall in production due to severe drought in the main growing regions of the world. Since then exports of pearl millet have been increasing mainly to meet the growing demand for bird feed from developed countries. (Basavaraj et al 2010; FAO-ICRISAT 1996).

Grain Structure of Pearl Millet Pearl millet grains are shaped like liquid drop. They thresh free of hull. The grain can be up to 2mm in length and their weight ranges from 3mg to 15 mg. Pearl millet consists of small tear shaped kernels. The grains are small in comparison to cereal grains such as maize and sorghum. Due to their size they pack closely together leaving little air space. Pearl millet has a density of ~1.6 g/cm3 which is significantly higher that wheat (1.39 g/cm3), maize (1.39 g/cm3), rice (1.24 g/cm3), and sorghum (1.24 g/cm3). The color of the grains varies from pearly white to yellow, slate grey, brown and purple. The germ in pearl millet is large (17%) in proportion to the rest of the kernel. The germ of pearl millet is composed of two parts, the embryonic axis (rudimentary root and shoot) and the scutellum which functions as storage organ. The germ is relatively high in protein, sugar, oil and minerals. It also contains vitamins such as vitamin B and vitamin E. High protein and oil content in pearl millet is due to Page 38

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its large germ. Other components of pearl millet are 7.2 – 10.6% pericarp and 71 – 76% endosperm. The endosperm is comprised mostly of starch and protein with small amounts of fat and fiber. The bran of pearl millet consists of cellulose, hemicelluloses, minerals, protein, phosphorus, phytate phosphorus and fat (Taylor 2004; Hoseney 1994; Jain et al 1997a).

Chemical Composition of Pearl Millet Nutritionally pearl millet is comparable and even superior to major cereals with respect of energy value, proteins, fat and minerals. It makes an important contribution to human diet due to high levels of calcium, iron, zinc, lipids and high quality proteins. Besides, it is also a rich source of dietary fiber and micro nutrients (Anu Sehgal et al 2006; Malik et al 2002). Carbohydrates Carbohydrate components of pearl millet grains comprise of starch, dietary fiber and soluble sugars. Starch which consists of glucose in form of amylose and amylopectin is a predominant component of pearl millet endosperm. Pearl millet starches have amylose content ranging 20-21.5% and have a higher swelling power and solubility than other starches. In different pearl millet genotypes the starch content of the grain varies from 62.8 to 70.5 %, soluble sugar from 1.2 to 2.6 % and amylose from 21.9 to 28.8%. The grain is gluten-free. Free sugars like glucose, fructose, sucrose and raffinose are present in a range of 1.2 to 2.5%. Monosaccharides like arabinose, xylose glucose and uronic acids are the found in the non – starch polysaccharides fraction of the pearl millet (Taylor 2004; Hadimani et al 2001; Hoseney 1994). Page 39

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Starch is the major constituent of pearl millet. The isolation and characterization of pearl millet starch has been studied (Wankhede et al 1990; Hadimani et al 2001; Adelaide et al 1980; Hoover et al 1996). The yield of starch is approximately 50 - 60% on whole grain basis and contains about 20% amylose. The microscopic examination of pearl millet starch granules is morphologically similar to other millet starch granules. The starch granules ranged from polygonal to round in shape with characteristic dimensions in the range 10-16µm. Electron micrographs showed that some of the granules had deep indentations due to pressure exerted by protein bodies. Variations in shape and size of the starch granules have been attributed to premature biosynthesis, since the characteristic of any starch depends entirely on the time at which they were harvested and isolated (Wankhede et al 1990). Starch is classified as rapidly digestible (RDS), slowly digestible (SDS), and resistant starch (RS) based on its invitro digestibility. Starch fractions such as SDS and/or RS are nutritionally important as they have significant implications on human health, particularly glucose metabolism, diabetes management, colon cancer prevention, mental performance, and satiety (Patindol et al 2010). Studies on these nutritionally important starch fractions of pearl millet are lacking. Proteins Pearl millet, like sorghum, contains generally 9 to 13% protein, which is higher than in rice (7.2%) barely (11.5%), maize (11.1%) and sorghum (10.4%) (Desikachar 1975). When compared to maize by weight, pearl millet can be 8% - 60% higher in crude protein, 40% richer in the amino acids lysine and methionine, has good levels of cystine, and is 30% richer in threonine. It is regarded as having the highest scores of all the millets when comparing essential amino acids. The essential Page 40

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amino acid profile shows more lysine, threonine, methionine and cystine in pearl millet protein than in proteins of sorghum and corn (Adeola et al 1995). Its tryptophan content is also higher. The amino acid profile of pearl millet grain is better than that of normal sorghum or normal maize and is comparable to those of the small grains wheat, barley, and rice with a less disparate leucine/isoleucine ratio (Ejeta et al 1987; Hoseney 1994; Rooney et al 1987). The lysine content of the protein reported in pearl millet grain ranges from 1.9 to 3.9 g per 100 g protein. Pearl millet resembles maize in its distribution of proteins, especially with regards to the true prolamins, which are soluble in alcohol, and prolamins that are soluble in alcohol only after addition of a reducing agent. The albumin-globulin concentration of pearl millet is higher than normal sorghum and normal maize and is comparable to high-lysine sorghum lines. The level of tryptophan in pearl millet is probably close to that in high-lysine sorghum based on a calculated value from its fractions. The tyrosine level in pearl millet is lower than that in sorghum, maize, and rice but is comparable to that in barley and wheat. The isoleucine/leucine ratio in pearl millet is lower than that in sorghum and maize and compares favorably to the ratio in small grains (wheat, barley, and rice). This favorable amino acid balance with a high level of essential amino acids, coupled with the superior in vitro pepsin digestibility values, suggests that pearl millet is a nutritious and well-digested source of calories and protein for humans (Ejeta et al 1987). Among the essential amino acids, ariginine, threonine, valine, isoleucine and lysine had higher digestibility in pearl millet than corn. Pearl millet exhibits higher apparent small intestine digestibility of essential amino acids than other grains (Adeola et al 1995).

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Lipids Pearl millet contains up to 8% fat which is more than that in wheat, rice, barely sorghum and wheat (Lai et al 1980). The fatty acid in pearl millet is higher in palmitic, stearic and linolenic acids and lower in oleic and linoleic acids than corn (Adeola et al 1995). The energy density of pearl millet grain is relatively high, arising from its higher oil content relative to maize, wheat, or sorghum (Hanna et al 1990). Collins et al (1997) noted commercial hens given feed containing pearl millet grain had lower omega-6 to omega-3 fatty acid ratio, endowing the eggs with a fatty acid profile more favorable to human health. The total fat content of pearl millet is higher than all of the other millets. It is quite high in polyunsaturated fats, and linolenic acid comprises approx 4% of the fatty acids present. When the grain is used to feed layer hens, it has been noted that the eggs produced have a much higher concentration of the healthier omega-3 fatty acids. The overall lipid content in pearl millet grain ranges from 1.5 to 6.8% which is higher than all the millets (Taylor 2004). Pearl millet has proportionally large germ where most of the lipid is located. The free and bound lipid contents of pearl millet ranged from 5.6 to 6.1% and 0.6 to 0.9 % respectively. Free and bound non – polar lipid components in pearl millet were identified as triglycerides, diglycerides and monoglycerides (Hoseney 1994). Minerals There are wide fluctuations in the total mineral and trace elements contained in pearl millet, the biggest factor determining this is the nature of the soil it is grown in. It is found to be low in zinc, iron and manganese when compared to sorghum grain. The ash content of pearl millet ranged from 1.6 to 3.6% (Serna et al 1995). Mineral such as calcium, phosphorus, magnesium, manganese, zinc, iron and copper Page 42

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was found to be higher than corn. Minerals especially calcium, iron and phosphorus content of pearl millet is similar to cereals (Adeola et al 1995) Vitamins Pearl millet is an important source of thiamin, niacin and riboflavin (Taylor 2004). Riboflavin has, however, been implicated in lipid deterioration in presence of light (Hamilton 1999) Because of its high oil content, pearl millet is also a good source of fat – soluble vitamin E (2mg/100g). Vitamin E is known for its antioxidant activity in the form of tocopherol. Pearl millet is also a good source of vitamin A which is typically about 24 Retinol Equivalents (Taylor 2004). These lipid soluble vitamins are mainly located in germ. Anti – Nutrients Antinutritional factors present in considerable amounts in pearl millet limit protein and starch digestibility, hinder mineral bioavailability and inhibit proteolytic and amylolytic enzymes. Pearl millet grain appears to be generally free of any major anti-nutritional factors, such as the condensed tannins in sorghum grain having a pigmented testa, which reduces protein availability. Tannin content is low in the grain which makes the seeds very palatable to animals, and high tannin contents which are found in other grains like rye and sorghum have a tendency to inhibit protein digestion. On the other hand, pearl millet is often rich in fibre - associated antinutrients namely phytate and oxalate which have a negative influence on the bioavailability of minerals. Phytate content in pearl millet ranges from 172 to 327mg/100g. Phytate binds multivalent metal ions such as calcium and iron thereby interfering with their absorption in the gut (Taylor 2004). Pearl millet may not contain gluten, but it does contain goiterogens. Studies on rats fed high pearl millet diets also Page 43

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developed abnormal thyroid hormone patterns with hyperplasia. The substance found to cause this in pearl millet is known as Vitexin, 8-gycosylapeginin, and it inhibit thyroid perodixidase activity. However to put this into perspective, this will only cause problems if very high quantities of the seed are consumed. In areas of Sudan, where pearl millet is also a staple, these compounds have been implicated in goiter (Elnor et al 1997). Pearl millet is also known to contain saponin anti-metabolites at levels up to 200ppm. Saponins are found in many plants in their leaves, seeds, stems, roots, bulbs, blossoms or fruit. Saponins have the ability to dissolve in water to form a soapy froth. Saponins are known to be toxic to all cold blooded mammals, due to their ability to lower surface tension, but in humans saponins are believed useful in the diet as they have the ability to reduce cholesterol, however some plant species such as the soapberry that contain saponins are poisonous if swallowed and can cause urticaria (a type of skin rash) in many people. Some caution is recommended when feeding to fish that are sensitive to saponins (Taylor 2004).

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Chapter – III FOOD USES OF PEARL MILLET

Pearl millet grain is the staple diet for farm households in the world’s poorest countries and among the poorest people. In the Sahelian region of Africa and rural regions of northwestern India, pearl millet is an important cereal for consumption. Pearl millet stover is a valuable livestock feed in the growing regions in India and Africa. Exports and imports of pearl millet grain are negligible suggesting low demand, and/or unreliable availability of marketable surpluses for this commodity in world markets (Basavaraj et al 2010). Pearl millet is versatile millet used mainly as cooked, whole, dehulled or ground flour dough or as a grain like rice. In Sudan, millet is a staple diet of the people in the Western region (Darfur) and is consumed as thick porridge (aseeda), a thin porridge (nasha), kisra (unleavened bread) from fermented or unfermented dough. Jiria and Damierga are prepared from fermented dehulled pearl millet flour. Pearl millet contains more fat, proteins and minerals than cereals such as rice and millets such as sorghum. In spite of being nutritive, it has no place in the regular diet of the Indian people. Storability of pearl millet is poor and of its flour is poorer still due to its high fat content. Pearling of pearl millet has been tried as a means of producing low-fat pearled grains. Conditioning of pearl millet was investigated with a view to obtain in milling, different size fractions having different fat content. It was found that conditioning with water at the rate of 35ml/kg of the pearl millet produces low-fat grits having a fat content of 2.4% (Jain et al 1997). Pearl millet flour is highly susceptible to rancidity during storage. A study was conducted to produce shelf-stable and pre-cooked flours. Page 45

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A simple technique suitable of small scale food processors of Namibia was developed where pearl millet grains were subjected to thermal treatments of toasting, boiling and toasting and then boiling. The grains were milled, packed in brown paper bags and stored under ambient conditions for three months. Grains with wet thermal treatment showed no increase in the free fatty acid. Porridges of flour from untreated grain were associated with hydrolytic rancidity, whereas those of flours from thermally treated grains were not. This study indicated that thermal treatments can be successfully applied to extend whole pearl millet flour shelf life, and the treatment of boiling can be used to produce pearl millet flour that cooks more quickly (Komeine et al 2008). In Sudan, pearl millet, locally known as Dukhn is the third most important staple food crop after sorghum and wheat, with annual production of 800000 metric tons, and of immensely greater nutritional significance in the diets of poor people in drier parts of the country where drought causes frequent failure of other crops. Western Sudanese process pearl millet in several types of foodstuffs such as fermented or unfermented breads (Kisra), stiff (Aseda) or thin (Nasha) porridges, alcoholic beverages and Damirga, which is a fine sour and while flour obtained traditionally from pearl millet grains, which is used to make Asedat-damirga (stiff, white porridge), Nasha-beida (white nasha) or Kisra-beida (whilte kisra) (Abdalla et al 1998). Presence of pigments in the pericarp and endosperm regions of pearl millet imparts undesirable gray color to its products. Pearl millet grains were depigmented by soaking in 0.2N HCl for 18 h followed by washing, blanching at 98 oC for 30s and sun drying. Biscuits were prepared using depigmented pearl millet. Depigmentation improved the sensory attributes especially the color of pearl millet biscuits. The protein, fat, ash and total dietary fiber of pearl millet based biscuits were higher than Page 46

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the biscuits prepared out of refined flour. Depigmentation also improved the in vitro starch and protein digestibility as well as the soluble dietary fiber content of pearl millet biscuits. On the other hand, a significant decrease in protein, starch and insoluble dietary fiber was detected in pearl millet biscuits due to depigmentation. (Archana et al 2004). In another study, pasta was prepared using the depigmented pearl millet. Depigmentation of pearl millet significantly improved the sensory attributes particularly the color of pasta. Although depigmentation improved the in vitro protein and starch digestibility, decreases in protein and total dietary fiber were observed due to depigmentation (Rathi et al 2004). Pearl millet and maize were used in the preparation of masa, a fermented product originally made out of rice and tastes like dosa. Masa prepared out of millet had high protein content compared to that prepared out of rice (Ayo et al 2008). Biscuits were prepared from pearl millet grains that were subjected to processing treatment, i.e. blanching and malting. The pearl millet biscuits were organoleptically acceptable, with good mineral profile and low amount of anti-nutrients. However, biscuit prepared from blanched flour had high calcium, phosphorus, iron and manganese content as compared to that prepared from malted flour. Low anti-nutrient content and high in vitro digestibility were observed in biscuit prepared from blanched flour. Addition of soybean flour to biscuits helped to increase the mineral profile as compared to that prepared without incorporation of soybean flour (Singh et al 2006).

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Table 2. 8. Availability and Utilization of Pearl Millet in India between 1972 – 73 and 2004 – 05.

Year

Total Availability1 (million ton)

Food % Food % Demand Wastage Consumption Consumption (million (million (million ton) (million ton) ton) ton)

% Seed Demand (million ton)

Alternative % Alternative Uses Uses (million ton) (million ton)

1972–73

5.59

5.83

1002

0.1

0.01

1.8

0

0

1977–78

5.38

4.98

93

0.08

0.01

1.6

0.31

7

1982–83

6.13

6.30

1002

0.06

0.01

1.1

0

0

1987–88

5.91

4.06

69

0.06

0.01

1.1

1.78

30

1993–94

6.96

4.29

62

0.06

0.01

0.9

2.57

37

1999–2000

6.93

3.72

54

0.04

0.01

0.7

3.15

46

2004–05

9.19

4.05

44

0.04

0.01

0.5

5.04

55

1 - Production + Imports - Exports. 2 - The availability of pearl millet was less than the demand of pearl millet due to data discrepancy in consumption. Source: Basavaraj et al (2010)

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Based on the above data on household food uses, seed demand and exports of pearl millet, its alternative use were estimated. Seed consumption demand for cultivation of pearl millet has shown a continuous declining trend. The seed demand has been estimated after consultation with breeders on the trend in seed rate for pearl millet cultivation over the years. Seed rate is assumed to be 4 kg per ha during 1970s and 1980s and 3 kg per ha during the recent years. One of the factors that has contributed to the decline in seed demand is the introduction of hybrids in the 1980s, which are more vigorous than the local varieties and consequently require lower seed quantities per ha than the traditional seeds. The wide adoption of pearl millet hybrids is largely due to subsidies provided by various state governments for the purchase of these seeds and more importantly they are high yielding. It was found that the non-food utilization of pearl millet has rapidly increased over the years. The proportion of pearl millet that is being utilized in non-food uses has increased from 0% in the early 1970s to over 50% in 2004–05 (Table 2.8). Pearl millet is increasingly being diverted to other uses such as feed, alcohol production, food processing and other industrial uses. Some information on these uses was obtained through field surveys in Rajasthan and Haryana and conversation with industry experts. But the exact utilization of pearl millet in each of these sectors has to be estimated through an extensive study on industrial uses of pearl millet. Identifying the precise channels in which pearl millet is being utilized would be a necessary second step in tailoring research needs to cater to changing preferences. The findings of the study show that while food uses of pearl millet has declined sharply at the country level, its use as food though declining is still important in the major producing states. The decline in per capita consumption has plateaued between 2000 Page 49

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and 2004 with consumption increasing in a few states. Despite the overall decline in consumption a large share of pearl millet is consumed by the rural and urban poor while it only forms a small share in the basket of high income consumers. The increase in pearl millet production contrasted with its declining food use implies that its alternative use has been increasing. Alternative uses largely comprise demand for animal feed which includes mainly dairy (in rural parts of western Rajasthan) and to some extent in poultry, alcohol industry, starch industry, processed food industry and export demand. The potential demand for food processing, though at a budding stage, presents encouraging prospects for value addition. In addition to targeting increased yields, superior quality should be a dominant goal in continuing its usage as a staple in growing area and also other regions. Incentives should be provided to food industry to use pearl millet for new processed food products and traditional processed products (bread, biscuits, etc). Capitalizing on the niche markets that are developing in urban India would also benefit the pearl millet farmer and consumer simultaneously. Thus, research in understanding consumer preferences and profiling utilization needs of pearl millet will help in targeting the segments for better penetration. Hence, keeping in view the potential demand for pearl millet from these sectors, the prospects of pearl millet usage and production are encouraging (Basavaraj et al 2010).

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Chapter – IV IMPACT OF P ROCESSING ON N UTRIENTS IN P EARL MILLET

The main constraints in utilization of pearl millet in the industry include the small size of the grain and the large germ. The utilization of millets is also limited due to the presence of various anti-nutrients, poor digestibility of proteins and carbohydrates and low palatability. However, various processing technologies are able to affect positively the physicochemical composition of food grains in order to improve their nutritional value.

I. Impact of Processing on Bioavailable Minerals in Foods Bioavailability of minerals is an important function in food. Processing of foods has a positive impact though separation, partitioning or destroying inhibitors and transforming food components into complex ligands for metal ions thereby enhancing their availability. However the impact can also be negative by deactivating enzymes that degrade inhibitors or by generating insoluble metal compounds (e.g. oxidation, precipitation). Potential for the modulation of bioavailability will arise when the specification of metal ions and their ‘chemo-dynamics’ in processing and the body are better understood. The total amount of nutrients in food does not reflect the amount that is available to the body through absorption. Only certain amount is bioavailable. Bioavailability or biological availability are terms used to describe the proportion of a nutrient in food that can be utilized for normal body function. The term bioavailability was also introduced to better distinguish between the chemical availability (determination of ferrous iron by analytic chelating) and the availability in the bioassays (Heribert 1998). Damirga flour is characterized by an improved visual Page 51

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appearance, low phytic acid content and improved nutritive value. Traditional fermentation of pearl millet for 72 h at 37oC to produce fermented dough (Damirga) retained 25-84% of the major mineral such as calcium, magnesium, phosphorus, potassium, and sodium. Fermentation also retained around 52-65% of the minor minerals such as zinc, manganese and iron (Abdalla et al 1998). Table – 2.9. Factors Affecting Mineral Bioavailability

Diet – Related Factors •

Physiological Factors •

Gastric acidity



Luminal redox state



Intestinal secretion



Gut mortality

organic acids, sugars, mulin and oligofructose,



Body status (e.g. nutrient stores)

amino acids, peptides, fatty acids.



Short – term homeostatic mechanisms

Physiochemical forms of the minerals (e.g. solubility, dispersibility, ligand binding, non– specific absorption)



Oxidation state



Presence of enhancers, e.g. ascorbate (for iron)



(mediated through mucosal absorptive

Competitive inhibitors for transport protein binding

cells)

or absorption sites (e.g. minerals with similar binding characterizes)



Anabolic demands (e.g. infant growth, pregnancy, lactation)



Endocrine effects



Infections and stress



Genetic influences, metabolic degeneration and errors



Gut micro flora

Source: Heribert 1998.

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Processing methods like soaking, boiling and germination of pearl millet resulted in a significant reduction of phytate phosphorus. The concentrations of calcium, magnesium, iron and zinc increased upon soaking and germination, while boiling decreased calcium, magnesium and iron concentration. Solubility of minerals was higher in soaking and germination than in boiling (Sushma et al 2008). Decortication of grains is necessary for organoleptic and technological reasons such as astringency, texture etc. and helps in reducing the antinutrients localized in the bran fraction. Decortication of pearl millet reduced part of fiber and iron–binding phenolic compounds but did not successfully reduce phytate content as it was mainly located in germ and endosperm. (Lestienne et al 2005). Roasting is a dry – heat treatment reported to be beneficial in terms of retaining nutrition particularly proteins and iron. Pearl millet varieties considerably improved iron and zinc content upon roasting whereas the levels of calcium and copper decreased (Malik et al 2002). Processing methods like germination fermentation and roasting of the millet showed varied effects on the mineral composition of pearl millet however it reduced the antinutritional factors (Fasasi 2009). Two different exogenous phytases (plant phytase from wheat and microbial phytase form Aspergillus ficuum) were used simultaneously to obtain maximal hydrolysis products from two different pathways to achieve total myo – inositol 6 phosphate (IP6) degradation. Pearl millet grains were also subjected to abrasive decortication. Iron and zinc in-vitro availabilities of whole millet flour were significantly improved by phytate degradation, even if the IP6 were not all degraded. Total dephytinization of decorticated fraction led to a marked increase in iron and zinc in vitro availabilities, but that of bran fraction had no effect on either iron or zinc Page 53

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in vitro availability. Even if phytates are involved in reducing in vitro iron and zinc availability in pearl millet flour, fibres and tannins play an important role by chelating a high proportion of iron and zinc in grain hulls (Isabelle et al 2005). Fermentation, damirga preparation and sprouting caused appreciable changes in the chemical composition (moisture, ash, fiber, protein and oil contents), but markedly reduced the minerals contents (Na, K, Mg, Cu, Fe, Mn and Zn) of pearl millet (Adam et al 2009). Table – 2.10. Impact of Processing on Mineral Losses in Pearl Millet.

Processing

Possible Causes of Losses or Gains

References

Soaking &

Increased the concentrations of total calcium,

Sushma et al

germination

magnesium, iron and zinc.

2008

Solubility of minerals was high Milling Decortication

Reduced antinutrients localized in the bran fraction Did not reduce phytate content as it was mainly

Lestienne et al 2005

located in germ and endosperm Wet heat treatment Boiling

Decreased total calcium, magnesium and iron

Sushma et al

concentration

2008

Dry heat treatments Roasting

Improved iron and zinc content while decreased

Malik et al 2002

calcium and copper Phytates

Iron and zinc in-vitro availability improved by phytate

Isabelle et al

degradation

2005 Page 54

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II. Impact of Processing on Proteins Fermentation caused a reduction in the total protein content in pearl millet. This drop in protein content was attributed to the action of moulds and anaerobic bacteria, which degraded proteins and converted them to ammonia. However fermentation of pearl millet led to an improvement in IVPD which could be attributed to the partial degradation of complex storage proteins to more simple and soluble products and also due to the degradation of tannins, polyphenols and phytic acid by microbial enzymes (Abdalla et al 1998, Mardia et al 2002; Maha et al 2003; Selma et al 2002). On the other hand studies have reported that fermentation increased the crude protein content of pearl millet flour (Fasasi 2009). Nonetheless Damirga, fermented dough, significantly lowered protein content (Adam et al 2009). Culture fermentation by yeasts (S. diastaticus; S. cerevistiae) and lactobacilli (L. brevis; L. fermentum) at 30oC for 72 h improved protein digestibility (in vitro) of pearl millet flour significantly. Of the cultures used to ferment, Saccharomyces cerevisiae enhanced the in vitro protein digestibility of the flour significantly. Weaning mixtures prepared from the fermented flour were also found to be organoleptically acceptable (Khetrapaul et al 1990). Natural fermentation at 20, 25 and 30°C for 72 h brought about a significant reduction in phytic acid content and increased polyphenol content of pearl millet flour. An improvement in protein digestibility (in vitro) was noticed at all the temperatures of natural fermentation, the highest being at 30°C (Neelam et al 1991). Ionizing radiation is an efficient technique used worldwide, to preserve food, extend its shelf life and control food borne pathogens. The chemical structure of irradiated food is less modified than heat-treated one and this technique avoids the use of potentially harmful chemicals (Siddharaju et al 2002). Although radiation process Page 55

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alone did not cause any change in the IVPD, when combined with cooking, it reduced IVPD. In vitro studies have shown that phytate-protein complexes are insoluble and less subjected to attack by proteolytic enzymes than the protein alone (Ravindran et al 1995) and subsequently affect the functional properties of the protein. Moreover, the partial removal of tannin and phytate probably created a large space within the matrix, which increased the susceptibility to enzymatic attack (Rehman et al 2001) and consequently improved the digestibility of protein after radiation treatment. Higher protein digestibility after radiation treatment may be due to increased accessibility of the protein to enzymatic attack However; this effect could also be due to inactivation of proteinaceous antinutritional factors (Van der Poel 1990). The in vitro apparent digestibility of protein data indicated a beneficial effect for radiation when the in vitro digestibility of the studied cereal seeds was considered. The apparent improvement in in-vitro digestibility that being ensured through radiation treatment, may be attributed to appreciable effect of radiation treatment on the antinutritional factors present naturally in non-radiated flour which is more sensitive to enzyme action. It is well known that radiation could induce and (or) stimulate other factors. Molecular rearrangement and changes in peptide linkages between the amino groups of amino acids could affect the nutritive availability and the biological utilization of the irradiated proteins. Such changes could interfere with the protein digestibility and/or its biological value. Thus, protein digestibility may be decreased and/or increased without incurring amino acid destruction (El-Hakeim et al 1991). Therefore, it could be concluded that the radiation process offers a good treatment for millet to reduce or eliminate their antinutritional factors with consequent increase in their digestibility and thereby increase utilization of their proteins. Therefore, radiation can be applied Page 56

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to alleviate the severe problem of off-flavor and bitter taste production during storage. Moreover, radiation process when compared to chemicals or heat treatment emerges as an attractive and healthy alternative (Shazali et al 2011). Roasting a dry – heat treatment was beneficial in terms of retaining nutrients particularly proteins. Dehulling of the pearl millet grains increased the IVPD due to removal of antinutritional factors in the dehulled flour. Cooking as well as combination of dehulling and cooking of pearl millet significantly reduced the IVPD (Adam et al 2009; Malik 2002; Siddharaju et al 2002). Germination caused an increase in the total protein content in pearl millet (Fasasi 2009). On the other hand, pearl millet malt had low protein content which could be attributed to the loss of low molecular weight nitrogenous compounds during the steeping process and rinsing of the grains during the process of germination. The increase in nitrogen solubility index during malting was observed which could be due to gradual degradation of reserve protein into amino acids and short peptides caused by elevating the levels of protease enzymes which caused an increase in IVPD. The increase in IVPD can be attributed to an increase in soluble proteins, due to partial hydrolysis of storage proteins by endogenous proteases produced during the germination process. Such partially hydrolyzed storage proteins are more easily available for pepsin attack (Bhise et al 1998). The decrease in anti-nutrients like phytic acid may have also contributed to the high levels of IVPD levels. Although a change in the amino acid profile was observed due to germination, the total amino acid content remained the same since the protein content did not change. However, the lysine content of one pearl millet variety (SDMV 91018) increased throughout germination. The difference in lysine content could be due to slight differences in the Page 57

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proportion of germ in the pearl millet varieties investigated. The increase in the lysine content of the protein in one of the germinated pearl millet variety is related to the transamination (change of one amino acid into another one), which may have occurred during germination affecting the amino acid profile of pearl millet. This transamination was also reported in sorghum (Taylor 1983). The level of leucine in pearl millet malts was generally higher than the FAO Scoring Pattern (Pelembe et al 2003).

Table – 2.11. Impact of Processing on Protein in Pearl Millet.

Processing

Out Come

Soaking and Germination

Increased crude protein

Fermentation

Increased crude protein

Dehulling

Increased the IVPD

References Fasasi 2009 Adam et al 2009 Malik 2002

Cooking

Decreased the IVPD

Dehulling and Cooking

Decreased the IVPD

Roasting

Increased crude protein content

Siddharaju et al 2002

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III.

Effect of Processing on Starch Fermentation reduced the carbohydrate content, while germination and

roasting significantly increased the carbohydrate level thereby increasing the energy density of the flour (Fasasi 2009). Malting or germination, a potentially low cost method of processing is very important to the rural communities of Africa and India who rely on pearl millet foods for their energy and nutritional requirements. The reduction of carbohydrate content due to germination has led to a decrease in the energy value of food products prepared from germinated flours. In adults it is important that the amount of energy ingested be equal to the amount of energy expended. However, this decrease is compensated by the fact that carbohydrate of malted pearl millet would be more available than that of non-germinated grains. In infants the amount of energy ingested is more than they expend and they use the rest of the energy to build up their bodies. It is crucial that the reduction of the level of carbohydrates (starch) should not be very high if the malts are meant for the preparation of traditional southern African food products, such as opaque beers, called uphutsu in Mozambique, porridges, and traditional unleavened pancakes, called makati in Mozambique, as well as weaning foods for infants called nthlatu in the south of Mozambique, where minimum carbohydrate reduction may be advantageous (Pelembe et al 2003). Debranning increased starch in pearl millet due to removal of bran. While, soaking, dry heat treatment and germination reduced starch content. Reduction of starch caused by soaking and germination due to activation of amylase during these treatments resulted in the hydrolysis of starch. Autoclaving ruptured starch granules, which facilitate the amylolytic hydrolysis of starch granules resulting in improved Page 59

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starch digestibility. Soaking, debranning, and germination respectively reduced starch digestibility while coarse grinding significantly improved starch digestion. Dry heat treatment did not cause any significant changes in the starch digestibility. A higher value of starch digestibility on soaking was due to leaching of antinutrients like phytic acid and polyphenols, which inhibits – amylase. Similarly debranning removed the antinutrients with bran and hence improved starch digestibility. Germination resulted in an improved starch digestibility due to activation of amylase, which accelerates the hydrolysis of starch (Alka et al 1997). Traditional fermentation for 14 h at 37 oC reduced starch due to the action of αand β-amylases produced by microorganisms. (Abdalla et al 1998). Fermentation by yeasts (S. diastaticus; S. cerevistiae) and lactobacilli (L. brevis; L. fermentum) at 30oC for 72h improved starch and protein digestibility (in vitro) of pearl millet flour. The flour fermented by Saccharomyces diastaticus, a starch hydrolysing yeast, had the highest starch digestibility whereas fermentation by Saccharomyces cerevisiae enhanced the in-vitro protein digestibility of the flour significantly (Khetarpaul et al 1990). Natural fermentation of pearl millet at 20, 25 and 30°C for 72 h reduced phytic acid content while increased polyphenol content. An improvement in starch digestibility (in vitro) was noticed at all the temperatures of natural fermentation, the highest being at 30°C (Neelam et al 1991). Starch digestibility of ground pearl millet was significantly lower than the diet containing the unground (Whole seeds) pearl millet. The factor affecting starch digestibility in grains is enzyme accessibility to starch granules (Tester et al 2004), which is variable among cereal grains. Grinding cereal grains does not always result in nutritional improvement (Carre 2004). Rather, whole grains are believed to Page 60

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enhance gizzard function, which in turn may improve enzyme access to substrate particles (Garcia et al 2006).

Table – 2.12. Impact of Processing on Carbohydrate in Pearl Millet.

Processing

Outcome

References

Fermentation

Increased starch digestibility

Khetarpaul 1990

Soaking &

Decreased carbohydrate level but improved starch

Abdalla1998

germination

digestibility

Roasting

Increased carbohydrate level

Debranning

Increased starch content as well as starch digestibility

Autoclaving

Improved starch digestibility

Soaking

Improved starch digestibility

Fasasi, 2009 Alka 1997

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