Cereals processing technology

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56 Cereals processing technology biotic factors may be engineered using appropriate genes. Resistance to viruses, bacteria, fungi, nematodes and insects has been reported. 4.3.2 Manipulation of expression of native genes for disease resistance Classical cereal breeding has involved the combination of disease-resistant genes from different sources to produce commercial varieties with effective disease resistance (Hammondkosack and Jones 1997). Molecular markers or direct analysis for the presence of the required gene are now used to improve the efficiency of selection of disease-resistant lines in breeding. One option for the engineering of cereals with disease resistance is to manipulate or enhance the levels of expression of genes already present in the genome. Specific options include the expression of defence genes using constitutive promoters such that the defence gene product was always produced by the plant regardless of the presence of a specific pathogen. Promoters induced by the disease are also an important option. This approach allows defence gene products to be produced by the plant only in response to attack by the pest. 4.3.3 Novel genes for disease resistance Novel genes from other plants or non-plant sources (Bowles 1990) may provide durable resistant genes for use in cereals (Table 4.2). Examples have been described for bacteria, fungi, nematodes and insects (Shewry and Lucas 1997). The use of virus-derived sequences for breeding virus-resistant plants has been a notable success in many species (Buck 1991, Malik 1999). 4.3.4 Environmental impact of disease resistance Transgenic plants with resistance to pests and diseases may have a significant impact on the environment (Dale and Irwin 1998). The risks should be similar to Table 4.2 Some novel pest- and disease-resistant genes of potential value in cereals (Malik 1999) Type of Gene Source protection Virus Coat protection Barley yellow dwarf Coat protection Maize chlorotic mottle Maize chlorotic dwarf Maize chlorotic mosaic Bacterial Chitinase Various and fungi Glucanase Various Insects Bt toxin Bacillus thuringiensis
those of traditional resistance breeding. However, if the transgenic strategies prove dramatically more effective they could seriously deplete populations of plant pathogens and even lead to the extinction of highly specific pest organisms. Evaluation of these risks is important in successful applications of transgenic technology (Bergelson et al. 1999). 4.4 Improved nutritional properties Biotechnology, cereal and cereal products quality 57 4.4.1 Cereals and human nutrition Cereals are a very important part of human diets. The three major species, wheat, maize and rice, account for a large proportion of the calories and protein in human diets. The importance of cereals in the food chain is also attributable to the extensive use of cereals in the diets of animals. The major constituents of cereals are the carbohydrates and proteins. Other grain components such as lipids and vitamins may be of great significance in human nutrition because of the large contribution of cereals to the diet. Biotechnology provides new options for manipulation of the nutritional properties of cereal grains. The carbohydrates of cereals include the simple sugars, the more complex oligosaccharides such as fructans, storage polysaccharides of the grain (starch) and the cell wall polysaccharides, all of which are of nutritional value. All of these carbohydrate components are potential targets for manipulation in improvement of cereal quality. (For example, sugar beet has been transformed to produce fructans (Sevenier et al. 1998).) Benefits that may result include reduced cariogenic bacteria (dental health), lower energy value and stimulation of beneficial bacteria in the colon. The sugar content may also influence the quality of the grain for various products. Fructans may be considered to be important to human nutrition because of their possible role as soluble fibre (Ninees 1999). Starch, as the major component by weight of the grain, may have a great impact on nutritional quality. Resistant starches (not digested in the gut) may be considered critical in influencing the incidence of certain human diseases, such as heart disease. The cell wall polysaccharides may also be important as either soluble or insoluble fibre, depending on the composition of the polysaccharides in the cereal product. Soluble fibres may reduce the risk of heart disease while insoluble fibres contribute to reduced risk of colonic cancers. Cereal proteins are not well balanced in amino acids required in a nutritionally balanced diet, and genetic engineering may provide opportunities to improve the balance of essential amino acids in cereal-based diets. The lipids in cereals are generally of limited importance in human nutrition but may be important in animal diets. The manipulation of iron levels in cereals through the introduction of haemoglobin illustrates the potential application of biotechnology to enhancing the nutritional value of cereals.
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Related titles from Woodhead’s fo
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vi Contents 3.4 Recent developments
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viii Contents 9.11 References . . .
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x Contributors Chapter 6 Dr Jim Dex
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2 Cereals processing technology The
Page 14 and 15: Part I Cereal and flour production
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Page 20 and 21: Total UK area = 792,000 ha Total UK
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Page 86 and 87: 5 Rice production B. S. Luh, Univer
Page 88 and 89: Rice production 81 evaluating quali
Page 90 and 91: Rice production 83 Table 5.1 Range
Page 92 and 93: Table 5.2 Physicochemical (quality)
Page 94 and 95: Table 5.3 Physicochemical (quality)
Page 96 and 97: Table 5.4 Milled rice grades and re
Page 98 and 99: Rice production 91 caused by the va
Page 100 and 101: Rice production 93 Based on water r
Page 102 and 103: Rice production 95 Rice disease res
Page 104 and 105: Rice production 97 Fig. 5.1 Flow ch
Page 106 and 107: Rice production 99 The milling yiel
Page 108 and 109: 5.7.1 Frozen rice Frozen cooked ric
Page 110 and 111: Rice Chex Õ and Crispix Õ are mad
Page 112 and 113: cake puffing machine that has been
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5.16 References Rice production 107
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6 Pasta production B. A. Marchylo a
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Pasta production 111 dumpling-like
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Fig. 6.1 A simple schematic of a lo
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Pasta production 115 from the sprea
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environment with a final moisture c
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Pasta production 119 cooking qualit
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6.5 Raw material selection Pasta pr
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Pasta production 123 is directly re
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Pasta production 125 because of sup
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more difficult for farmers to grow
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Pasta production 129 Cereal Chem, (
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7 Asian noodle processing D. W. Hat
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Asian noodle processing 133 Most mi
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Fig. 7.1 Stages in different noodle
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Asian noodle processing 137 number
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Asian noodle processing 139 White s
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Asian noodle processing 141 Fig. 7.
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the final product. A two-stage proc
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Asian noodle processing 145 Table 7
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Asian noodle processing 147 Fig. 7.
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Asian noodle processing 149 with th
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7.7 Future of the industry Asian no
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percent, thus allowing the core to
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Asian noodle processing 155 PreHarv
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Asian noodle processing 157 43. KIM
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form as a breakfast food. He called
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Breakfast cereals 161 words. Jobber
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8.3 Recent trends and technology de
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Breakfast cereals 165 In continuous
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Breakfast cereals 167 were parallel
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Breakfast cereals 169 with quiet fa
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With the addition of personal compu
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9 Malting G. Gibson, Consultant, Co
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3. Muntons Malt This company operat
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Malting 177 of a barley corn. Signi
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Fig. 9.3 Diagrammatic layout of cir
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stored in relatively small hoppered
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allow gentle drying without subject
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Malting 185 situated externally, on
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Fig. 9.6 Capacity of circular flat
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convenient to convert their reinfor
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Malting 191 free filling of steeps
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Malting 193 Fig. 9.7 Fixed floor ge
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Malting 195 Fig. 9.8 Fixed floor ki
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Malting 197 with greater flexibilit
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Malting 199 machines, and an ideal
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storage to malt storage. Any additi
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9.10 Further reading BRIGGS D E (19
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The discovery that dough left for l
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Breadmaking 207 The development of
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the processes are similar to those
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ead to be ‘fresh’. When we coll
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such as unwanted holes or dense pat
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main function of yeast is to produc
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• Enzyme active materials have be
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Breadmaking 219 application of a mi
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Breadmaking 221 mixing, namely that
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Breadmaking 223 devices which roll
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Breadmaking 225 that a point which
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Breadmaking 227 10.9.2 Mixing and p
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Breadmaking 229 UK, pp. 1-17. CAUVA
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Index acid flavours 211 acidified l
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disease control 23-4 grain quality
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asic process 175-81 future of the i
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special and numerical grades 90 US
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