14 Nutrition Introduction elements. Also cereal proteins are deficientin certain essential amino acids, notably lysine. Nutrition in most adults is concerned with the Cereals however are rarely consumed alone, and supply and metabolism of those components of nutrients in foods consumed together, may mutu- the diet needed to maintain normal functioning ally compensate for each other's deficiencies. of the body(water and oxygen are also necessary but these are not generally regarded as nutrients). While it is indisputable that individuals and populations should consume the right amounts In the young and in pregnant and lactating of nutrients to avoid symptoms of deficiency and mothers additional nutritional requirements are imposed by the need to support growth or milk excess, defining those amounts'is' not easy, not least because the requirements vary from one production. Nutrients-the substances that provide energy individual to another. The British Government and raw materials for the synthesis and main- for more than 30 years issued standards in the tenance of living matter, in the diet of humans form of Recommended Intakes for Nutrients(DHSS, 1969)and Recommended Daily Amounts(RDA)of and other animals, comprise protein, carbohydrate, food energy and nutrients (DHSS, 1979).In fat, all of which can provide energy, minerals and vitamins. Those nutrients that cannot be made revising the recommendations for the dietary in sufficient quantities by conversion of other M requirements of the nation, the Committee on Medical Aspects of Food Policy (COMA), noted nutrients in the body, are called essential. They that the standards were frequently used in a way include some vitamins, minerals, essential amino that was never intended, that is they were used acids and essential fatty acids. An insufficiency of an essential nutrient causes a specific deficiency to assess the adequacy of the diets of individuals. In order to ensure that deficiencies were avoided disease. Deficiency diseases are now rare in the the RDAs represented at least the minimum West where food is plentiful, but they remain a problem in the Third world, where natural disasters requirements of those individuals with the greatest need. In terms of the population as a whole, and confflict frequently lead to malnutrition and even starvation. Aid provided for the relief of therefore, they were overestimates, and indivi- such disasters always includes a high proportion duals ingesting less than the RDA for any nutrient of cereals, demonstrating their high nutritional may be far from deficient. Instead of revized RDAS, Dietary Reference Values(DRV) for Food value. Although cereals make an important contribu- Energy and Nutrient for the United Kingdom tion to the diet they cannot alpport life (DH, 1991)were issued. They applied to energy, because they are lacking in vitamins A(except for for proteins, fats, sugars, starches, non-starch poly- yellow maize), B12 and C. Whole cereals also saccharides, 13 vitamins and 15 minerals,and contain phytic acid, which may interfere with they comprised: the absorption of iron, calcium and some trace Estimated Average Requirement(EAR)-an 276
14 Nutrition Introduction elements. Also cereal proteins are deficient in certain essential amino acids, notably lysine. Cereals however are rarely consumed alone, and ally compensate for each other’s deficiencies. While it is indisputable that individuals and populations should consume the right amounts of nutrients to avoid symptoms of deficiency and excess, defining those ‘right amounts’ is not easy, not least because the requirements vary from one individual to another. The British Government, for more than 30 years issued standards in the form of Recommended Intakes fm Nutrients (DHSS, 1969) and Recommended Daily Amounts (RDA) of food energy and nutrients (DHSS, 1979). In revising the recommendations for the dietary requirements of the nation, the Committee on Medical Aspects of Food Policy (COMA), noted that was never intended, that is they were used to aSSeSS the adequacy of the diets of individuals. In order to ensure that deficiencies were avoided the RDAs represented at least the minimum requirements of those individuals with the greatest need. In terms of the population as a whole, therefore, they were overestimates, and individuals ingesting less than the RDA for any nutrient may be far from deficient. Instead of revized RDAs, Dietary Reference Values (DRV) for Food Energy and Nutrient for the United Kingdom (DH, 1991) were issued. They applied to energy, proteins, fats, sugars, starches, non-starch polysaccharides, 13 vitamins and 15 minerals, and they comprised: Estimated Average Requirement (EAR) - an Nutrition in most adults is concerned with the the diet needed to maintain normal functioning of the body (water and oxygen are also necessary but these are not generally regarded as nutrients). In the young and in pregnant and lactating mothers additional nutritional requirements are imposed by the need to support growth or milk production. Nutrients - the substances that provide energy and raw materials for the synthesis and maintenance of living matter, in the diet of humans and other animals, comprise protein, carbohydrate, fat, all of which can provide energy, minerals and vitamins. Those nutrients that cannot be made in sufficient quantities by conversion of other include some vitamins, minerals, essential amino acids and essential fatty acids. An insufficiency of an essential nutrient causes a specific deficiency disease. Deficiency diseases are now rare in the West where food is plentiful, but they remain a problem in the Third world, where natural disasters and conflict frequently lead to malnutrition and even starvation. Aid provided for the relief of such disasters always includes a high proportion of cereals, demonstrating their high nutritional value. Although cereals make an important contribution to the diet they cannot alone support life because they are lacking in vitamins A (except for yellow maize), BIZ and C. Whole cereals also contain phytic acid, which may interfere with the absorption of iron, calcium and some trace suPP1Y and metabo1ism Of those components Of nutrients in foods consumed together, may mutunutrients in the bodyY are ca11ed essentia1* They that the standards were frequently used in a way 276
NUTRITION 277 estimate of the average requirement or need for excessive and should be avoided So also should food energy or a nutrient table salt and foods cooked or preserved in Reference Nutrient Intake(RNI)- enough of excessive salt nutrient for almost every individual,even In the U.S. A. the USDA/USDHHS published someone who has high needs for the nutrient. guidelines (1985) for a healthy diet including the Lower reference Nutrient Intake (LRND-the following recommendations amount of a nutrient that is enough for only a small number of people with low needs Eat a variety of foods Safe intake-a term normally used to indicate Maintain desirable weight the intake of a nutrient for which there is not Avoid too much fat, saturated fat and cholesterol enough information to estimate requirements Eat foods with adequate starch and fibre A safe intake is one which is judged to be Avoid too much sugar adequate for almost everyone's needs but not Avoid too much sodium so large as to cause undesirable effects f you drink alcoholic beverages, do so in In recognition of the fact that people of different Both U. K. and U.S. recommendations acknow sexes, ages(e.g. infants, children, adults) and ledge the importance of cereals, particularly as a conditions(e.g. pregnant and lactating mothers) source of energy and non-starch polysaccharides have different requirements, DRVs appropriate In addition, however, cereals provide many other to the different groups were defined aluable nutrients, including proteins, vitamins Deficiency diseases, such as rickets, stunting, and minerals as several of the tables and figure deformities and anaemia, are now rare in Western in this chapter demonstrate countries and, in considering the relationship between food and disease, emphasis has shifted to other diseases that are thought to be diet Cereals in the diet related: these include cancer of the colon(associ- For the majority of the world's human popula ated with animal protein intake, particularly tion, cereal-based foods constitute the most meat), breast cancer(associated with fat intake), important source of energy and other nutrients In and stroke and heart disease, associated with the poorest parts of the world starchy foods consumption of salt and animal( saturated )fat including cereals, may supply 70% of total energy ( Bingham, 1987 In the wealthiest nations the proportion obtained from cereals has declined fairly rapidly: in the Recommendations U.S.A. during the present century the proportion of total energy provided by cereals has dropped Recommendations appropriate to the U. K. from 40% to between 20 and 25%. The propor- situation are that cereals, particularly whole grain, tions of some important nutrients derived from together with potatoes, should be eaten in generous cereals and products in Britain are shown in Table amounts at each main meal to satisfy appetite, 14.1 three or more portions of fresh vegetables or fruit, preferably green or yellow, should be eaten per Positive attributes of cereals as foods containing the most protein. Low fat dairy foods should be chosen in preference to high fat ones Starch and all sugar, refined starches, and foods made Cereals are a particularly rich source of starch from them, such as biscuits, cakes, sweets, etc. as it constitutes by far the most abundant storage should be used sparingly. product in the endosperm Starch is an important More than 80g per day for men and more than source of energy, it is found only in plants 50g per day for women, of alcohol is considered (although the related compound glycogen occurs in
NUTRITION 277 excessive and should be avoided. So also should table salt and foods cooked or preserved in excessive salt. In the U.S.A. the USDAAJSDHHS published guidelines (1985) for a healthy diet including the following recommendations: Eat a variety of foods. Maintain desirable weight. Avoid too much fat, saturated fat and cholesterol. Eat foods with adequate starch and fibre. Avoid too much sugar. Avoid toO much sodium. If you drink alcoholic beverages, do so in moderation. Both U.K. and U.S. recommendations acknowledge the importance of cereals, particularly as a source of energy and non-starch polysaccharides. In addition, however, cereals provide many other valuable nutrients, including proteins, vitamins and minerals as several of the tables and figures in this chapter demonstrate. estimate of the average requirement or need for food energy or a nutrient. Reference Nutrient Intake (RNI) - enough of a nutrient for almost evey individual, even someone who has high needs for the nutrient. Lower Reference Nutrient Intake (LRNI) - the amount of a nutrient that is enough for only a small number of people with low needs. Safe Intake - a term normally used to indicate the intake of a nutrient for which there is not enough information to estimate requirements. A safe intake is one which is judged to be adequate for almost everyone’s needs but not so large as to cause undesirable effects. In recognition of the fact that people of different sexes, ages (e.g. infants, children, adults) and conditions (e.g. pregnant and lactating mothers) have different requirements, DRVs appropriate to the different groups were defined. Deficiency diseases, such as rickets, stunting, deformities and anaemia, are now rare in Western countries and, in considering the relationship between food and disease, emphasis has shifted to other diseases that are thought to be diet related: these include cancer of the colon (associ- For the majority of the world’s human populaated with animal protein intake, particularly tion, cereal-based foods constitute the most meat), breast cancer (associated with fat intake), important source of energy and other nutrients. In and stroke and heart disease, associated with the poorest parts of the world starchy foods, consumption of salt and animal (saturated) fat including cereals, may supply 70% of total energy. (Bingham, 1987). In the wealthiest nations the proportion obtained from cereals has declined fairly rapidly: in the U.S.A. during the present century the proportion of total energy provided by cereals has dropped from 40% to between 20 and 25%. The proportions of some important nutrients derived from cereals and products in Britain are shown in Table 14.1. Positive attributes of cereals as foods Starc, Cereals are a particularly rich source of starch as it constitutes by far the most abundant storage product in the endosperm. Starch is an important More than 8Og per day for men and more than source of energy, it is found only in plants (although the related compound glycogen occurs in Cereals in the diet Recommendations Recommendations appropriate to the U.K. situation are that cereals, particularly whole grain, together with potatoes, should be eaten in generous amounts at each main meal to satisfy appetite, three or more portions of fresh vegetables or fruit, preferably green or yellow, should be eaten per day and two or more portions of low fat foods containing the most protein. Low fat daiy foods should be chosen in preference to high fat ones and all sugar, refined starches, and foods made from them, such as biscuits, cakes, sweets, etc. should be used sparingly. 50g per day for women, of alcohol is considered
TECHNOLOGY OF CEREALS TABLE 14.1 Contributions (%)Made by Cereal Products to the Nutritional value of Household Food in Britain. 1990* Bread Cereals B and Breakfast wholemeal cereals 1.0 0.8 7.6 0.5 Fatty acids 12.1 0.6 1.8 0.7 Starch 73.0 Calcium 954 15, Sodium 38.3 12.6 070.53 5.4 1.0 Vitamin D 12.3 Values calculated from appendix b, Table 14, Household Food and Expenditure 1990 MAFF, HMsO, London, 1991 nil. Reproduced with the permission of the Controller of Her Majesty's Stationery Office animal tissues). In the past, starch has been under- low and gelatinization takes place at an elevated valued by nutritionists, who have emphasized temperature its association with obesity, and recommended Energy is released from starch by digestion of reduction in, for example, bread consumption by starch polymers to produce glucose, which is those wishing to control their weight. However, absorbed into the bloodstream glucose yields 16 starch is preferable, as an energy source, to fat, kilojoules or 4 kilocalories per gram (joules are now and a further advantage of starch consumed as the preferred unit in which to express energy part of a cereal food is that it is accompanied 4.184J= 1 cal) by vitamins, minerals and protein. In the best Starches from ' amylo'mutant types of cereals balanced diet starch would probably contribute (mainly maize), which have a higher than usual rather more than the 20% that it provides in the amylose content, are less readily digested. After average U.K. diet today (nearly 40% comes from cooking at high temperatures, the indigestibility fat, and 13% from sugar). The value of 31. 5% may be enhanced, giving rise to a small propor- for energy contributed by cereals (Table 14. 1) tion of resistant starch. Even in other cooked cereal refers only to foods consumed in the home products some resistant starch can arise; it behaves Most starch is consumed in cooked products, like fibre, passing unchanged through the gut in the majority of which the starch granules are The method of cooking is important in deter gelatinized, making them readily digestible by mining the amount of resistant starch formed. In amylase enzymes pesent in the gut. For this to corn fakes produced by extrusion cooking the occur however, abundant water is required as proportion of resistant starch is less than in starch can absorb more than 20 times its own conventionally produced flakes( Ch. 11) mass during gelatinization. In some baked Energy is a vital requirement of every healthy products, such as shortbread, much fat and individual but energy that is not expended in little water are present; consequently few of the physical or physiological activity is stored either granules are gelatinized Other factors, such as as adipose tissue or glycogen. These provide osmotic conditions, affect gelatinization, these a necessary store from which energy may be are much affected by the amount of sugar in the released when required The superiority of starch recipe: in high sugar conditions water activity is as a dietary energy source does not derive from
278 TECHNOLOGY OF CEREALS TABLE 14.1 Contnbutwns (“h) Made by Cereal Products to tk Nurn’tional Value of Household Food in Britain. 1990* Bread Cakes, Cereals White Brown and pastries, Breakfast wholemeal biscuits cereals Energy 31.5 7.2 3.4 8.2 3.4 Fat 12.8 1 .o 0.8 7.6 0.5 Fatty acids: Saturated 12.1 0.6 0.3 9.0 0.3 Polyunsaturated 13.7 2.2 1.4 5.0 1.4 Sugars 18.7 1.8 0.7 10.0 2.8 Starch 73.0 20.4 9.0 9.9 8.5 Fibre 45.5 7.4 11.6 5.0 9.9 Calcium 24.6 7.5 2.8 4.0 1 .o Iron 49.0 8.7 7.7 6.7 15.4 Sodium 38.3 12.6 6.5 5.0 5.4 Vitamin C 1.5 - 1.0 Vitamin A 1.1 - - 0.5 - Vitamin D 12.3 - - 1.3 9.6 - - * Values calculated from appendix B, Table 14, Household Food and Expenditure 1990 MAFF, HMSO, London, 1991. -_ - nil. Reproduced with the permission of the Controller of Her Majesty’s Stationery Office. animal tissues). In the past, starch has been under- low and gelatinization takes place at an elevated valued by nutritionists, who have emphasized temperature. its association with obesity, and recommended Energy is released from starch by digestion of reduction in, for example, bread consumption by starch polymers to produce glucose, which is those wishing to control their weight. However, absorbed into the bloodstream. Glucose yields 16 starch is preferable, as an energy source, to fat, kilojoules or 4 kilocalories per gram (joules are now and a further advantage of starch consumed as the preferred unit in which to express energy, part of a cereal food is that it is accompanied 4.184 J = 1 cal). by vitamins, minerals and protein. In the best Starches from ‘amylo’ mutant types of cereals balanced diet starch would probably contribute (mainly maize), which have a higher than usual rather more than the 20% that it provides in the amylose content, are less readily digested. After average U.K. diet today (nearly 40% comes from cooking at high temperatures, the indigestibility fat, and 13% from sugar). The value of 31.5% may be enhanced, giving rise to a small proporfor energy contributed by cereals (Table 14.1) tion of resistant starch. Even in other cooked cereal refers only to foods consumed in the home. products some resistant starch can arise; it behaves Most starch is consumed in cooked products, like fibre, passing unchanged through the gut. in the majority of which the starch granules are The method of cooking is important in detergelatinized, making them readily digestible by mining the amount of resistant starch formed. In amylase enzymes pesent in the gut. For this to corn flakes produced by extrusion cooking the occur however, abundant water is required as proportion of resistant starch is less than in starch can absorb more than 20 times its own conventionally produced flakes (Ch. 11). mass during gelatinization. In some baked Energy is a vital requirement of every healthy products, such as shortbread, much fat and individual but energy that is not expended in little water are present; consequently few of the physical or physiological activity is stored either granules are gelatinized. Other factors, such as as adipose tissue or glycogen. These provide osmotic conditions, affect gelatinization, these a necessary store from which energy may be are much affected by the amount of sugar in the released when required. The superiority of starch recipe: in high sugar conditions water activity is as a dietary energy source does not derive from
NUTRITION 279 a particularly high calorific value; in fact that of fat is higher, at 37 k(9 kcal) per gram, as is alcohol at 29 k7(7 kcal)per gram than that of 3 starch Protein content and quali Cereals including bread, contribute approxim tely 25% of the protein in the average adult diet in the u. K. Three thin slices of bread contribute much protein as an egg In nutritional terms there are two factors of a prime importance in relation to protein: the total 2 protein content, and the contribution that essen- tial amino acids make to the total There are eight essential amino acids(out of a 你N total of 20 or s methionine, tryptophan, tonnes oa aline, isoleucine, leucine, phenylalanine and lysine. Two other amino acids are sometimes classified as essential but they can be made in the Cow's miLkBeef body- tyrosine from phenylalanine and cysteine/ cystine from methionine. Their presence in foods reduces the requirements of the relevant FIG 14. 1 The essential amino acids in food proteins. The roportions of each essential amino acid are she essential amino acids. In foods derive d as the percentage of the total essential amino acids plants in general, the sulphur-containing ultate,1989, by courtesy of The Royal Society of acids methionine and cysteine are most likely to be limiting, but this is not true of cereal grains Protein n cereals, lysine is the first to be limiting: rice, oat and rye are relatively rich among wholegrain Embryo Scutellum cereals but they are deficient in relation to the FAO/WHO(1973)reference amino acid pattern in which the lysine content is 5.5 g/16g of N Perica and test Maize protein is also limiting in tryptophan, based on the reference value of 1.0 g/16g of N, which the other cereals just reach. A comparison between wheat protein and protein from other food sources is shown in Fig. 14.1 FIG. 14.2 Distribution of total pr The figures show the percentage of the total protei In the h was made of of animal-derived proteins, containing, as they by J.J.C, Hinton. From The Research Association of Brtish do, the correct proportions of essential amino acids. However, protein types are rarely eaten alone and they tend to complement each other; anatomical parts of the grain; and in the endo- for example bread may be eaten with cheese, a sperm, by the contributions of the different good source of lysine. Even in vegetarian diets, protein fractions(albumins, globulins, prolamins, many legumes and nuts supply essential amino glutelins) acids. a good combination is rice and peas The insoluble fractions are particularly deficient in Both content(Fig. 14.2)and composition of lysine, as illustrated in the comparison of the solu- protein are affected by the contributions of different bility fractions of wheat endosperm(Table 14. 2)
NUTRITION 279 a particularly high calorific value; in fact that of 20 fat is higher, at 37 kJ (9 kcal) per gram, as is 15 alcohol at 29 kJ (7 kcal) per gram than that of g starch. 25 Protein content and quality 0 Cereals including bread, contribute approximately 25% of the protein in the average adult diet in the U.K. Three thin slices of bread contribute as much protein as an egg. In nutritional terms there are two factors of prime importance in relation to protein: the total protein content, and the contribution that essential amino acids make to the total. There are eight essential amino acids (out of a total of 20 or so) - methionine, tryptophan, threonine, valine, isoleucine, leucine, phenylalanine and lysine. Two other amino acids are sometimes classified as essential but they can be made in the body - tyrosine from phenylalanine and cysteine/ cystine from methionine. Their presence in foods reduces the requirements Of the re1evant 'parent' essential amino acids. In foods derived from plants in general, the sulphur-containing amino acids methionine and cysteine are most likely to be limiting, but this is not true of cereal grains. In cereals, lysine is the first to be limiting: rice, oat and rye are relatively rich among wholegrain cereals but they are deficient in relation to the FAO/WHO (1973) reference amino acid pattern, in which the lysine content is 5.5 g/16 g of N. Maize protein is also limiting in tryptophan, based on the reference value of 1.0 g/16 g of N, which the other cereals just reach. A comparison between wheat 'rotein and 'rotein from Other food soLlrces is shown in Fig. 14.1. In the past, much was made of the superiority of animal-derived proreins, containing, as they do, the correct proportions of essential amino acids. However, protein types are rarely eaten alone and they tend to complement each other; for example, bread may be eaten with cheese, a good source of lysine. Even in vegetarian diets, many legumes and nuts supply essential amino acids. A good combination is rice and peas. Both content (Fig. 14.2) and composition of protein are affected by the contributions of different IO 0 2 25 20 - - .$ 5 l5 f 1o 5 0 FIG 14.1 The essential amino acids in food proteins. The relative proportions of each essential amino acid are shown expressed as the percentage of the total essential amino acids. From Coultate, 1989, by courtesy of The Royal Society of Chemistry. Protein FIG. 14.2 Distribution of total protein in the wheat grain. The figures show the percentage of the total protein found in the various anatomical parts. (Based on micro-dissections by J. J. C. Hinton. From The Research Association of Bntzsh Flour Millers 1923-60.) anatomical parts of the grain; and in the endosperm, by the contributions of the different protein fractions (albumins, globulins, prolamins, glutelins). The insoluble fractions are particularly deficient in lysine, as illustrated in the comparison of the solubility fractions of wheat endosperm (Table 14.2)
TECHNOLOGY OF CEREALS within the last 20 or so, attention has been mino Aftbdumin Globo i tg amain p ratid g mirogen ladins, focussed on them by the assertion that the high Amino acid Glutenin* Gliadin* Albumint Globulint infective diseases common in the West where 3.9 4.5 refined carbohydrates are more commonly con 69 7,2 9,2 sumed. Some of the more extreme claims for the beneficial effects of fibre, emanating from the nine surge of activity consequent upon these assertions 01520432223012 4.5 have now been seriously challenged, as popula Tryptophan tions of Third-world states eating lower fibre diets valine but not showing high incidence of the relevant diseases have been discovered. Nevertheless Alanine 3 dietary fibre has been shown to have palliative Aspartic acid effects on diseases, particularly those of the gut Glutamic acid 177 nd diabetes mellitus 4.5 Histidine 2.2 11.0 cholestero/ This is much publicized as an indicator as moles of anye droamino acids per 10of recovered anhydro of potential health problems, particularly heart amino acids disease, strokes and blocked arteries , but it is not t from Waldshmidt-Leitz and Hochstrasse(1961) t From Fisher et al.( 1968 all bad. Some cholesterol is necessary in the body as a precursor of hormones and bile acids Cholesterol is transported in the blood in three principal forms: free cholesterol or bound to Among samples of the same cereal, there lipoprotein as either high density lipoprotein (hdl Because there is a consistent relationship between confers some protection against heart disease, Q are considerable variations in protein content. or Low density lipoprotein(LDL). Hdl eve protein content and the proportions of the frac- reduction below a threshold actually increases tions present, protein composition in whole grains risk. About 80%of blood cholesterol is associated also varies. Nevertheless, the differences among with LDL, however, and it is this form which is samples of the same cereal are generally less than believed to deposit in the arteries. It is also this differences among cereal species, and proteins form that increases as a result of consumption of characteristic of individual species can be des- saturated fats. Considerable reduction in blood cribed. It must however be remembered that cholesterol levels have been reported in response values cited in comparisons are only at best to increased cereal fibre in the diet. Several averages, representing points within a range mechanisms have been proposed to account for typical of the species the hypocholesterolaemic effect of soluble fibres Values for the proportions of classified amino viscous soluble fibre may exert an effect by acids in whole grains of cereals are given in Table physically entrapping cholesterol or bile acids 14.3 in the digestive tract, thereby preventing the absorption and resulting in their increased excre- Fibre tion.Alternatively, B-glucans may be fermented by colonic bacteria to short chain fatty acids The laxative properties of fibre or roughage,, Several of these compounds have been suggested as it was previously picturesquely described, have as inhibitors of cholesterol synthesis. In relation been well known for many hundreds of years to the first possibility, it has been found that (Hippocrates advocated it around 400 B C. )but different bile acids are bound more effectively by
280 TECHNOLOGY OF CEREALS TABLE 14.2 within the last 20 or so, attention has been Amino Acid Composition of Wheat Proteins: Glutenin, Gliadin, focussed on them by the assertion that the high Albumin, Globulin (g amino acid116 g nitrogen) fibre of African diets prevents many chronic nonAmino acid Glutenin* Gliadin* Albumin+ Globulin* infective diseases common in the West, where refined carbohydrates are more commonly con- Isoleucine 3.9 4.5 4.1 1.4 Leucine 6.9 7.2 10.7 9.2 sumed. Some of the more extreme claims for the Lysine 2.3 0.7 11.0 12.2 beneficial effects of fibre, emanating from the surge of activity consequent upon these assertions Methionine 1.7 1.5 0 0.4 Phenylalanine 4.8 5.6 5.0 3.2 Threonine 3.3 2.3 2.9 4.5 have now been seriously challenged, as populaTryptophan 2.1 0.7 n.d. n.d. tions of Third-world states eating lower fibre diets but not showing high incidence of the relevant Valine 4.5 4.4 8.1 2.2 Cystine 2.5 3.1 6.7 12.6 Tyrosine 3.6 2.6 3.4 2.3 diseases have been discovered. Nevertheless, Alanine 3.1 2.3 5.6 4.3 dietary fibre has been shown to have palliative effects on diseases, particularly those of the gut Arginine 4.2 2.7 7.5 14.5 Aspartic acid 3.9 3.0 7.9 6.3 Glutamic acid 34.1 40.0 17.7 5.9 and diabetes mellitus. Glycine 4.5 1.8 3.1 5.6 Histidine 2.4 2.3 4.3 2.2 Proline 11.0 14.7 8.4 3.3 Ch o les te ro I Serine 5.9 5.1 4.7 9.1 This is much publicized as an indicator disease, strokes and blocked arteries, but it is not all bad. Some cholesterol is necessary in the body as a precursor of hormones and bile acids. Cholesterol is transported in the blood in three principal forms: free cholesterol or bound to Among samples of the same cereal, there lipoprotein as either High density lipoprotein (HDL), or Low density lipoprotein (LDL). HDL even confers some protection against heart disease, so reduction below a threshold actually increases risk. About 80% of blood cholesterol is associated with LDL, however, and it is this form which is believed to deposit in the arteries. It is also this form that increases as a result of consumption of saturated fats. Considerable reduction in blood cholesterol levels have been reported in response to increased cereal fibre in the diet. Several mechanisms have been proposed to account for the hypocholesterolaemic effect of soluble fibres: viscous soluble fibre may exert an effect by physically entrapping cholesterol or bile acids in the digestive tract, thereby preventing their absorption and resulting in their increased excretion. Alternatively, P-glucans may be fermented by colonic bacteria to short chain fatty acids. Several of these compounds have been suggested as inhibitors of cholesterol synthesis. In relation to the first possibility, it has been found that different bile acids are bound more effectively by * From Ewart (1967), recalculated. Original data are given as moles of anhydroamino acids per lo5 of recovered anhydro t From Waldshmidt-Leitz and Hochstrasse (1961). $ From Fisher et al. (1968). n.d. = not determined. Of potential hea1th problems, particularly heart amino acids. are considerable variations in protein content. Because there is a consistent relationship between protein content and the proportions of the fractions present, protein composition in whole grains also varies. Nevertheless, the differences among samples of the same cereal are generally less than differences among cereal species, and proteins characteristic of individual species can be described. It must however be remembered that values cited in comparisons are only at best averages, representing points within a range typical of the species. Values for the proportions of classified amino acids in whole grains of cereals are given in Table 14.3. Fibre The laxative properties of fibre or ‘roughage’, as it was previously picturesquely described, have been well known for many hundreds of years (Hippocrates advocated it around 400 B.C.!) but
28 TABLE 14.3 Amino Acid Content of Cereal Grains*(g amino acid/16 g nitrogen, Whea Triticale Rye Barley Rice Essential 8 6.0 7.2 8.0 Phenylalanine 5.2 3. 3.3 3.3 4.1 1.6 on-essential 2.6 3.0 6.6 Aspartic acid 345 30.9 27 20,4 5.0 12.1 14.5 17,9 Amino acid Millets Maize rl foxtail 4.0 3.8 6.1 Leucine 2508 0.8 3125315 Cysteine/cystine 5 4 10 4.0 Alanin 3136 6 2.3 Aspartic acid 18.8 21.7 3.9 2.3 l.2 2.1 13.5 12.4 2.5 Data for wheat, barley, oats, rye, triticale and pearl millet from Tkachuk a (1969); data for rice ano et al.(1964); data fe Dfrom bus erger(1965); data for foxtail and proso m Casey 1977); tryptophan data from Hughes(1967). All data are for whe except oats hulled and rye dark rye t Nx 5.7, d b Original data for maize and sorghum given as n x 6.25, viz. 11.6% and 11.5% respectively
NUTRITION 281 TABLE 14.3 Amino Acid Content of Cereal Grains* (g amino acid116 g nitrogen) Amino acid Wheat Triticale Rye Barley Oats Rice Essential Isoleucine 3.8 4.1 3.6 3.8 4.2 3.9 Leucine 6.7 6.7 6.0 6.9 7.2 8.0 Methionine 1.7 1.9 1.2 1.6 1.8 2.4 Phenylalanine 4.8 4.8 4.5 5.1 4.9 5.2 Threonine 2.8 3.1 3.3 3.5 3.3 4.1 Tryptophan 1.5 1.6 1.2 1.4 1.6 1.4 Valine 4.4 5.0 4.9 5.4 5.6 5.7 Cysteinelcy stine 2.6 2.8 2.3 2.5 3.3 1.1 Tyrosine 2.7 2.3 1.9 2.5 3.0 3.3 Arginine 4.0 4.9 4.2 4.4 6.6 7.7 Lysine 2.3 3.0 2.9 3.5 3.7 3.7 Non-essential Alanine 3.3 3.6 3.7 4.1 4.6 6.0 Aspartic acid 4.7 5.9 6.5 6.1 7.8 10.4 Glutamic acid 33.1 30.9 27.5 24.5 21.0 20.4 Glycine 3.7 3.9 3.6 4.2 4.8 5.0 Histidine 2.2 2.5 2.1 2.1 2.2 2.3 Proline 11.1 10.7 10.4 10.9 4.7 4.8 Serine 5.0 4.6 4.3 4.2 4.8 5.2 Protein? 16.3 12.1 17.8 14.5 17.9 11.1 Amino acid Millets Maize Sorghum pearl foxtail proso Essential Isoleucine 4.0 3.8 4.3 6.1 4.1 Leucine 12.5 13.6 13.1 10.5 12.2 Lysine 3.0 2.0 1.7 0.7 1.5 Methionine 1.8 1.5 2.4 2.4 2.2 Phenylalanine 5.1 4.9 5.6 4.2 5.5 Threonine 3.6 3.1 3.1 2.7 3.0 Tryptophan 0.8 1.c 1.4 2.0 0.8 Valine 5.2 5.0 5.4 4.5 5.4 Cysteineicystine 2.5 1.1 1.8 1.4 1.0 Non-essential Tyrosine 4.4 1.5 3.7 1.6 4.0 Alanine 7.7 9.5 11.3 Arginine 4.7 2.6 3.3 2.3 3.2 Aspartic acid 6.4 6.3 6.4 Glutamic acid 18.8 21.7 22.2 Glycine 3.9 3.1 2.3 Histidine 2.8 2.1 2.3 1.2 2.1 Proline 8.8 7.9 6.9 Serine 4.9 4.3 6.9 Protein? 10.6 10.5 13.5 12.4 12.5 * Data for wheat, barley, oats, rye, triticale and pearl millet from Tkachuk and Irvine (1969); data for rice (except tryptophan) from Juliano et al. (1964); data for maize (except tryptophan) from Busson et al. (1966); data for sorghum from Deyoe and Shellenberger (1965); data for foxtail and proso millets from Casey and Lorenz (1977); tryptophan data for rice and maize calculated from Hughes (1967). All data are for whole grains, except oats and rice - hulled grains - and rye - dark rye flour, ash 1.1% d.b. t Nx 5.7, d.b. Original data for maize and sorghum given as N X 6.25, viz. 11.6% and 11.S0/o respectively
TECHNOLOGY OF CEREALS different types of fibre; pentosans of different fats, include lauric, myristic (14: 0)and palmitic types of rice even vary in their effectiveness and (16: 0)acids- the three which have been impli their'preferredbile acids(Normandet al 1981). cated in raising the levels of cholesterol in blood It has been found that eating bran is an effective Palmitic acid (16: 0) is the most nly cure for constipation and diverticular disease. It is ring fatty acid comprising 35% of animal fats more doubtful whether dietary fibre is as effective and palm oil, and 17% of other plant oils and in preventing problems other than constipation. fish oils. The most commonly occurring mono- An important factor, though not the only one, unsaturated fatty acid is oleic acid(18: 1),it contributing to the beneficial effects of bran is its contributes 30-65% of most fats and oils. all ability to hold water, thus increasing stool weight cereal grain lipids are rich in unsaturated fatty and colonic motility. The relative water-holding acids(see Table 14.5) capacities of cereal brans and other sources of Palmitic(16: 0)is a major saturated, and linoleic fibre, given by Ory(1991)are shown in Table 14.4. (18: 2)a major unsaturated fatty acid in most cereals, exceptions being brown rice and oats Water-holding Capacity of Cereal Brans and Other Fibre- which are rich in oleic acid(18: 1). Millets are richer in stearic acid(18: 0)than are other cereals Fibre source No plant oils contain cholesterol Two advantages of rice bran oil are the low g/100g dm content of linolenic acid and its high content of Sugar beet pulp tocopherols, both important from the point of view Apple pomace 235-509 of oxidative stability. Its high content of linoleic Apple, whole fruit acid makes it a good source of essential fatty acid All bran Wheat bran 109290 Oat groats contain 7% oil, pearl millet 5.4% Rice bran maize 4. 4%, sorghum 3. 4%, brown rice 2.3% Maize bran barley 2. 1% and wheat 1.9% The hard, high-melting fraction of rice bran wax has lustre-producing qualities similar to 3367 hose of carnauba wax. It has been approved by Orange pulp the u.s. Food and Drug Administration as a ole vegetable constituent of food articles up to 50 mg/kg and for use as a plastisizer for chewing gum at 2% Potato, minus skin juliano, 1985b) Sources: Gormley, 1977; Hetler and Hackler, 1977(their Maize germ oil is rich in essential fatty acids values are reported as, for fresh weight basis ); and (about half of its fatty acid content is linoleic).It Chen et aL., 1984. Reprinted with permission from Ory, R L, 1991. Copyright, 1991, American Chemical Society is used as a salad oil and for cooking ts Minerals Apart from essential fatty acids, the liver is At least 15 minerals are required by humans able to make all the fat that the body requires Of these, deficiencies are unlikely to occur in from carbohydrates and protein, provided these phosphorus, sodium, chlorine or potassium,even are eaten in sufficient quantities. About 10 g of though daily requirements are relatively high essential fatty acids are needed every day by Anaemia, due to iron deficiency, is one of the most the human body, but in the U. K. the average common nutritional disorders, particularly in consumption is 10-fold this pre-menopause women. Iron from exhausted red Nearly all the fat in the diet is composed of blood cells is re-used in new cells, so that almost triacylglycerols (triglycerides). Saturated fatty the only requirement is to replace blood that has acids, found mainly in animal fats and hardened been lost Wholegrain cereals contain sufficient
282 TECHNOLOGY OF CEREALS different types of fibre; pentosans of different types of rice even vary in their effectiveness and their ‘preferred’ bile acids (Normand et al., 198 1). It has been found that eating bran is an effective cure for constipation and diverticular disease. It is more doubtful whether dietary fibre is as effective in preventing problems other than constipation. An important factor, though not the only one, contributing to the beneficial effects of bran is its ability to hold water, thus increasing stool weight and colonic motility. The relative water-holding capacities of cereal brans and other sources of fibre, given by Ory (1991) are shown in Table 14.4. TABLE 14.4 Containing Foods fats, include lauric, myristic (14:O) and palmitic (16:O) acids - the three which have been implicated in raising the levels of cholesterol in blood. Palmitic acid (16:O) is the most commonly occurring fatty acid, comprising 35% of animal fats and palm oil, and 17% of other plant oils and fish oils. The most commonly occurring monounsaturated fatty acid is oleic acid (18:1), it contributes 3045% of most fats and oils. All cereal grain lipids are rich in unsaturated fatty acids (see Table 14.5). Palmitic (16:O) is a major saturated, and linoleic (18:2) a major unsaturated fatty acid in most cereals, exceptions being brown rice and oats richer in stearic acid (18:O) than are other cereals. No plant oils contain cholesterol. Two advantages of rice bran oil are the low content of linolenic acid and its high content of tocopherols, both important from the point of view Sugar beet pulp Apple pomace of oxidative stability. Its high content of linoleic Apple, whole fruit acid makes it a good source of essential fatty acid. Oat groats contain 7% oil, pearl millet 5.4%, All bran 436 Wheat bran 109-290 Rice bran 131 maize 4.4%, sorghum 3.4%, brown rice 2.3%, Oat bran 66 barley 2.1% and wheat 1.9%. The hard, high-melting fraction of rice bran Maize bran 34 Cauliflower 28 Lettuce 36 wax has lustre-producing qualities similar to Carrot 33-67 those of carnauba wax. It has been approved by the U.S. Food and Drug Administration as a Orange, whole fruit 20-56 Orange pulp 176 Onion, whole vegetable 14 constituent of food articles up to 50 mg/kg and Banana, whole fruit 56 for use as a plastisizer for chewing gum at 2%. (Juliano, 1985b) Potato, minus skin 22 Maize germ oil is rich in essential fatty acids (about half of its fatty acid COntent is linoleic). It is used as a salad oil and for cooking. Water-holding Capacity of Cereal Brans and Other Fibre- which are rich in oleic acid (18: 1). Millets are Fibre source Water-holding capacity. g/lOOg d.m. 1449 235-509 17-46 Sources: Gormley, 1977; Hetler and Hackler, 1977 (their values are reported as ‘corrected’ for fresh weight basis); and Chen et al., 1984. Reprinted with permission from Ory, R. L., 1991. Copyright, 1991, American Chemical Society. Fats Minerals Apart from essential fatty acids, the liver is able to make all the fat that the body requires from carbohydrates and protein, provided these are eaten in sufficient quantities. About 10 g of essential fatty acids are needed every day by the human body, but in the U.K. the average consumption is 10-fold this. Nearly all the fat in the diet is composed of triacylglycerols (triglycerides). Saturated fatty acids, found mainly in animal fats and hardened At least 15 minerals are required by humans. Of these, deficiencies are unlikely to occur in phosphorus, sodium, chlorine or potassium, even though daily requirements are relatively high. Anaemia, due to iron deficiency, is one of the most common nutritional disorders, particularly in pre-menopause women. Iron from exhausted red blood cells is re-used in new cells, so that almost the only requirement is to replace blood that has been lost. Wholegrain cereals contain sufficient
83 TABLE 14.5 The Fatty Acid Composition of Cereal lipids* Saturated Unsaturated Material myristic Oleic 12.6 33.1 23.1 52.3 pear 178 .7 23.9 3.0 foxtail 11.0 4.7 11.5 43.5 808 21.0 61.0 13.2 18.7 24.5 11.5 3 18.5 0.4 17,3 endosperm 18.0 1.2 194 56.2 3.1 Source: Kent(1983 iron to supply a large proportion of an adults wholemeal might seem illogical(since wholemeal daily requirement, but there is some doubt as to of all types of four contains the largest amount of whether it can be absorbed from cereal and phytic acid, and would seem to require the largest legume sources because of the presence of phytic addition of chalk), it must be remembered that acid. About 900 mg of calcium are present in the consumers of this particular product are concerned average U. K. diet, and of this, 25% is supplied to an exceptional extent with the concept of absence by cereals. Growing children and pregnant and of all additions lactating mothers have a higher requirement of Bran and wheat germ are good sources of about 1200 mg per day. The aged hay with other minerals, absorpti enhanced requirement for calcium as it may be can be impaired by the phytate also present depleted by insufficient vitamin D. Adequate In addition to the above, the following elements calcium consumed during growth affords some are require the body, but in much smaller protection against osteoporosis in later years. a traceamounts: iodine, copper zinc, manganese, further protective function served by adequate molybdenum, selenium and chromium and even isotope strontium 90(S70), produced as part of fluorine may be needed on, tin, nickel, arsenic and calcium in the diet concerns the radioactive smaller quantities of silic the fall-out of nuclear explosions, which can arise Wholegrain cereals can contribute to the supply from weapons or accidents in nuclear power of zinc, although its absorption might be impaired stations. Sr%0 can replace calcium in bones, causing by phytic acid. The selenium content of grain irritation and disease, but in the presence of high depends upon the selenium status of the soil on calcium levels this is less likely. Flours, other which the crop was grown. In North America than wholemeal, malt flours and self-raising many selenium-rich soils support cereals, and fours (which are deemed to contain sufficient wheat imported from that continent has relatively calcium), are required to be supplemented with large amounts present, enabling half the daily chalk (calcium carbonate) in the U. K. but it is requirement to be met from cereals. Soils in the doubtful if this is necessary. If the exception of U.K. have less selenium and hence the grains
NUTRITION 283 TABLE 14.5 The Fatty Acid Composition of Cereal Lipids* Saturated Unsaturated Material Myristic Palmitic Stearic Oleic Linoleic Linolenic c14.0 c16.0 C18.0 CIS., CIS2 Cl8.3 (“h) (%) (%) (%) (“h) (%) Barley 6-row 3.3 7.7 12.6 19.9 33.1 23.1 2-row 1.0 11.5 3.1 28.0 52.3 4.1 Maize - 14.0 2.0 33.4 49.8 1.5 Millet pearl - 17.8 4.7 23.9 50.1 3.0 foxtail 0.6 11.0 14.7 21.8 38.2 6.4 11.5 - 25.8 50.6 7.8 proso - Oats 0.5 15.5 2.0 43.5 35.5 2.0 Rice - 17.6 47.6 34.0 0.8 Rye - 21.0 - 18.0 61.0 - Sorghum 0.4 13.2 2.0 30.5 49.7 2.0 Triticale 0.7 18.7 0.9 11.5 61.2 6.2 Wheat grain 0.1 24.5 1 .o 11.5 56.3 3.7 germ - 18.5 0.4 17.3 57.0 5.2 endosperm - 18.0 1.2 19.4 56.2 3.1 * Source: Kent (1983). iron to supply a large proportion of an adult’s daily requirement, but there is some doubt as to whether it can be absorbed from cereal and legume sources because of the presence of phytic acid. About 900 mg of calcium are present in the average U.K. diet, and of this, 25% is supplied by cereals. Growing children and pregnant and lactating mothers have a higher requirement of about 1200 mg per day. The aged have an enhanced requirement for calcium as it may be depleted by insufficient vitamin D. Adequate calcium consumed during growth affords some protection against osteoporosis in later years. A further protective function served by adequate calcium in the diet concerns the radioactive isotope strontium 90 (Sr9’), produced as part of the fall-out of nuclear explosions, which can arise from weapons or accidents in nuclear power stations. Sr90 can replace calcium in bones, causing irritation and disease, but in the presence of high calcium levels this is less likely. Flours, other than wholemeals, malt flours and self-raising flours (which are deemed to contain sufficient calcium), are required to be supplemented with chalk (calcium carbonate) in the U.K. but it is doubtful if this is necessary. If the exception of wholemeal might seem illogical (since wholemeal, of all types of flour contains the largest amount of phytic acid, and would seem to require the largest addition of chalk), it must be remembered that consumers of this particular product are concerned to an exceptional extent with the concept of absence of all additions. Bran and wheat germ are good sources of magnesium but, as with other minerals, absorption can be impaired by the phytate also present. In addition to the above, the following elements are required by the body, but in much smaller ‘trace’ amounts: iodine, copper, zinc, manganese, molybdenum, selenium and chromium and even smaller quantities of silicon, tin, nickel, arsenic and fluorine may be needed. Wholegrain cereals can contribute to the supply of zinc, although its absorption might be impaired by phytic acid. The selenium content of grain depends upon the selenium status of the soil on which the crop was grown. In North America many selenium-rich soils support cereals, and wheat imported from that continent has relatively large amounts present, enabling half the daily requirement to be met from cereals. Soils in the U.K. have less selenium and hence the grains
TECHNOLOGY OF CEREALS produced on them are poorer in the element. and vitamin E, that are most important in cereal Symptoms of selenium deficiency have been grains. The average contents of B-vitamins are reported in countries with notably deficient soils, shown in Table 14.7 cluding New Zealand and some areas of china The table also includes values for inositol The mineral composition of cereal grains is and p-amino-benzoic acid Although essential shown in table 3. 6 for some micro-organisms, these substances are no longer considered essential for humans. Their status as vitamins is thus dubious, Choline and inositol are by far the most abundant but cereals Vitamins comprise a diverse group of organic are not an important source as many foods compounds. They are necessary for growth and contain them and deficiencies are rare(Bingham, metabolism in the human body, which is incapable 1987) of making them in sufficient quantities to meet its needs, hence the diet must supply them to Distribution of vitamins in cerea/s aintain good health. Most vitamins are known today by their chemical descriptions, rather than variation in content from one cereal to another the earlier identification as vitamin A, B, c etc. is remarkably small except for niacin (nico- a table of equivalence relates the two methods tinic acid), the concentration of which is rela of nomenclature(Table 14.6). Those in bold tively much higher in barley, wheat, sorghum type occur in cereals in significant quantities(in and rice, than in oats, rye, maize and th relation to daily requirements) Details of the distribution in grains were worked TABLE 14.6 out by Hinton and his associates, who assayed the Vitamins and their Occurrence in Cereals dissected morphological parts of wheat, maize Vitamin Chemical Name Concentration in cereals and rice. Their results for wheat are shown in Table 14. 8 Retinol and Carotene Thiamin Embryo(scutellum The distribution of these vitamins in the wheat Riboflavin Most parts grain is also shown diagrammatically in Fig 14.3 Nicotinic acid(niacin) Aleurone(not maize The proportions of total thiamin and niacin are shown for rice and maize in Table 14.9 Pantothenic acid Aleurone, endosperm The distributions of thiamin in rice and wheat are quite similar: it is concentrated in the scutel Carnitine lum, though not to the same degree as in rye and Cholicalciferol and maize. The embryonic axis of rice, which has a relatively high concentration of thiamin, contains E Tocopherol and tocotrienol Embryo over one tenth of the total in the grain, a larger K Phyllo qUinone proportion than that found in the other cereals (see Table 14.10 Vitamins are sometimes classified according to Cereals, except maize, contain tryptophan, which solubility; thus A, D, E and K are fat soluble, can be converted to niacin in the liver in the and B and C are water soluble. Fat soluble presence of sufficient thiamin, riboflavin and vitamins are the more stable to cooking and pyridoxin. The distributions of in wheat, processing. rice and maize are similar, it is concentrated in It is clear from Table 14.6 that it is the b the aleurone layer. About 80% of the niacin itamins(more specifically thiamin, riboflavin, in the bran of cereals occurs as niacytin, a com- pyridoxine nicotinic acid and pantothenic acid) plex of polysaccharide and polypeptide moieties
284 TECHNOLOGY OF CEREALS produced on them are poorer in the element. Symptoms of selenium deficiency have been reported in countries with notably deficient soils, including New Zealand and some areas of China. The mineral composition of cereal grains is shown in Table 3.6. Vitam ins Vitamins comprise a diverse group of organic compounds. They are necessary for growth and metabolism in the human body, which is incapable of making them in sufficient quantities to meet its needs, hence the diet must supply them to maintain good health. Most vitamins are known today by their chemical descriptions, rather than the earlier identification as vitamin A, By C etc. A table of equivalence relates the two methods of nomenclature (Table 14.6). Those in bold type occur in cereals in significant quantities (in relation to daily requirements). millets. and vitamin E, that are most important in cereal grains. The average contents of B-vitamins are shown in Table 14.7. The table also includes values for inositol and p-amino-benzoic acid. Although essential for some micro-organisms, these substances are no longer considered essential for humans. Their status as vitamins is thus dubious. Choline and inositol are by far the most abundant but cereals are not an important source as many foods contain them and deficiencies are rare (Bingham, 1987). Distrjbution of vitamins in cerea,s Variation in content from one cereal to another is remarkably small except for niacin (nicotinic acid), the concentration of which is relatively much higher in barley, wheat, sorghum and rice, than in oats, rye, maize and the Details of the distribution in grains were worked out by Hinton and his associates, who assayed the dissected morphological parts of wheat, maize Vitamin Chemical Name Concentration in cereals and rice. Their results for wheat are shown in Table 14.8. A Retinol and Carotene The distribution of these vitamins in the wheat B1 B2 Riboflavin Most parts grain is also shown diagrammatically in Fig. 14.3. B6 Pyridoxin Aleurone Bl2 Nicotinic acid (niacin) Aleurone (not maize) The proportions of total thiamin and niacin are Folic acid shown for rice and maize in Table 14.9. Biotin Pantothenic acid Aleurone, endosperm The distributions of thiamin in rice and wheat Choline are quite similar: it is concentrated in the scutellum, though not to the same degree as in rye and Carnitine C Ascorbic acid D Cholicalciferol and maize. The embryonic axis of rice, which has a ergocalciferol relatively high concentration of thiamin, contains Tocopherol and over one tenth of the total in the grain, a larger E tocotrienol Embryo K Phylloquinone proportion than that found in the other cereals (see Table 14.10). Cereals, except maize, contain @pt@hn~ which can be converted to niacin in the liver in the presence of sufficient thiamin, riboflavin and pyridoxin. The distributions of niacin in wheat, rice and maize are similar, it is concentrated in the aleurone layer. About 80% of the niacin in the bran of cereals occurs as niacytin, a complex of polysaccharide and polypeptide moieties TABLE 14.6 Vitamins and their Occurrence in Cereals Thiamin Embryo (scutellum) Vitamins are sometimes classified according to solubility; thus A, D, E and K are fat soluble, and B and c are water soluble. Fat soluble vitamins are the more stable to cooking and processing. It is clear from Table 14.6 that it is the B vitamins (more specifically thiamin, riboflavin, pyridoxine nicotinic acid and pantothenic acid)
TABLE 14.7 B Vitamin Content of the Cereal Grains*(ug/g) Thiamin Riboflavin Niacin Pantothenic Biotin Wheat Barley 23011101 4521266946733 0.05 7.5 0.06 Rice(brown) Maize 3.5 114 3. Cereal Pyridoxin acid Wheat 2.4 Dats(whole) Rice(brown) 4.0 5 5.3 4.8 0.2 Sources of data are as quoted in Kent (1983). a dash indicates that reliable data have not been found The above data are similar to those given by holland et al.(1991) of cereal products also TABLE 14. 8 Distribution of B vitamins in the W heat Grain. Concentration in ug/g and of total in parts Part of grain Thiamin Riboflavin cint Pyridoxin Pantothenic acid Concn Concn. Concn Pericarp, testa, hyaline 12 32 0.3 3943 nic axIs Whole grain Sources of data: Clegg(1958); Clegg and Hinton( 1958); Heathcote et al. (1952); Hinton(1947); Hinton et al. (1953) t Wheat variety ilmorin 27 Wheat variety Thatch
N UTRlTl ON 285 TABLE 14.7 B Vitamin Content of the Cereal Grains* (pgig) Cereal Thiamin Riboflavin Niacin Pantothenic Biotin acid Wheat 10 0.1 45 Barley 4.4 1.5 72 5.7 0.13 Oats (whole) 5.8 1.3 11 10 0.17 Rye 4.4 2.0 12 7.2 0.05 Triticale 9.2 3.1 16 7.5 0.06 Rice (brown) 3.3 0.7 46 9 0.1 Maize 4.0 1.1 19 5.3 0.1 Sorghum 3.5 1.4 41 11 0.19 Millet pearl 3.6 1.7 26 11.4 - foxtail 5.9 0.8 7 proso 2.0 1.8 23 finger 3.6 0.8 13 54 1 hard 4.3 1.3 soft 3.4 1.1 - - - - - - Cereal Pyridoxin Folic Choline Inostiol p- Amino Wheat hard soft acid benzoic acid ] 4.5 0.5 1100 2800 2.4 Barley 4.4 0.4 1000 2500 0.5 Oats (whole) 2.1 0.5 940 Rye 3.2 0.6 450 - - Triticale 4.7 0.7 Rice (brown) 4.0 0.5 900 Maize 5.3 0.4 445 - - Sorghum 4.8 0.2 600 - - Millet - - - - - I - pearl - - - - - foxtail proso finger - - - - - * Sources of data are as quoted in Kent (1983). A dash indicates that reliable data have not been found. The above data are similar to those given by Holland et al. (1991) who provide comprehensive tables of vitamin contents - - - - - - - - - - of cereal products also. TABLE 14.8 Distribution of B Vitamins in the Wheat Grain.* Concentration in pgig and YO of total in parts Part of grain Thiamint Riboflavin$ Niacin$ Pyridoxin$ Pantothenic acid$ Concn. YO Concn. % Concn. YO Concn. YO Concn. YO wig Pdg Pgk Pgk Pgk Pericarp, testa, hyaline 0.6 1 1.0 5 25.7 4 6.0 12 7.8 9 Endosperm 0.13 3 0.7 32 8.5 12 0.3 6 3.9 43 Embryonic axis 8.4 2 13.8 12 38.5 1 21.1 9 17.1 3 Scutellum 156 62 12.7 14 38.2 1 23.2 12 14.1 4 Whole grain 3.75 1.8 59.3 4.3 7.8 Aleurone layer 16.5 32 10 37 741 82 36 61 45.1 41 * Sources of data: Clegg (1958); Clegg and Hinton (1958); Heathcote et al. (1952); Hinton (1947); Hinton et al. (1953) t Wheat variety Vilmorin 27. $ Wheat variety Thatcher