Barley for Food and Health: Science, Technology, and Products

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BARLEY AND HEART DISEASE 179 2007; DeVries 2007; Jenkins 2007; Jones 2007). More recent approaches to the basis of the glycemic effect of barley are the amylose/amylopectin ratios (Behall et al. 1989) and the presence of resistant starch due to the processing of amylose (Topping and Clifton 2001). Pins and Kaur (2006) reviewed the effects of barley β-glucan on the risk of both cardiovascular disease and diabetes, stressing the importance of lifestyle changes such as diet before initiating drug therapy. In this chapter we review the healthful benefits of barley, focusing on blood lipids and glycemic responses. Other health benefits, such as gastrointestinal health, are also discussed briefly. It is important to note that the cutting edge of nutritional research delves into underlying mechanisms and biological controls, and future studies will more specifically provide answers to today’s questions regarding the “how” of physiological responses. BARLEY AND HEART DISEASE It has been well established that elevated serum cholesterol is a risk factor for coronary artery disease, which remains a major cause of chronic illness and continues to be the leading cause of death in the United States (NCEP, 2001; CDC, 2007). Trowell (1975) promoted the hypothesis that dietary fiber may play an important role in regulating serum cholesterol; however, at that time, investigations centered on wheat fiber. Rimm et al. (1996) conducted a prospective study of over 50,000 male health professionals and concluded that there was an inverse relationship between fiber intake and myocardial infarction. Within the three main food contributors to total fiber intake (i.e., vegetables, fruit, and cereals), cereal fiber was most strongly associated with the prevention of heart disease. DeGroot et al. (1963) had earlier reported the cholesterol-lowering effect of rolled oats, and throughout the 1980s and 1990s a large number of research studies followed this trend, as summarized by Truswell (2002). The cholesterol-reducing property of barley was shown initially in chickens by Fisher and Griminger (1967) and later confirmed by Fadel et al. (1987), Martinez et al. (1992), and Bengtsson et al. (1990). Danielson et al. (1997) reported on the hypocholesterolemic effect of barley milling fractions as related to the viscosity of the gut digesta of chickens, and Mori (1990) demonstrated the relationship of barley soluble fiber and fecal excretion of lipids with consequent lowering of blood cholesterol in rats. Kalra and Jood (2000) fed diets made from three barley cultivars to rats and compared them with a casein control diet. Dolma, the barley with the highest β-glucan content (5.39%), produced the greatest reduction in total and LDL cholesterol. Bird et al. (2004a) reported reduced serum cholesterol in young pigs fed a high-amylose barley cultivar with high β-glucan content. One long-term study (Li et al. 2003a) showed that barley diets in rats produced sustained depression of plasma total cholesterol, triglycerides, and free fatty acids over nine months. A recent Japanese study (Araki et al. 2007) reported reduced accumulation of abdominal adipose tissue in rats fed diets with high-β-glucan barley, as well as reduced size of adipose cells, compared with animals fed wheat diets.
180 HEALTH BENEFITS OF BARLEY FOODS Mechanisms Responsible for Cholesterol Effects As reports of cholesterol-lowering effects of both oats and barley increased, speculation about the causative mechanisms occurred among scientists. One early consideration concerned the intestinal viscosity effect of β-glucan, which is believed to increase the thickness of the unstirred layer of the small intestine, slowing and inhibiting the absorption of lipids and cholesterol (Wang et al. 1992). The cholesterol-lowering property of oats is attributed to viscosity formed in the intestine due to β-glucans (Tietyan et al. 1990). Oat and barley β-glucans are basically the same, varying primarily in the concentration and degree of solubility and molecular weight among varieties (Wood 1986). Delaney et al. (2003) reported increased fecal neutral sterol concentrations and reduced aortic cholesterol levels in hamsters fed either oats or barley, and concluded that the two grains were equal in cholesterol-lowering effect. Arabinoxylans are also capable of producing viscous solutions and hence contribute somewhat to the hypocholesterolemic effect of both grains. Quantitatively, some barley varieties are known to have a wide range in β-glucan levels, as described in Chapter 3. β-Glucans are also believed to cause binding of bile acids in the intestine, causing them to be excreted in fecal waste, with the result of body cholesterol being broken down to replace them. Thus, changes in bile acid metabolism in response to β-glucan have been implicated in their hypocholesterolemic action (Kahlon et al. 1993). Jenkins et al. (1993) conducted a crossover study with hyperlipidemic men and women on a low-fat diet, in which foods with either soluble or insoluble fiber from various sources were consumed. When soluble fiber was consumed, subjects’ LDL cholesterol was the lowest and fecal bile acid excretion was the greatest. In an in vitro study, Kahlon and Woodruff (2003) reported that dehulled barley and β-glucan-enriched barley both exhibited bile acid binding under physiological conditions. Yang et al. (2003) fed diets with 30% waxy barley to cholesterol-fed rats. There was greater bile acid excretion in animals fed barley compared to controls, and serum total and LDL cholesterol were decreased 19 and 24% respectively. In addition, activity of cholesterol 7α-hydroxylase was up-regulated 2.3-fold in barley-fed rats, indicating increased synthesis of bile acids to replace those excreted. Human Clinical Studies Barley has been shown to be equally effective in human lipid metabolism trials as in animal studies (Behall and Hallfrisch 2006). Because wheat is a commonly used grain in baked products and differs from barley in the proportion of soluble fiber, it is generally used as a control product. Newman et al. (1989a) compared a variety of baked products and cereal foods made from barley or wheat in a clinical study to measure possible effects on plasma cholesterol levels. Fourteen healthy volunteers consumed three products containing either barley or wheat daily for four weeks. Subjects who consumed wheat foods had small but significant increases in total and LDL cholesterol compared with pretreatment levels, whereas those who consumed barley had significantly lower cholesterol levels. In
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BARLEY FOR FOOD AND HEALTH Science,
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On a Seed “This was the goal of t
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Cover design by Jean Rose Johnston.
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CONTENTS Preface xiii 1 Barley Hist
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CONTENTS ix Infrared Processing, 12
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CONTENTS xi Asia, 221 Barley Mixed-
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xiv PREFACE In the concluding two c
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2 RELATIONSHIP OF HUMANS AND BARLEY
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10 RELATIONSHIP OF HUMANS AND BARLE
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2 Barley: Taxonomy, Morphology, and
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20 BARLEY: TAXONOMY, MORPHOLOGY, AN
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3 Barley Biotechnology: Breeding an
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34 BARLEY BIOTECHNOLOGY: BREEDING A
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4 Barley: Genetics and Nutrient Com
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58 BARLEY: GENETICS AND NUTRIENT CO
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96 BARLEY PROCESSING: METHODS AND P
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98 BARLEY PROCESSING: METHODS AND P
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100 BARLEY PROCESSING: METHODS AND
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Page 145 and 146: 128 BARLEY PROCESSING: METHODS AND
Page 151 and 152: 134 EVALUATION OF FOOD PRODUCT QUAL
Page 161 and 162: 7 Barley Food Product Research and
Page 163 and 164: 146 BARLEY FOOD PRODUCT RESEARCH AN
Page 195: 8 Health Benefits of Barley Foods I
Page 199 and 200: 182 HEALTH BENEFITS OF BARLEY FOODS
Page 221 and 222: 9 Current Status of Global Barley P
Page 223 and 224: 206 CURRENT STATUS OF GLOBAL BARLEY
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Page 227 and 228: 10 Barley Foods: Selected Tradition
Page 229 and 230: 212 BARLEY FOODS: SELECTED TRADITIO
Page 242 and 243: APPENDIX 1 Glossary: Botany and Pla
Page 244 and 245: APPENDIX 2 Glossary: Food and Nutri
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APPENDIX 3 Glossary: Barley Terms T
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APPENDIX 4 Equivalent Weights and M
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SOURCES OF BARLEY AND BARLEY PRODUC
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Rancho Cucamonga, CA 91730 Ph: 888-
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SOURCES OF BARLEY AND BARLEY PRODUC
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E-mail:Tony.Steeper@csiro.au Web: h
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BARLEY RESOURCE ORGANIZATIONS 241 P
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INDEX Air classification, 102, 122-
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INDEX 245 Meat and barley casserole
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