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

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GLYCEMIC RESPONSE TO CARBOHYDRATE CONSUMPTION 185 contend that the GI is merely an approximate prediction of glycemic response. Other physiological markers have recently been utilized as alternative methods to indicate and measure glycemic responses to foods. The term incretin refers to the hormones glucagon-like polypeptide (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which are now measured in glycemic studies. Incretin hormones are involved in the interaction between glucose ingestion and insulin response (Nauck et al. 2004; Gentilcore et al. 2006; Milton et al. 2007). It is believed that dietary interventions with the potential of controlling postprandial glycemic responses are more definitive if the level of incretin hormone secretion is determined. Breath hydrogen (H 2 ) is frequently measured postprandially to assess colonic fermentation of indigestible carbohydrates such as soluble dietary fiber. The degree of fermentation is assessed by the quantity of H 2 expired over a specified time period (Thorburn et al. 1993). An increasing amount of breath H 2 is indicative of increased fermentation in the large intestine, also resulting in the formation of the short-chain fatty acids (SCFAs): acetic, propionic, and butyric. Plasma free fatty acids (FFAs) are produced by lipolysis of triglyceride stores and are involved in the dynamic energy balance in body cells. Insulin and other hormones have a direct influence on serum FFA concentration, and high FFA levels tend to decrease insulin effectiveness in moving glucose into body cells. Foods with a high GI tend to result in elevation of FFAs, creating a cycle leading to insulin resistance. Hence, a lowering of FFA levels following a dietary intervention for glycemic effect would be seen as a positive benefit (Ferannini et al. 1983; Wolever et al. 1995). FFA levels are also believed to be responsive to the presence of SCFAs produced by colonic fermentation of indigestible carbohydrates. Adiponectin, a hormone that is secreted from adipose tissue, modulates glucose regulation and fatty acid catabolism. Because it has been associated with protection from metabolic conditions related to diabetes, such as obesity, adiponectin has recently been measured in glycemic studies (Kim et al. 2007). Insulin resistance in susceptible individuals (impaired glucose tolerance, obesity, or hyperlipidemia) can be detected or predicted by various indices, such as the homeostasis model assessment (HOMA) and other methods (Behall et al. 2005). Insulin resistance has been detected and measured using the euglycemic–insulinemic clamp in experimental animals, in which decreased insulin uptake by peripheral tissues is recorded (Yokayama and Shao 2006). Finally, interleukin 6 (IL-6), a pro-inflammatory cytokine, is a metabolic marker of immune response to inflammation. Elevated levels of IL-6 are associated with hepatic glucose production, and thus have implications for glycemic evaluations. Increased levels of cytokines inhibit translocation of glucose transporters to the cell surface in response to insulin (Kishimoto 1989). Future research will undoubtedly clarify the roles of these mechanisms in terms of carbohydrate metabolism for both healthy individuals and those with metabolic syndrome or diabetes. Effect of Barley on Carbohydrate Metabolism Investigation of the effect of barley on carbohydrate metabolism has intensified since Sato et al. (1990) reported that plasma glucose concentration in patients
186 HEALTH BENEFITS OF BARLEY FOODS both with and without diabetes was lower after barley consumption than after rice consumption. Research studies on the glycemic effects of barley have focused on one of two major aspects: (1) β-glucan as a viscous fiber, and (2) starch composition ratio of amylose to amylopectin. In many cases the glycemic response to barley foods will be due to a combination of these two factors. Ikegami et al. (1991) in Japan measured glycemic responses in normal and diabetic rats fed a barley diet. All animals exhibited improved glucose tolerance, and fasting blood glucose in diabetic rats fed barley was reduced to normal levels. Similar results in diabetic rats were reported by Li et al. (2003a). Narain et al. (1992), from India, studied metabolic responses to barley in healthy human subjects. Chapatis made from barley flour were consumed in a quantity to provide 40% of the total daily cereal intake. After four weeks, the incremental area under the 3-hour glucose curve decreased from 107.9 mg/dL to 91.5 mg/dL. Battilana et al. (2001) investigated the mechanism of action of β-glucan in postprandial glucose metabolism in healthy men. These researchers concluded that the lowered glycemic response following a meal containing β-glucan is related to delayed and/or decreased absorption of glucose due to increased viscosity in the gut. Following these early studies on barley as an agent for modulation of blood glucose, together with recognition of the GI, there was heightened interest in the development of products containing barley, especially due to the growing incidence of diabetes. The Department of Applied Nutrition and Food Chemistry at the University of Lund in Sweden has rapidly become a recognized center for research in glucose metabolism related to cereal grains. Liljeberg et al. (1996) measured postprandial blood glucose and insulin responses to cereal products made from common barley, oats, and Prowashonupana (PW) barley (later renamed Sustagrain). The latter barley contained 19.6% soluble fiber, most of which was β-glucan. Porridges made from the oats and common barley produced postprandial glucose and insulin responses similar to the white bread reference control. In contrast, porridge made from PW barley induced significantly lower responses than that of the control. Also studied were two types of flour-based bread products (flatbreads) composed of whole-meal flour made from PW and common barleys in ratios of 50 : 50 and 80 : 20, respectively. The glycemic response of these products was significantly lower than in a similar flatbread product made from white wheat flour. The high-fiber barley products were generally liked by the subjects, especially the breads. Conclusions reached in this report were that porridge and flatbreads made from PW barley were consumer-acceptable and effective in producing a lowered glycemic response. Lifschitz et al. (2002) compared PW barley (15% β-glucan) with a standard barley cultivar (5.3% β-glucan) grown in a chamber containing radioactive carbon dioxide ( 13 CO 2 ), in order to measure the rate of CO 2 absorption in subjects who consumed the barley cooked in a whole-grain form. This study determined absorption using two indicators: (1) oxidation by means of digestion and absorption, and (2) malabsorption. For oxidation, breath CO 2 wasmeasuredasan indicator of utilization of carbon from barley. Malabsorption of the indigestible β-glucan was determined by measuring breath hydrogen. The results of this study
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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 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 and 196: 8 Health Benefits of Barley Foods I
Page 197 and 198: 180 HEALTH BENEFITS OF BARLEY FOODS
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Page 221 and 222: 9 Current Status of Global Barley P
Page 223 and 224: 206 CURRENT STATUS OF GLOBAL BARLEY
Page 225 and 226: 208 CURRENT STATUS OF GLOBAL BARLEY
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
Page 246 and 247: APPENDIX 3 Glossary: Barley Terms T
Page 248 and 249: APPENDIX 4 Equivalent Weights and M
Page 250 and 251: 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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