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

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5 Barley Processing: Methods and Product Composition INTRODUCTION As with other cereal grains, barley requires one or more processing procedures in order to reduce or change the kernels into a usable, edible form. Modern processing methods do one or more of the following: alter physical form or particle size, isolate and concentrate specific parts of the grain, improve mouthfeel and palatability, alter nutrient digestibility, and improve product stability or shelf life. Some form of milling, either dry or wet, is the processing most commonly applied to cereal grains. With the exception of malting and extrusion, we deal primarily with dry milling processes in this chapter. Dry milling encompasses a variety of abrasion, grinding, flaking, and separation procedures utilizing numerous types of specialized mills. The earliest processing method used to prepare cereal grains such as barley was a crude form of grinding or crushing the kernels with handheld stones in the style of a mortar and pestle. As civilization developed, a more advanced form of stone milling was developed using a quern, which consisted of two stones, a rotating “capstone” and a stationary “netherstone.” Rotary stone mills, whose invention is attributed to the Romans in the second century b.c., were used almost exclusively to grind grain until the mid nineteenth century. The first stone mills were hand operated, then powered by animals, and were later water powered (Kent and Evers 1994; Owens 2001). A multitude of food products can be produced from barley using one or more of several processing or milling procedures that are available in commerce. Barley may be milled by blocking (dehulling), pearling, flaking, cutting, grinding, roller milling, and further processed by air classifying, sieving, extruding, and infrared heating. Malting is a separate process used to prepare barley as a specialty food additive and in alcoholic beverage production. These processes will be discussed briefly along with products produced and nutrient composition of these products. The purpose of this chapter is not to give detailed analyses of the processes, but Barley for Food and Health: Science, Technology, and Products, By Rosemary K. Newman and C. Walter Newman Copyright © 2008 John Wiley & Sons, Inc. 95
96 BARLEY PROCESSING: METHODS AND PRODUCT COMPOSITION to provide the reader with a basic understanding of how barley is transformed from a raw grain into edible food products with enhanced nutrient profiles and to provide credible references to obtain detail information. WHOLE-GRAIN PROCESSING Cleaning, Sizing, and Conditioning The first step in processing barley is cleaning to remove foreign grains, weed seed, and impurities such as dirt, sand, dust, straw, chaff, and string, and to remove broken kernels. This is accomplished by use of specialized equipment, including screens, magnets, de-stoners, gravity tables, separators, and scourers, and aspiration with air currents. A process of sieving with selective screens is effective in separating small, less hazardous impurities once larger contaminants are removed. Specific-gravity separations utilizing air currents may also be accomplished once the partially decontaminated grain leaves the sieving process. This will separate lighter material, such as dust, chaff, straw, and string, from the grain (Wingfield 1980; Kent and Evers 1994). Kernels preferred for milling are more or less uniform in size, white or creamy in color, of medium hardness, and thin-hulled (if hulled barley). Depending on the milling process to be used, barley kernels may be sorted for desired size and shape with rejected kernels channeled into other, more appropriate processes or utilized for animal feed. Sizing and separation may be achieved by disk separators such as the Carter–Day (Carter-Day Company, Minneapolis, Minnesota). Selection of the desired size of kernel is based on length, as the width of the kernel is of no consequence. Disks mounted on a horizontal axle are positioned in a trough that receives the grain mixture to be sorted. Each disk has a series of indentations arranged concentrically, conforming to the size of kernel desired. Acting as pockets, the indentations in the disk pick up kernels of the same size and lift them as they are rotated. The kernels fall out of the disk at the apex of the rotation into a collection channel, where they are moved to a point for accumulation and further processing (Kent and Evers 1994). In most processing centers, cereal grains are no longer cleaned by washing with water, although there is a pretreatment process called damping, which means the controlled addition of moisture. This process is often referred to as conditioning or tempering of the grain, which alters some of the physical properties. Conditioning is not a single process for all grains, being specific for the individual grain and the milling process. The volume and temperature of the water added will have major effects on processing. Considerably less is known about conditioning barley for milling compared to wheat and oats. Recent research has focused on understanding conditioning of barley, especially in the production of flour through roller milling; however, recommendations are limited for barley milling other than for pearling. According to Kent and Evers (1994), the moisture content of barley grain should be adjusted to 15% through tempering, and allowed to rest or lie for 24 hours prior to pearling. For producing barley
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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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Page 61 and 62: 44 BARLEY BIOTECHNOLOGY: BREEDING A
Page 73 and 74: 4 Barley: Genetics and Nutrient Com
Page 75 and 76: 58 BARLEY: GENETICS AND NUTRIENT CO
Page 111: 94 BARLEY: GENETICS AND NUTRIENT CO
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Page 117 and 118: 100 BARLEY PROCESSING: METHODS AND
Page 151 and 152: 134 EVALUATION OF FOOD PRODUCT QUAL
Page 161 and 162: 7 Barley Food Product Research and
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146 BARLEY FOOD PRODUCT RESEARCH AN
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8 Health Benefits of Barley Foods I
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180 HEALTH BENEFITS OF BARLEY FOODS
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9 Current Status of Global Barley P
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206 CURRENT STATUS OF GLOBAL BARLEY
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208 CURRENT STATUS OF GLOBAL BARLEY
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10 Barley Foods: Selected Tradition
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212 BARLEY FOODS: SELECTED TRADITIO
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APPENDIX 1 Glossary: Botany and Pla
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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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