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- Kategorie: Fachliteratur
- Sprache: Englisch
Applied Malting and Brewing Science
The landmark guide to malting and brewing science is available in English for the first time
Humans have been producing fermented beverages for at least ten thousand years. Chief among them is beer, which has arguably never been more popular than it is at this point in history. The United States alone boasts more than 9,500 breweries, a number which has risen steadily as the market for craft beer continues to grow in that country. Thus, maltsters and brewers there and around the world are constantly looking for ways to hone their skills to create products of the highest quality as consistently as possible. With the detailed information presented in this book, they will not only be able to reacquaint themselves with the basic tenets of their profession but will also acquire an in-depth scientific foundation and a wide range of practical knowledge in all aspects of advanced malting and brewing.
This landmark work on malting and brewing, originally entitled Abriss der Bierbrauerei, is currently in its eighth edition and has hitherto only been offered in the German language. However, it is now finally available for the first time in translation, as an unabridged and updated English edition. Applied Malting and Brewing Science is a reference for those interested in any facet of malt and beer production, including all of the most recent technical innovations in equipment and processes. This book represents the collective knowledge amassed over many decades of research by Ludwig Narziß in his tenure as Professor at the Chair for Brewing Technology at Weihenstephan.
Readers of Applied Malting and Brewing Science will find the following:
- Comprehensive treatment of topics covering raw materials, malt and wort production, fermentation, packaging and much more
- A team of authors with decades of experience in the fields of malting and brewing science, both in academia and in their application in the industry
- A design which facilitates use of the book as both a student textbook and as a practical guide
Written by the late Ludwig Narziß and his team, Applied Malting and Brewing Science is an indispensable source for students at any level in related scientific disciplines and for anyone working in the malting and brewing industry.
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Seitenzahl: 2028
Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Table of Contents
Title Page
Copyright
A Few Words of Thanks
Preface
1 The Technology of Malting
1.1 Malting Barley
1.2 Preparing Barley for Malting
1.3 Steeping the Barley
1.4 Germination
1.5 Various Malting Systems
1.6 Kilning the Green Malt
1.7 Malting Losses
1.8 The Properties of Malt
1.9 Malt from Other Grains
2 The Technology of Wort Production
2.1 Raw Materials for the Brewing Process
2.2 Milling the Malt
2.3 Wort Production
2.4 Extracting the Wort (Lautering)
2.5 Boiling and Hopping the Wort
2.6 Brewhouse Yield
2.7 Wort Chilling and Elimination of Break Material
2.8 Cold Wort Yield
Note
3 The Technology of Fermentation
3.1 Brewing Yeast
3.2 Yeast Metabolism
3.3 Bottom‐fermenting Yeast in Brewing Operations
3.4 Beer Production with Bottom‐fermenting Yeast
3.5 Maturation and Lagering
3.6 Modern Fermentation and Lagering Methods in Beer Production
4 Beer Filtration
4.1 The Theory of Filtration
4.2 Filtration Technology
4.3 Combined Clarification Processes
4.4 Options for Replacing Diatomaceous Earth as a Filter Medium
4.5 Filtration – Auxiliary Equipment and Monitoring Devices
4.6 Beginning and Ending a Filtration Run
4.7 Tank Bottoms
4.8 Compressed Air
5 Packaging Beer
5.1 Beer Storage After Filtration
5.2 Filling Barrels and Casks
5.3 Bottling and Canning
5.4 “Sterile Filling” and the Pasteurization of Beer
5.5 The Layout of a Bottling Plant
6 Beer Losses
6.1 Factors Affecting Beer Losses
6.2 Calculating Beer Losses
7 The Finished Beer
7.1 The Composition of Beer
7.2 The Classification of Beer
7.3 Properties of Beer
7.4 The Aroma of Beer
7.5 Beer Foam
7.6 Factors Affecting the Physico‐chemical Properties of Beer and Their Stabilization
7.7 Filterability of Beer
7.8 Microbiological Stability of Beer
7.9 Physiological Effects of Beer
7.10 Bottom‐fermented German Beer Styles
7.11 Special Beers
8 Top Fermentation
8.1 General Information
8.2 Top‐fermenting Yeast
8.3 Top Fermentation Techniques
8.4 Production Methods for Various Top‐fermented German Beers
8.5 Gluten‐Free Beer
9 High‐gravity Brewing
9.1 High‐gravity Wort Production
9.2 Fermentation of High‐gravity Wort
9.3 Dilution of High‐gravity Beer After Maturation
9.4 The Properties of Beer Produced with High‐gravity Techniques
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 The influence of various malt parameters on the extract difference...
Table 1.2 The influence of various malt parameters on the friability of the ...
Table 1.3 The percentages of soluble nitrogen in the malt according to molec...
Table 1.4 The influence of various malt parameters on the Kolbach index, i.e...
Table 1.5 The influence of various malt parameters on the α‐...
Table 1.6 The influence of various malt parameters on the α‐...
Table 1.7 Heat energy generated during germination.
Table 1.8 The effects of curtailing the steeping/germination period and comp...
Table 1.9 A germination regime with rising temperatures.
Table 1.10 A germination regime with falling temperatures.
Table 1.11 Fan and evaporator settings in the boxes of a
Wanderhaufen
system...
Table 1.12 Withering and curing Pilsner malt in a single‐deck kiln.
Table 1.13 Air‐on and air‐off temperatures in a two‐deck kiln.
Table 1.14 Temperatures in the four drying zones of a vertical kiln.
Table 1.15 Changes in the volume and mass of barley over the course of the m...
Chapter 2
Table 2.1 Hardness of selected brewing liquors.
Table 2.2 The soft resin content of two hop varieties, Polaris and Hersbruck...
Table 2.3 The influence of the pH of the wort and the duration of the boil o...
Table 2.4 Duration of the boil and isohumulone content of the wort.
Table 2.5 The influence of wort pH on the isomerization rate of α‐acids.
Table 2.6 The relative instability of the trans isomer of
iso
...
Table 2.7 The isomerization rates of α‐acids...
Table 2.8 The transfer rates of various hop aroma compounds through addition...
Table 2.9 Ratios of linalool to α‐acids for selected...
Table 2.10 Relationship between the grist composition, the grist volume and ...
Table 2.11 Quantitative evaluation of the grist quality through sieve analys...
Table 2.12 Sample of the grist composition for a two‐roller mill.
Table 2.13 Sample of the grist composition for a four‐roller mill.
Table 2.14 Sample of the grist composition for a six‐roller mill.
Table 2.15 Dry and conditioned grist in a three‐roller mill with husk separa...
Table 2.16 The throughput of the grist and the rotational rate of the grist ...
Table 2.17 Bulk weight of coarse and fine grist.
Table 2.18 The effects of the temperature and pH of the mash on saccharifica...
Table 2.19 The influence of the duration of saccharification rests on the li...
Table 2.20 Optimal conditions for the activity of the proteases during mashi...
Table 2.21 The influence of the duration of the boil on the concentrations o...
Table 2.22 Protein precipitation in the presence and absence of hop polyphen...
Table 2.23 A comparison of the brewhouse yield and the air‐dried laboratory ...
Table 2.24 Comparison of a coolship combined with a Baudelot chiller versus ...
Table 2.25 The overall brewhouse yield.
Chapter 3
Table 3.1 Fermentation by‐products [mg/l] generated by selected flocculent y...
Table 3.2 The duration of lagering, beer temperature, and residual extract d...
Table 3.3 Bung or “spund” pressure, beer temperature, and the CO
2
content of...
Chapter 4
Table 4.1 The relationship between flow rate and the cross‐sectional diamete...
Chapter 5
Table 5.1 Dimensions for Euro, Euroform III, and NRW bottles.
Table 5.2 The oxygen uptake for bottling lines without filling tubes.
Table 5.3 Carbon dioxide usage for oxygen‐free filling starting at the lager...
Table 5.4 Minimum number of pasteurization units for eliminating beer spoile...
Table 5.5 Output of the individual units of a filling line, given a nominal ...
Chapter 6
Table 6.1 Calculation of volumetric beer losses
Table 6.2 Calculation of volumetric beer surpluses
Table 6.3 Calculation of the quantity of wort and beer obtained from 100 kg ...
Table 6.4 Extract losses commencing in the process at the cast‐out wort
Chapter 7
Table 7.1 The effects of bentonite stabilization on the properties of beer....
Table 7.2 The effects of diatomaceous earth stabilization on the properties ...
Table 7.3 The effects of bentonite and silica gel stabilization on chill haz...
Table 7.4 The effects of PVPP and combined silica gel/PVPP stabilization on ...
Table 7.5 Non‐alcoholic beers produced by limiting the generation of alcohol...
Table 7.6 Non‐alcoholic beers produced through alcohol removal.
Chapter 8
Table 8.1 Fermentation by‐products in beer for selected top‐fermenting yeast...
Table 8.2
Weissbier
yeast – fermentation by‐products.
Chapter 9
Table 9.1 Lautering high‐gravity wort (lauter vessel
ø
...
List of Illustrations
Chapter 1
Figure 1.1 Protein degradation.
Chapter 7
Figure 7.1 Stepwise quality control in the brewery.
Guide
Cover
Table of Contents
Title Page
Copyright
A Few Words of Thanks
Preface
Begin Reading
Index
End User License Agreement
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Applied Malting and Brewing Science
A Weihenstephan Compendium
Ludwig Narziß, Werner Back, Martina Gastl, and Martin Zarnkow
Authors
Prof. Dr. Ludwig Narziß †
Emeritus Chair of Brewing and Beverage Technology
TU Munich
Weihenstephaner Steig 20
85354 Freising
Germany
Prof. Dr. Werner Back
Emeritus Chair of Brewing and Beverage Technology
TU Munich
Weihenstephaner Steig 20
85354 Freising
Germany
Prof. Dr.‐Ing. Martina Gastl
Research Center Weihenstephan for Brewing and Food Quality
TU Munich
Alte Akademie 3
85354 Freising
Germany
Dr. Martin Zarnkow
Research Center Weihenstephan for Brewing and Food Quality
TU Munich
Alte Akademie 3
85354 Freising
Germany
Cover Images: Courtesy of New Glarus Brewing Company; Courtesy of Krones AG
All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing‐in‐Publication Data
A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2024 WILEY‐VCH GmbH, Boschstraße 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978‐3‐527‐34734‐6
ePDF ISBN: 978‐3‐527‐82713‐8
ePub ISBN: 978‐3‐527‐82714‐5
Cover Design: Formgeber, Mannheim, Germany
A Few Words of Thanks
No brewer has made a greater contribution to the Science and Practice of Malting and Brewing than Professor Ludwig Narziß. The Professor educated generations of Weihenstephan brewers, leading Germany to the forefront of the modern malting and brewing industry. His passion advanced technology without compromising traditional values. His influence can be tasted in beer steins around the world. His sharp mind and dedication to sharing knowledge is reflected in this volume, representing a lifetime's wealth of experience. Every German‐speaking brewmaster owns a copy of Abriss der Bierbrauerei. Until now, this jewel was only available in the German language. We at New Glarus Brewing Company are proud to have facilitated the Professor's translation of this work. Now his knowledge will be passed onto generations of English‐speaking maltsters and brewers. Most importantly, through his writing, I know others will appreciate the enormous contributions that the Professor has made to those of us who dedicate our lives to great brewing. I will forever be grateful for his wit, wisdom, and the time we spent together. Thank you Ludwig.
The enormity of this complex work represents four years of diligent and passionate labor by Nancy and Christopher McGreger. I am grateful to them for their translation. Special thanks also to Professor Werner Back, Dr. Adrian Forster, Professor Martina Gastl, and Dr. Martin Zarnkow for their contribution to the text. None of this could have occurred without their combined passion and dedication. Thank you all.
I hope you'll appreciate this book as much as I do.
Daniel Carey
New Glarus Brewing
December 4, 2022
Preface
This German language text on malting and brewing science, Abriss der Bierbrauerei, was first published in 1937 and updated in 1949 by Prof. Dr. Hans Leberle of the Technische Hochschule of Munich who was also a member of the board of the Versuchs‐ und Lehrbrauerei at Weihenstephan (a pilot brewery for performing research and instruction at the university). The text was originally conceived as a summary of his two texts Die Bierbrauerei, volume I: Technologie der Malzbereitung and volume II: Technologie der Bierbereitung, published in 1921 and 1925, respectively. I assumed authorship of Abriss der Bierbrauerei with the third edition which was published in 1972.
The eighth edition of the German language text was published in 2016 and has been expanded, particularly with regard to hops and their application, to produce this ninth edition, which appears in English for the first time under the title of Applied Malting and Brewing Science – A Weihenstephan Compendium. The team of coauthors comprises my colleague and successor at the former Chair for Brewing I at the Technical University of Munich‐Weihenstephan, Prof. Dr. Werner Back, who has made significant and valuable contributions to this work, as well as Prof. Dr.‐Ing. Martina Gastl (Director of the Research Center Weihenstephan) and Dr. Martin Zarnkow (also of the Research Center Weihenstephan). The four of us had previously worked together as coauthors to produce updated editions of the German language standard work on malting and brewing in two volumes, Die Bierbrauerei, volume I: Die Technologie der Malzbereitung and volume II: Die Technologie der Würzebereitung. Their deep understanding of the latest research and technology and also their wide‐ranging experience in malting and brewing operations are evident in their contributions. Dr. Gastl and Dr. Zarnkow both studied under Prof. Back and have also worked with me for the better part of 20 years. As prominent brewing scientists and lecturers with a wealth of practical experience, they have inherited the mantle of continuing to update this book to reflect the latest innovations in malting and brewing, as I have done for almost 60 years. I would like to express my sincere gratitude to all three of the coauthors for their exceptional cooperation and their contributions.
I am very grateful to Dr. Adrian Forster, coauthor of the seminal work Hops – Their Cultivation, Composition and Usage, who has greatly enhanced this edition with his unparalleled expertise in the field of hop cultivation and the application of hops in brewing. In the chapter on the raw materials used in the brewing process, he focuses on all of the most relevant aspects of hops and hop products in the production of beer.
I would also like to thank Prof. Dr. Thomas Becker, Prof. Back's successor at the Chair for Brewing and Beverage Technology, for allowing me access to the academic work carried out at the Chair, whether in closed‐door meetings, lectures, or seminars. His kind assistance and that of his staff made every visit enjoyable. Adriana Brunner, secretary at the chair, deserves special mention for her keen and constant helpfulness.
Likewise, I would like to express my gratitude to Prof. Dr. Fritz Jacob, former director of the Research Center Weihenstephan, and his staff for access to the dissertations and theses carried out at their institute and for the stimulating dialogue regarding the application of these concepts to malting and brewing practice. My thanks also go out to the industry suppliers, especially of malting and brewing equipment, and to the breweries across Germany and the world for their interesting insights and counsel as well as for the trust and collaboration that has lasted for decades.
The fact that this work is now available in English is due to the persistence and passion of Dan Carey of New Glarus Brewing Company in New Glarus, Wisconsin, who initiated and financed the project. Without his efforts, this translation of the Abriss der Bierbrauerei would not have been possible. The considerable effort of translating the German text into English was carried out by native English speakers Christopher and Nancy McGreger, who also studied malting and brewing science under Prof. Back at the TUM‐Weihenstephan. Their comprehensive knowledge of German and an understanding in both languages of the highly specialized and technical nature of the raw materials, equipment, and processes involved in malt and beer production enabled them to provide a true and accurate reflection of the German text in English.
I would also like to thank the publisher Wiley for their patience and conscientious attention in compiling the texts and for the enormous effort involved in publishing the book. I hope this first English edition meets with a reception at least as good as “my” previous editions published in German.
Weihenstephan, 2022
Ludwig Narziß
1The Technology of Malting
Malting refers to the germination of cereal grains under artificially created or controlled conditions.
The process of germination results in green malt, which must be dried; for this reason, germination is followed by kilning. Once this has been accomplished, the final product is referred to as kilned malt.
The primary purpose of the malting process is to produce enzymes in the kernels. During germination, these enzymes bring about certain transformations in the substances stored as reserves in the grain. The formation of enzymes and their effects during germination should occur only to the extent necessary to carry out the desired function. Too much or too little enzyme activity will have a negative impact on the quality of the final product.
1.1 Malting Barley
A number of different cereal grains can be employed to produce malt (refer to Section 1.9); however, two‐rowed barley is best suited for this process if the kernels have undergone consistent growth and uniform development. Barley with multiple rows, the original form of the grain, is not utilized for malt production in Europe to any great extent due to the weak, asymmetrical formation of the lateral spikelets (less space to develop on the ear means they are thin and crooked). Outside of Europe, however, this kind of barley is used in malt production due to its higher protein content and greater enzymatic power, facilitating the use of large quantities of adjuncts in brewing.
Two‐rowed barley is divided into two main groups:
Upright barley
: the spike is dense, wide, and usually stands erect while it is maturing; the individual kernels are arranged, so that they are close together (
Hordeum vulgare
ssp.
distichum erectum
).
Nodding barley
: the spike is long, narrow, and bends, so that the ear hangs during maturation. The kernels are spaced further apart (
H. vulgare
ssp.
distichum nutans
).
Several varieties of nodding barley have found use as malting barley. These are primarily planted and cultivated as spring barley. The characteristics of the barley remain quite stable if breeding efforts focus on creating highly productive varieties that are adapted to the cultivation and harvest conditions of either a Continental European or a maritime climate. Additionally, these barley varieties are bred for enhanced resistance to plant diseases (mildew, barley rust, net blotch, etc.) in order to reduce the number of pesticide applications.
Some varieties of two‐rowed winter barley have attained a qualitatively high level due to recent efforts in breeding, although how widely they will be available around the world in the coming years will ultimately be determined in part by policy decisions concerning malting barley. Breeding naked barley has not yet become established. This is also the case for procyanidin‐free barley (refer to Section 1.1.2.6), for varieties with low lipoxygenase activity, and barley with thin cell walls, i.e., varieties with a lower β‐glucan content (refer to Section 1.1.2.2). The quality of these barley varieties suffers under unfavorable climatic conditions, and they exhibit severe losses in yield compared to normal malting barley varieties.
A single mature kernel of barley can be classified as belonging to one of the two main groups based on the shape of the base of the kernel as well as the shape of the rachilla and the type of hair covering it. In addition to these characteristics, the shape of the lodicules and the spiculation of the inner lateral spinal nerves can be used for varietal identification.
Electrophoresis is one method offering a greater degree of certainty for identification through separation of the prolamin fraction (refer to Section 1.1.2.8). Immunological analysis is also possible. Recently, polymerase chain reaction (PCR) has been conducted in two stages for distinguishing barley varieties and has proven useful for this purpose as well. The advantage of analyzing the DNA in this manner is that the determination is not undermined by the malting process as is the case with electrophoretic methods when the malt is overmodified.
Malting barley is commercially classified and traded according to its provenance and variety. Depending on the climatic conditions and the characteristics of each individual variety, there may be substantial differences in the degree to which a particular variety can be malted and in its value as a brewing grain. For this reason, blending should be avoided.
1.1.1 The Morphology of Barley
The barley kernel, which is the fruit of the plant, can be described morphologically as follows:
1.1.1.1 The Embryo The embryo is the living part of the seed and is situated at the proximal end of the kernel on the dorsal side. It consists of the following structures: the shoot apical meristem (future stalk), cotyledon (seed leaf), and radicles (future roots). Merged with the embryo is the scutellum, which is also affixed to the endosperm and channels nutrients to the growing embryo from there. This function is performed primarily by the scutellar epithelium with its tube‐like cells facing the endosperm.
1.1.1.2 The Endosperm The endosperm chiefly consists of two layers of tissue: those containing starch and those containing fat.
The core of the endosperm is made up of cells containing starch embedded in a framework of protein and gum substances.
The cells containing starch are surrounded by a triple layer of rectangular, thick‐walled cells known as the aleurone or subaleurone layer. It is composed of proteins and fats. The layer close to the embryo is only one cell thick. A thin layer of empty compressed cells, the depleted endosperm layer, lies between the starchy tissue of the endosperm and the embryo. The contents of the cells in this layer have already been consumed by the embryo.
All biological and chemical changes in the barley kernel take place in the endosperm. As the plantlet develops, the endosperm is broken down to its constituent parts and utilized. Consumption of the endosperm during malting should be kept to a minimum for economic reasons. In this respect, the formation of enzymes and the degradation of structural and support substances take on a singular importance.
1.1.1.3 Tissues Surrounding the KernelThe tissues surrounding the kernel: the husks protect the kernel, which houses the developing plantlet, and consist of the inner husk on the ventral side, the palea, and the outer husk covering the dorsal side, the lemma. Under the husks, barley kernels possess two fused layers, an ovary wall or pericarp, and an inner wall, the seed coat or testa. Both are composed of multiple layers of cells that appear to be fused. The testa is semi‐permeable, e.g., water can penetrate the membrane while higher molecular weight substances are retained. In addition, water brings various ions to the interior of the kernel.
1.1.2 The Chemical Composition of Barley
Barley consists of dry matter (80–88%) and water (12–20%). The dry matter contains organic compounds, with and without nitrogen, as well as inorganic components (ash).
1.1.2.1 Starch Carbohydrates, especially starch, are the main component of nitrogen‐free organic compounds. Barley contains 60–65% starch (calculated as dry matter). With the help of chlorophyll, CO2 and H2O are ultimately converted to starch under the influence of sunlight, releasing oxygen in the process.
The reason that barley kernels accumulate starch is to create a store of nutrients for the plantlet, which can later be utilized in the early phases of its development. The starch is deposited as granules. They occur in two forms: the large granules are lens‐shaped, while the small ones are more spherical. The latter increase with the protein content of the barley, and they are richer in minerals compared to the larger starch granules.
A starch granule consists of two structurally different carbohydrates, amylose and amylopectin. Amylose (normal or n‐amylose) makes up 17–24% of the starch. It is usually located inside of the starch granule and consists of long, unbranched chains wound into a spiral configuration. Amylose chains are composed of 60–2000 glucose residues connected through α‐1→4 bonds (maltose bonds). The length of the molecules varies with the molecular weight ranging from 10,000 to 500,000 Da. Amylose turns pure blue with iodine; it dissolves to create a colloidal suspension in water and does not form a gel. Enzymatic degradation of amylose, e.g., by α‐amylase and β‐amylase, results in the formation of the disaccharide maltose.
Amylopectin (iso‐amylose or i‐amylose) accounts for about 76–83% of the starch. In contrast to amylose, it consists of branched chains of molecules, which in addition to the predominant α‐1→4 bonds, amylopectin also possesses α‐1→6 bonds (at a ratio of about 15 to 1). The amylopectin chain branches at approximately every 15 glucose units, on average. This three‐dimensional, branched structure is what determines the gelatinization capacity of amylopectin. Encompassing 6000–40,000 glucose residues, the molecular weight of amylopectin ranges from 1 to 6 million Da. Amylopectin also contains about 0.23% phosphoric acid incorporated in ester‐like bonds. The aqueous solution turns violet to pure red in the presence of iodine.
Starch is tasteless and odorless with a specific gravity of 1.63 g/cm3 in the anhydrous form. Its energy of combustion is 17,130 kJ/kg (4140 kcal/kg), and the molecule exhibits a specific optical rotation value of 201–204.
1.1.2.2 Non‐starch Polysaccharides In addition to starch, 10–14% of the barley kernel is made up of non‐starch polysaccharides. For example, cellulose is found in husks where it serves as structural support, but it is absent in the endosperm. Like starch, cellulose consists of glucose residues; however, cellulose is linked glycosidically through β‐1→4 bonds. Cellulose is tasteless and odorless, insoluble in water, and difficult to degrade either chemically or enzymatically. It does not play a role in plant metabolism and remains in the region of the kernel where it was formed. The cellulose leaves the malthouse unchanged, first serving a function in brewing as part of the filter (grain bed) during lautering. Analytically, cellulose is measured as crude fiber, comprising 3.5–7% of barley, expressed as dry matter.
The hemicelluloses are part of the structure of cell walls and aid in maintaining their strength. The type of hemicellulose found in the husks is made up of an abundance of pentosans, low amounts of β‐glucan, and small amounts of uronic acids. These hemicelluloses have a low viscosity in an alkaline solution. During germination, the “husk” hemicelluloses remain virtually unchanged. By contrast, as structural components, the “endosperm” hemicelluloses possess a high specific viscosity. This type is high in β‐glucan, low in pentosans, and contain no uronic acids. It is composed of glucose residues linked with β‐1→4 bonds (70%) and β‐1→3 bonds (30%). If degradation is incomplete, then the disaccharides cellobiose and laminaribiose are present. The pentosans consist of xylose units linked by β‐1→4 bonds to which side chains of the husk pentosans, xylose, arabinose, and uronic acids are attached with β‐1→3 and β‐1→2 bonds. The endosperm pentosans consist solely of arabinose molecules linked with β‐1→3 or β‐1→2 bonds. The pentosan chains in the cell walls of the endosperm contain ferulic acid, which is bound to arabinose by an ester bond. Cross‐linking occurs between the two ferulic acid molecules on the arabinose side chains as well as between the amino acid tyrosine and the pentosans and proteins. Hemicelluloses are linked to proteins with ester bonds, which causes these complexes to be insoluble in water. Their molecular weight can reach up to 40 × 106 Da. They can be converted into a soluble form through treatment with a dilute sodium hydroxide solution or through the action of enzymes.
The content of hemicelluloses and gum substances (non‐starch polysaccharides) in barley depends on the variety and where it is grown (climate).
Gum substances are water‐soluble hemicelluloses of a high viscosity. They consist of β‐glucan and pentosan and form colloidal solutions in water. Their molecular weight is approximately 400,000 Da. The content of water‐soluble gum substances can vary over a considerable range, but it is normally around 2%.
Lignin is a substance embedded in the cell walls of the husks.
1.1.2.3 Lower Molecular Weight Carbohydrates The lower molecular weight carbohydrates in barley include 1–2% sucrose, 0.3–0.5% raffinose, and 0.1% each of maltose, glucose, and fructose.
1.1.2.4 LipidsLipids (fats) make up 2.2–2.5% of the dry matter found in barley. They are present in small quantities in the husks and in the endosperm, while 60% are located in the aleurone layer and about 30% in the embryo. Barley lipids are composed primarily of approximately 70% neutral lipids, the majority of which are triglycerides, along with around 10% glycolipids and 20% phospholipids. The triglycerides may contain up to three different fatty acids, which each form an ester with the glycerin. Thus, the number of potential triglyceride combinations is very substantial. They are partially consumed as the embryo grows, supporting respiratory metabolism and the formation of cells in the acrospire and rootlet.
1.1.2.5 Organic Compounds Containing Phosphoric AcidOrganic compounds containing phosphoric acid supply the majority of the acidic compounds (primary phosphates) and buffer substances during germination. One example is phytin, an ester of phosphoric acid and inositol, a cyclic sugar, which is present as a calcium/magnesium salt in the husk. Compounds containing phosphoric acid play a role in maintaining the proper acidity level during germination.
1.1.2.6 PolyphenolsPolyphenols or tannins are found in barley husks and in the endosperm. Although they only comprise 0.1–0.3% of the dry matter, through the precipitation of proteins, they influence the color and flavor of beer, not to mention its stability and shelf life. The phenolic group of substances comprise simple phenolic acids, which are present in their free form, bound as glycosides or as more complex polyphenols. Proanthocyanins (anthocyanogens), catechins, and flavones represent different types of polyphenols, the polymerization and oxidation of which lead to higher molecular weight compounds. They can deepen the color and precipitate substances inherent to malt, wort, and beer. Polyphenols are considered reducing substances due to their capacity to be oxidized. The “tannoids,” as they are known, also belong to the group of polyphenols and can be determined analytically. They have a molecular weight of 600–3000 (2–10 flavan rings) and are characterized by a protein‐precipitating effect, along with strong reducing properties. The quantity of phenolic substances in barley depends on the variety as well as the growing conditions. Compared to continental barley, maritime barley contains a higher concentration of polyphenols on average, especially more tannoids. Carlsberg laboratories used genetic mutants to develop a special kind of barley which is unable to synthesize catechins and procyanidins (anthocyanogens) as it grows. Wort and beer produced with this barley contain only around 12% of the normal anthocyanogen content and therefore possess a much better physico‐chemical stability than beers brewed with conventional malts.
1.1.2.7 Bitter Substances in BarleyBitter substances in barley belong to a class of substances known as lipoids. They exhibit an antiseptic effect and are characterized by a harsh bitterness. These bitter substances are found primarily in the husks and are readily soluble in water containing bicarbonate.
1.1.2.8 Proteins In general, proteins are an essential part of biological processes. Despite their occurrence in relatively small quantities, they nevertheless play a significant part in every step of beer production. An elemental analysis of key proteins yields the following limit values: C = 50–52%, H = 6.8–7.7%, N = 15–18% (average 16%), S = 0.5–2.0%, and P = 0–1%. The average nitrogen content of the proteinaceous substances is about 16%. Once the nitrogen content has been determined according to the Kjeldahl analysis, the value is multiplied by 6.25 to obtain the crude protein content of the barley.
The protein content (calculated as dry matter) ranges from 8–13.5% (1.30–2.15% nitrogen), normally between 9.0% and 11.5% (1.45–1.85% N). Barley with a lesser protein content is generally considered to be more suitable for brewing and is indispensable for producing light‐colored malts and beers. Barley lacking in protein can result in wort deficient in the proteins necessary for foam formation and a full‐bodied character in the finished beer. Furthermore, the wort may also lack the amino acids important for yeast nutrition. Protein‐rich barley (over 11.5% protein) is more difficult to process in the malthouse. It also has a lower starch content and will result in a darker beer color with a fuller flavor, but one that sometimes can be perceived as harsh. Dark beers, on the other hand, require malt produced from barley with a higher protein content.
The protein content of the barley kernel depends mainly on the soil composition, crop rotation, fertilizer application, and weather conditions. The length of the growing period between sowing and harvesting is of particular importance. Protein is found in the material surrounding the kernel, in the endosperm and in the embryo.
Proteinaceous substances are stored in the endosperm in three localized places:
in the aleurone layer as gluten
under the adhesive layer along the outer edge of the endosperm as storage protein
in the starchy endosperm itself as histological or tissue protein.
Gluten extends beneath the pericarp and testa. Gluten is partially degraded during the germination process, while the remainder stays behind in the spent grain.
The variability in the protein content of barley is attributable to the reserve protein. As germination commences, the enzymes degrade the reserve protein first. The reserve protein supplies the majority of the water‐soluble proteins.
The histological protein is enmeshed in the membranes of the endosperm cells and, along with other substances, plays a role in the cohesion of the cells. The more histological protein is present, the more difficult it is to degrade the cell walls.
Proteins are formed from amino acid residues. These are each linked by a peptide bond, which is a bond between the carboxyl group of an amino acid and the amino group of a second amino acid. Of the 130 amino acids known to date, 18–20 are primarily involved in the synthesis of plant proteins. Dipeptides are formed when two amino acids bond, and tripeptides from three amino acids. Oligopeptides consist of 3–10 amino acids, polypeptides of 10–100, and macropeptides of more than 100 amino acids. The sequence (order) of amino acids organized in a polypeptide chain is called the primary structure. The spiral helices or folded sheets stabilized by hydrogen bridges are referred to as the secondary structure. Their arrangement in loops or coils is known as the tertiary structure. Where the secondary structure ends, and the tertiary structure begins, is often difficult to distinguish. In addition to the peptide bond, the tertiary structures feature hydrogen bonds as well as strong disulfide bonds, which, along with electrostatic interactions and hydrophobic bonds, are responsible for the characteristic structure of proteins. The quaternary structure is formed by assembling several tertiary groups with no covalent bonds (e.g., disulfide bridges).
The barley kernel contains the following protein fractions: albumins (soluble in distilled water), globulins (soluble in dilute salt solutions), prolamins (soluble in 50–90% alcohol), and glutelins (soluble in alkaline media). Each of these protein groups can be subdivided using electrophoresis into 7–15 different fractions or even more in some cases. Their molecular weight ranges from 10,000 Da to several million. While albumins and globulins are located in the starchy endosperm, reserve proteins are primarily made up of prolamins and glutelins.
The albumins also include protein Z, which can also bind β‐amylase. In beer, it is responsible for colloidal haze as well as foam. Its molecular weight is 40,000 Da. The albumins also include the lipid transfer proteins LTP 1 and LTP 2. As with protein Z, they undergo little modification during malting and brewing. They contribute to beer foam and also to colloidal turbidity. Furthermore, they also may play a role in the gushing phenomenon (spontaneous foaming over) of beer.
The barley kernel also contains other proteinaceous substances as well as small amounts of nitrogenous compounds of low to medium molecular weight. These compounds result from the interrupted formation of true proteins, halted at an intermediate stage of development as the barley kernel matures, or they are products of the physiological degradation of higher molecular weight proteins.
Classification of the proteins and their degradation products is based on their distinctive chemical and physical properties, their occurrence, their varying degrees of accessibility to enzymes, and their physiological functions.
The protein bodies are colloids; they do not diffuse through membranes due to their size. They are hydrated, and like their constituent amino acids, they are amphoteric. Depending on the prevailing pH, excess negative or positive charges are present. At the isoelectric point, the protein is electroneutral. The protein can be denatured by altering the environmental conditions, e.g., through the application of heat, the addition of reagents that extract water, and a shift nearer to the isoelectric point. Denaturation is a structural change in a protein which brings about the loss of its biological properties (e.g., enzymatic activity). It can be reversible or irreversible, depending on the conformation that results. Denaturation is irreversible if the peptide chains of covalent bonds (e.g., disulfide bonds) are unfolded. Macroscopic flakes are formed as denatured particles are moved or enriched at interfaces (e.g., gas/liquid), where they combine as “break” material. This process is called coagulation.
During germination, proteolytic enzymes cleave high molecular weight proteins, creating simpler compounds such as amino acids. Protein degradation, which occurs during malting, also continues during mashing.
1.1.2.9 EnzymesEnzymes are complex organic substances, which are of great importance for all biological processes and thus also for the germination of the barley kernels. They have the ability to degrade organic substances of a high molecular weight without being consumed in the process. Most enzymes consist of a protein constituent (apoenzyme) and a non‐proteinaceous constituent (prosthetic group or coenzyme). The apoenzyme determines the substrate specificity, while the prosthetic group or the coenzyme serves as the reactive region. Simple enzymes, such as hydrolases, consist exclusively of protein. In these enzymes, the reactive region is made up of functional groups of different amino acids. A certain steric arrangement must be present in the overall complex for the enzyme to have the desired effect on a specific substrate. The enzyme interacts with the substrate to be degraded through an exchange of electrons, releasing the cleavage product and the unmodified enzyme that continues to react with additional substrate. The effect of the enzymes is largely dependent on environmental influences, the most important being temperature and reactivity of the substrate. The enzymes are promoted by activators and inhibited by inhibitors.
Enzymes are only active within a specific range of temperatures. Every enzyme functions in an optimal manner at a certain temperature. As the substrate is heated above this optimum temperature, the enzyme increasingly loses its effectiveness. Most enzymes can only tolerate temperatures between 60 and 80 °C.
The reactivity of the substrate and its pH influence the dissociation of enzymes and their degree of hydration. Every enzyme functions most favorably at a certain acidity or optimal pH at which its activity reaches a maximum. The optimum pH can shift with changes in the temperature of the substrate. It is at their pH optimum that enzymes are usually the most resistant to heat.
The progression of the reaction is influenced by the concentration of the enzymes as well as the concentration of the substrate.
Heavy metals, such as copper and tin, as well as oxidizing agents, colloid‐modifying substances, and the like have an inhibiting effect on enzyme activity. Alcohol, ethers, and formaldehyde are damaging to enzymes in higher concentrations, especially at high temperatures. Enzyme activators include acids, neutral salts, colloids, and other substances that either bind to or activate the enzyme. Substances can also serve as activators if they free the enzyme from inhibitors, e.g., proteins adhering to their surface.
A group of enzymes occur in soluble form (lyo enzymes), while others are released from their protoplasmic bonds over the course of a degradation process, through which they are rendered effective (desmo enzymes).
The quantity of active enzymes initially present in the barley kernel is low. After the existing soluble nutrients in the endosperm have been consumed, enzyme formation is induced to meet the nutritional needs of the embryo during germination. Furthermore, enzymes that are present, yet still inactive, are activated (e.g., β‐amylase and some proteases through SH groups); however, the majority of the enzymes are produced by secretion of a substance similar to gibberellin, a growth hormone that induces the development of cell wall‐degrading glucanases (hemicellulases), α‐amylase, endopeptidase, and acid phosphatase in the aleurone layer.
In addition to these hydrolytic enzymes, oxidases such as catalase, peroxidases, polyphenol oxidases, and lipoxygenases I and II as well as superoxide mutase also play a role. They are also present, in part, in the dormant kernel in an active form, or they are formed or activated during germination.
The enzymes of the respiratory complex are important for the advancing metabolic processes.
The distribution of the enzymes is not uniform. The largest concentration is in the dormant grain near the embryo. The process of identifying and classifying enzymes is based on their effect on specific substrates.
1.1.2.10 Inorganic Constituents The inorganic constituents of barley are incombustible and remain as ash after combustion. Their total amount calculated and expressed as dry matter is 2.4–3% and consists predominantly of potassium phosphates (56%) and silica (approximately 26% as SiO2). Inorganic constituents play an important role in maintaining acidity as chemical buffers during germination and mashing, during fermentation, and in the finished beer, which is largely attributable to the action of the acidic primary phosphates. These inorganic constituents provide essential nutrients for the embryo and the yeast.
1.1.2.11 Moisture Content The moisture content of barley can vary between 12% and 20%. Barley from warmer climates with low amounts of precipitation may exhibit a moisture content of 12–14%, while that cultivated in wetter climates can have a moisture content of 16–18% or even in excess of 20%. The moisture content varies with the weather conditions from year to year, with the harvesting method, and according to how the barley is treated after the harvest. A high moisture content is disadvantageous from an economic standpoint because the barley contains less dry matter. Moist barley is not stable in storage and possesses a low germinative energy and a high water sensitivity. It is also slow in overcoming dormancy. Storing undried barley is difficult since it is very susceptible to warming, prone to mold growth, and, as a result, may develop an undesirable odor and experience subsequent problems with germinative capacity. Moist barley requires constant temperature monitoring and frequent redistribution in storage. It is more difficult to malt and produces a less‐uniform product and likewise sustains higher losses than barley with a lower moisture content.
1.1.3 Determining and Evaluating the Properties of Barley
An important prerequisite for properly assessing malting barley is the collection of a truly representative sample. The grain sampling spear developed by Barth, referred to as “Barth's sampler,” allows samples to be collected from various areas of a bag or bulk shipments of barley. Automatic sampling devices are advantageous when larger quantities of bulk barley are delivered, or when the barley is transferred from silo to silo. The sample should be kept in well‐sealed containers (to maintain the moisture content); however, it is not recommended that samples be stored in sealed containers over a longer period.
1.1.3.1 External Features of the Barley Kernel External features
Appearance
: lustrous, indicating that the barley was allowed to mature and was harvested under dry conditions; the moisture content is usually low.
Color
: uniform, light yellow; kernels that are not quite mature are greenish in color. Kernels subjected to rain and completely mature kernels both exhibit brownish or brown tips. Gray kernels or those exhibiting red or black spots have been infected by microorganisms. Frequently, fungal mycelium infiltrates the endosperm of the kernel. Barley kernels that are extremely pale (white) are often hard and glassy.
Odor
: pure and straw‐like; kernels that have been rained upon, those with a high moisture content, or those stored under poor conditions have a musty, moldy odor.
Husk character
: as thin as possible and wrinkled; the smaller the husk fraction is (7–9%), the finer and milder the quality of the barley is. Fine, transverse wrinkling is a sign of high extract content, low protein, and low moisture. A higher husk content (11–13%) is undesirable for pale, high‐quality beers. Winter barley usually has 0.5–1% more husks than comparable spring barley. Six‐rowed barley often contains an even higher proportion of husks.
Purity
: the barley should be free of foreign cereals, extraneous seeds, plant and animal pests, and damaged or pre‐germinated kernels.
Pre‐germination
(kernels that germinated on the plant in the field prior to the harvest) can be recognized by the dried rootlets on the kernels (“open” or visible pre‐germination). However, as these are often dislodged and separated from the kernels during transportation, it is recommended that the barley be examined for the presence of “hidden pre‐germination,” e.g., to determine if acrospire growth has occurred that is not yet visible. This can be determined visually, e.g., by steeping in boiling water, through copper sulfate, and through the determination of lipase activity. The majority of these kernels will have lost their ability to germinate. Excessive acrospire growth may be apparent. In some instances, the kernels may already be friable, allowing water to penetrate the kernels unhindered during steeping. During germination, abnormal metabolism may be observed, indicated by an odor uncharacteristic of germinating malt; mold formation also increases (resulting in a greater tendency for the beer to gush when poured). Barley with more than 4% pre‐germinated kernels should be rejected.
Cracked grains can result from exposure to rainfall during the later stages of maturation. They are split longitudinally along the kernel; the endosperm is exposed, and strong microbial growth is readily evident during storage as well as during steeping and germination. This is also accompanied by the risk of excessive moisture uptake. For this reason, barley lots with more than 3% cracked grains are to be rejected.
Incomplete lateral husk closure occurs when the lemma (dorsal husk) does not entirely cover the palea (ventral husk). Even if the endosperm is undamaged, this is nevertheless considered to be another kind of kernel anomaly. Furthermore, damage to the husk which is not attributable to awn removal may be present. Secondary growth occurs when the barley plant creates an additional set of kernels due to the prevailing weather conditions. These kernels are not fully developed; they often do not mature completely and therefore exhibit poorly formed kernels (apparent during sorting or grading). Due to the short vegetative growth period, the kernels are low in enzymes.
If multiple deficiencies are present, the barley should not contain more than 5% abnormal kernels in total, in order to be considered of a sufficient quality for malting.
Mold growth by Fusarium species results in a discoloration on the surface of the kernel; however, these “field molds” may already have formed a mycelium in the endosperm. Molds commonly found in storage silos such as Mucor, Rhizopus, and Alternaria species are visible as a black film. Mold‐infested barley has a musty odor. The germinative capacity of these kernels may have already suffered as a result of unsuitable storage conditions (moisture content and temperature). These findings give rise to further analyses, e.g., the determination of relevant red kernels (from Fusarium species, a maximum of five infected kernels per 200 g or 1%) and finally the gushing test (refer to Sections 1.9.1.4 and 7.6.8). Furthermore, any barley infested with insect pests, such as grain beetles, must be rejected.
Uniformity
: mixing two or more barley varieties, barley from different regions or crop years is detrimental to achieving a uniform malting process. Likewise, mixing barley with different protein levels or from dried and undried lots is prohibited. The purity of the variety can be determined on the basis of morphological characteristics (base of the kernel, rachilla, lodicule, and spiculation of the lateral nerves), while the latter factors can be detected to some extent by determining the capacity for water uptake, kernel hardness, and water sensitivity. An electrophoretic separation of the prolamin fraction provides a reasonable basis for varietal identification.
1.1.3.2 Physical Examination of the Barley Kernel Physical examination
Size and uniformity of the kernels
: the plumper the barley kernel, the higher its starch and extract content are and thus its value for brewing. A high moisture content in barley can often make it appear to be plump. The size and uniformity of a barley is determined by a sieving test with three sieves of 2.8, 2.5, and 2.2 mm slot widths. At least 85% of the barley kernels are retained on the first two sieves in uniform barley samples. The higher the proportion of kernels larger than 2.8 mm, the higher the extract content is in malt produced from this barley.
Endosperm character
: the endosperm may be friable as well as more or less glassy. Barley can be steeped briefly in water and gently dried to determine whether glassiness is permanent or only temporary. The character of the endosperm can be tested using grain testers or grain cutters (farinatome). The friabilimeter developed by Chapon may also be used to determine the friability of barley kernels. Classifying kernels into categories according to their hardness allows insight into the homogeneity of a barley sample.
The diaphanoscope allows the direct evaluation of the condition of the endosperm by illuminating the kernels. Glassy kernels are permeable to light rays, while friable kernels appear dark.
A white, friable endosperm is preferable to a glassy, oily one. Extremely dry, hot weather conditions during barley maturation and harvest as well as poor soil quality are often the causes of glassiness.
The
hectoliter weight
of barley ranges from 66–75 kg. For malting barley, 68–72 kg is standard, rarely more. Heavy barley is preferable for malting applications.
The
thousand kernel weight
of air‐dried barley is between 35 and 48 g, while that of anhydrous barley ranges from 30 to 42 g. One thousand kernels of air‐dried barley weighing 37–40 g is considered to be light, 40–44 g to be medium heavy, and 45 g is heavy. Heavy barley is more desirable for malting.
Germinative capacity
: chemical methods (e.g., application of hydrogen peroxide, dinitrobenzene, or tetrazolium) are used to determine the number of viable kernels. This figure must not be lower than 96%. Germination is the most important characteristic for malting barley. Kernels that fail to germinate may be non‐viable or dormant and are referred to as “lie‐backs.” These kernels will never become malt but instead will remain unmalted grain.
Germinative energy
: this indicates how many kernels will actually germinate within a certain period of time, e.g., after 3 or 5 days. As a measure of maturity and the germinative potential of a barley sample, it should be as close as possible to the value for germinative capacity.
Germination index
: this value provides an overview of how uniformly germination progresses. It is usually performed for the same period as the analysis for germinative capacity (5 days) in Petri dishes containing 100 kernels and 4 ml of water. The germinating grains are counted and removed after 24, 48, 72 h, and so on. A uniform germination process results in a germination index of around 8, whereas barley with poor, irregular germination has an index close to 5.
Water sensitivity
: based on the Pollock test (a steeping test of 100 kernels, in 4 and 8 ml of water, respectively), this analysis provides information on the sensitivity of barley to excessive contact with water when steeping. It is heavily dependent on the particular stage of kernel maturity and is therefore also linked to the weather conditions during the ripening and harvesting of barley. The difference between the kernels germinating in the 4 and 8 ml sample after 120 h is evaluated as follows: up to 10% as very low sensitivity, 10–25% as low sensitivity, 26–45% as satisfactory, and over 45% as very sensitive to water. However, this analysis result is only of significance if the maximum germinative energy has been reached.
Water uptake capacity
according to Hartong–Kretschmer: this method assesses the capacity of a barley to absorb water, which is determined 72 h after performing a special steeping regimen. The water uptake capacity is primarily influenced by the degree of maturity, the variety, and where the barley is grown. A value of 50% is considered to be very good, 47.5–50% good, 45–47.5% satisfactory, and less than 45% inadequate.
1.1.3.3 Chemical Analysis of the Barley Kernel Chemical analysis of barley
Moisture content:
normally, barley kernels contain 15–16% moisture, 13–14% in dry years and 16–20% in wet years. A determination of the moisture content forms the basis for calculating dry matter in all chemical analyses for barley.
The
protein content
of barley, expressed as dry matter, ranges from 8% to 13.5%, with average values between 9% and 11.5%. Higher levels of protein reduce the extract yield of malt and create difficulties in processing and modification. For pale beers, low‐protein barley is necessary for the malt, whereas dark beers require more protein‐rich barley.
The
starch content
varies between 58% and 66%, expressed as dry matter.
The
extract content
is a measure of all water‐soluble compounds and is performed by means of an enzyme additive. Barley contains 72–80% extract, expressed as dry matter, and is therefore 14.75% higher on average than the starch content. This provides an approximation of the extract content found later in the malt; however, the extract does not reach this level. For this reason, micromalting is being conducted on barley samples with increasing frequency to determine the extract value of malt. Bishop's formula provided below can be used for general orientation:
A = a constant, P = protein content (d.m.), G = thousand kernel weight (d.m.)
Near‐infrared transmission spectroscopy (NIT) represents one option for estimating the extract content of barley, especially when analyzing small sample quantities in the early stages of breeding. Calibration using wet chemistry methods is required for the use of routine analysis. Micromalting yields reliable values for extract content (refer to Section 1.9.5).
1.2 Preparing Barley for Malting
(Delivery, conveyance, cleaning, sorting, and storage of barley)
1.2.1 Receiving Barley in Bulk
Receiving should take place on a covered, draft‐free ramp. Barley is predominantly transported as a bulk material. A number of spacious barley bunkers is necessary to facilitate the rapid unloading of the transport vehicle. At the very least, these bunkers should be able to accommodate the contents of a single transport unit (1–8 bunkers, each with the capacity to store 10–25 t of barley).
Monitoring the weight of the barley being delivered is an absolute necessity. This can be done using a weighbridge or an automatic scale built into the conveyor for transporting the delivered barley.
Collecting a representative sample with a sampling device is highly recommended for establishing the uniformity of the lot upon delivery. The decision to accept the lot of barley and to commence unloading is based on the values determined for the moisture content and germinative capacity. In some instances, the protein content may also be determined using a rapid method (NIT).
