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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Serie: IFST Advances in Food Science
- Sprache: Englisch
Interest in cereals and other healthy grains has increased considerably in recent years, driving the cereal processing industry to develop new processing technologies that meet consumer demands for sustainable and nutritious cereal products. Innovative Processing Technologies for Healthy Grains is the first dedicated reference to focus on advances in cereal processing and bio-refinery of cereals and pseudocereals, presenting a broad overview of all aspects of both conventional and novel processing techniques and methods. Featuring contributions from leading researchers and academics, this unique volume examines the selection and characteristics of raw ingredients, new and emerging processing technologies, novel cereal-based products, and global trends in cereal and pseudocereal use, processing and consumption. The text offers balanced coverage of advances in both the development and processing of cereal and pseudocereal products, exploring topics including gluten-free products, cereal-based animal feed, health and wellness trends in healthy grain consumption, bioaccessibility and bioavailability of nutritional compounds, gluten-free products, and the environmental impact of processed healthy grains. This timely and comprehensive volume: * Focuses on innovative cereal processing and bio-refinery of cereals and pseudocereals * Provides informed perspectives on the current global trends in cereal and pseudocereal use, processing and consumption * Describes the characteristics of healthy grains and their production, nutritional value, and utilization * Explains the origin, production, processing, and functional ingredients of pseudocereals * Reviews healthy grain products such as cereal-based beverages, fortified grain-based products, and cereal-based products with bioactive benefits * Part of Wiley's IFST Advances in Food Science series Innovative Processing Technologies for Healthy Grains is an essential resource for food scientists, technologists, researchers, and other professionals working in the grain industry, and academics and advanced students of food technology and food science.
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Seitenzahl: 683
Veröffentlichungsjahr: 2020
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Table of Contents
Cover
Title Page
Copyright Page
About the
IFST Advances in Food Science
Book Series
Forthcoming Titles in the IFST Series
List of Figures and Tables
List of Figures
List of Tables
List of Contributors
Preface
1 Processing Technologies for Healthy Grains: Introduction
1.1 Healthy Grains: What Are They?
1.2 Cereals and Pseudocereals: Production, Nutritional Value, and Utilization
1.3 Cereal Byproducts for Food and Feed Utilization
1.4 Challenges in Healthy Grain Processing: Traditional vs Innovative Processing
1.5 Relevance of this Book
Acknowledgment
References
2 Introduction to Cereal Processing: Innovative Processing Techniques
2.1 Introduction
2.2 Characteristics of Cereals
2.3 Kernel Structures
2.4 Processing of Cereals
2.5 Innovations in Post‐harvest Processing
2.6 Innovations in Primary Cereal Processing
2.7 Innovations in Secondary Cereal Processing
2.8 Conclusion
Acknowledgment
References
3 Pseudocereals as Healthy Grains: An Overview
3.1 Introduction
3.2 Pseudocereals: Origin, Production, and Utilization
3.3 Processing of Pseudocereals
3.4 Emerging Significance of Pseudocereals
3.5 Functional Ingredients of Pseudocereals
3.6 Conclusion and Future Perspectives
References
4 Advances in Conventional Cereal and Pseudocereal Processing
4.1 Introduction
4.2 Conventional Grain Processing
4.3 Bioprocessing of Cereals and Pseudocereals
4.4 The Impact of Processing on the Nutritional Composition of Cereals and Pseudocereals
4.5 Conclusion and Perspectives of Emerging Technologies in Cereal Processing
References
5 Healthy Grain Products
5.1 Introduction to Different Types of Healthy Grain Products and Their Specific Features
5.2 Nutritional Profile and Health Benefits of Healthy Grain Products
5.3 Bioaccessibility and Bioavailability of Nutritional Compounds
5.4 Rheological and Structural Properties of Healthy Grain Products
5.5 Technological Challenges in the Production of Healthy Grain Products
5.6 Conclusion
Acknowledgment
References
6 Sprouted Cereal Grains and Products
6.1 Introduction
6.2 Definition
6.3 Mechanisms of Grain Germination
6.4 Nutritional Profile of Germinated Cereal Grains and Their Health Benefits
6.5 From Traditional to Industrial Germination Processes
6.6 Utilization of Germinated Cereal Grains in Different Food Products
6.7 Monitoring of Seed Germination
6.8 Conclusion and Further Remarks
References
7 Novel Ingredients from Cereals
7.1 Introduction
7.2 Structure, Biochemistry, and Bioactivity of Cereal Ingredients
7.3 Production Strategies for Cereal Ingredients
7.4 Food Applications of Cereal Ingredients
7.5 Conclusion and Future Outlook
References
8 Innovative Gluten‐Free Products
8.1 Introduction
8.2 Gluten‐Free Foods
8.3 Processing Techniques for Improving Gluten‐Free Products
8.4 Conclusion and Further Remarks
References
9 Cereal‐Based Animal Feed Products
9.1 Introduction
9.2 Cereal Grains and By‐Products as Feedstuff
9.3 Processing Methods of Cereal Grains for Feed Purposes
9.4 Safety Risk and Hazards
9.5 Conclusion and Future Perspectives
References
10 The Consumption of Healthy Grains: Product, Health, and Wellness Trends
10.1 Introduction
10.2 Benefits of Wholegrain Consumption and Consumers
10.3 Consumers' Attitudes Toward Behavior
10.4 Consumers' Attitudes Toward Consumption of Healthy Grains
10.5 Clean‐Label Trend in Grain Products
10.6 Healthy Grain Products on the Market
10.7 Conclusion and Future Perspectives
Acknowledgment
References
11 Assessing the Environmental Impact of Processed Healthy Grains
11.1 Introduction
11.2 Impact Assessment: Life Cycle Assessment
11.3 LCA Study
11.4 LCA Studies on Cereal and Cereal‐Based Products Processing
11.5 Conclusion
References
Index
End User License Agreement
List of Tables
Chapter 2
Table 2.1 Composition of cereals.
Chapter 3
Table 3.1 Content of flavonoids and phenolic compounds in pseudocereal grains...
Table 3.2
In vitro
and pre‐clinical studies of health effects of amaranth and buc...
Chapter 4
Table 4.1 Examples of reported enzyme‐induced product quality improvements in...
Chapter 5
Table 5.1 Healthy grain and bakery products according to the functional foods...
Chapter 6
Table 6.1 Effect, cause, and potential health benefits of cereal germination ...
Table 6.2 Main useful approaches for characterizing flour from sprouted wheat...
Chapter 7
Table 7.1 Amino acid contents of some commonly‐consumed cereals and pseudocer...
Table 7.2 Vitamin contents of some commonly consumed cereals and pseudocereal...
Chapter 8
Table 8.1 Overview of common processing technologies and their impact on glut...
Table 8.2 Enzyme technology used for modification of gluten‐free products.
Chapter 9
Table 9.1 Anti‐nutritional factors (ANFs) in feed ingredients and processing ...
Table 9.2 Chemical composition of cereal by‐products on a dry matter basis.
Table 9.3 Summary of the effect of various processing techniques on the cerea...
Chapter 10
Table 10.1 Cereal‐related health claims approved by EFSA (Annex 1, 2006).
Table 10.2 Glycemic index (GI) of various cereal‐based foods (reference food ...
Chapter 11
Table 11.1 Summary of some of the LCA databases containing process data relat...
List of Illustrations
Chapter 1
Figure 1.1 Global production of cereals and pseudocereals from 2000 to 2018....
Chapter 2
Figure 2.1 Taxonomic relationships of cereals..
Figure 2.2 Structure of wheat (left) and rice kernels (right).
Figure 2.3 Innovative processing technologies in the cereal value chain.
Chapter 3
Figure 3.1 Food and Agriculture Organization (FAO) data on the total product...
Figure 3.2 Pseudocereal seed structures: (a) buckwheat; (b) quinoa; (c) amar...
Chapter 4
Figure 4.1 Schemes of (a) single‐screw food extruder; (b) twin‐screw food ex...
Figure 4.2 Scheme of a wheat‐based biorefinery.
Chapter 5
Figure 5.1 Versatility of ingredients for healthy grain products.
Figure 5.2 The average content of arabinoxylans in different grains and thei...
Chapter 6
Figure 6.1 Number of scientific articles on sprouting (1998–2018).
Figure 6.2 Sequence of main metabolic events during the sprouting process in...
Figure 6.3 Flow‐chart of the controlled sprouting process.
Figure 6.4 Slices of bread made with flour from (a) unsprouted wheat and (b)...
Figure 6.5 Bread loaves and slices of bread prepared with flour from (a) uns...
Figure 6.6 Examples of RVA plots of wheat flours with different values of Fa...
Figure 6.7 Flours with similar Falling Number (about 62 seconds) but with di...
Chapter 7
Figure 7.1 Chemical structures of some cereal‐derived lysophospholipids.
Figure 7.2 Chemical structure of some cereal glycolipids; monogalactosyldiac...
Figure 7.3 Types and chemical structures of some secondary metabolites from ...
Figure 7.4 Mineral composition of commonly consumed cereals and pseudocereal...
Figure 7.5 Nutritional composition of selected cereals and pseudocereals (pe...
Chapter 8
Figure 8.1 Impact of different enzymes on cross‐sections of corn bread: (a) ...
Chapter 10
Figure 10.1 Conceptual model of the attitude toward healthy grain food.....
Figure 10.2 Typical nutritional label of a cereal‐based product.
Figure 10.3 Trends in the cereal market and consumption.
Chapter 11
Figure 11.1 A generalized system for the production, processing, distributio...
Figure 11.2 The interaction of human systems of interest (in this case grain...
Figure 11.3 The structure of an LCA study, adapted from the ISO standard to ...
Figure 11.4 A simple representation of a process (ideally a unit process, bu...
Figure 11.5 Conceptual structure of the LCI in terms of interconnected proce...
Figure 11.6 The generalized procedure for life cycle impact assessment (LCIA...
Figure 11.7 Example of LCIA data, by crop type, illustrated for the midpoint...
Guide
Cover
Table of Contents
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Innovative Processing Technologies for Healthy Grains
Edited by
Milica Pojić
Institute of Food Technology
University of Novi Sad
Novi Sad
Serbia
Uma Tiwari
School of Food Science and Environmental Health
Technological University Dublin
City Campus
Dublin
Ireland
This edition first published 2021© 2021 John Wiley & Sons Ltd
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Milica Pojić and Uma Tiwari to be identified as the authors of the editorial material in this work has been asserted in accordance with law.
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Library of Congress Cataloging‐in‐Publication Data
Names: Pojić, Milica, editor. | Tiwari, Uma, editor.Title: Innovative processing technologies for healthy grains / edited by Milica Pojić, Uma Tiwari.Description: Hoboken, NJ : Wiley‐Blackwell, [2020] | Includes bibliographical references and index.Identifiers: LCCN 2020028487 (print) | LCCN 2020028488 (ebook) | ISBN 9781119470168 (cloth) | ISBN 9781119470212 (adobe pdf) | ISBN 9781119470199 (epub)Subjects: LCSH: Cereal products. | Grain–Processing–Technological innovations.Classification: LCC TP434 .I55 2020 (print) | LCC TP434 (ebook) | DDC 664/.7–dc23LC record available at https://lccn.loc.gov/2020028487LC ebook record available at https://lccn.loc.gov/2020028488
Cover Design: WileyCover Images: courtesy of Milica Pojić
About the IFST Advances in Food Science Book Series
The Institute of Food Science and Technology (IFST) is the leading qualifying body for food professionals in Europe and the only professional organization in the UK concerned with all aspects of food science and technology. Its qualifications are internationally recognized as a sign of proficiency and integrity in the industry. Competence, integrity, and serving the public benefit lie at the heart of the IFST philosophy. IFST values the many elements that contribute to the efficient and responsible supply, manufacture, and distribution of safe, wholesome, nutritious, and affordable foods, with due regard for the environment, animal welfare, and the rights of consumers. IFST Advances in Food Science is a series of books dedicated to the most important and popular topics in food science and technology, highlighting major developments across all sectors of the global food industry. Each volume is a detailed and in‐depth edited work, featuring contributions by recognized international experts, and which focuses on new developments in the field. Taken together, the series forms a comprehensive library of the latest food science research and practice, and provides valuable insights into the food processing techniques that are essential to the understanding and development of this rapidly evolving industry. The IFST Advances series is edited by Dr. Brijesh Tiwari, who is Senior Research Officer at Teagasc Food Research Centre in Ireland.
Forthcoming Titles in the IFST Series
Food Formulation: Novel Ingredients and Processing Techniques edited by Shivani Pathania and Brijesh K. Tiwari.
Recent Advances in Micro‐ and Macroalgal Processing: Food and Health Perspectives edited by Gaurav Rajauria and Yvonne V. Yuan.
Oil and Oilseed Processing: Opportunities and Challenges edited by Tomás Lafarga, Gloria Bobo, Ingrid Aguiló.
List of Figures and Tables
List of Figures
Figure 1.1
Global production of cereals and pseudocereals from 2000 to 2018.
Figure 2.1
Taxonomic relationships of cereals.
Figure 2.2
Structure of wheat (left) and rice kernels (right).
Figure 2.3
Innovative processing technologies in the cereal value chain.
Figure 3.1
Food and Agriculture Organization (FAO) data on the total production of quinoa and buckwheat.
Figure 3.2
Pseudocereal seed structures: (a) buckwheat; (b) quinoa; (c) amaranth.
Figure 4.1
Schemes of (a) single‐screw food extruder; (b) twin‐screw food extruder.
Figure 4.2
Scheme of a wheat‐based biorefinery.
Figure 5.1
Versatility of ingredients for healthy grain products.
Figure 5.2
The average content of arabinoxylans in different grains and their anatomic parts.
Figure 6.1
Number of scientific articles on sprouting (1998–2018).
Figure 6.2
Sequence of main metabolic events during the sprouting process in the wheat kernel.
Figure 6.3
Flow‐chart of the controlled sprouting process.
Figure 6.4
Slices of bread made with flour from (a) unsprouted wheat and (b) sprouted wheat characterized by excessive amylase and protease activities.
Figure 6.5
Bread loaves and slices of bread prepared with flour from (a) unsprouted and (b) sprouted wheat.
Figure 6.6
Examples of RVA plots of wheat flours with different values of Falling Number.
Figure 6.7
Flours with similar Falling Number (about 62 seconds) but different gluten aggregation properties as measured with the GlutoPeak
®
(Brabender GmbH & Co. KG, Duisburg, Germany).
Figure 7.1
Chemical structures of some cereal‐derived lysophospholipids.
Figure 7.2
Chemical structure of some cereal glycolipids; monogalactosyldiacyl glycerolipids (MGDGs), digalactosyl diaglycerolipids (DGDGs), and sulfoquinovosyl diacylglycerolipids (SQDG).
Figure 7.3
Types and chemical structures of some secondary metabolites from cereals.
Figure 7.4
Mineral composition of commonly consumed cereals and pseudocereals.
Figure 7.5
Nutritional composition of selected cereals and pseudocereals (per 100 g).
Figure 8.1
Impact of different enzymes on cross‐sections of corn bread: (a) Control, (b) Protease, (c) Lipase, (d) Glucose oxidase.
Figure 10.1
Conceptual model of the attitude toward healthy grain food.
Figure 10.2
Typical nutritional label of cereal‐based product.
Figure 10.3
Trends in the cereal market and consumption.
Figure 11.1
A generalized system for the production, processing, distribution, consumption, and end‐of‐life for grain derived food products.
Figure 11.2
The interaction of human systems of interest (in this case grain utilization for food) and the planetary boundary.
Figure 11.3
The structure of an LCA study, adapted from the ISO standard to indicate that all stakeholders should potentially have an influence within the study and not merely as external consumers of the study.
Figure 11.4
A simple representation of a process with the types of data that need to be quantified for the life cycle inventory.
Figure 11.5
Conceptual structure of the LCI in terms of interconnected processes, each of which is described by activity data representing mass and energy flows into and out of the process.
Figure 11.6
The generalized procedure for life cycle impact assessment (LCIA) illustrated using climate change associated with grain production.
Figure 11.7
Example of LCIA data, by crop type, illustrated for the midpoint impact, climate change.
List of Tables
Table 2.1
Composition of cereals.
Table 3.1
Content of flavonoids and phenolic compounds in pseudocereal grains.
Table 3.2
In vitro
and pre‐clinical studies of health effects of amaranth and buckwheat extracts or products.
Table 4.1
Examples of reported enzyme‐induced product quality improvements in baking.
Table 5.1
Healthy grain and bakery products according to the functional foods concept.
Table 6.1
Effect, cause, and potential health benefits of cereal germination on selected nutrients.
Table 6.2
Main useful approaches for characterizing flour from sprouted wheat.
Table 7.1
Amino acid contents of some commonly consumed cereals and pseudocereals.
Table 7.2
Vitamin contents of some commonly consumed cereals and pseudocereals.
Table 8.1
Overview of common processing technologies and their impact on gluten‐free products and/or their properties.
Table 8.2
Enzyme technology used for modification of gluten‐free products.
Table 9.1
Anti‐nutritional factors (ANFs) in feed ingredients and processing conditions to remove them from feed.
Table 9.2
Chemical composition of cereal by‐products on a dry matter basis.
Table 9.3
Summary of the effect of various processing techniques on the cereal grain.
Table 10.1
Cereal‐related health claims approved by EFSA.
Table 10.2
Glycemic index (GI) of various cereal‐based foods (reference food is glucose).
Table 11.1
Summary of some of the LCA databases containing process data related to grain crops.
List of Contributors
Mehran Aalami Department of Food Science & Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, I.R. Iran
Caleb Acquah School of Nutrition Sciences, University of Ottawa, Ottawa, Ontario, Canada
Dominic Agyei Department of Food Science, University of Otago, Dunedin, New Zealand
Catherine Barry‐Ryan School of Food Science and Environmental Health, Technological University Dublin, Dublin, Ireland
Gaetano Cardone Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
Michael Kobina Danquah Department of Chemical Engineering, University of Tennessee, Chattanooga, TN, USA
Tamara Dapčević Hadnađev Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
Christian Kwesi Ofotsu Dzuvor Bioengineering Laboratory, Department of Chemical Engineering, Monash University, Clayton, Victoria, Australia
Bojana Filipčev Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
Abirami R. Ganesan School of Applied Sciences, College of Engineering, Science and Technology, Fiji National University, Nabua Campus, Suva, Nabua, Fiji Islands
Muriel Henrion Nestlé Research Center Orbe, Société des Produits Nestlé SA, Orbe, Switzerland
Nicholas M. Holden UCD School of Biosystems and Food Engineering, University College Dublin, Dublin, Ireland
Jaison Jeevanandam CQM – Centro de Química da Madeira, Universidade da Madeira, Funchal, Portugal
Nivedha Krishnakumar Flour Milling, Baking and Confectionery Technology Department, CSIR‐Central Food Technological Research Institute, Mysore, Karnataka, India
Emilie Labat Nestlé Research Center Orbe, Société des Produits Nestlé SA, Orbe, Switzerland
Lisa Lamothe Nestlé Research, Société des Produits Nestlé SA, Lausanne, Switzerland
Sahar Akhavan Mahdavi Department of Food Science & Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, I.R. Iran
Anamarija Mandić Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
Alessandra Marti Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
Aleksandra Mišan Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
Maria Ambrogina Pagani Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy
Sharadwata Pan School of Life Sciences, Weihenstephan, Technical University of Munich, Freising, Germany
Milica Pojić Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
Pichan Prabhasankar Flour Milling, Baking and Confectionery Technology Department, CSIR‐Central Food Technological Research Institute, Mysore, Karnataka, India
Gaurav Rajauria School of Agriculture and Food Science, University College Dublin, Lyons Research Farm, Celbridge, Co. Kildare, Ireland
Cristina M. Rosell Institute of Agrochemistry and Food Technology (IATA‐CSIC), Paterna, Spain
Vijaykrishnaraj Muthugopal Sasthri Flour Milling, Baking and Confectionery Technology Department, CSIR‐Central Food Technological Research Institute, Mysore, Karnataka, India
Uma Tiwari School of Food Science and Environmental Health, Technological University Dublin, City Campus, Dublin, Ireland
Chibuike C. Udenigwe School of Nutrition Sciences, University of Ottawa, Ottawa, Ontario, Canada
Marco Vassallo CREA ‐ Research Centre for Agricultural Policies and Bio‐Economy, Rome, Italy
Mingjia Yan UCD School of Biosystems and Food Engineering, University College Dublin, Dublin, Ireland
Preface
Cereals and other “healthy” grains have captured the consumer's interest in recent times, with growing health awareness and an increasing motivation for plant‐based eating, thus challenging the cereal processing industry to deliver products without compromising their healthiness, tastiness, and overall likability. Although cereal processing is one of the oldest forms of food processing, a holistic approach to cereal processing is nowadays needed more than ever before, not only to preserve the health benefits of cereal grains, but also to increase safety, assure sustainability, and decrease the carbon footprint, which is possible by coupling alternative processing techniques with conventional ones.
The concept of healthy grains is based on both the major and minor cereals, and pseudocereals (also known as gluten‐free grains), being important sources of energy and macro‐ and micronutrients in the human and animal diets. Healthy grains are utilized in many food products with high nutritional and biological values, which are required more and more by consumers with high levels of nutrition knowledge and healthy food behaviors.
Throughout its 11 chapters, this book provides an overview of recent advances and innovations, not only those limited to cereal and pseudocereal product development, but also in processing. Hence, topics such as advances in traditional and innovative cereal and pseudocereal processing techniques and innovative products thereof and their functionality, cereal‐based animal feed, trends that are driving market demands, and the consumption of healthy grains, as well as the environmental impact of healthy grain processing are represented. The contents of this book provide useful information not only for researchers, academia and students, but for all stakeholders along the cereal and pseudocereal value chain – industry, policy makers, civil society, and retailers – to understand the need for innovation in the cereal and pseudocereal processing sector. Once the challenge of innovation is accepted, whether it is continuously incremental or radical, improvements in terms of productivity, cost, speed, quality, and/or flexibility of production and products are made possible for the benefit of all.
Both editors wish to thank all the contributors for their valuable expertise and their invaluable time in contributing to this book. Also, we thank the editorial support and assistance from series editor Prof. Brijesh Tiwari for helpful suggestions at all stages of the book’s development.
Dr. Milica Pojić
Dr. Uma Tiwari
1Processing Technologies for Healthy Grains: Introduction
Milica Pojić1 and Uma Tiwari2
1 Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
2 School of Food Science and Environmental Health, Technological University Dublin, City Campus, Dublin, Ireland
1.1 Healthy Grains: What Are They?
Cereal grains have been a principal part of humans’ daily diet, consumed in different forms and/or products, for many years. Cereals are traditionally utilized as a breakfast meal or as a main meal of the day, not only to provide carbohydrates, but also to increase the level of dietary fiber. Nowadays, the increase in awareness of health and demand for healthy products by consumers are becoming a challenge for the food industry to develop new and nutritious cereal products. However, when it comes to nutrition, health, and wellbeing, one might think cereal grains inadequate foodstuffs, considering that they have been attributed as a major contributor to obesity due to their high content of easily digestible carbohydrates. Thus, in the early 2000s a decline in wheat consumption was observed in the USA, attributed to the “low carb” diet craze. Moreover, protein, iron, zinc, and vitamin A deficiencies are observed in developing countries with the highest per capita consumption of refined cereal grains, which are low in micronutrients. On the other hand, a vast number of scientific studies that have been emerging demonstrate protective positive effects of whole grains against cardiovascular disease, cancer, diabetes, obesity, and other chronic noncommunicable diseases, which have resulted in a growing consumption of whole‐grain products (Awika 2011). The consumption of gluten (and “gluten‐like”) proteins from major cereals – wheat (including khorasan and spelt), barley (including malts), rye, and triticale – as well as gluten‐containing food additives (in the form of flavoring, stabilizing, or thickening agents) and foods contaminated with gluten‐containing products (such as oat) causes gastrointestinal problems and malabsorption syndrome in approximately 0.5–1.0% of the world’s population, i.e. those diagnosed with celiac disease (El‐Chammas and Danner 2011). Gluten‐free diets, although predominantly designed for patients with celiac disease and nonceliac gluten sensitivity, have been gaining increasing popularity in recent years. A growing demand for gluten‐free food is not only due to the increasing number of diagnosed patients, but also due to the higher availability of different gluten‐free foods in the market (e.g. salty snacks, crackers, fresh bread, pasta, ready‐to‐eat cereals, baking mixes, cookies, flour, frozen bread/dough, etc.) and due to the advertising campaigns, press coverage and promotion of this type of diet (Newberry et al. 2017). As a result, in the period 2004–2011 the sale of gluten‐free products had an annual growth of nearly 28% and in 2012 was close to US$2.6 billion (Asbran 2017; Remes‐Troche et al. 2020). Moreover, a survey conducted in 2015 in the US, whose results were published in the report Gluten‐Free Foods in the US (5th Edition), showed varying attitudes of the population toward these products. The survey indicated that 36% of respondents consumed gluten‐free products for reasons other than gluten sensitivity: 65% because they thought it was healthier, 27% because they thought it helped in weight loss, 7% to reduce inflammation, and 4% to fight depression, whilst only 5.7% of respondents claimed the consumption of gluten‐free products due to formal medical conditions (Békés et al. 2017). Therefore, in recent years the utilization of pseudocereals, being gluten‐free, has captured consumers’ interest and more research is now focused on partial or full utilization with cereals to produce “healthy” grain products. Furthermore, health and wellness retail showed growth in healthy products of 3.3% in Asia and the Pacific and 4.2% in the Middle East and Africa (Mascaraque 2018). Similarly, in Europe, the sales of healthy grain products reached €12.8 billion in 2018, with a projection for the market value to increase about 6% from the previous year (CBI 2019). Globally, over the last few years an increase in market demand was observed for products perceived as more natural and “healthier” – a product group consisting of organic, “free‐from”, and naturally “healthy” products (Mascaraque 2018).
1.2 Cereals and Pseudocereals: Production, Nutritional Value, and Utilization
Cereals (monocotyledonous) and pseudocereals (dicotyledonous) are species that are taxonomically not closely related to each other, but share certain characteristics, such as the structure and composition of their kernels, especially in terms of starch and protein content in approximately the same relative proportions. Moreover, they are cultivated, harvested, processed, and used in the same manner as cereals (Rosentrater and Evers 2018).
Although the increasing worldwide demand for pseudocereals in recent years caused their increased production, they are still considered underutilized feedstock. Their significance is increasing due to high‐quality allergy‐free proteins and large amounts of micronutrients and bioactive compounds, which increases their market price. Although the worldwide interest in pseudocereals is a relatively recent phenomenon, some of the species were cultivated as traditional crops in certain part of the world for centuries (Rosentrater and Evers 2018). Among pseudocereals, amaranth, quinoa, and buckwheat are of the highest commercial potential. On the other hand, traditional cereals are considered major and minor based on the volume of their production and utilization. Wheat, maize, rice, and barley are classified as major cereals, while sorghum, millet, oats, rye, spelt, and primitive and wild wheat species are minor cereals. The differences between major and minor cereals are not only in the quantity of production, but also in the nutritional profile, with higher levels of certain antioxidant substances, which makes minor cereals useful in preventing a wide range of diseases linked with oxidative damage (Akkoc et al. 2019).
According to the Food and Agriculture Organization of the United Nations (FAO) Statistics Database (FAOSTAT), the total production level of cereal crops worldwide significantly increased from the year 2000 to 2018. For example, crop production increased by 80% for wheat, 52% for maize, and 77% for rice, followed by barley, sorghum, millet, oats, and rye. Similarly, FAOSTAT also estimated pseudocereal production of buckwheat decreased slightly, while quinoa production increased over the 18 years to 2018 (Figure 1.1). Additionally, FAOSTAT also showed that production increased by 67% for quinoa, but reported a significant decrease by 30% for buckwheat (FAO 2020). However, due to the growing demand to feed the growing world population, the estimated world buckwheat utilization is expected to increase to 7 million tonnes by 2020 (FAO 2020). They predicted that wheat consumption will increase by 12 million tonnes, while world rice utilization will increase to 514 million tonnes in the year 2019–2020.
The major nutritional components of cereals are starch and nonstarch carbohydrates accounting for approximately 87%, while their protein content ranges from 6 to 15% (Goldberg 2003). The major storage proteins present in the cereal grains are gliadins and glutenins for wheat, oryzenin for rice, zeins for maize, kafirins for sorghum and millet, and hordeins and glutelins for barley, while in oats the main proteins are albumins and globulins (Kulp and Ponte 2000). Pseudocereal grains mainly consist of starch and proteins accounting for 55–75% (Venskutonis and Kraujalis 2013) and 12–16% (Mota et al. 2016), respectively. Unlike true cereals, pseudocereals contain high amounts of essential amino acids, particularly methionine, lysine, arginine, tryptophan, and sulfur‐containing amino acids (Schoenlechner et al. 2008). Additionally, cereals and pseudocereals also contain good amounts of bioactive compounds including dietary fibers, phenolic acids, carotenoids, β‐glucans, as well as other phytochemicals such as tocopherols, alkylresorcinols, and flavonoids associated with the prevention of diseases (Akkoc et al. 2019).
Figure 1.1 Global production of cereals and pseudocereals from 2000 to 2018.
Source: FAO (2020).
Based on the healthy and nutritive value of cereal and pseudocereal grains, consumers are attracted toward increasing their consumption of the combination of these grains. For this reason, the popularity of healthy grains in many countries has gained importance and researchers are focused on creating new and innovative products.
1.3 Cereal Byproducts for Food and Feed Utilization
The increased demands for sustainability of food production, climate change, and limited natural resources for food for an increasing global population reaching 10 billion by 2050 impose the need to improve the efficiency of food systems and find alternative food solutions (Fasolin et al. 2019; Galanakis 2020). One of them is valorization of byproducts and side streams, and when it comes to cereals and pseudocereals, they are generated in dry milling, pearling, and malting processes. These processes generate byproducts in different forms composed of highly valuable compounds, which are most commonly utilized directly as animal feed livestock with no additional processing costs. Numerous recent studies have shown that cereal byproducts can be also redirected from animal to human consumption and used directly, as in the case of cereal brans and germs which can be used as food ingredients in a wide range of food products as natural sources of fibers and other bioactive compounds. Moreover, cereal byproducts can be further subjected to fractionation, extraction, and purification to obtain high added value compounds for food, feed, and nonfood uses (pharmaceutical, biomedical, cosmetic, etc.) (Dapčević‐Hadnađev et al. 2018; Galanakis 2020). However, whether used for food or animal feed purposes, certain challenges in the valorization of cereal byproducts have arisen related to safety – the presence of toxic compounds (mycotoxins, heavy metals, and pesticides) and the presence of high amounts of antinutritional factors (Pojić et al. 2018).
A further increase of the efficacy of cereal material utilization can be achieved within the biorefinery concept of processing which enables the integral valorization of byproducts to obtain antioxidants, biofuels, bioenergy, bioproducts, and biofertilizers, as well as improve the technological and nutritional functionality of byproducts for their further use (Galanakis 2020).
1.4 Challenges in Healthy Grain Processing: Traditional vs Innovative Processing
The most common cereal and pseudoceral processing operations – dry milling, wet milling, pearling, malting, and baking – are confined to traditional technologies characterized by a small pace of innovation. In an era in which innovation is considered a key driver of economic growth, the innovation of cereal and healthy grain processing needs to be boosted. Innovation in the cereal processing sector is not only driven by increasing consumer demands for sustainable, safe, and nutritious high‐value cereal and gluten‐free products, but also the need to decrease the environmental impact of processing by minimizing energy demands and reducing food losses and waste. For example, traditional milling and baking processes are characterized by the implementation of incremental innovation, which improved the efficacy of processing, reduced energy consumption and decreased the need for manpower.
On the other hand, we are witnessing increasing research dynamics in the field of innovative process technologies, mainly applied to increase the extraction of bioactive compounds by means of cell rupture and disrupting or damaging the cellular membrane (Hernández‐Hernández et al. 2019). Their implementation in the cereal processing sector can be perceived through the improvement of product quality, enhancement of (techno‐) functionality, alteration of allergenicity, enzyme deactivation, microbial and chemical decontamination (removal of pesticides, mycotoxins, and antinutritive factors), acceleration of heat and mass transfer, control of Maillard reactions, and extension of shelf‐life (Hernández‐Hernández et al. 2019). Therefore, if they are combined with traditional cereal processing methods they can provide benefits to consumers, while companies that have implemented them can maintain or increase their market share and profitability (Albertsen et al. 2020). However, especially in the food sector, scientific or technological innovations often encounter mistrust and rejective reactions from consumers, resulting in decreasing acceptance of those innovations. It was found that consumer acceptance of innovative food products is conditioned by relative advantage, naturalness, and novelty, but also by discomfort described by insecurity and uneasiness. Therefore, in order to increase consumer acceptance of food innovations, effective communication strategies must be applied to reduce existing mistrust (Albertsen et al. 2020). It must be noted that the majority of innovative processing technologies are still in the research and development stage, while those already commercialized are barely applied in the food industry and only on a small scale. Another condition for their higher commercial exploitation is the development of high‐capacity industrial‐scale equipment (Pojić et al. 2018).
1.5 Relevance of this Book
This book, Innovative Processing Technologies for Healthy Grains, aims to address innovative cereal science and technology and create a knowledge base relevant for students, educators, researchers, food processors, and product developers by bringing together essential information on the nutritional and techno‐functional properties of cereals and pseudocereals and processing techniques utilized to deliver final products in line with consumer expectations. Innovative cereal processing is associated with the addition of value to raw materials and final products – increasing safety, modification of technological properties, and better utilization of functional ingredients and byproducts. Therefore, innovative cereal processing has a huge potential, but also represents a real challenge for science, industry, and policymakers, and to a certain extent for consumers, too. The acceptability of novel foods by consumers is a complex and challenging issue influenced by many factors, including sensory preferences and personal factors that need to be perceived and overcome as a prerequisite for the increased acceptance of food innovations.
This book comes at a time when food and nutrition are intertwined with a number of trends: the trend toward healthful eating patterns, the increasing adoption of plant‐based diets, and the consumption of high‐protein foods, as well as “clean” and “free‐from” labelling – all of them being mostly favorable for grain and cereal‐based food. Moreover, this book comes at a time when efforts are made to ensure the sustainability of production and the utilization of byproducts, when legislative restrictions limit the number of fumigants and storage insecticides, and when the safety and technological properties of grains are compromised by incidents of extreme weather conditions as a result of climate change (e.g. mycotoxin contamination).
Acknowledgment
M. Pojić would like to acknowledge the financial support of the Ministry of Education,Science and Technological Development of the Republic of Serbia (No. 451‐03‐68/2020‐14/200222).
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2Introduction to Cereal Processing: Innovative Processing Techniques
Uma Tiwari1 and Milica Pojić2
1 School of Food Science and Environmental Health, Technological University Dublin, City Campus, Dublin, Ireland
2 Institute of Food Technology, University of Novi Sad, Novi Sad, Serbia
2.1 Introduction
Globally, cereals and their products have become a part of one’s daily diet. Cereals are edible grains of the family of Poaceae or Gramineae. The largest group within this grass family, cereals consist of more than 10 000 species and are commonly consumed around the world. Shewry and Tatham (1999) studied the taxonomy of cultivated cereals and classified them under different subfamilies: Bambusoideae, Festucoideae, Panicoideae and Chloridoideae (Figure 2.1).
Many cereals belong to the subfamily Pooideae (also known as Festucoideae), such as wheat, barley, and rye, belonging to the tribe Triticeae, while oats belong to the tribe Aveneae. Rice belongs to the subfamily Bambusoideae, while the minor grains such as finger millet (also known as ragi) and teff are classified under the subfamily Chloridoideae (Shewry and Tatham 1999). According to the Food and Agriculture Organisation of the United Nations (FAO) Statistics Database (FAOSTAT) on crop statistics (FAO 2016), rice, wheat, maize (corn) and sorghum occupy vast harvested areas compared with other cereal crops. Therefore, they are classified as major cereals, as opposed to minor cereals based on their production and utilization levels. For instance, according to Healthy Minor Cereals (2016), wheat and barley are the most important cereals while spelt, einkorn, rye, and oats are minor cereals.
The FAOSTAT database shows that the overall production of cereal grains increased from the year 2018 to 2000 for maize (48.4%), wheat (20%), rice (23%), sorghum (6%), and barley (6%). The OCED‐FAO Agricultural Outlook (2018–2027) indicates that global cereal (e.g. wheat, rice, and maize) production will increase by 17.6 Mha between 2017 and 2027. Thus, cereal production is indispensable to feeding the growing population (i.e. 6–8.3 billion by 2030) and world consumption is forecast to increase from 2.6 to 2.9 billion tonnes (OECD‐FAO 2018). Due to the high content of starch, cereal foods provide high amounts of energy in a diet; this is followed by other major nutrients such as dietary fiber, nonstarch carbohydrates, and proteins, and minor nutrients. Cereals are utilized in various forms (e.g. bread and bakery products, breakfast cereals, cookies, porridges, extruded snacks, etc.) around the world and consumed either partially or fully processed. However, cereals require appropriate post‐harvest management followed by primary and/or secondary processing to produce suitable end products. Nowadays, researchers working on cereal and cereal products are focussed on the implementation of innovative processing methods in combination with traditional methods to achieve healthy and beneficial cereal‐based products. Cereal scientists are moving toward the trend of sustainable production of end or final products with more nutrients, that are high in functional properties and low in allergenicity, and increase the safety of the products with processing techniques. Therefore, this chapter provides a detailed overview of cereal characteristics, grain structure and composition, and processing methods with special emphasis on innovative processing techniques.
Figure 2.1 Taxonomic relationships of cereals.
Source: adapted from Shewry et al. (1992)
.
2.2 Characteristics of Cereals
The characteristics of cereals vary in terms of the specification of inflorescences, roots, stem, types of leaves, and kernel structure. The kernel structure is the main characteristic that determines the mode of processing.
2.2.1 Cereal’s Inflorescences
Inflorescence structure directly affects the yield of grains and it varies with species, diversity of branching architecture, size, and number of kernels (Kyozuka et al. 2014; Bommert and Whipple 2018). Cereals such as wheat, rye, barley, and oats have a spiral arrangement of leaves on the stem while some species consist of alternate leaf arrangements (Kellogg et al. 2013). In cereals, each flower produces one seed, depending on the design of the inflorescence (panicle or spike), which controls the yield of the cereal grains – the panicle inflorescence (rice and sorghum), spike inflorescence (wheat, barley, and rye), panicle attached to the central axis (oats and millet), etc. Inflorescences also differ in their arrangements of branches, i.e. short or long branches. For example, rice has many long branches bearing single spikelets whereas sorghum consists of short branches bearing two spikelets (Doust 2007; McSteen et al. 2000; Vollbrecht et al. 2005).
2.2.2 Cereal’s Roots
Gramineae possess two distinct root systems, mainly consisting of primary or seminal roots and coronal roots. Most cereals, such as rice, wheat, oats, millet, and sorghum, have both primary and secondary root systems. The root system of rice is generally shallow and suitable for flooded conditions, while maize has a more complex root system with an embryogenic primary root (first root) followed by seminal roots, crown roots and aerial nodal roots (Hetz et al. 1996). The primary roots or seminal roots are generally intact until the time of harvest, while the coronal root provides stronger anchorage and prevent the plant falling over. These root systems absorb and secure uptake of water and nutrients including nitrogen (Aiken and Smucker 1996).
2.2.3 Cereal’s Stems and Leaves
The stems are usually hollow, divided into series of nodes and internodes, elongated in shape, and grow up to approximately 30–40 m long, but this varies with different species. In rice, the lower internodes are shorter than the upper internodes, providing greater plant resistance against waterlogging (Weaver and Zink 1945). As is well known, the stem connects the roots and other parts of the plant, and thus helps the transport of water, minerals, and sugars. In some rice varieties, aerenchyma tissue formation enables oxygen to be supplied to the roots and root nodules, thus reducing waterlogging. In some cases, the stem diameter and height also influence the resistance of the plant to waterlogging. The leaves of the grass family consist of a sheath that encloses the culm and opens out into the leaf blade, which is long and narrow with blunt tip. For example, sorghum leaf blades are smaller, flat, and pointed in structure while maize leaves are broader in shape. Moreover, leaves are arranged alternately on the stem with one leaf per node, allowing the production of sufficient carbohydrates during photosynthesis (Weaver and Zink 1945).
2.3 Kernel Structures
All cereals share the common basic anatomy of a kernel (Alldrick 2017). The anatomy of wheat and rice kernels is given in Figure 2.2.
Following the fertilization stage, seeds are developed from the ovule and contain the embryo surrounded by outer layers such as the husk, seed coat (pericarp and testa), aleurone layers and endosperm. Monocotyledon grains (rice, wheat, barley, oats, etc.) consist of seeds that contain one cotyledon or one embryonic seed leaf (Hoseney 1994). The kernel tissue of greatest nutritional significance is the endosperm, composed of cells filled with nutrients to sustain the embryo during the germination process. It is well known that cereals are major source of carbohydrates, protein, certain vitamins, minerals, and phytochemicals, which satisfy energy needs and provide health benefits for humans (Goldberg 2003). In particular, cereals mainly consist of carbohydrates in the form of polysaccharides – primarily starch located in the endosperm (56–74%) and fiber, primarily arabinoxylans, β‐glucans, and cellulose located in the bran layer – followed by protein ranging from 8 to 12% (Koehler and Wieser 2013). Table 2.1 gives an overview of the major nutrients present in cereals.
2.3.1 Rice
Rice or paddy is covered by a hull or husk, which constitutes about 18–28% of the weight of the grain, and the caryopsis (also known as brown rice), which constitutes about 72–82% of the weight of the grain. The caryopsis consists of the outer pericarp layer (1–2%), the aleurone layer or bran (5%), the germ or embryo (2–3%), and the starchy endosperm (89–91%). The aleurone layer, which encloses the embryo, has one to five cell layers, being thicker at the dorsal surface than the ventral surface. Generally, the aleurone layers are thicker in short‐grain than in long‐grain rice, and the starchy endosperm is the whitest portion of the rice caryopsis (Juliano and Tuaño 2019). Milling of rice removes the outer cover by dehusking (removal of husk) and polishing (removal of bran), producing the edible endosperm (white polished rice) for human consumption. The dehusking process also removes the different layers of rice and thereby removes quantities of fat, carbohydrates, protein, and fiber, influencing the nutritional value of rice (Fernando 2013). The more that polishing given to the rice grains, the more that fats, proteins, thiamine, and other vitamin‐rich compounds are removed.
Figure 2.2 Structure of wheat (left) and rice kernels (right).
Table 2.1 Composition of cereals.
(Source: FAO 1999; Saldivar 2003)
Cereals
Crude protein (%)
Crude fat (%)
Ash (%)
Crude fiber (%)
Digestible CHO (%)
Starch (%)
Total dietary fiber (%)
Total phenolics (mg/100 g)
Wheat
10.6
1.9
1.4
1
69.7
64
12.1
20.5
Maize
9.8
4.9
1.4
2
63.6
62.3
12.8
2.91
Brown Rice/ Paddy
7.3
2.2
1.4
0.8
64.3
77.2
3.7
2.51
Barley
11
3.4
1.9
3.7
55.8
58.5
15.4
16.4
Sorghum
8.3
3.9
2.6
4.1
62.9
73.8
11.8
43.1
Pearl Millet
11.5
4.7
1.5
1.5
63.4
60.5
7
51.4
Oats
9.3
5.9
2.3
2.3
62.9
52.8
15.4
16.4
Rye
8.7
1.5
1.8
2.2
71.8
68.3
16.1
13.2
2.3.2 Wheat
The wheat kernel consists of three main anatomical parts: the bran (seed coat), the endosperm and the embryo (germ). Generally, the germ comprises about 2–3% of the kernel, the bran 13–17%, and the starchy endosperm makes up about 83–85% of the kernel’s weight (Pomeranz 1982). The aleurone layer is the outermost layer of the endosperm, generally attached to the outer coat, which in successive grinding and sieving operations in an industrial roller mill ends up in tail‐end break and reduction flour mill streams or attached to bran particles (Pojić et al. 2014). Milling separates these layers from the wheat kernel prior to the production of refined flour. Generally, the inner bran layer is high in protein, fat, and minerals, and the outer layer of the bran is high in cellulose and hemicelluloses. Wheat germs are also good sources of vitamins B and E, minerals, lysine, and unsaturated fatty acids.
2.3.3 Maize
The maize kernel consists of the pericarp, the hull or bran, the germ or embryo, the endosperm, and the tip cap, a conical structure of dead tissue where the kernel joins the cob. The maize kernel has a relatively larger germ than other cereals, placed in the lower portion of the endosperm. The endosperm represents approximately 70–86% of the kernel and contains mainly starch (87.6%) and protein (8%). Maize germ ranges from 7 to 22% of the kernel and consists of high levels of lipids (18–41%), protein (12–21%), and starch (6–21%), but it is also rich in unsaturated fatty acids, tocopherols, tocotrienols, and carotenoids (FAO 1992; Navarro et al. 2016). Moreover, the maize kernel also contains phytate, acting as an endogenous toxic compound and antinutritive factor in monogastric species that are not able to utilize a large amount of minerals (Humer et al. 2015). The corn kernel is flattened, wedge‐shaped, and broader at the apex end than at the point of attachment to the cob. Maize kernels are processed by dry milling to produce primary products such as brewers’ grains, snack food grits, and flour, and wet milling to obtain corn starch and a wide assortment of byproducts such as corn bran, germ meal, and corn protein meal (FAO 1992; Papageorgiou and Skendi 2018).
2.3.4 Barley
Barley kernels are spindle‐shaped, comprising the caryopsis (one‐seeded fruit) covered by the hull or husk. The hull or husk represents 10–13% of the dry weight of the kernel, but this might vary with the dehulling process, which may remove up to 20% of the kernel weight. The endosperm cell walls are mostly composed of β‐glucan (70%) (Tiwari and Cummins 2009). The aleurone layer contains cells in two or three layers, depending on cultivars. The caryopsis consists of the pericarp, the seed coat, the germ or embryo, and the starchy endosperm, accounting for 80% of the total grain weight. The barley embryo is generally located at the end of the caryopsis on its dorsal side. “Hull‐less” barley has a loosely attached hull that falls off during harvesting and threshing (the removal of grains from the chaff) (Evers and Millar 2002).
2.3.5 Oats
Oat caryopses (groats or kernels) are similar to those of wheat and barley, and composed of the bran, the endosperm and the germ. The caryopsis and the hull account for 65–75% and 25–35% of the whole kernel respectively. The oat germ is located on the dorsal side of the caryopsis so that it is partly covered by the lemma, which comprises about 2–3 leaf shoots of the plumule and about 2–3 rudimentary roots of the radicle (Welch 2012). The bran comprises layers of tissue and aleurone cells located in the outer layers of the groat, whereas the endosperm (55–80%) is located inside the wall layers of the groat and composed of starch, protein, lipids, and the major concentration of β‐glucans (Tiwari and Cummins 2009).
2.3.6 Rye
Rye grains are arranged in a zigzag fashion on the rachis and are covered with a lemma, a palea, and a glume. On maturity the grains fall off easily during threshing. The grains are usually grayish‐yellow in color with a shrivelled and rough surface. Rye kernels are composed of 86.5% starchy endosperm, followed by the bran (10%) and the germ (3.5%). During the milling process, the bran and germ of the rye kernel are separated from the endosperm and milled into flour (Bushuk 2004).
2.3.7 Sorghum
The three principal anatomical components of the basic sorghum kernel are the pericarp, the germ, and the endosperm, which account for 6, 10, and 84% of kernel weight, respectively. However, these proportions vary with different sorghum cultivars. The endosperm is the largest part of the kernel and has a comparatively poor mineral and oil content. The endosperm contributes mainly to the kernel’s protein (80%), starch (94%) and B‐complex vitamin (50–75%) compositions, whereas the germ contains 68% of the minerals, 75% of the oil and 15% of the protein of the whole kernel (FAO 1995). Therefore, processing leads to removal of the outer pericarp, increases the relative protein level, and reduces the cellulose, lipid, and mineral content in the grain. For example, Alvarenga et al. (2018) demonstrated the effects of milling sorghum into various fractions to produce animal feed with a good protein content. They concluded that mill‐feed fractions contained a higher level of crude protein (13.4%) compared with flour (9.68%), indicating the potential benefits of utilizing the milling fraction for human and animal feed.
2.3.8 Millet
Millet kernels comprise about 7–10% pericarp, 15–21% germ, and 70–76% endosperm. Four major millet species are pearl millet, foxtail millet, proso millet, and finger millet. The pericarp of pearl millet is strongly attached to the seed (caryopsis), whereas in proso, finger, and foxtail millets the pericarp is attached to one point on the seed. The endosperm of millet is divided into the peripheral, outer, hard endosperm and the inner, floury endosperm, while the germ constitutes up to one third of the pearl millet caryopsis. The relative proportions of the endosperm and germ in millet are about 4.5 : 1, i.e. the germ constitutes ~20% of the weight of the whole kernel (FAO 1995). The distribution of the total amount of protein within the pearl millet grain is 60% in the endosperm, followed by 31% in the germ, and 9% in the pericarp. The protein content in pearl millet is in the range 8–23%, while proso millet contains 11–13% protein (Lestienne et al. 2005; Serna‐Saldivar and Rooney 1995).
2.4 Processing of Cereals
In order to derive the nutritional benefit from cereal grains and increase their digestibility and palatability they must be subjected to a certain type of processing involving one or a combination of different mechanical treatments – threshing during which the outer seed coats are removed, milling during which the particle size is reduced and grain converted into a flour of some type, and/or thermal processing (e.g. cooking, roasting, or baking).
The anatomy of the cereal kernel also affects the types and routes of contaminants (e.g. mycotoxins, pesticides, or heavy metals) and endogenous toxic compounds presenting a potential hazard when consumed. Although the level of endogenous toxic compounds in cereals is low, two compounds of interest are phytate and tannins. Their anatomical distribution depends on the type of cereal grain: phytate is found to be predominantly located in the germ of maize, the aleurone layer of wheat, and uniformly distributed through millet (Alldrick 2017). The need to make grain digestible and palatable, but also safe for consumption, conditioned the development of novel process technologies as one of the mitigation strategies to reduce the risk of contamination (Alldrick 2017).
