Table of Contents

Cover

Title Page

Contributors

Preface

Chapter 1: The flavor of citrus fruit

Introduction
Taste components of citrus fruit
Aroma compounds of citrus fruit
Citrus genes involved in flavor production
The unique flavor of different citrus species
Accumulation of off-flavors in fresh citrus fruit during postharvest storage
Flavor of citrus essential oils
Acknowledgments
References

Chapter 2: Aroma as a factor in the breeding process of fresh herbs – the case of basil

The importance of selecting for aroma in breeding of aromatic plants
The importance of genetic factors regarding the essential oil composition in aromatic plants
Sweet basil and the Ocimum genus
Uses of sweet basil
The chemistry of the aroma factors of plants: the essential oil
Essential oil profiles of common commercial basil varieties
Comparison of chemical analysis methods
Variation of the volatile compound composition within the plant
Variation of aroma compounds within cultivars and the potential for selection
Biosynthetic pathways of basil aroma components
Inheritance of aroma compounds in basil
Interspecific hybridization among Ocimum species
Applications of biotechnology-based approaches to modification of basil aroma
References

Chapter 3: Novel yeast strains as tools for adjusting the flavor of fermented beverages to market specifications

Introduction
Wine, beer, and saké yeasts
Acids
Alcohols
Esters
Carbonyl compounds
Volatile phenols
Sulfur compounds
Monoterpenoids
Conclusion
References

Chapter 4: Biotechnology of flavor formation in fermented dairy products

Introduction
Biochemistry of dairy fermentations
Biotechnology and flavor
Flavor production from bacteria
Comparative genomics of flavor production
Expression and metabolite analysis
Predictive bioinformatics
Non-culturable lactococci
Translation of omics to biotechnology
Conclusion
References

Chapter 5: Biotechnological production of vanillin

Introduction
Biosynthesis of vanillin
Production of vanillin by biotechnology
Use of physical and mild chemistry methods
Synthetic vanillin
Vanillin from vanilla beans
Regulations
Conclusions and future outlook
References

Chapter 6: Plant cell culture as a source of valuable chemicals

Introduction
Establishment of callus culture
Concluding remarks
References

Chapter 7: Increasing the methional content in potato through biotechnology

Flavor compound methional in foods
Formation of methional
Synthesis of Met in plants
Biotechnology to enhance Met and methional
References

Chapter 8: Flavor development in rice

Introduction
Old flavors of rice
Rice texture
Fragrant rice
The chemistry of rice fragrance
The genetics of rice fragrance
BAD enzymes and 2AP synthesis
The future
References

Chapter 9: Tomato aroma: biochemistry and biotechnology

The major aroma impact volatiles in tomato and their biosynthetic pathways
Biosynthesis of tomato volatiles
Carotenoid pigmentation affects the flavor and volatile composition of tomato fruit
Genetic engineering of tomato aroma
Contribution of “omics” to improving our understanding of aroma biosynthesis and perception
Conclusion
Acknowledgment
References

Chapter 10: Breeding and biotechnology for flavor development in apple (Malus × domestica Borkh.)

Quality
Apple volatiles
Ester compounds and ester biosynthesis
Measurement techniques
Varietal and developmental differences
Effect of storage
Effect of processing
Effect of 1-methylcyclopropene treatment
Hypoxia
Gene isolation
Genetic studies, linkage maps, and marker-assisted selection
ESTs
Transgenic approaches
Ethylene production and softening (ACS–ACO)
Consumer perceptions and sensory testing
References

Chapter 11: Biosynthesis and perception of melon aroma

Introduction
Volatile composition of melon fruit
Odor perception
Biosynthesis of melon aroma volatiles
Concluding remarks
References

Index

End User License Agreement

List of Illustrations

Chapter 1: The flavor of citrus fruit

Figure 1.1 Morphological structure of citrus fruit. (a) Cross-sectional view of an orange fruit. (b) Cross-section of the flavedo layer with oil glands beneath; magnification ×8. Source: Ron Porat.
Figure 1.2 Model describing the biochemical pathways involved in ethyl ester synthesis, responsible for the formation of over-ripe and off-flavor sensations during postharvest storage of citrus fruit. AAT, alcohol acyltransferase.
Figure 1.3 Oil gland of sweet orange flavedo stained with Sudan Red III and observed with an optical microscope. Source: Sophie Deterre, 2012. Color: Dennis Margosan, USDA, ARS, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, USA.

Chapter 2: Aroma as a factor in the breeding process of fresh herbs – the case of basil

Figure 2.1 Examples of morphological variation among basil cultivars.
Figure 2.2 Structures of some of the main components of the essential oil of basil.
Figure 2.3 Variability in the levels of aroma compounds in leaf extracts from a single plant. The percentages of the total oil for the aroma compounds methyleugenol, eugenol, linalool, 1,8-cineole and (E)-b-farnesene are shown and also the total percentage of oil based on the fresh weight (FW) of the sample. The inset illustrates the positions of the leaves used for analysis.
Figure 2.4 Coefficient of variation (CV) of selected volatile content in the essential oil of 24 randomly selected single plants of three basil cultivars.
Figure 2.5 Biosynthetic pathway for methyleugenol and methylchavicol. Source: Adapted from Gang et al. (2002), Koeduka et al. (2006), and Vassao et al. (2006).
Figure 2.6 Biosynthetic pathway for geranial and neral. Source: Iijima et al. (2006) Reproduced with permission from Elsevier.

Chapter 3: Novel yeast strains as tools for adjusting the flavor of fermented beverages to market specifications

Figure 3.1 The metabolic role of yeast in the development of flavor compounds in wine, beer and saké. Source: adapted from Swiegers et al. (2005a).
Figure 3.2 Pathway of leucine and valine biosynthesis. ILV2, acetolactate synthase; ILV5, acetohydroxy acid reductoisomerase; ILV3, dihydroxy acid dehydratase; BAT1, branched-chain amino acid aminotransferase; BAT2, branched-chain amino acid transaminase; LEU9, α-isopropylmalate synthase; LEU4, α-isopropylmalate synthase; LEU1, isopropylmalate isomerase; LEU2, β-isopropylmalate dehydrogenase.
Figure 3.3 Flavor-active esters produced by Saccharomyces yeast in wine, beer, and saké.
Figure 3.4 Volatile phenols in wine produced by yeast. Source: adapted from Swiegers and Pretorius (2005). Reproduced with permission from Elsevier.
Figure 3.5 Sulfur amino acid metabolism in S. cerevisiae and its role in the production of hydrogen sulfide.
Figure 3.6 Hydrolysis of neryl β-d-glucoside to nerol and glucose through β-glycosidase enzymes produced by yeast. Source: adapted from Swiegers and Pretorius (2005). Reproduced with permission from Elsevier.

Chapter 4: Biotechnology of flavor formation in fermented dairy products

Figure 4.1 Representation for production of fermented dairy products. In some cases, coagulants are not added. Processing aids may include sodium chloride, calcium chloride, sodium gluconate, glucono-δ-lactone, or citrate, among others.
Figure 4.2 General scheme for flavor production in fermented dairy products.
Figure 4.3 Genome rearrangements between the L. cremoris strains' chromosomes (strains are SK11 and MG1363), depicted using the output of the MUMmer software.
Figure 4.4 Genetic reconstruction of the TCA cycle in Lactococcus lactis subsp. cremoris SK11. The glyoxylate shunt (solid line across the circle) and the ketoglutarate bridge (dashed line) are shown. Boxes indicate specific compounds that out link to other pathways of importance for dairy fermentations. This was reconstructed using Cremacyc, a Pathway Tools database built using the SK11 genome, which predicts the metabolic ability based on the genome sequence (www.usu.edu/westcent/procyc). Gene symbols and EC numbers are shown between the reactions.
Figure 4.5 Metabolic interconnections for the production and consumption of α-ketoglutarate and keto acids in general (top panel), succinate (middle panel), and methionine (bottom panel) in L. cremoris SK11. This was predicted using Cremacyc, a Pathway Tools database reconstructed from the SK11 genome (located at www.usu.edu/westcent/procyc) using pathway webbing.

Chapter 5: Biotechnological production of vanillin

Figure 5.1 Cross-section of a mature green vanilla fruit after catechin·HCl staining. Vanillin is stained red in the placenta and neighboring endocarp cells, and also in the secreted matrix that surrounds the seeds in the fruit cavity. The fruit vascular bundles that are rich in lignin also stained red. Scale bar = 5 mm. Source: Joel et al. (2003). Reproduced with permission from Taylor and Francis.
Figure 5.2 The central portion of the fruit, showing a dense catechin·HCl staining of the secreted matrix in the fruit cavity around the seeds, and a weaker staining in endocarp cells adjacent to the cavity. Scale bar = 2 mm. Source: Joel et al. (2003). Reproduced with permission from Taylor and Francis.
Figure 5.3 Possible biosynthetic route to vanillin in Vanilla planifolia, showing the ferulate and benzoate pathways.
Figure 5.4 Proposed vanillin biosynthetic pathway in Vanilla planifolia (Havkin-Frenkel et al. 1996).
Figure 5.5 The route from ferulic acid to vanillin in Pseudomonas strains. 4-Hydroxy-3-methoxyphenyl-β-hydroxypropionyl-CoA is presumed to be an enzyme-bound intermediate. Source: modified from Walton et al. (2003). Reproduced with permission from Elsevier.
Figure 5.6 Oxidative and non-oxidative pathways for the chain-shortening of cinnamic acid derivatives in plants. The upper pathway shows the oxidative pathway to 4-hydroxybenzoic acid via the coenzyme A ester. The lower pathway shows the non-oxidative pathway to 4-hydroxybenzaldehde via an intermediate product, 4-hydroxyphenyl-β-hydroxypropionic acid. Source: Podstolski et al. (2002). Reproduced with permission from Elsevier.

Chapter 7: Increasing the methional content in potato through biotechnology

Figure 7.1 Formation of the flavor compound methional.
Figure 7.2 Met biosynthesis pathway and metabolism in plants. Cys, cysteine; Asp, aspartate; Lys, lysine; OPH, O-phosphohomoserine; Thr, threonine; Hcy, homocysteine; Met, methionine; SMM, S-methylmethionine; SAM, S-adenosyl-l-methionine; CGS, cystathionine γ-synthase; TS, threonine synthase.

Chapter 8: Flavor development in rice

Figure 8.1 Structure of the fragrance gene (fgr) (KOME ID: Rice Genome Database: http://cdna01.dna.affrc. go.jp/CDNA) showing initiation codon (ATG), 15 exons (purple), 14 introns (blue) and the termination site (TAA). The nucleotide sequence of exon 7 is shown for both non-fragrant and fragrant rice varieties. The fragrant variety shows a large deletion and three SNPs which then terminate prematurely (stop codon underlined in red) within this exon. The truncated enzyme encoded in fragrant rice varieties would therefore lack the highly conserved sequences, encoded by exons 8, 9 and 10, and which are believed to be required for correct function of this enzyme. Adapted from Bradbury et al. (2005a).
Figure 8.2 Clustal W alignment of the amino acid sequence of the BAD2 enzyme from non-fragrant rice, encoded for on rice chromosome 8, and the predicted amino acid sequence of the truncated BAD2 enzyme from fragrant rice. Highlighted is the sequence that is conserved in all BADs and is believed to be required for catalytic activity; these conserved regions are absent from the truncated version present in fragrant rice varieties. Adapted from Bradbury et al. (2005a).
Figure 8.3 Single-tube allele-specific PCR for fragrance genotype in rice. (a) Diagrammatic representation of a section of the gene encoding BAD2 in fragrant and non-fragrant rice, showing introns and exons, primer binding sites and PCR product size. (b) Sequence of primers used in the PCR. (c) Agarose gel with artificially coloured bands, showing reaction products from: Nipponbare, a non-fragrant variety (lane 1); Kyeema, a fragrant variety (lane 2); Kyeema/Gulfmont hybrid, a heterozygous individual (lane 3); a non-DNA negative control sample (lane 4); and Roche DNA ladder XIV, showing relevant sizes. (d) Agarose gel showing a sample of individuals from an unselected F2 population segregating for fragrance and analysed using allele specific PCR, flanked by Roche DNA ladder XIV.
Figure 8.4 Theoretical biochemical pathway for 2-acetyl-1-pyrroline formation in rice.

Chapter 9: Tomato aroma: biochemistry and biotechnology

Figure 9.1 Distribution of the main volatiles present in fresh tomato by their metabolic pathway and main precursors. Volatiles present at levels >1 nL/L and considered to have a contribution to tomato aroma (based on Buttery and Ling, 1993) are shown along with their chemical structures.
Figure 9.2 Short-chain aldehyde and alcohol production from the degradation of fatty acids in tomato fruits via the lipoxygenase (LOX)/hydroperoxide lyase (HPL) pathway. Genetic manipulations of the fatty acid catabolism pathway in three key points of the pathway are described.
Figure 9.3 Tomato fruit color mutants and their carotenoid biosynthetic pathways. The carotenoid pigment molecules function as a precursor for tomato norisoprenes and their putative. Genetic evidence indicates that carotenoids are degraded into their respective norisoprene and monoterpene aroma volatiles. Source: modified from Lewinsohn et al. (2005a,b).
Figure 9.4 Diversion of the existing plastid terpenoid pathway (DOXP, deoxy-d-xylulose 5-phosphate pathway), which leads to carotenoids, into the production of new monoterpenes in ripening transgenic tomatoes by the expression of the Clarkia breweri linalool synthase (LIS) and Ocimum basilicum geraniol synthase (GES) and zingiberene synthase (ZIS). Derivatives of linalool and geraniol produced in transgenic tomatoes were probably formed by the action of enzymes present in tomato fruit. The accumulation of monoterpenes produced by the expression of ZIS in tomato indicates GDP export to cytosol. Source: Lewinsohn et al. (2001) and Davidovich-Rikanati et al. (2007, 2008).

Chapter 11: Biosynthesis and perception of melon aroma

Figure 11.1 Main biosynthetic routes to aroma volatiles in melon fruits. The precursors are shown in shaded boxes at the top. The enzymes involved in volatiles formation are shown in italics. Enzymes that have not been demonstrated in melons are shown in parentheses. GPP, geranyl diphosphate; FPP, farnesyl diphosphate; TPS, terpene synthases; CCD, carotene cleavage dioxygenase; LOX, lipoxygenase; HPL, hydroperoxide lyase; ADH, alcohol dehydrogenase; AAT, alcohol acyl transferase; AT, aminotransferase (transaminase); Dec, decarboxylase.
Figure 11.2 Biosynthesis of phenylalanine-derived aroma volatiles in different plants. The phenylalanine precursor is shown in the green box. Enzymes involved in phenylalanine-derived aroma volatiles formation are shown in italics. Enzymes that have not been demonstrated in the relevant plant are shown in parentheses. ArAT, aromatic amino acid aminotransferase; PAAS, phenylacetaldehyde synthase; AADC, aromatic amino acid decarboxylase; Dec, decarboxylase; AO, amine oxidase.
Figure 11.3 Biosynthesis of methionine-derived aroma volatiles in melon fruits. The methionine precursor is shown in the shaded box at the top. Enzymes involved in phenylalanine-derived aroma volatiles formation are shown in italics. MetAT, methionine aminotransferase; MGL, methionine-γ-lyase.

List of Tables

Chapter 1: The flavor of citrus fruit

Table 1.1 Average TSS and acidity levels, and ripening ratios of different citrus fruit
Table 1.2 Odor and taste thresholds of terpene hydrocarbon compounds in a deodorized orange juice matrix, and comparison with thresholds in water. Values are in µg/L. Source: adapted from Plotto et al. (2004)
Table 1.3 Compositions of concentrated sweet orange essential oil (EO) produced from distillation or solvent (ethanol) extraction. Values are percent of oil composition. Source: Adapted from Owusu-Yaw et al. (1986)

Chapter 2: Aroma as a factor in the breeding process of fresh herbs – the case of basil

Table 2.1 Essential oil profiles of various commercial basil varieties. Values given are the percentage of the essential oil. The major components are highlighted in bold
Table 2.2 Effect of the extraction method on the volatiles composition in basil. Values given are the percentage of the essential oil
Table 2.3 Content of selected aroma components of 12 randomly selected single sweet basil plants of Variety 22. The analysis was done by extraction of the third leaf pair from plants with five nodes above the cotyledons. Values are the percentage of total essential oil
Table 2.4 Gene model for inheritance of phenylpropenes in F2 progeny from a cross between a Genovese-type cultivar and a Thai-type cultivar

Chapter 3: Novel yeast strains as tools for adjusting the flavor of fermented beverages to market specifications

Table 3.1 Threshold values for higher alcohols produced by yeast and their concentrations in wine. Source: data from Swiegers et al. (2005a)
Table 3.2 Threshold values for higher alcohols commonly found in beer. Source: data from Meilgaard (1975)
Table 3.3 Threshold values for esters and their concentrations in wine. Source: data from Swiegers et al. (2005a)
Table 3.4 Threshold values, concentration range, and average concentration of aroma-active esters in lager beer. Source: data from Meilgaard (1975)
Table 3.5 Acetaldehyde concentrations in alcoholic beverages. Source: data from Liu and Pilone (2000)
Table 3.6 Threshold values for volatile phenols and their concentrations in wine
Table 3.7 Threshold values for hydrogen sulfide and mercaptans and their concentrations in wine
Table 3.8 Threshold values for volatile thiols and their concentrations in wine. Source: data from Swiegers et al. (2005a)
Table 3.9 Threshold values for monoterpenes and their concentrations in wine

Chapter 4: Biotechnology of flavor formation in fermented dairy products

Table 4.1 Flavor compounds formed during cheese ripening . Source: data from Urbach (1993) and El Soda (1993)
Table 4.2 Genomic comparison of lactic acid bacteria, brevibacteria, and yeast for functional characteristics important to cheese flavor development

Chapter 5: Biotechnological production of vanillin

Table 5.1 Natural occurrence of vanillin in plants

Chapter 6: Plant cell culture as a source of valuable chemicals

Table 6.1 Elicitation of secondary metabolite synthesis in cell culture by constituents of microorganisms
Table 6.2 Elicitation of plant cell cultures with signaling compounds
Table 6.3 Abiotic elicitation of secondary metabolite production in plant cell cultures
Table 6.4 Increase in secondary metabolite production by precursor feeding of plant cell cultures

Chapter 8: Flavor development in rice

Table 8.1 Concentration, thresholds and odor descriptions of significant volatile aroma compounds in fragrant and non-fragrant rices

Chapter 11: Biosynthesis and perception of melon aroma

Table 11.1 Chemical diversity within one melon fruit. Aroma compounds found in a single melon flesh sample of a recombinant inbred line (PI 414723 × “Dulce”)
Table 11.2 Some key aroma volatiles of melons, their chemical structures, and odor descriptors
Table 11.3 Melon odorants with the highest reported impact on melon aroma

Biotechnology in Flavor Production

Second Edition

Edited by

Daphna Havkin-Frenkel

Department of Plant Biology and Pathology
School of Environmental and Biological Sciences
Rutgers, The State University of New Jersey
New Brunswick
New Jersey, USA

Nativ Dudai

Unit of Medicinal and Aromatic Plants
Newe Ya'ar Research Center,
Agricultural Research Organization,
Ramat Yishay, Israel

Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell.

The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.

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 the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book.

Limit of Liability/Disclaimer of Warranty: While the publisher and author(s) have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Title: Biotechnology in flavor production / edited by Daphna Havkin-Frenkel, Nativ Dudai.

Description: Second edition. | Chichester, West Sussex, UK : John Wiley & Sons Inc., 2016. | Earlier edition edited by: Daphna Havkin-Frenkel, Faith C. Belanger. | Includes bibliographical references and index.

Identifiers: LCCN 2016014538| ISBN 9781118354063 (cloth) | ISBN 9781118354032 (epub)

Classification: LCC TP248.65.F66 B637 2016 | DDC 664/.07–dc23 LC record available at http://lccn.loc.gov/2016014538

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Contributors

Balasubramanian Ganesan, Western Dairy Center, Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan, Utah, USA
Faith C. Belanger, Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
Louis M.T. Bradbury, Grain Foods CRC, Centre for Plant Conservation Genetics, Southern Cross University, Lismore, New South Wales, Australia
Susan K. Brown, New York State Agricultural Experiment Station (NYSAES), College of Agriculture and Life Sciences, and School of Integrative Plant Science, Horticulture and Plant Breeding Sections, Cornell University, Geneva, New York, USA
Yosef Burger, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Chee-Kok Chin, Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
Rachel Davidovich-Rikanati, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Sophie Deterre, USDA, ARS, US Horticultural Research Laboratory, Fort Pierce, Florida, USA
Rong Di, Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
Nativ Dudai, Unit of Medicinal and Aromatic Plants, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Natalia Dudareva, Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, USA
Aaron Fait, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Pierre Giampaoli, AgroParisTech, Massy, France
Itay Gonda, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, and The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Daphna Havkin-Frenkel, Department of Plant Pathology and Biology, Rutgers, The State University of New Jersey, Foran Hall, Cook College, New Brunswick, New Jersey, USA
Robert J. Henry, Grain Foods CRC, Centre for Plant Conservation Genetics, Southern Cross University, Lismore, New South Wales, Australia
Mwafaq Ibdah, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Nurit Katzir, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Efraim Lewinsohn, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Eran Pichersky, Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
Anne Plotto, USDA, ARS, US Horticultural Research Laboratory, Fort Pierce, Florida, USA
Ron Porat, Department of Postharvest Sciences of Fresh Produce, ARO, the Volcani Center, Bet Dagan, Israel
Isak S. Pretorius, Macquarie University, Sydney, NSW, Australia
Sofie M.G. Saerens, Chr Hansen A/S, Hørsholm, Denmark
Arthur A. Schaffer, Institute of Plant Sciences, The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel
Yaron Sitrit, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Jan H. Swiegers, Chr Hansen A/S, Hørsholm, Denmark
Ya'akov Tadmor, Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, Ramat Yishay, Israel
Daniel L.E. Waters, Grain Foods CRC, Centre for Plant Conservation Genetics, Southern Cross University, Lismore, New South Wales, Australia
Bart C. Weimer, University of California, Davis, School of Veterinary Medicine, Davis, California, USA

Preface

Throughout history, human beings have sought ways to enhance the flavor of the foods they eat. However, the scaling up of food production leads to enhanced development of new varieties, intensive cultivation, and industrial methods that often cause losses in their aroma and flavor quality. This trend increases the importance of research on and development of the aroma and flavor of agricultural and industrial food products. In the 21st century, biotechnology is playing an important role in the flavor improvement of many types of food. The prediction today is that the world will eventually run out of protein for animal and human consumption; the food industry is gearing up to develop new alternatives. The new protein will need to be flavored, and the task will be harder than ever.

Here we present an updated version of the first edition of 2008, with two new chapters that deal with the flavor of very important crops: melon (Gonda et al.) and citrus fruits (Porat et al.). The remainder of the chapters were updated by their original authors, and cover several of the biotechnological approaches currently being applied to flavor improvement. The contribution of microbial metabolism to flavor development in fermented beverages and dairy products has been exploited for thousands of years. The recent availability of whole genome sequences of the yeasts and bacteria involved in these processes is stimulating targeted approaches to flavor improvement. The chapters by Swiegers et al. and by Ganesan and Weimer discusses recent developments in the flavor modification of wine, beer, and dairy products through the manipulation of the microbial species involved. Biotechnological approaches to the production of specific flavor molecules in microbes and plant tissue cultures, and the challenges that have been encountered, are discussed in the chapters by Havkin-Frenkel and Belanger and by Chin. Metabolic engineering of food crops for flavor enhancement is also a current area of research. The chapters of Davidovich-Rikanati et al. and by Di discuss the metabolic engineering of tomatoes and potatoes for enhanced production of specific flavor compounds. Biotechnological approaches are also being applied to crop breeding through marker-assisted selection for important traits, including flavor. The chapters by Brown and by Dudai and Belanger discuss the application of the biotechnological approach to breeding for enhanced flavor in apples and basil. The commercial application of metabolic engineering for flavor enhancement in foods or for extraction from microbes or tissue cultures is subject to governmental regulation. The topics covered in this book will be of interest to those in the flavor industry and also to academic researchers interested in flavors.

The authors of the chapters are experts in their fields and we would like to thank them all for an excellent job of summarizing the latest research developments regarding approaches to the flavor enhancement of foods.

Daphna Havkin-Frenkel
Nativ Dudai