Essential Oils in Food Processing: Chemistry, Safety and Applications E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Serie: Institute of Food Technologists Series
- Sprache: Englisch
A guide to the use of essential oils in food, including information on their composition, extraction methods, and their antioxidant and antimicrobial applications
Consumers’ food preferences are moving away from synthetic additives and preservatives and there is an increase demand for convenient packaged foods with long shelf lives. The use of essential oils fills the need for more natural preservativesto extend the shelf-life and maintaining the safety of foods. Essential Oils in Food Processing offers researchers in food science a guide to the chemistry, safety and applications of these easily accessible and eco-friendly substances.
The text offers a review of essential oils components, history, source and their application in foods and explores common and new extraction methods of essential oils from herbs and spices. The authors show how to determine the chemical composition of essential oils as well as an explanation of the antimicrobial and antioxidant activity of these oils in foods. This resource also delves into the effect of essential oils on food flavor and explores the interaction of essential oils and food components. Essential Oils in Food Processing offers a:
- Handbook of the use of essential oils in food, including their composition, extraction methods and their antioxidant and antimicrobial applications
- Guide that shows how essential oils can be used to extend the shelf life of food products whilst meeting consumer demand for “natural” products
- Review of the use of essential oils as natural flavour ingredients
- Summary of relevant food regulations as pertaining to essential oils
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Veröffentlichungsjahr: 2017
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Table of Contents
Cover
Title Page
List of Contributors
Acknowledgements
Introduction
1 Essential Oils and Their Characteristics
1.1 Introduction
1.2 Conclusions
References
2 Extraction Methods of Essential Oils From Herbs and Spices
2.1 Introduction
2.2 Conventional Methods of Extraction
2.3 Novel Extraction Methods
2.4 Conclusions
Acknowledgements
References
3 Identification of Essential Oil Components
3.1 Introduction
3.2 Essential Oils as Multicomponent Complex Mixtures
3.3 Essential Oil Component Identification
3.4 GC‐MS
3.5 Isolation of Individual Components or Enriched Fractions
3.6 Conclusions
References
4 Chemical Composition of Essential Oils
4.1 Introduction
4.2 Chemical Composition of Essential Oils
4.3 Synthesis and Biosynthesis of Essential Oils
4.4 Effective Factors on the Composition of Essential Oils
References
5 Basic Structure, Nomenclature, Classification and Properties of Organic Compounds of Essential Oil
5.1 Introduction
5.2 Final Conclusions
References
6 Antimicrobial Activity of Essential Oil
6.1 Chemical Composition of Essential Oils
6.2 Antimicrobial Activity of Essential Oils
6.3 Synergistic and Antagonism Effect of Essential Oils with Other Antimicrobials
6.4 Interaction Between Essential Oils and Essential Oils with Other Food Antimicrobials
6.5 Food Packaging Containing Essential Oils
6.6 Encapsulation of Essential Oils
6.7 Application of Essential Oils as Antimicrobial Agents in Different Food Products
References
7 Bioactivity of Essential Oils Towards Fungi and Bacteria
7.1 The Main Traits of Essential Oils
7.2 Antibacterial Activity of EOs
7.3 Antifungal Activity of EOs
7.4 Mathematical Tools
References
8 Antioxidant Activity of Essential Oils in Foods
8.1 Introduction
8.2 In Vitro Antioxidant Activity of Essential Oils
8.3 Edible Oils and Fats
8.4 Meat and Poultry Products
8.5 Dairy Products
8.6 Conclusions
References
9 Mode of Antioxidant Action of Essential Oils
9.1 Introduction
9.2 Lipid Oxidation and Antioxidant Activity of Chemical Compounds
9.3 Methods for Determining the Antioxidant Properties of Chemicals
9.4 Antioxidant Activity of Essential Oils
9.5 Antioxidant Activity of EOs in Real Food Samples
9.6 Conclusions
References
10 Principles of Sensory Evaluation in Foods Containing Essential Oil
10.1 Introduction
10.2 Sensory Aspects of Essential Oils
10.3 Desirable Applications of Essential Oils and Their Relation with Sensory Analysis
10.4 The Relationship Between Composition of Essential Oils and Sensory Properties
10.5 Factors Influencing Sensory Measurements
10.6 Selection and Training of Panelists
10.7 Sample Preparation
10.8 Sensory Analysis Methods
10.9 Descriptive Tests
10.10 Discrimination Tests
10.11 Time‐Intensity Methods
10.12 Preference Tests
10.13 Sensory Analysis Reports
10.14 New Approaches to Reduce Undesirable Sensory Effects of Essential Oils
References
11 Global Regulation of Essential Oils
11.1 Introduction
11.2 Global Institutions Involved in Essential Oil Regulation
11.3 Conclusion
References
12 Safety Evaluation of Essential Oils
12.1 Introduction
12.2 Essential Oils and General Safety
12.3 Safety of Essential Oils Used in Cosmetics and Industrial Applications
12.4 Safety of Essential Oils Used in Agriculture
12.5 Topical Administration of Essential Oils — Safety Issues
12.6 Essential Oils and Eye Safety
12.7 Phototoxicity of Essential Oils
12.8 Acute and Sub‐Chronic Oral Toxicity of Essential Oils
12.9 Constituents‐Based Toxicity Evaluation of Essential Oils
12.10 Genotoxicity and Carcinogenicity of the Essential Oils
12.11 Conclusion
References
Index
End User License Agreement
List of Tables
Chapter 02
Table 2.1 Characteristics, main disadvantages and advantages of various processes for essential oils extraction.
Table 2.2 Effect of different steam distillation (SD) durations on the essential oil composition.
Chapter 03
Table 3.1 Molecular ion (M
+.
) and some typical fragment‐ions (
m/z
, intensity, %) in the mass spectra (EI, 70 eV) of three homologous cannabinoids.
Table 3.2 Linear retention indices (LRI) of isomeric essential oil phenolic compounds (thymol, carvacrol and their acetates), calculated in columns with different stationary phase polarities.
Table 3.3 Types of ions in mass spectra obtained by electron ionisation and the structural information that they may provide.
Table 3.4 Examples of some of the most common dissociation processes resulting from electron ionisation (simple rupture and rearrangement) in organic molecules.
Chapter 04
Table 4.1 Some main components of essential oils.
Table 4.2 Major components of selected EOs that exhibit antibacterial properties.
Table 4.3 Terpene nomenclature for isoprenes.
Chapter 05
Table 5.1 Extraction of essential oils from
Murraya
.
Table 5.2 Extraction yield and phenolic content of
C. violaceum
essential oil.
Table 5.3
Anisomeles indica
essential oil composition.
Table 5.4 Chemical composition (%) of C
itrus aurantium
essential oil from peel.
Table 5.5
C. violaceum
essential oil composition.
Table 5.6 Cinnamon essential oil composition.
Table 5.7
S. ringens
yield, total phenolic content (TPC), flavonoid content (FC) and antioxidant activities evaluated by DPPH, ABTS and FRAP assays.
Table 5.8 Essential oils cytotoxicity.
Table 5.9 Cinnamon essential oil bactericide characteristics.
Table 5.10
Artemisia Vulgaris L
. essential oil IC
50
values in human cell lines.
Chapter 06
Table 6.1 Different types of monoterpenes and sesquiterpenes.
Table 6.2 Chemical structures of some selected components of EOs with antimicrobial activity.
Table 6.3 Antimicrobial activities of the most important plant families producing EOs.
Chapter 07
Table 7.1 Possible uses of EOs.
Chapter 08
Table 8.1 F‐value and IP of rapeseed oil samples.
Table 8.2 Effect of EO, BHT and UV irradiation on anisidine value of rapeseed oil samples.
Table 8.3 Comparison of the AA of BHT, BHA and EO in sunflower oil based on the peroxide value test during storage at 37 and 47 °C.
Chapter 09
Table 9.1 Rates of reactions of selected (poly)phenols with peroxyl radicals, from autoxidation studies.
Table 9.2 Antioxidant activity of essential oil evaluated with the Rancimat assay.
Table 9.3 Examples of the use of EOs or their components as antioxidants in food. The assays employed to evaluate the antioxidant properties of the added EOs are indicated in parenthesis.
Chapter 10
Table 10.1 Aspects evaluated for sensory flavour profile of pepper essential oils.
Table 10.2 Some of the major components of selected basil essential oils and their odour description.
Table 10.3 Psychological errors influencing sensory measurements.
Table 10.4 Adjective descriptors used to describe sensory profile of selected essential oils and herbs.
Table 10.5 Sensory analysis of selected foods by means of descriptive tests.
Table 10.6 Adjective descriptors used to describe sensory profiles of selected foods added with essential oils.
Table 10.7 Sensory analysis of selected foods by means of preference tests.
Chapter 12
Table 12.1 LD50 values of essential oils from different plants and their mode of administration.
List of Illustrations
Chapter 01
Figure 1.1 Synthesis of mevalonic acid in plants, from classical MVA pathway. HMG‐CoA reductase: 3‐hydroxy‐3‐methylglutaryl CoA reductase and HMG‐CoA synthase: 3‐hydroxy‐3‐methylglutary CoA synthase. From Thayumanavan & Sadasivam (2003).
Figure 1.2 Synthesis of isopentenyl diphosphate (IPP) and dimethylallyldiphosphate (DMAPP). From Thayumanavan & Sadasivam (2003).
Figure 1.3 Synthesis of geranylgeranyl diphosphate (GGPP). From Thayumanavan & Sadasivam (2003).
Figure 1.4 Enzymes involved in isoprenoid biosynthesis through cytosol (MVA) and plastids pathway (MEP): FPPS, farnesyl diphosphate synthase; GGPPS, geranylgeranyl diphosphate synthase; GPPS, GPP synthase; and HMGR, 3‐hydroxy‐3‐methylglutaryl CoA reductase. FPP, farnesyl diphosphate; GGPP, geranylgeranyl diphosphate; G3P, D‐glyceraldehyde 3‐P; and HMG‐CoA, 3‐hydroxy‐3‐methylglutaril‐CoA.
Chapter 02
Figure 2.1 Schematic representation of hydrodistillation (A) and steam distillation set‐up (B).
Figure 2.2 Schematic mechanism of membrane permeabilisation induced by an external electrical field. Irreversible, large membrane pores are formed by increasing treatment intensity.
Figure 2.3 Microwave experimental set‐up used at laboratory scale for the extraction of EOs from herbs and spices. A. Influence of electromagnetic field on dipolar molecules. B. Vacuum microwave hydrodistillation. C. Microwave hydrodiffusion and gravity. D. Solvent‐free microwave extraction.
Chapter 03
Figure 3.1 Chromatograms obtained by GC‐FID and the major compounds of the essential oils isolated by hydrodistillation from three aromatic plants of
Lippia
genus (Verbenaceae family).
A
.
Lippia alba
(Monoterpenoid type);
B
.
Lippia dulcis
(Sesquiterpenoid type) and
C
.
Lippia micromera
(Phenolic type).
Figure 3.2
A
. Compositional variation of ylang‐ylang (
Cananga odorata
, Annonaceae family) essential oils obtained by hydrodistillation from flowers at different stages of their development. High‐quality essential oil could be obtained from yellow fully mature flowers picked during the early morning.
B
. Variation of nitrogen‐containing compounds (GC‐NPD) in ylang‐ylang essential oils obtained by hydrodistillation from mature flowers gathered at different collection times.
Figure 3.3
In vivo
HS‐SPME‐GC/FID/MS analysis of the volatile fractions from Angel trumpet flowers (
Brugmansia suaveolens
, Solanaceae family), monitored at different times.
A
. Volatile emission during the day measured as a total GC peak area with respect to that of the internal standard (Istd,
n
‐tetradecane);
B
. Volatiles produced by flowers at different times, classified per compound families. The flowers emit nitrogen‐containing compounds mostly during the night time.
Figure 3.4
A
. SPME‐fibre saturation with the derivatising agent (PFPH, pentafluorophenyl hydrazine);
B
. Set‐up for
in vivo
headspace‐SPME monitoring of plant volatiles.
C
. Chromatogram obtained by GC‐μ‐ECD (micro‐electron capture detection) of carbonyl compounds (detected as their hydrazones), isolated from
Swinglea glutinosa
fruits (Rutaceae family) by
in vivo
HS‐SPME, using the fibre saturated with PFPH‐derivatising agent.
Figure 3.5
A
. Typical chromatogram obtained by GC‐FID of the essential oil hydrodistilled from
Swinglea glutinosa
(Rutaceae family) fruit peels. Non‐polar (PDMS) 30 m‐capillary column. Characteristic elution order according to the component retention time increase, as follows: hydrocarbon monoterpenes → oxygenated monoterpenes → hydrocarbon sesquiterpenes → oxygenated sesquiterpenes.
B
. Typical chromatogram (TIC) obtained by GC‐MS (electron ionisation, 70 eV) of the essential oil hydrodistilled from
Cannabis sativa
inflorescences. Three compound families, that is, monoterpenoids, C
10
; sesquiterpenoids, C
15
, and cannabinoids, C
17–21
are clearly distinguishable.
Figure 3.6 Typical chromatograms of steam‐distilled
Pogostemon cablin
(patchouli, Labiatae family) essential oils, obtained with GC‐FID on:
A
. Polar column (60 m x 0.25 mm), coated with poly (ethyleneglycol), PEG; and
B
. Non‐polar column (60 m x 0.25 mm), coated with 5%‐phenyl‐poly(dimethylsiloxane). For the same compound, for example, patchouli alcohol, linear retention indices (LRI) change notoriously with the stationary phase polarity.
Figure 3.7
A
. Dependence of the GC peak area of a compound on the injection port temperature.
B
. Repeatability of GC retention times and GC peak areas when injecting the same compound several times (n = 3, s – standard deviation and RSD – relative standard deviation).
C
. Retention time dependence on the amount of compound injected.
Figure 3.8
A
. Total ion current (TIC) obtained by GC‐MS (electron energy, 70 eV) of the volatile fraction isolated by
in vivo
HS‐SPME (PDMS/DVB‐fibre) from
Moringa oleifera
flowers (Moringaceae family).
B
. Extracted ion chromatogram (EIC) based on the ‘diagnostic’ for isothiocyanates fragment‐ion (
m/z
101 and
m/z
115) currents.
Figure 3.9
A
. Typical chromatogram obtained by GC‐MS (total ion current, TIC, EI, 70 eV, full scan) of
Spilanthes americana
(Asteraceae family) hydrodistilled essential oil. Internal standard, Istd,
n
‐tetradecane;
B
. Chromatogram of the
S. americana
essential oil, obtained with the nitrogen‐phosphorous detection system (NPD), showing spilanthol [
(2E, 6Z, 8E)‐
N‐isobutyl‐2,6,8‐decatrienamide, C
14
H
23
NO] as the main nitrogen‐containing compound;
C
. Mass spectrum and principal fragment‐ions of spilanthol, registered at 70 eV‐electron energy.
Figure 3.10 Gas chromatographic analysis of the volatile fraction obtained by purge‐and‐trap (P&T) method from toasted coffee grains, using different detection systems, as follows:
A
. Mass selective detector (MSD) operated in full scan mode;
B
. Nitrogen‐phosphorous detection (NPD) and
C
. Flame‐photometric detection (FPD). These detection systems register all substances, only nitrogen‐containing compounds or sulphur‐containing compounds, respectively, in the coffee volatile fraction.
Figure 3.11
A
. Kovàts retention indices (KI) calculation, when the regime of the chromatographic oven is isothermal. The logarithm of the
n
‐paraffin retention time depends on the number of carbon atoms.
B
. Linear retention indices (LRI) calculation when the chromatographic oven temperature is programmed. The
n
‐paraffin retention time depends on the number of carbon atoms.
Figure 3.12
A
. Sandwich‐injection mode of an
n
‐paraffin mixture and the
Lippia alba
essential oil solutions.
B
. Typical gas chromatogram used for calculation of the essential oil component linear retention indices (LRI): compound X, which elutes after C
23
‐paraffin, but before C
24
‐paraffin, will have its LRI higher than 2300, but lower than 2400 according to eqn. 3.2.
Figure 3.13 Mass spectra and typical fragment‐ions of 2,4‐diketo‐pentane, obtained at different electron‐ionisation energies (10 eV and 70 eV).
Figure 3.14 GC‐MS analysis of the essential oil isolated by hydrodistillation from
Cannabis sativa
inflorescences.
A
. Part of the chromatogram (TIC, GC‐MS, see
Figure
3.5
B
) of hydrodistilled
C. sativa
in florescence essential oil: different GC peaks correspond to various cannabinoid compounds, and their mass spectra (EI, 70 eV,
m/z
50–350), as follows:
B
. Tetrahydrocannabiorcol, C
17
;
C
. Tetrahydrocannabivarin, C
19
, and
D
. Tetrahydrocannabinol, C
21
. Similar fragmentation patterns are observed for these three homologous compounds (Table 3.1).
Figure 3.15 Mass spectra (electron ionisation, 70 eV) of isomeric phenolic compounds, present in many essential oils (
e.g.
, thyme, oregano,
Lippia origanoides, L. micromera
):
A
. Thymol.
B
. Carvacrol and their acetates:
C
. Thymyl acetate and
D
. Carvacryl acetate. Although the mass spectra of these isomeric compounds are similar, their linear retention indices (LRI) vary in the columns of different stationary phase polarities (Table 3.2).
Figure 3.16 Mass spectra (electron ionisation, 70 eV) of isomeric hydrocarbons:
A
.
(E)
‐1,3,5‐Hexatriene;
B
.
(Z)
‐1,3,5‐Hexatriene;
C
. 1,3‐Cyclohexadiene and
D
. 1,4‐Cyclohexadiene. The high similarity of these mass spectra could be explained by the formation of the molecular ion, M
+.
, rearranged in the same molecular structure, during the ionisation process of these isomers.
Figure 3.17 Mass spectra (electron ionisation, 70 eV) of two terpenic compounds:
A
. Dihydroeudesmol;
B
. α‐Terpineol. Formation of the common fragment‐ion at
m/z
59.
Figure 3.18 Mass spectrum (electron ionisation, 70 eV) and typical fragment‐ions of benzyl acetate.
Figure 3.19 Mass spectra (electron ionisation, 70 eV) of monoterpenoids:
A
. Limonene, and
B
. Carvone. Fragment‐ions at
m/z
68 and at
m/z
82 correspond to retro‐Diels‐Alder reaction (RDA) products occurred through the loss of C
5
H
8
from limonene and carvone molecular ions, M
+.
, respectively.
Figure 3.20 Mass spectrum (electron ionisation, 70 eV) and typical fragment‐ions of ethyl benzoate. Fragment‐ion at
m/z
122 is a product of McLafferty rearrangement of the molecular ion M
+.
. The ion at
m/z
105, usually of high intensity (70–100%), is a typical fragment of benzoates.
Figure 3.21 Mass spectra (electron ionisation, 70 eV) and typical fragment‐ions of isomeric esters:
A
. Methyl ester of 4‐amino benzoic acid, and
B
. Methyl ester of 2‐amino benzoic acid (methyl anthranilate). Fragment‐ion at
m/z
119 in methyl anthranilate mass spectrum is a product of
ortho
‐effect rearrangement, that is, methanol CH
3
OH elimination.
Figure 3.22
A
. Part of the chromatogram (GC/MS, TIC, electron impact, 70 eV) of the volatile fraction isolated by
in vivo
HS‐SPME from
Moringa oleifera
flowers (Moringaceae family). Polar column (PEG, 60 m).
B
. GC peak at t
R
= 17.61 min, is symmetric and apparently homogeneous, possibly representing just one compound. Different points of the peak in which the mass spectra were obtained.
C
. Mass spectra of three different substances, that is, butyl isothiocyanate (1), hexyl acetate (2) and
p
‐cymene (3), obtained at the beginning, in the middle and at the end of the peak.
D
. Extracted ion chromatograms (EIC) of the base‐peak ions in the mass spectra of these three substances and their GC areas, which permit to find approximately the ratio of these substances present in the co‐eluted mixture.
Figure 3.23 Comparison of two GC‐MS acquisition modes.
A
. Full scan mode is when all ions are registered and their full mass spectra, which permit compound identification, are obtained. Reconstructed or total ion current (TIC) is measured and plotted as a function of time and constitutes a chromatogram.
B
. Selected ion(s) monitoring (SIM) is carried out when only one or few ‘diagnostic’ ions are registered and permits to selectively detect a compound or several compounds which share the same ions in their mass spectra. Mass fragmentogram is obtained in SIM‐mode.
C
.
Cannabis sativa
inflorescence hydro distilled essential oil, analysed by GC‐MS operated in SIM mode, using
m/z
136 and
m/z
204 ions for selective detection of monoterpene and sesquiterpene molecular ions, M
+.
, respectively.
D
.
Brugmansia suaveolens
(Solanaceae family) CO
2
‐supercritical fluid extract (SFE), analysed by GC‐MS in full scan‐mode and SIM‐mode. ‘Diagnostic’ ions at
m/z
94, 138 and 303 were used for selective detection of scopolamine.
Figure 3.24 Tandem (in space) mass spectrometry: triple quadrupole, QqQ.
A
. Multiple reaction monitoring, MRM. Precursor ions (f
1
) are selected in the analyser I (Q
1
), operated in SIM‐mode and are directed to the collisionally‐activated dissociation cell (q
2
, operated only with radiofrequency, RF), where they are fragmented; the Analyser II, Q
3
, filters the selected product ions (f
2
); the signal of the ion transition (reaction) f
1
→ f
2
is monitored as a function of time.
B
. Comparison of two mass spectra obtained in full scan acquisition mode and MRM‐mode; the f
1
and f
2
ions are highlighted in the first (left) mass spectrum.
Figure 3.25 General scheme of the multidimensional gas chromatography (MDGC) system with two orthogonal columns (polar and non‐polar), connected through the switching device, which performs the heart‐cutting, diverting the eluting compounds from the first to the second column.
Figure 3.26
A
. GCxGC chromatogram (TIC), obtained with high‐resolution time‐of‐flight analyser (HRTOF‐MS), of
Cannabis sativa
inflorescence essential oil. Cryogenic dual jet/loop modulator; secondary oven installed in the main GC oven; 1D – first column: Rxi‐5MS, 30 m, L, 250 µm, ID, 0,25 µm, d
f
, and 2D – second column: Rxi‐17Sil MS, 2 m, L, 250 µm, ID, 0,25 µm, d
f
; modulation time: 5 s.
B
. Fragment of the TIC showing the separation of limonene and β–phellandrene in the second dimension (2D, polar column).
Chapter 04
Figure 4.1 The chemical structures of some EOs.
Figure 4.2 Structures of selected typical terpenes. (A) Monoterpenes: 13 = myrcene, 14 = Citronellol, 15 = carvone, 10 = limonene; (B) sesquiterpenes: 16 = caryophyllene, 17 = farnesol; (C) diterpene: 18 = granylgeraniol; (D) triterpene: 19 = lanosterol; (E) tetraterpene: 20 = β‐carotene.
Figure 4.3 The structure of some aromatic compounds.
Figure 4.4 A general sketch of biosynthetic pathway of secondary metabolites in plants.
Figure 4.5 The head‐to‐tail method of two isoprene coupling.
Figure 4.6 Systematically process and proposal possible intermediates in the thiamin (TPP)‐dependent biosynthesis of IPP from GA‐3‐P and pyruvate.
Figure 4.7 The proposed compartmentation of IPP and the biosynthesis of isoprenoid in higher plants between plastids (DOXP process) and cytosol (acetate/MVA process).
Figure 4.8 Biosynthesis of isoprene from IPP and DMAPP via the isoprene synthase.
Figure 4.9 The chemical structures of Prenol (3‐Methyl‐2‐buten‐1‐ol), Isopentenylpyrophosphate, (S)‐3‐Methyl‐3‐buten‐2‐ol and 4‐Methoxy‐2‐methyl‐2‐butanthiol.
Figure 4.10 The acid part of some natural esters.
Figure 4.11 A typical modification reaction that causes the biosynthesis of molecules to have increased volatility properties.
Figure 4.12 Outline biosynthesis of
p
‐menthane monoterpene.
Figure 4.13 The production of menthols by the hydrogenation process using Raney nickel.
Figure 4.14 The hydrogenations of thymol.
Figure 4.15 Isoprene units in some common terpenoids.
Figure 4.16 The biosynthesis of terpenoid by C5 units coupling reaction.
Figure 4.17 Formation of monoterpenoid skeletons.
Figure 4.18 Some of usual terpenoid skeleton.
Figure 4.19 The chemistry and structure of some monoterpenoidindole alkaloids.
Figure 4.20 Produced component through acid catalyzed deglycosylation reaction of 8,10‐dihydro‐
N‐
methylbakankosine (108).
Figure 4.21 Some pyronene and cyclocitral derivatives.
Figure 4.22 The structures from Pd–Al
2
O
3
catalyzed hydrogenation of dehydrolinalool.
Figure 4.23 Chemical structure of some terpenes and terpenoids.
Figure 4.24 Some glycoside derivatives extracted from plants.
Figure 4.25 The structure of some obtained menthanes.
Figure 4.26 Some molecules observed via Mitsunobu reactions.
Figure 4.27 The chemical structures frommetabolisation of
Glomerella cingulate
,
Rhizoctoniasolani
and
Aspergillusniger
.
Figure 4.28 The structure of
α
‐ and
β
‐Pinen.
Figure 4.29 Some structures produced from
α
‐ and
β
‐Pinen.
Figure 4.30 Some new camphanes from roots and rhizomes of Glehnialittoralis.
Figure 4.31 Rigid camphanes that have been applird to progress asymmetric syntheses.
Figure 4.32 The structure of some synthesised unsaturated thiols.
Figure 4.33 Chemical structures of some carane, vinylic bromides and glycoside derivatives.
Figure 4.34 Some normegastigmane derivatives.
Figure 4.35 Chemical structures of (−)‐sabinene, (−)‐
α
‐thujone, antirrhinolide and imide linavuline.
Figure 4.36 Synthesis of polyisoprenoid.
Figure 4.37 Chemical structures of nerolidol, bisabolene, bisabolol, zingiberene and 6‐p‐methoxyphenyl‐2‐methylhepta‐2,5‐diene.
Figure 4.38 Chemical structures of cadalene, calamenene, ketone and diketone intermediate in cadinanes synthesis, 4‐isopropyl‐6‐methoxy‐l‐tetralone, (−)‐cryptone and (±)‐cadinene hydrochloride.
Figure 4.39 Chemical structures of cloven and acorone.
Figure 4.40 Synthesis of cedrol.
Figure 4.41 Three precursors for sesquiterpenoids.
Figure 4.42 Several biosynthetic approaches from (
Z,E
)‐farnesol.
Figure 4.43 Some possibilities that biosynthetically utilised (
E,E
)‐farnesol.
Figure 4.44 Carotenoid degradation products.
Figure 4.45 Polyketide biosynthesis and oakmoss components.
Figure 4.46 Key intermediates from shikimic acid.
Chapter 05
Figure 5.1 Monoterpenes from essential oils.
Figure 5.2 Sesquiterpenes from essential oils.
Figure 5.3 Key compounds in common essential oils.
Figure 5.4 Compounds isolated from
M. tetramera
and
M. kwangsiensis
essential oils.
Chapter 07
Figure 7.1 Mode of action of EOs against bacteria and fungi.
Figure 7.2 Bioactivity of an extract. Definition of MIC and NIC.
Chapter 09
Figure 9.1 Increasing number of publications concerning EOs with antioxidant activities and food in the last 18 years.
Scheme 9.1 Mechanism of peroxidation of hydrocarbons with bis‐allylic (
e.g.
, linoleic acid) C‐H bonds. The overall process is a radical‐chain reaction in which the LOO
•
radical is the chain‐carrier. The typical three phases of chain reactions, that is, initiation, propagation and termination, are shown. The hydroperoxide IIIa does not form because its precursor radical III quickly regenerates the pentadienyl radical by oxygen loss.
Scheme 9.2 Schematic representation of the peroxidation of a substrate. The equation that appears in the scheme is the kinetic rate‐law for free (
i.e.
, not inhibited) peroxidation.
R
O2
is the rate of O
2
uptake;
k
p
the rate constant of propagation;
k
t
the rate constant of termination, and finally
R
i
the rate of initiation. The points of attack of preventive and chain‐breaking antioxidants on the chain‐reaction are shown: preventive antioxidants block the formation of radical initiators; chain‐breaking antioxidants remove ROO
•
radicals from the system limiting therefore the propagation process.
Scheme 9.3 Mechanism of transformation of γ‐terpinene in
p
‐cymene in the presence of linoleic acid. The transformation that occurs during the co‐oxidation of linoleic acid causes the release of HOO
•
radicals which cross‐terminate quite rapidly the (linoleic acid) chain‐carrier, LOO
•
.
Figure 9.2 Example of typical oxygen consumption plots measured during the autoxidation of an organic substrate initiated by an azoinitiator in the absence of inhibitors (a) and in the presence of a weak (b) or of a strong (c) antioxidant.
Scheme 9.4 Phenolic and non‐phenolic constituents of EOs with antioxidant properties.
Figure 9.3 Formation of peroxides during spontaneous oxidation of triacylglycerols from lard (A) or from sunflower oil (B) at 22 °C in the absence (×) and in the presence of 0.05% of carvacrol (●) and thymol (○).
Scheme 9.5 Carvacrol generates a phenoxyl radical after H‐abstraction by LOO
•
, reaction A. This phenoxyl radical can quench another LOO
•
radical, reaction B, terminating therefore two oxidation chains (antioxidant action) or it can abstract an H‐atom from the bis‐allylic positions of the polyunsaturated lipids, reaction C. This last reaction produces another LOO
•
which propagates oxidation.
Figure 9.4 Antioxidant effect of some EO components compared to reference antioxidants, measured by the Rancimat test in corn oil at 121.6 °C.
Chapter 10
Figure 10.1 Main components of citrus essential oils.
Figure 10.2 Descriptive sensory analysis of odour attributes from an essential oil.
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Essential Oils in Food Processing
Chemistry, Safety and Applications
Edited by
Seyed Mohammad Bagher Hashemi
Fasa UniversityIran
Amin Mousavi Khaneghah
University of CampinasBrazil
Anderson de Souza Sant'Ana
University of CampinasBrazil
This edition first published 2018© 2018 John Wiley & Sons Ltd
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Names: Hashemi, Seyed Mohammad Bagher, editor. | Khaneghah, Amin Mousavi, editor. | Sant’Ana, Anderson de Souza, editor.Title: Essential oils in food processing : chemistry, safety and applications / edited by Seyed Mohammad Bagher Hashemi, Amin Mousavi Khaneghah, Anderson de Souza Sant’Ana.Description: Hoboken, NJ : John Wiley & Sons, 2018. | Series: IFT Press Series | Includes bibliographical references and index. |Identifiers: LCCN 2017030692 (print) | LCCN 2017043887 (ebook) | ISBN 9781119149354 (pdf) | ISBN 9781119149378 (epub) | ISBN 9781119149347 (cloth)Subjects: LCSH: Essences and essential oils–Industrial applications. | Food industry and trade. | Food additives industry.Classification: LCC TP958 (ebook) | LCC TP958 .E875 2018 (print) | DDC 664/.06–dc23LC record available at https://lccn.loc.gov/2017030692
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List of Contributors
Hamid AkbariiradDepartment of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Saeedeh Shojaee‐AliabadiDepartment of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Riccardo AmoratiDepartment of Chemistry ‘G. Ciamician’, University of Bologna, Italy
Francisco J. BarbaUniversitat de València, Faculty of Pharmacy, Nutrition and Food Science Area, Valencia, Spain
Antonio BevilacquaDepartment of the Science of Agriculture, Food and Environment (SAFE), University of Foggia, Italy
Farid ChematUniversitéd’ Avignon et des Pays de Vaucluse, France
Maria Rosaria CorboDepartment of the Science of Agriculture, Food and Environment (SAFE), University of Foggia, Italy
Duarte, M.C.T.Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Microbiology Division, Campinas, São Paulo, Brazil
Duarte, R.M.T.Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Microbiology Division, Campinas, São Paulo, Brazil
Ismail EsDepartment of Material and Bioprocess Engineering, Faculty of Chemical Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
Hassan EslahiDepartment of Chemistry, College of Sciences, Shiraz University, Iran
Nafiseh FahimiDepartment of Chemistry, College of Sciences, Shiraz University, Iran
Mario C. FotiIstituto di Chimica Biomolecolare del CNR, Italy
Ralf GreinerDepartment of Food Technology and Bioprocess Engineering, Max Rubner‐Institut, Federal Research Institute of Nutrition and Food, Germany
Seyed Mohammad Bagher HashemiDepartment of Food Science and Technology, College of Agriculture, Fasa University, Fasa, Iran
Seyede Marzieh HosseiniDepartment of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Amin Mousavi KhaneghahDepartment of Food Science, Faculty of Food Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
Anissa KhelfaSorbonne Universités, Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable, France
Shima Bazgir KhorramDepartment of Food Science and Technology, College of Agriculture, Fasa University, Fasa, Iran
Mohamed KoubaaSorbonne Universités, Université de Technologie de Compiègne, Laboratoire Transformations Intégrées de la Matière Renouvelable, France
Ramadasan KuttanDepartment of Biochemistry, Amala Cancer Research Centre, Kerala, India
Sze Ying LeongDepartment of Food Science, University of Otago, New Zealand;Department of Safety and Quality of Fruit and Vegetables, Max Rubner‐Institut, Federal Research Institute of Nutrition and Food, Germany
Vijayasteltar B. LijuDepartment of Biochemistry, Amala Cancer Research Centre, Kerala, India
Aurelio López‐MaloDepartamento de Ingeniería Química y Alimentos,Universidad de las Américas Puebla, Puebla, Mexico
Ana Cecilia Lorenzo‐LealDepartamento de Ingeniería Química y Alimentos, Universidad de las Américas Puebla, Puebla, Mexico
Emma Mani‐LópezDepartamento de Ingeniería Química y Alimentos,Universidad de las Américas Puebla, Puebla, Mexico
Jairo Rene MartinezResearch Centre for Biomolecules, CIBIMOL‐CENIVAM, Universidad Industrial de Santander, Bucaramanga, Colombia
Liela MirmoghtadaieDepartment of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Enrique PalouDepartamento de Ingeniería Química y Alimentos,Universidad de las Américas Puebla, Puebla, Mexico
Marianne PerriconeDepartment of the Science of Agriculture, Food and Environment (SAFE), University of Foggia, Italy
Rodrigues, M.V.N.Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Chemistry of Natural Products Division, Campinas, São Paulo, Brazil
Rodrigues, R.A.F.Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Organic Chemistry and Pharmaceutical Division, Campinas, São Paulo, Brazil
Shahin RoohinejadDepartment of Food Technology and Bioprocess Engineering, Max Rubner‐Institut, Federal Research Institute of Nutrition and Food, Germany; Burn and Wound Healing Research Centre, Division of Food and Nutrition, Shiraz University of Medical Sciences, Iran
Anderson de Souza Sant’AnaDepartment of Food Science,University of Campinas (UNICAMP), Campinas, São Paulo, Brazil
Ali Reza SardarianDepartment of Chemistry, College of Sciences, Shiraz University, Iran
Milena SinigagliaDepartment of the Science of Agriculture, Food and Environment (SAFE), University of Foggia, Italy
Maryam SohrabiDepartment of Food Science and Technology, College of Agriculture, Fasa University, Fasa, Iran
Barbara SperanzaDepartment of the Science of Agriculture, Food and Environment (SAFE), University of Foggia, Italy
Elena E. StashenkoResearch Centre for Biomolecules, CIBIMOL‐CENIVAM, Universidad Industrial de Santander, Bucaramanga, Colombia
Iuliana VintilăFood Science, Food Engineering and Applied Biotechnology Department, University ‘Dunărea de Jos’ Galaţi, România
Acknowledgements
Seyed Mohammad Bagher Hashemi would like to thank Allah for the opportunity to gain knowledge to write this book. He sincerely acknowledges the sacrifices made by his parents during his education. He also would like to express his appreciation to Fasa University.
Amin Mousavi Khaneghah and Anderson de Souza Sant’Ana gratefully acknowledge University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
Amin Mousavi Khaneghah likes to thank the support of CNPq‐TWAS Postgraduate Fellowship (Grant # 3240274290).
Anderson de Souza Sant’Ana would like to thank the support of Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq) (Grant #CNPq 302763/2014‐7).
Introduction
Amin Mousavi Khaneghah, Anderson de Souza Sant’Ana
In recent years, due to their application in therapeutic, food, cosmetic, aromatic, fragrance and spiritual uses, the essential oil industry has gained increased importance. Essential oils are complex mixtures of small molecular weight compounds including saturated and unsaturated hydrocarbons, alcohol, aldehydes, esters, ethers, ketones, oxides phenols and terpenes. Because of their natural origin and of their widely described potential beneficial properties, essential oils can find several applications in the field of food processing.
The use of natural compounds for food applications has attracted more attention in the last years due to the perception of people about synthetic food additives. Among the beneficial properties of essential oils, their antimicrobial activity can be considered one of the main factors driving their application in foods. The antimicrobial property of an essential oil is known to be influenced by composition, configuration, amount and their possible interaction. Despite the antimicrobial properties of some essential oils, to achieve the desired results regarding antimicrobial effectiveness, high concentrations are required that ending up limiting their extensive application in food formulations. Despite this, essential oils can serve as additional preservative factors using the concept of hurdle technology. In addition to the antimicrobial properties, the antioxidant properties of essential oils can be considered another high relevant beneficial property of these natural products. As synthetic antioxidants (i.e., BHA) are recently suspected to be potentially harmful to human health, essential oils with their antioxidant activity are found to be a better choice to reduce oxidative reactions in foods. For their application in foods and other matrixes, it is essential to ensure the properties are not lost from obtainment to food formulation, processing and storage. In this context, extraction processes play a major role to ensure essential oils have the expected results when added to foods. Extraction processes are the most time‐ and effort‐consuming processes for obtainment of essential oils. There are several methods to extract oils from their natural sources, such as distillation and expression, are considered as two key methods for extraction of the essential oils. The extraction method has been reported to affect the essential oil composition significantly. Moreover, there are other factors that also influence the chemistry of essential oils including plant variety, growth conditions (e.g., fertilisers, climate), storage and so on. Therefore, to ensure a stable composition and the resulting properties of essential oils remains a complicated issue.
This book provides a comprehensive perspective of the pertinent aspects of essential oils including antimicrobial, toxicology, chemistry, extraction methods, composition, applications and other practical topics required for the development of this industry and wide application of essential oils.
1Essential Oils and Their Characteristics
M.C.T. Duarte1, R.M.T. Duarte1, R.A.F. Rodrigues2 and M.V.N. Rodrigues3
1 Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Microbiology Division, Campinas, São Paulo, Brazil
2 Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Chemistry of Natural Products Division, Campinas, São Paulo, Brazil
3 Research Centre for Chemistry, Biology and Agriculture – CPQBA/UNICAMP – Organic Chemistry and Pharmaceutical Division, Campinas, São Paulo, Brazil
1.1 Introduction
Essential oils are the main raw material for the aroma and fragrance, food and pharmaceutical industries. They have important biological activities that have been disclosed often in recent years. However, as the industry seeks its practical application and the development of new natural drugs containing active compounds from essential oils, there is an urgent need to standardise the plant material source. For this to become achievable, it is necessary to know the different factors that affect the production of essential oils by plants, in terms of its quantity as well as its quality.
It is known that plants produce essential oils as secondary metabolites in response to a physiological stress, pathogen attack and ecological factors. Also, in nature, the essential oils are recognised as defence compounds and attractors of pollinators, facilitating the reproduction of the vegetal species. The environmental variations, in turn, are also important in a plant’s ability to produce these compounds. Considering all of these factors, the main problems related to the cultivation of aromatic plants are due to variations that occur in quantitative and qualitative changes in the essential oils production. The main factors involved in the biosynthesis of essential oils by medicinal and aromatic plants are discussed in this chapter.
In order to optimise its commercial exploitation, the different factors involved in the production of essential oils must be taken into account, since the induction into its substance synthesis could affect the specific compounds of interest and their economic applications, as well as affecting the standard amount of produced oil.
1.1.1 Chemical Characteristics of Essential Oils
The designation essential oil originated from Aristotle’s era, because the of the idea of life‐essential elements — fire, air, earth and water. In this case, the fifth element was considered to be the soul or the spirit of life. Distillation and evaporation were the processes of removing the soul from the plant or essential oils. Nowadays, these oils are also known as volatile oils, but far from being soul, essential oils are a complexity of aroma’s composition. Those constituents of essential oils are generally derived from phenylpropanoid routes (Thayumanavan & Sadasivam, 2003).
The studies of those routes have disclosed the relevance of the aspect of physiology regulation, but certainly the isoprenoid exemplifies the major group of secondary metabolites in herbs, which exhibit extremely vast varieties of chemical structures and biochemical functions. Since primary metabolites exist in all plant cells that are qualified by division, secondary metabolites are there exclusive by accident, and are not essential for that herb. In contrariety to primary metabolites, secondary compounds vary extensively in their occurrence in those herbs and some may appear only in a unique or a few species (Krings & Berger, 1998).
Due to the connection of terpenoids in many pharmacological properties and their great value added specially for pharmaceutical, cosmetic and food industries, the isoprenoid route has been a spotlight for most related articles. Essential oils are nearly always rotational and have a high refractory index; they are sparingly soluble in water, usually less dense than water and liquid at room temperature, but there is some exception, as trans‐anethole (anise camphor) from the oil of anise (Pimpinella anisum L.), and they may be classified using different criteria: consistency, origin and chemical nature. As stated by their consistency, essential oils are classified as essences, balsams or resins. Depending on their origin, essential oils are natural, artificial or synthetic. Essential oils are aromatic chemical compounds that came from plant’s glands. Due to their volatility, flavour and toxicity, this class of compounds also plays significant aspects in the defence’s herbs, communication between plants and pollinator attractiveness (Muñoz‐Bertomeu et al., 2007; Thayumanavan & Sadasivam, 2003).
A lot of herbs can be view as being composed of a basic unit called isoprene or isopentane. Terms such as isoprenoid or terpenoid are employed concurrently. Many terpenoids are assemble of carbon atoms from acyclic disposition to a cyclic disposition by different chemical reactions, like, condensation, addition, cyclisation, deletion or rearrangements to be transformed in a basic unit, and generally, are very extensively diffused throughout the total plant kingdom. These compounds comprise a structurally varied class that can be splitted into the main and the minor terpenoids (Daviet & Schalk, 2010; Muñoz‐Bertomeu et al., 2006; Daniel, 2006; Thayumanavan & Sadasivam, 2003).
Biosynthesis of terpenes can occur in distinct sector of the herb, such as bark, flowers, fruits, leaves, roots, ryzomes, seeds and wood, and have all been described to concentrate them in different herbs. Terpenes that are main metabolites include carotenes, regulators of growth, proteins, quinones, polyprenols and the sterol, substitutes of terpenes with an alcohol functional group (Daviet & Schalk, 2010). These constituents are indispensable for preserving the membrane to keep the entirety of its structure, also to protection against light, and securing the maintenance of its biological functionality. Terpenes are a large class of chemical compounds, classified by the molecular weight, being monoterpenes, sesquiterpenes, diterpenes, seterterpenes, triterpenes, tetraterpenes and phytosterols amongst others (Thayumanavan & Sadasivam, 2003).
Monoterpenes are the major contributor of most important essential oils in nature. Since the monoterpenes (C10H16) are small molecules with two isoprene units, such as menthol and linalool, and they are lipophilic; they are promptly consumed through the skin. Synthetic compounds can be used to break down the problems come across with herbal products by creating actions for the construction of such molecules, regardless of the original species. Indeed, ways have been developed for most of the natural molecules, but, given their commonly complex spatial arrangements, the industrial production is not practicable for the majority of examples (Daviet & Schalk, 2010; Muñoz‐Bertomeu et al., 2006; Daniel, 2006; Thayumanavan & Sadasivam, 2003).
Characteristically, plant’s secondary metabolites are cumulated and stored in relatively huge quantities, which can be explained by their role as chemical signals or defence compounds. Terpenes are built up from the union of the two carbon units with five members each by condensation, isopentenyl diphosphate synonym isopentenyl pyrophosphate (IPP) and dimethylallyldiphosphate synonym dimethylallyl pyrophosphate (DMAPP), with different modes of structure formation, number of unsaturated bonds and type of linker groups. Not all terpenoids have a composition of their structures in the repetition of five carbon atoms, as can be habitual of them, considering that they are formed usually from isoprene as forming matrix (Daniel, 2006; Thayumanavan & Sadasivam, 2003).
Terpenes consisting of more than five isoprene structures appear in all herbs, and simpler terpenes (C10–C25) are mainly restricted in the phylogeny classification to the vascular plants/higher plants or, synonym Tracheophyta, while sesquiterpenes have been found broadly in division Bryophyta and in the kingdom Fungi. Monoterpenoids are colourless, distilled by steam, liquids insoluble in water with a typical scent, with a range of boiling points of 140 until 180 °C. Some of them have shown potentiality as insect plague management because they simply provide herbs with defences against insects that feed from it. Many terpenes also operate as insect captivate, being green and innocuous to humans and other animals (Daniel, 2006; Thayumanavan & Sadasivam, 2003).
More than a thousand sesquiterpenes are known today. Sesquiterpenes are the biggest category of terpenoids with a broad molecular structures and are constitutes of three isoprene matrixes, that is, they are composed with 15 carbon atoms, such as farnesol, guaiazulene, bisabolol and become from medicinal plants in distilleries equipments, in the bitter‐tasting substances and essential oils in a lot of herbs. Diterpenes are formed by 20 carbon atoms, by their condensation of four isoprene residues, such as taxol, gibberellins, phytol and fusicocsin. Like sesquiterpenes, we know a thousand or more C20 compounds in this category, which fit into 20 main typical skeletons. Triterpenes are categorised based on the linear composition or number of cyclic compounds actual. Triterpenes relate to an inharmonious compilation of chemical compounds, which are consider to be aquired from squalene; the C30 non cyclic component by types of rings and ligands. Pentacyclic triterpenes are usually distributed in vascular plants, occurring as glycosides with sugar ligands (saponins) or without sugar ligands (aglycones) (Daniel, 2006; Thayumanavan & Sadasivam, 2003).
Two routes have been extensively studied, leading to these precursors, through the mevalonate (typically known as MVA route; C6) and the 1‐deoxyxylulose‐D‐5‐phosphate (coded as the DXP route) pathways. The DXP compound, also known as the 2‐C‐methyl‐D‐erythritol‐4‐phosphate or methylerythritol phosphate (coded as the MEP route), takes place in plant plastids (chloroplast) and also by bacteria, while the MVA track different sources such as fungus, in the herb’s cytosol and in some animals. In the mevalonic acid route, the key enzyme is 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase (HMG‐CoA reductase coded as HMGR). HMGR assemble the initial sequence of the MVA route by converting HMG‐CoA to MVA using NADPH as coenzyme (Muñoz‐Bertomeu et al., 2007; Muñoz‐Bertomeu et al., 2006; Thayumanavan & Sadasivam, 2003).
The synthesis of mevalonic acid is illustrated in Figure 1.1.
Figure 1.1 Synthesis of mevalonic acid in plants, from classical MVA pathway. HMG‐CoA reductase: 3‐hydroxy‐3‐methylglutaryl CoA reductase and HMG‐CoA synthase: 3‐hydroxy‐3‐methylglutary CoA synthase. From Thayumanavan & Sadasivam (2003).
In higher plants, the condensation of the basic C5 units, isopentenyl diphosphate (coded as IPP) and dimethylallyldiphosphate (coded as DMAPP), is catalysed by the enzyme prenyltransferases (Figure 1.2), which builds the chain of prenyldiphosphate, designated as the original source for each category of terpenoids: geranyl diphosphate (coded as GPP; C10), farnesyl diphosphate (coded as FPP; C15) and geranylgeranyl diphosphate (coded as GGPP), respectively for the monoterpenes, sesquiterpenes and diterpenes (Figure 1.3) (Muñoz‐Bertomeu et al., 2007; Muñoz‐Bertomeu et al., 2006; Thayumanavan & Sadasivam, 2003).
Figure 1.2 Synthesis of isopentenyl diphosphate (IPP) and dimethylallyldiphosphate (DMAPP). From Thayumanavan & Sadasivam (2003).
Figure 1.3 Synthesis of geranylgeranyl diphosphate (GGPP). From Thayumanavan & Sadasivam (2003).
The production of IPP and DMAPP proceeds via two alternative routes (Figure 1.4): the usual cytosolic mevalonate (MVA) route and the methylerythritol phosphate (MEP) route. The MEP route, confined in the plastids, is responsible to provide isopentenyl diphosphate and dimethylallyldiphosphate for monoterpenoid and sesquiterpenoid synthesis. The following achievement implicates the terpenoid synthases, which are presenting a vast enzyme group. Terpenoid synthases play an important function in the terpenoid synthesis, since they are responsible for the formation of farnesyl diphosphate, geranyl diphosphate and geranylgeranyl diphosphate to form the main structures of the terpenoids, and are thus at the source of the highly large number of possibilities of compounds such as squalene, generated by squalene synthase that catalyses the head‐to‐head reaction of two farnesyl diphosphate units, the initial important reaction in sterol category synthesis; end‐product sterols (β‐sitosterol and stigmasterol). Given the vast range of terpenoid configuration, many terpenoid synthetic genes, that is, terpenoid synthases, P450, and so on, continue to be identified (Daviet & Schalk, 2010; Daniel, 2006; Muñoz‐Bertomeu et al., 2007; Muñoz‐Bertomeu et al., 2006; Wink, 1987).
Figure 1.4 Enzymes involved in isoprenoid biosynthesis through cytosol (MVA) and plastids pathway (MEP): FPPS, farnesyl diphosphate synthase; GGPPS, geranylgeranyl diphosphate synthase; GPPS, GPP synthase; and HMGR, 3‐hydroxy‐3‐methylglutaryl CoA reductase. FPP, farnesyl diphosphate; GGPP, geranylgeranyl diphosphate; G3P, D‐glyceraldehyde 3‐P; and HMG‐CoA, 3‐hydroxy‐3‐methylglutaril‐CoA.
The production of aroma relies on the genetic consideration and also on the growth phase of herbs. Other important factor is the environmental impact which could transform biochemically and physiologically those herbs modifying the amount and the constituents of the aroma. For this reason, the biotechnological formation of natural aroma compounds is speedily expanding although the conventional pathways of chemical reactions or removal from herbs are yet feasible. Terpenes are more costly to produce in relation to other metabolites due to the complexity of reactions. Since the advent of common food in the human life, such as beer, bread, yogurt, cheese, soy derivatives, wine and other fermented foods, microbial reactions have normally take part an important act in the production of complex mixtures of food aromas. This background of biotechnology in our days has evolved from craft origins into big, attention‐getting industries. Starting at the beginning of the last decade, the renewal of some techniques in the volatiles analysis area facilitated the separation and structural identification of essentials oils, such as gas chromatography. There is no doubt that the use of molecular biological strategy is helping our comprehension of some herb metabolites and how they are used in the area of physiology. Monoterpenes, which are widely distributed in nature with around 400 structures, constitutes a satisfactory precursor basis. Transformations of composition and the amount from industrial production of aroma area by genetic engineering should have an impact in the commercial sector. In recent years, substantial progress has been made in biotechnology and in the genetic area; in particular, the progress of the molecular biology apparatus has been used to discover a lot of biosynthetic routes. The combination of this expertise with the apparatus accessible for the genetic area and metabolic engineering nowadays opens a large possibility to obtain new pathways for the generation of herbal compounds. This approach has been mainly applied to the obtention of high‐value pharmacological actives (Prins et al., 2010; Muñoz‐Bertomeu et al., 2007; Krings & Berger, 1998; Rhodes, 1994; Gershenzon, 1994).
1.1.2 Factors Influencing the Quantity and Quality of Essential Oil in Plants
The essential oils market is in constant expansion, moving tens of millions of dollars annually (Marques et al., 2012). The greatest producing countries are Brazil, India, China and Indonesia, and the greatest consumers of essential oils are the United States (40%), European Union (30%) and Japan (7%). In addition to its employ as the main raw material for aroma and fragrance, food and pharmaceutical industries (Prins et al., 2010), essential oils have important biological activities that have been disclosed in recent years. However, as it seeks its practical application and the development of new natural drugs containing active compounds from essential oils, there is an urgent need to standardise the plant material source. For this to become achievable, it is necessary to know all factors that exert influence on the production of essential oils by plants (Prins et al., 2010).
