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Essential oils are natural materials widely used in many fields all over the world and have become an integral part of everyday life. There is increasing demand for essential oils, which has resulted in cases of adulteration. Authentication is thus a matter of critical importance for both consumers and chemical companies. This comprehensive overview covers known adulterations in essential oils, and some analytical methodologies adopted for their detection. We first list recommended tests, and then we explain and discuss common analytical techniques, such as chiral gas chromatography, isotope-ratio mass spectrometry, and nuclear magnetic resonance spectroscopy. We also present (high-performance) thin-layer chromatography, vibrational spectroscopy, coupled and multidimensional chromatography, high-performance liquid chromatography, and combination with chemometrics-metabolomics. This review provides a critical overview of existing techniques.
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Authenticity of essential oils
Thi Kieu Tiên Do a,b,Francis Hadji-Minaglou a, Sylvain Antoniotti b,Xavier Fernandez b,*
aBotaniCert, Espace Jacques-Louis Lions, 4 Traverse Dupont, 06 130 Grasse, France
bInstitut de Chimie de Nice, UMR 7272, Université Nice Sophia Antipolis – CNRS, Parc Valrose, 06108 Nice Cedex 2, France
ARTICLE INFO
Keywords:
Analytical methodology
Adulteration
Authentication
Chiral gas chromatography
Detection
Essential oil
Isotope-ratio mass spectrometry
Natural extract
Nuclear magnetic resonance spectroscopy
Quality control
ABSTRACT
Essential oils are natural materials widely used in many fields all over the world and have become an
integral part of everyday life. There is increasing demand for essential oils, which has resulted in cases
of adulteration. Authentication is thus a matter of critical importance for both consumers and chemical
companies. This comprehensive overview covers known adulterations in essential oils, and some analytical
methodologies adopted for their detection. We first list recommended tests, and then we explain and
discuss common analytical techniques, such as chiral gas chromatography, isotope-ratio mass spectrometry,
and nuclear magnetic resonance spectroscopy. We also present (high-performance) thin-layer
chromatography, vibrational spectroscopy, coupled and multidimensional chromatography, high-
performance liquid chromatography, and combination with chemometrics-metabolomics. This review
provides a critical overview of existing techniques.
© 2014 Elsevier B.V. All rights reserved.
Contents
1. Introduction ........................................................................................................................................................................................................................................................ 147
2. Overview on essential oils ............................................................................................................................................................................................................................. 147
2.1. Definition and composition ............................................................................................................................................................................................................. 147
2.2. Regulations ............................................................................................................................................................................................................................................ 148
2.3. Characterization ................................................................................................................................................................................................................................... 148
2.4. The problem of authentication ....................................................................................................................................................................................................... 148
3. Known cases of authentication issues ....................................................................................................................................................................................................... 148
3.1. Addition of other products: oil and solvents ............................................................................................................................................................................. 148
3.2. Addition of specific compounds: synthetic and natural ........................................................................................................................................................ 148
3.3. Addition of another essential oil ................................................................................................................................................................................................... 150
3.4. Other cases ............................................................................................................................................................................................................................................ 150
4. Techniques of authentication ........................................................................................................................................................................................................................ 150
4.1. Tests recommended by the authorities ....................................................................................................................................................................................... 150
4.2. Analytical techniques commonly used for the detection of adulteration ....................................................................................................................... 151
4.2.1. Chiral GC analysis ............................................................................................................................................................................................................... 151
4.2.2. Isotope-ratio mass spectrometry .................................................................................................................................................................................. 151
4.2.3. NMR spectroscopy ............................................................................................................................................................................................................. 152
4.3. Additional techniques ........................................................................................................................................................................................................................ 152
4.3.1. (HP)TLC analysis ................................................................................................................................................................................................................. 152
4.3.2. Vibrational spectroscopy ................................................................................................................................................................................................. 152
4.3.3. Coupled and multidimensional chromatography ................................................................................................................................................... 152
Abbreviations: AFNOR, Association Française de Normalisation; AED, Atomic emission detector; ANRT, Association Nationale de la Recherche et de la Technologie; BS,
British Standard; DSC, Differential scanning calorimetry; EFSA, European Food Safety Authority; EO, Essential oil; FID, Flame-ionization detector; FTIR, Fourier-transform
infrared spectroscopy; GC, Gas chromatography; HPTLC, High-performance thin-layer chromatography; IFRA, International Fragrance Association; IR, Infrared; IRMS, Isotope-
ratio mass spectrometry; ISO, International Standard Organization; LC, Liquid chromatography; MDGC, Multidimensional gas chromatography; MS, Mass spectrometry; NIR,
Near-infrared; NMR, Nuclear magnetic resonance; Ph. Eur, European Pharmacopoeia; PS, Photoacoustic spectroscopy; SFE, Supercritical fluid extraction; SNIF, Site-specific
natural isotopic fractionation; TLC, Thin-layer chromatography; TOF, Time of flight; USP, United States Pharmacopoeia.
* Corresponding author. Tel.: +33 4 92076469; Fax: +33 4 92076125.
E-mail address: xavier.fernandez@unice.fr (X. Fernandez).
http://dx.doi.org/10.1016/j.trac.2014.10.007
0165-9936/© 2014 Elsevier B.V. All rights reserved.
Trends in Analytical Chemistry 66 (2015) 146–157
Contents lists available at ScienceDirect
Trends in Analytical Chemistry
journal homepage: www.elsevier.com/locate/trac
4.4. Emerging techniques ......................................................................................................................................................................................................................... 152
4.4.1. Application of chemometrics ......................................................................................................................................................................................... 153
4.4.2. HPLC ....................................................................................................................................................................................................................................... 153
4.4.3. Other techniques ................................................................................................................................................................................................................ 153
5. The main problems and recommended analytical methods ............................................................................................................................................................. 153
6. Conclusion ........................................................................................................................................................................................................................................................... 153
Acknowledgements .......................................................................................................................................................................................................................................... 156
References ............................................................................................................................................................................................................................................................ 156
1. Introduction
Essential oils have been widely used all over the world and their
use is constantly increasing because of the strong demand for pure
natural ingredients in many fields. Thus, large quantities of essential
oil are produced worldwide to fuel the industries of flavors and fra-
grances, and cosmetics, and the health industry with aromatherapy
and phytomedicine [1,2]. Some essential oils are produced on a very
large scale (e.g., in 2008, production of orange oils was ~51,000 tons,
corn mint oils ~32,000 tons, and lemon oils ~9200 tons). Essential
oils of citrus, which included a great number of fruits from genus
Citrus, are the most popular natural essential oils and account for
the largest proportion of commercial natural flavors and fragrances
[3]. Some others are produced on a much smaller scale due to their
rarity, but are traded at very high prices [e.g., agar wood oil (6000–
11,000€/kg), iris (6200–100,000 €/kg depending on the concentration
of irones), or rose oil (6000–10,000 €/kg). These prices vary and may
be related to the scarcity of the raw material, harvesting issues,
climate dependence, or extraction yield. Essential oil industries’ cu-
mulative sales represented several billions US$ in 2008 [2,4].
The use of natural extracts is seen as a strong marketing advantage
in the manufacture of many goods, but the prices for natural extracts
are often much higher than those of synthetic materials, so there
are many cases of adulteration [5]. Authenticity can be defined as
free from adulteration in the sense of absence of foreign bodies or
extraneous matter, but it also suggests free from impurities in the
raw material itself [6]. Thus, authentication is an important subject
for consumers. From the regulatory point of view, quality standards
have been established through the requirement for quality labels
that specify the chemical composition of each essential oil. From
an economic point of view, authentication is of critical importance
to avoid unfair competition that can destabilize the market and disrupt
local and even national economies of producing countries [7].
This comprehensive overview covers analytical techniques that
could be used in detecting known adulterants. It is known that the
chemical constituents of essential oils may vary depending on harvest
season, habitat, drying processes, extraction and isolation techniques
used and many other factors. Thus, it is necessary to determine a
profile of the constituents of essential oils. Several regulations take
into account the variability in chemical composition. In this way,
authenticity is controlled using the quantitative values in the
monographs. In general, few compounds or markers in essential oils
have been used to evaluate their quality and their authenticity. Out
of the scope of this review are cases of non-compliance of essential
oils caused by degradation. We consider different analytical methods,
including physical, chemical, chromatographic, spectroscopic and
thermal techniques. We present an overview on essential oils and
their different known problems of authentication and adulteration,
followed by the recommended analytical techniques for each case.
2. Overview on essential oils
2.1. Definition and composition
According to the “Association Française de Normalisation” (AFNOR)
and to the European Pharmacopoeia (Ph. Eur.), an essential oil is
clearly defined as a manufactured product from pure, identified raw
materials of plant origin, obtained by hydrodistillation and steam
distillation, mechanical processes (e.g., EO from Citrus), or by “dry”
distillation for some woods (Table 1).
The essential oil is then separated from the aqueous phase by
physical processes [9,10]. Essential oils can be terpene-less,
sesquiterpene-less, corrected, or deprived of a substance by partial
removal, such as methyleugenol in rose oil or furocoumarines in
citrus oil [11]. Due to the various processes and the multiple pa-
rameters involved, essential oils are complex matrices comprising
hundreds of compounds with various structures and functional
groups (Table 2). These compounds are mainly derived from three
biosynthetic pathways: mevalonate, methyl erithrytol and shi-
kimic acid [4].
Among these components, the most common are volatile ter-
penoid compounds derived from a common precursor: isopentenyl
diphosphate. Once biosynthesized, terpenes are diversified through
various enzymatic reactions, such as isomerization and oxidation
[1,2,13,14]. This chemical diversity could also be enhanced by chem-
ical modification during the extraction process by thermal activation
of chemical reactions. For example, distillation by dry vapor stream
is known to reduce the risk of hydrolysis of esters (e.g., linalyl acetate),
flame distillation is known to promote “burnt” olfactory notes, and
cohobating is known to increase the content of certain compounds
(e.g., sulfur compounds) [15]. Essential oils can also be produced
from different chemotypes (providing distinct chemical entities within
the same botanical species), such as thyme essential oil that is known
Table 1
Differences in term of composition of lime oil with different processes of extrac-
tion, obtained by GC/FID on apolar column [8]
Hydrodistillation (SD) Expression
Limonene (36.0–46.0%) Limonene (38.0–44.0%)
γ-terpinene (10.0–13.0%) β-pinene (17.0–19.0%)
α-terpineol (6.0–8.0%) β-bisabolene (4.0–4.5%)
p-cymene (1.5–2.8%) α-pinene (1.7–2.0%)
Table 2
Examples of compounds found in essential oils [12]
Compound Essential oil
Menthol Mint
Linalool Lavender, cardamom
Thymol Thyme
Eugenol Clove
Carvone Caraway
α-vetivone, β-vetivone Vetiver
Benzoic acid Almond
Cinnamic acid Cinnamon
Citral Lemon
Cinnamic aldehyde Cinnamon
Geranyl acetate Geranium
Linalyl acetate Lavender
Limonene Orange, lemon
Pinene Geranium, star anise
Caryophyllene Clove
147T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
to have seven chemotypes. We do not address authentication of
chemotypes in this review.
2.2. Regulations
The diversity of chemical functions encountered in essential oils
offers a variety of properties, and subsequently a variety of uses.
Sometimes, these compounds can also have undesirable properties,
such as allergenicity or toxicity, resulting in safety and security
concerns. For this reason, standards and specifications have been
established by national authorities and international organizations
to limit and to control the use of essential oils. To achieve this, mono-
graphs contain specifications that define the qualitative and
quantitative characteristics of a substance in order to ensure optimum
quality compatible with the requirements of public health. These
monographs are produced by international organizations
[e.g., International Standards Organization (ISO), Ph. Eur., Codex
Alimentarius Commission, Food Chemicals Codex, Flavor and Extract
Manufacturers Association (FEMA), or Research Institute for Fragrance
Material (RIFM)]. Some other national authorities issuing recom-
mendations are British Standards Institution (BSI), AFNOR Standards
(France), Essential Oil Association of USA, US Pharmacopoeia (USP),
Indian Standards, and German DIN Standard (Deutsch Arzneibuch).
[13,16]. The use of essential oils is also governed by specific regulations
for application areas [e.g. European Union Cosmetics Regulation (CE
1223/2009) and European Food Safety Authority (EFSA)]. There are
also non-governmental organizations supported by industrial com-
panies that study and gather chemical, technical, and toxicological
information about the ingredients used in perfumery {e.g., Inter-
national Fragrance Association (IFRA), which publishes recommended
practices of use, usually followed by professionals [17]}.
2.3. Characterization
Essential oils are complex matrices that need to be analyzed
by different techniques to ensure quality, consumer safety and fair
trade. Thus, there is a wide range of instrumental techniques avail-
able (e.g., physical, organoleptic, chemical, chromatographic, and
spectroscopic analysis) (Fig. 1)[16,18–20]. Olfactory analysis could
be envisaged, but is typically performed by a trained evaluator. It
is often carried out by comparison with a standard sample. Phys-
ical measurements required in most monographs are: density,
refractive index and optical rotating power. The density of an es-
sential oil is the ratio between its volumic mass and the volumic
mass of a reference compound (water). The refractive index is the
ratio between the sine of the angle of incidence and the sine of
the angle of refraction of a luminous ray of a predetermined wave-
length in the essential oil maintained at a constant temperature.
The optical rotation of an essential oil is the angle of rotation of
the plane of polarization of light radiation at a wavelength of
589 ±0.3 nm when it passes through a thickness of 100 mm of es-
sential oil in well-defined temperature conditions [15,19]. Physical
analysis and organoleptic analysis are simple, cheap, fast tech-
niques for identifying gross falsifications, but do not identify more
subtle adulterations.
With respect to chemical analysis, analyses are mostly carried
out by titration to determine water content, ester and iodine values,
carbonyl index, alcohol content and total free alcohol content, phenol
content, or peroxide content [15]. These techniques are simple, fast,
and cheap, and they solve simple problems.
The control of essential oils could also involve chromatograph-
ic techniques, such as gas chromatography (GC) and spectroscopic
analysis, to provide more accurate information on the chemical com-
position of the extract and to quantify the compounds of interest
via universal or specific detectors [1,21,22].
2.4. The problem of authentication
Essential oils are used all around the world, but the problem of
adulteration can slow or jeopardize the development of international
trade [23]. Prices typically range from few to thousands euros (US$)
and vary from one year to another. The prices correlate with the
importance of use of essential oils, and have resulted in adultera-
tion for dishonest profits [24,25]. Adulteration of essential oils can
be due to several factors. In some cases, falsification can be defined
by the addition of: cheaper synthetic material; cheap volatiles from
other natural sources [24]; or, vegetable oils to increase the weight.
Adulterations can also involve partial or total substitution of part
of the original plant by other plants [26], or the addition of non-
volatile products.
All these adulteration methods can degrade the quality and, in
adding one or more synthetic compounds, adulteration can lead to
safety issues or non-compliance with the natural grade. Conse-
quently, authentication is an important topic for consumer protection
and the quality of essential oil production [27]. Adulteration of es-
sential oils can also have an effect on the regulatory aspect, as an
essential oil may no longer comply with specifications of standard-
ization. Most of the time, adulterants are added at a low level (5–8%)
to avoid detection by common analytical methods [28].
3. Known cases of authentication issues
Control methods and standardization of essential oils are in-
tended to attest compliance with monographs or standards of quality,
but non-compliance results do not necessarily reveal adulteration.
For example, aging, processing or storage can induce a racemiza-
tion of chiral compounds or polymerization reactions of terpenoids,
and can take the optical activity values out of specification without
there being adulteration [29].
Some cases of adulterations are already known (e.g., adding a
non-volatile ingredient, synthetic or natural compounds, or a cheaper
essential oil) [22].
3.1. Addition of other products: oil and solvents
Essential oils have significant volumes and turnover, so they are
sometimes subject to dilution by adding a non-volatile ingredient
to reduce the cost (e.g., adding vegetable or mineral oils because
of their relatively low cost, their easy availability, their density being
close to that of essential oils, and a greasy texture similar to that
of essential oils) [2,7,22]. This kind of adulteration only results in
dilution, which reduces the scent of the essential oil [30].
A study on lemongrass oil identified kerosene or coconut oil as
adulterants [31,32]. Another example of this kind of adulteration
is sandalwood oil diluted with polyethylene glycol [32]. Other sol-
vents that could be used are triacetin, triethyl citrate or benzyl
alcohol, ethyl alcohol, and, in the case of aromatherapy, vegetable
oils, such as almond oil [33].
3.2. Addition of specific compounds: synthetic and natural
Standardization of essential oils is defined by values with low
and/or high limits for the content of selected compounds. Com-
mercial essential oils need to comply with such standards [16].
For this reason, cases of adding a compound, synthetic and nature-
identical or natural, can be found. By definition, natural compounds
are obtained directly from natural sources by enzymatic, microbial,
or physical procedures [13,28]. Those specific types of adultera-
tion can have different motivations. One reason could be to enhance
the quality of the essential oil, in terms of compound contents.
This kind of adulteration can be done to increase the benefit of
essential oils and to meet the needs of industry [34] {e.g., adding
148 T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
Fig. 1. Advantages and disadvantages of quality assessment techniques (++: Advantages; - -: Disadvantages).
149T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
citral to lemon (Citrus lemon L.) essential oil [35], benzyl benzoate
to balsam of Peru (Myroxylan balsamum (L.) Harms) [26], or synthetic
irone to iris oil [36]}.
The price of the iris essential oil varies greatly depending on the
percentage of irone. For example, the price of an iris oil containing 8%
irone is 6200 €/kg, while with 10% irone it increases to 9750 €/kg,
and could even reach 101,000 €/kg for pure irone. The price differ-
ence can be really large, which is a good reason for adulterating iris
oil, particularly because a mixture of isomers of synthetic α-irone
and β-irone cost only around 25 €/mL. Another reason could be to
improve the olfactory quality of the essential oil, as is the case for
bergamot oil (Citrus aurantium L. spp. Bergamia) or lavender oil
(Lavandula angustifolia Mill.) for which the addition of linalyl acetate
or linalool was reported, or vetiver oil (Vetiveria zizanioides (L) Nash)
with the addition of a mixture of terpenyl cyclohexanols, in order
to increase the sandalwood note [22,24]. Essential oils are sometimes
used for medicinal properties [37] so they can be altered by the
adding other oils containing the bioactive compound(s) of interest
{e.g., chamomile oil (Chamomilla recutita, syn. Matricaria chamomilla),
which is used for its content of α-bisabolol, and could be altered
with synthetic bisabolol [24,38]}.
3.3. Addition of another essential oil
The addition of another essential oil can be motivated by olfactory
and/or economic reasons. To do this, the addition can be an essen-
tial oil of lower quality but with similar olfactory notes [35,39].
This is especially the case when there is a significant price differ-
ence between the two oils. One of the most known examples is
the adulteration of essential oils from citrus by sweet orange essential
oil, which is the cheapest citrus oil. Another typical example is lav-
ender essential oil (Lavandula angustifolia Mill.), whose price can
reach 130 €/kg, and which could be mixed with the essential oil
of other species of genus Lavendula, whose prices are around 20 €/kg
[24]. Lemon-balm essential oil (Melissa officinalis L.), a highly valued
raw material (~5000 €/kg), produced in low yields and featuring
pronounced medicinal interest, could be mixed with cheap citro-
nella oil (Cymbopogon winterianus Jowitt ex Bor) [40].
Adulteration can also occur by mixing different essentials oils
obtained by the extraction of different parts of the same plant. Cin-
namon bark essential oil can be adulterated by leaf cinnamon essential
oil to reduce the presence of allergens, such as cinnamaldehyde. The
leaf oil, while possessing the same olfactory notes, although less
“gourmand”, has indeed reduced cinnamaldehyde contents. This type
of fraud can reduce the allergenic effect but also increase the volume,
and hence the profit [41]. Concerning all types of citrus oils, another
well-known falsification is the addition of orange essential oil
(Citrus aurantium var. sinensis L.) [42]. Another case concerning citrus
oil is neroli oil made from flowers (Citrus aurantium L. spp. Amara
L. var. pumilia), frequently mixed with cheaper petitgrain oil made
from leaves [24].
3.4. Other cases
Another example of fraud worth mentioning is the case of win-
tergreen essential oil that can be completely substituted by methyl
salicylate [43]. A gross case of adulteration could be the use of syn-
thetic oil, consisting in a mixture of synthetic compounds resembling
the formulae of the natural essential oil, in lieu of the valuable natural
material. Also, bergamot oil or geranium oils can be obtained by
mixing monoterpenes and distilled oils of different origins, linalyl
acetate and other citrus oils [33,44].
In summary, the diversity of the adulteration strategies relates
to the large, diverse collection of essential oils used in manu
facture of valuable products, making each case different from the
others.
4. Techniques of authentication
Two main approaches to the determination of adulteration are
possible: monitoring the global fingerprint of the product, or search-
ing for one or more specific markers in the product. To carry out
these controls, modern analytical techniques are typically used [7],
but simple tests are also available, set up long before the advent
of powerful analytical devices. These methods proved useful and
were widely used, but showed deficiencies over time. For example,
the iodine test can be used to characterize the oxidation of the
product, considered an indication of adulteration by vegetable oils
[45]. Another test can be performed using a saponification reac-
tion with aqueous potassium hydroxide; and, the formation of
crystals indicates a potential fraud by addition of esters [46].
4.1. Tests recommended by the authorities
Control of the conformity of an essential oil starts with a series
of tests according to the recommendations of certification and reg-
ulatory authorities (e.g., ISO, and Pharmacopoeia) to ensure identity,
quality, safety and efficiency of the extract [47].
The first step is sensory analysis, which is, by definition, exam-
ination of the organoleptic properties of a product by the sense
organs. This type of analysis can be performed by a sensory-
analysis panel that evaluates the essential oil, or, as indicated by
ISO recommendations, by a group of assessors selected to form the
sensory-analysis panel that will be a true “measuring instrument”
[48]. However, this necessary step has the disadvantage of involv-
ing trained panelists in time-consuming operations [49]. There are
indeed two types of experts: the “expert assessor” and “special-
ized expert assessor”. The former is an assessor selected with a high
degree of sensory sensitivity and experience of sensory method-
ology, able to make consistent, repeatable sensory assessments of
various products. The latter is a subject who has additional expe-
rience as a specialist in the product and/or process and/or marketing,
and able to perform sensory analysis of the product and to evalu-
ate or predict effects of variations (e.g., raw materials, recipes,
processing, storage, and ageing). Selection of individuals for the
sensory-analysis panel must be performed with care and requires
guidelines for selection, training and monitoring of assessors [48].
Once the assessors are selected, a standard methodology follow-
ing ISO recommendations must be applied. Sensory analysis has
the advantage of avoiding costly investments in analytical instru-
ments, but requires time and assiduity of the assessors for training
and evaluation [49]. The result of the sensory-analysis panel can
be as simple as just indicating compliance or non-compliance of
the essential oil, or more complicated with statistical analysis and
comparison with an essential oil used as reference [48].
The second step comprises a series of physical and chemical anal-
yses. The physico-chemical properties are determined by
standardized methods, such as measuring the ester, acid or car-
bonyl index, or the refraction, density, optical rotation, freezing or
boiling points, or quantification of ethanol or moisture [8]. Quality
control (QC) and assessment of essential oils can be performed based
on these techniques, and possible adulteration can be detected [50].
Some essential oils, such as citrus oils, which contain predomi-
nantly (+)-limonene, will have a lower specific gravity and a lower
optical rotation on adding turpentine because α-pinene, its major
component, has a lower boiling point and a lower optical rotation
[22]. On adding synthetic anethole in star anise (Illicium verum L)
essential oil, a change in the optical rotation could be observed and
used as evidence of fraud. For peppermint oil, adding turpentine
is characterized by a freezing point lower than 10.5°C [41].
However, these simple, effective methods are insufficient for more
subtle adulteration. It is then necessary to use more powerful an-
alytical techniques: separation techniques [GC, liquid chromatography
150 T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
(LC), high-performance thin-layer chromatography (HPTLC)) and spec-
troscopic techniques (vibrational techniques, and nuclear magnetic
resonance)]. Adulteration with ethanol, edible oils, or liquid par-
affin can be detected by TLC, GC or infrared (IR) spectroscopy. [41]
GC analysis is the last step recommended in some monographs, as
it is a key technique in the analysis of essential oils. The analysis of
qualitative and quantitative composition by GC provides a chro-
matogram sufficiently fine to highlight defects in quality. In this regard,
comparisons use the chromatographic profile obtained by GC
equipped with a flame-ionization detector (FID), which provides a
large range of linearity and has relatively simple maintenance re-
quirements. GC is effective for the QC of an essential oil, by comparing
the chromatogram of the product with a standard meeting the chosen
specifications. The required steps are, first, to identify the appear-
ance or the disappearance of peaks on the chromatogram and, second,
to compare the relative percentage area to determine whether their
differences are significant for the product being analyzed, although
this technique gives only an approximation of the real quantity of
a component present in the sample tested.
Various perfumery materials were characterized qualitatively and
quantitatively by GC coupled to mass spectrometry (GC-MS) in order
to characterize and to detect adulteration accurately [51]. For san-
dalwood oil, GC-MS analysis reliably evaluated the santalol content
as a valuable marker in detecting adulteration by the addition of
synthetic matertial, such as Sandalore [52], Verdox, Santaliff, Vertofix
Coeur, or Ebanol [53].
4.2. Analytical techniques commonly used for the detection of
adulteration
4.2.1. Chiral GC analysis
Chiral GC is a practical, powerful technique for the authentica-
tion of essential oils and is becoming crucial for the detection of
adulterants [33,34,54–56]. Plants produce metabolites in many in-
stances as chiral molecules, and enantiomers can differ from one
species to another within the same genus. Although presenting the
same physicochemical properties, except for their optical activity,
enantiomers can exhibit divergent biological activities, one enan-
tiomer being harmless while the other is toxic, so appropriate, efficient
chemical analyses are essential [57]. For example, (R)-limonene is
responsible for the odor of oranges while (S)-limonene accounts for
the odor of lemon. (S)-carvone is the key odorant of the essential
oil of caraway (smell of cumin), and (R)-carvone is in the essential
oil of spearmint (smell of spearmint). In others cases, one or more
stereoisomers could be less active or even odorless, such as (R)-
linalool, which has a powerful flowery note, while (S)-linalool is less
intense, or (2S,4R)-cis-rose oxide, which has a powerful rosy scent,
while (2R,4S)-cis-rose oxide is odorless [29].
Compounds from essential oils are, in most cases when applicable,
chiral compounds occurring in specific enantiomer ratios, often spe-
cific to the essential oil (e.g., α-pinene, β-pinene and limonene,
making these compounds good markers of the origin and subse-
quently of adulteration by mixing these materials from different
origins) (Table 3)[48]. Chiral analysis allows detection of adulter-
ation of natural products with synthetic substitutes, usually in the
racemic form, or bulking oils from other crops, by using values of
enantiomeric purity and enantiomeric excess. Those values com-
prise a measured ratio of detected enantiomers expressed as a
percentage, and by the relative difference of the separated
enantiomers also expressed as a percentage [29,34,48,58].
One example is the case of rose and geranium essential oils
with (-)-trans rose oxides, which are a specific indicators of genuine
rose oils and can discriminate rose oils from geranium oils [29].
Chiral analyses also detect the addition of synthetic linalool and
linalyl acetate in lavender oil [6,7,59]. Another case of chiral analysis
is the analysis of limonene, which shows a high ee-value in favor
of (R)-limonene for bergamote, orange, mandarin, lemon, or lime
oils, and a high ee-value in favor of (S)-limonene for lemongrass
or citronella oils [29].
In this way, chiral analysis plays a critical role in essential oil anal-
ysis and has been among the most important analytical techniques
in recent times. It is a cheap, sensitive technique, but it requires
method development that can take some time especially because
there is no universal chiral stationary phase [60]. In essential oils,
some non-enzymatic reactions or racemization can occur during pro-
cessing or storage, which can induce false-positive responses in chiral
analysis [30].
4.2.2. Isotope-ratio mass spectrometry
To certify the naturality of one or more components of an es-
sential oil, another kind of analysis to be performed is isotope-ratio
analysis using isotope-ratio MS (IRMS) or stable-isotope-ratio anal-
ysis (SIRA). Plants can be discriminated by their metabolic assimilation
of atmospheric CO2, in particular by reaction intermediates derived
from incorporating carbon dioxide (molecules of three or four carbon
atoms). Most plants go through 3-phosphoglycerate, an interme-
diate with three carbon atoms (C3). The C4 plants pass through a
malate intermediate with four carbon atoms. Some plants are able
to select the glycerate pathway or the malate pathway (CAM cycle)
depending on their environment. These metabolites do not exhibit
the same isotopic fractionation, and this difference therefore allows
plants to be distinguished by their isotopic ratio [61,62]. The mea-
surement of isotopic variations in natural compounds is based on
the principle that the majority of chemical elements have different
stable isotopes that result in distinct molecular weights [63].For
each element, one or more isotopes are present at different levels,
with a specific distribution pattern. The stable-isotope ratios of carbon,
hydrogen, oxygen, or nitrogen within the metabolites can allow the
detection of accidental or deliberate addition of a synthetic product
(predominantly of fossil origin), or even the discrimination of dif-
ferent geographical or botanical origins [16,24,25,34,44,64]. This
evaluation of isotopic data has been established as the premium anal-
ysis of the origin and the naturality of flavors and fragrances [65].
IRMS is most of time coupled to combustion/pyrolyze (C/P-IRMS)
for adulteration control. This technique can reliably differentiate
natural from synthetic for mandarin essential oil regarding the
C-isotope-ratio measurements for terpinen-4-ol, γ-terpinene,
α-terpineol, and terpinolene. The authenticity of thyme and oregano
essential oils can be based on the H-isotope-ratio measurements
for carvacrol and thymol [25,39,55]. IRMS also detects addition of
synthetic benzaldehyde in bitter almond oil [66].
IRMS is a very powerful technique, but it requires a significant
financial investment and an experienced operator. Also, its use re-
quires databases that take a relatively long time to build.
Table 3
Enantiomeric Ratio (%) of α-pinene, β-pinene and limonene [29]
α-pinene β-pinene limonene
1S1R1S1R4S4R
Oil of bergamot 72 28 94 6 14 86
Oil of bitter orange 8 92 97 3 1 99
Oil of grapefruit - 100 34 66 tr 100
Oil of lemon 67 38 95 5 1 99
Oil of lime 76 24 97 3 2 98
Oil of orange tr 100 46 54 tr 100
Oil of neroli 77 23 96 4 3 97
Oil of petitgrain 82 18 98 2 12 88
Oil of mandarin 43 57 3 97 tr 100
Oil of citronella 23 77 tr tr 96 4
Oil of lemongrass 96 4 tr tr 100 tr
tr =trace <0.5%.
151T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
4.2.3. NMR spectroscopy
NMR spectroscopy provides information for the control of au-
thenticity by determining stable-isotope ratios, affording a means
for measuring isotopic patterns within natural and synthetic mol-
ecules for the purposes of differentiation [7,34,43,67,68]. Investigation
of site-specific natural-isotope fractionation (SNIF-NMR), based on
the measurement of deuterium/hydrogen (D/H) ratios at specific
positions of a molecule, has enabled characterization of the nature
of plant precusors [7,69]. Quantitative deuterium NMR measured
significant variations of deuterium-isotope distribution, according
to the origin of the molecule, and has discriminatory potential to
characterise the enantiomeric purity of compounds, such as
α-pinene, or methyl salicylate [43]. SNIF-NMR is also used to de-
termine the addition of synthetic linalool in essential oils, or to
detect the addition to chamomile oil of (-)-α-bisabolol extracted
from plants of the genus Vanillosmopsis [16].
NMR is a powerful technique but its use needs the isolation of
compounds, databases, an experienced operator and significant
investment.
4.3. Additional techniques
4.3.1. (HP)TLC analysis
Even though GC-MS is the method of choice for the analysis of
essential oils, (HP)TLC has become widely accepted by pharmaco-
poeias and regulatory agencies as a tool well suited to identification
of essential oils and detection of adulteration [14,34,46,70]. (HP)TLC
enables the mobile phase to progress by capillarity over a plate
charged with a stationary phase along with compounds from a
mixture. Different lengths of migration are observed for each com-
pound, depending on mechanisms of partition between the mobile
and stationary phases and adsorption phenomenon.
The most recent advances in this technique were mainly ob-
served in the quality of stationary phases and the efficiency of
detection techniques. High-performance stationary phases, char-
acterized by smaller particle sizes with narrow size distribution, were
developed. These increased the resolution and the reproducibility
of TLC analysis. Similarly, new stationary phases, such as chiral
phases, were developed and are now commercially available. The
detection systems were also considerably improved (e.g., the set-
up of scanners for densitography for the range 190–900 nm [71].
TLC can be coupled with powerful detection systems: MS, and
IR and Raman spectroscopies [19]. (HP)TLC was quickly estab-
lished as a method of choice for analysis and control (e.g., in the
adulteration of ylang-ylang essential oil by sunflower oil) [72]. The
Ph. Eur. provides a few TLC methods for identifying adulteration of
essential oils, such as adulteration of anise oil by fennel oil, or Chinese
Star anise oil by Japanese Star anise oil [70].
HPTLC can be automated and allows fast analysis of numerous
samples (more or less complex) simultaneously, and is considered
as a greener technique by reducing the amount of waste material
(including volatile organic compounds) and energy costs.
Despite these advantages, HPTLC has some disadvantages as an
off-line technique and requires initial investement for acquisition
of the equipment.
4.3.2. Vibrational spectroscopy
Vibrational spectroscopy is a chemical-analysis technique fo-
cusing on covalent chemical bonds of molecular constituents within
the sample. This technique is based on the interaction of light and
matter and the resulting molecular vibrations. Raman spectrosco-
py provides information about spectrometric diffusion from the
vibrational state of a molecule. IR spectroscopy is based on the mod-
ification of vibrational and rotational energies of chemical bonds.
The IR spectrum ranging from microwave to visible wavelengths of
the electromagnetic spectrum, or in mid-IR regions. For near-IR
reflectance (NIR), the nominal range of wavelengths used is
1100–2500 nm [57,73–76].
Combined with chemometric algorithms (metabolomics), those
techniques are gaining importance in the fast QC of essential oils
[1,23,77]. For example, using spectroscopy analysis discriminated
between different eucalyptus essential oils [78]. IR and Raman can
also be used for the detection of cottonseed oil and paraffin oil in
different essential oils by the presence of absorption bands char-
acteristic of ester and unsaturated ester (1705–1720 cm1), acetates
(1 245 cm1) and carbonyl group (1250–1170 cm1) for cottonseed
oil, and saturated and unsaturated hydrocarbons (3 000 cm1)for
paraffin oil [41]. NIR spectroscopy is promising in QC, since large
sets or single samples can be quickly analyzed in order to identify
suspect samples without requiring further testing by more time-
consuming, expensive methods [23].
4.3.3. Coupled and multidimensional chromatography
Essential oils are complex matrices and their chromatographic
analyses on one dimension do not avoid co-elution issues. It is under
these circumstances that multidimensional chromatographic tech-
niques can solve the problem because they offer better separation
capacities. Multidimensional separation is defined as an orthogo-
nal two-step separation. The sample is transferred from separation
system 1 (e.g., column 1 for GC) to separation system 2 (column
2) [60]. Two orthogonal columns are commonly used: usually a
non-polar first column and a polar second column.
Two main approaches are adopted in GC analysis of complex
volatile fractions of plant matrices: so-called heart-cut GC-GC and
the two-dimensional comprehensive GC (GCxGC) [79]. In heart-
cut GC-GC, analytes or individual segments eluting from a first
column (1D, first dimension) are on-line and directly transferred
to the second column (2D, second dimension) for further separations,
using a valve or Deans switch device [80]. With a comprehensive
GCxGC system, the entire sample passes through the two capillar-
ies connected in series with a transfer device [81].
Multidimensional GC (MDGC) finds application in environmen-
tal analysis, oil-refining and petrochemical industry, and natural
extracts [79,82,83]. MS coupled to MDGC (MDGC-MS), or GC-time-
of-flight MS (GC-TOF-MS) are analytical techniques available for the
control of essential oil, but the use of TOF-MS is not very affordable
and requires trained users [34,55]. For sandalwood essential oil,
MDGC-MS or MDGC-FID enabled the high-resolution separation of
santalol isomers, and provided elements of proof of the genuine
quality of the sandalwood oil [53]. Besides the question of co-elution
of one or more metabolites of the sample, GCxGC gives access to
more detailed, comprehensive overview of the chemical composi-
tion, thereby increasing the number of possible markers, or the
reliability of fingerprinting. Multidimensional chromatographic
techniques coupled or not to an MS detector have greatly en-
hanced separation power, which has simplified sample preparation
in target analysis. GCxGC has the disadvantage of needing a slow
temperature-program rate in the first dimension, and a detector with
a high frequency. The data processing is not easy and the instrument
is not very affordable.
The combination of chiral analysis with MDGC (enantio-MDGC)
is an option for analysis of essential oils with a high degree of mo-
lecular complexity [34]. Enantioselective GC coupled on-line with
IRMS was recently used in origin-specific analysis of flavor and fra-
grance compounds. Analyses focused on the 13C/12C ratio of the
detected enantiomers [65].
4.4. Emerging techniques
Some existing techniques are already used in natural extracts but
for different purposes.
152 T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
4.4.1. Application of chemometrics
The fingerprint of an essential oil can be defined as a charac-
teristic profile reflecting the complex chemical composition of the
sample, and can be obtained by many analytical techniques.
In essential oils, there are a lot of unknown components often pre-
sent only in trace amounts. Even if chromatographic instruments
have shown a great improvement in terms of separation over the
years, selection of just a few components should not be consid-
ered for evaluating the quality and the authenticity of samples of
essential oils. Consequently, to obtain reliable fingerprints that
represent chemically characteristic components is not an easy
task.
Chemometrics, such as multivariate analysis, and chemical-
pattern-recognition methods with principal component analysis and
soft-independent modelling of class analogy, is now greatly appre-
ciated for providing reasonable characterization of essential oils.
Chemometrics is defined by The International Chemometrics Society
as: “the chemical discipline that uses mathematical and statistical
methods:
1 to design or to select optimal measurement procedures and
experiments; and,
2 to provide maximum chemical information by analyzing chemical
data”.
Nowadays, chemometrics is applied in many fields, such as an-
alytical chemistry, including separation methods, such as
chromatography (LC, GC, TLC), electrophoresis, and spectroscopic
methods, such as Raman, Fourier transform IR spectroscopy (FTIR),
NIR, mid-NIR [19,84–87]. Indeed, reprocessing data by using
chemometrics obtains more information about samples.
Several application areas already benefit from the advantages
provided by chemometrics, such as metabolomics, which is a
chemometric approach used for phenotyping and biomarker re-
search [88]. In essential oil authenticity, chemometrics is playing
an increasingly important role. Indeed, more and more articles are
published on integrating the chemometric approach in studying
essential oils.
The combination of GC-MS with chemometric tools, such as
multivariate curve resolution (MCR), overcomes the problems of
background, baseline offset and overlapping/embedded peaks [89,90].
In vibrational spectroscopy combined with chemometrics, model-
ling in essential oil studies, several articles mentioned that this
combination could be an alternative for the quality assessment of
essential oils (e.g., lavender oil) [91]. Another technique based on
a statistical model is “electronic-nose technology”, which is defined
as “an instrument including a set of electronic chemical sensors
with a cross selectivity, and a fitted pattern-recognition system
capable of recognizing simple or complex odors” [19].
More techniques are being developed in response to specific re-
quests from regulation bodies concerning authentication of essential
oils. A study on the QC of bergamot oils showed the efficiency of
electronic-nose systems with subsequent discriminant factorial anal-
ysis treatment of data [92].
This technique gives good results but requires the availability of
a large number of well-defined samples to build the model, and the
authenticity of the samples used must be certain.
4.4.2. HPLC
High-performance LC (HPLC) is not widely used in essential oils,
but is rather a method of choice for analyzing less volatile or
non-volatile constituents. HPLC highlights non-volatile markers of
adulteration, such as synthetic compounds or vegetable oils [87].
This technique was used to detect a mixture of essential oils (e.g.,
adding orange oil in lemon oil) [93,94].
4.4.3. Other techniques
Other techniques have seen their applications evolve towards adul-
teration control. For example, differential scanning calorimetry (DSC),
which is mainly used in the field of polymers, is by definition “the
measurement of the change of the difference in the heat flow rate
to the sample and to a reference sample while they are subjected
to a controlled temperature program” [95]. It is based on measur-
ing the consequences of applying temperature-programmed scans
that can cause some structural modifications or decompositions [7].
Its use has changed and has been tested in QC because of its
applicability in assessing the purity of samples. This use has been
applied to some essential oils, such as orange, lemongrass and basil
oils. They show predominant substances in their composition
(respectivelyaround 90% limonene, 66% citral and 84% methyl chavicol),
and, in this way, have specific DSC profiles. In such cases, DSC can
provide fingerprints with a relatively good degree of accuracy [96].
Authentication can also be based on thermal diffusivity, such as
photoacoustic spectroscopy (PS), which is mainly used for gas
analysis. Since the advent of more efficient lasers, its application
areas have expanded. For example, in essential oils, PS was used to
measure the thermal diffusivity in discriminating between different
extraction processes for a study on concentrated citrus oils [97].
All these methods offer interesting perspectives, but there are
few data, in the literature, on their use in essential oils and their
adulteration.
5. The main problems and recommended analytical methods
Recent advances in knowledge and the chemical analysis of
essential oils allowed a summary of the main authentication prob-
lems of essential oils to be established and the analytical methods
recommended (Table 4).
6. Conclusion
Adulteration, particularly adulteration in essential oils, is a topic
of growing interest. Despite this, only a few hundred articles refer
to this major issue with economic consequences that challenge the
analytical chemist. Essential oils are sometimes adulterated due to
their cost, their increasing usage, and, for some of them, their scar-
city, which contrasts with the ever-increasing demand.
Different methods are used to detect adulteration. Apart from
tests recommended by pharmacopoeias and regulations (e.g., or-
ganoleptic examination, and physico-chemical analyses), GC, GC-MS,
enantioselective, and IRMS analyses have made the major contri-
bution towards detecting adulteration of essential oils. Other
techniques, less frequently used to identify adulteration, are vibra-
tional. The ability of (HP)TLC to provide fingerprints makes it accepted
by the pharmacopoeias and regulations, and it is increasingly used
to detect adulteration of essential oils. Some techniques are gaining
in importance in authenticating essential oils, such as the use of
coupled techniques, GCxGC, or new phases in GC, HPLC, or HPTLC.
Recent advances in analytical techniques, particularly in chroma-
tography systems, coupled to MS and NMR, the automation of sample
preparations, and the computerization of data systems make
chemometric approaches very promising.
Along with progress in chemical analysis, adulteration methods
are also improving, and solving these problems requires a case-by-
case approach, since there is no general method.
The ingenuity of fraudsters is a reflection of the interest in natural
ingredients. The methods of adulteration, more and more techni-
cal, involve development of appropriate methods of analysis, which
becomes a perpetual problem for the chemical analyst.
The cost of implementation is extremely varied, from relatively
cheap to very expensive, so a balanced evaluation of analytical per-
formance has to take into account cost, efficiency and speed.
153T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
Table 4
Table of the main problems of authenticating essential oils and their associated analytical methods
Latin name Kind of adulteration Analytical methods and target of the analysis Ref.
Bergamot (Citrus aurantium L. spp. Bergamia) Addition of linalool Enantioselective GC (Only the R-enantiomer is present) [24,41]
SNIF- NMR (linalool) [69]
Discrimination of natural cold-pressed bergamot oil from those
deterpenated and bergapten-free
Electronic nose system [92]
Addition of linalyl acetate HRGC-P-IRMS, or SNIF NMR (Linalyl acetate) [41,55,98]
Buchu (Agathosma betulina (P.J. Bergius)
Pillans)
Addition of synthetic compounds Enantio-MDGC ((1S,4R)-menthone, isomenthone, (1S)-pulegone, k(1S,4R)-
cis-3-oxo-p-menthane-8-thiol, (1S,4R)-trans-3-oxo-p-menthane-8-thiol, (1S,
4R)-cis-3-oxo-p-menthane-8-thiol acetate, (1S,4R)-trans-3-oxo-p-menthane-
8-thiol acetate are specific indicators of genuine of buchu leaf oil)
[29]
Chamomile (Chamomilla recutita (L.) Rauscher) Addition of α-bisabolol from cheaper oil such as candeia oil
(Vanillosmopsis erythropappa L.)
Enantioselective GC (α-bisabolol is present only as a single stereoisomer,
so the three other stereoisomers prove adulteration)
[24]
Addition of α-bisabolol from cheaper oil such as candeia oil
(Vanillosmopsis erythropappa L.)
SNIF-NMR ((-)-α-bisabolol) [16]
Cinnamon (Cinnamomum cassia Nees ex
Blume)
Addition of cinnamaldehyde in China bark essential oil GC-MS (Presence of impurities such as phenyl pentadienal, benzyl alcohol
and eugenol in synthetic cinnamaldehyde)
[41]
Cinnamon (Cinnamomum zeylanicum Blume) Addition of twig oil in bark essential oil HPLC/PLS-DA (Seven major bioactive: coumarin, 2-hydroxyl cinnamaldehyde,
cinnamyl alcohol, cinnamic acid, eugenol, cinnamaldehyde, 2-methoxy
cinnamaldehyde)
[99]
Citrus oil Addition of turpentine Polarimeter, densitometer (Specific gravity and optical rotation are reduced) [22]
Clary sage (Salvia sclarea L.) Addition of sage oil (Salvia officinalis L.) HPTLC (Presence of black zone (Rf =0.47)) [100]
Addition of Spanish sage oil (Salvia lavandufolia L.) HPTLC (Presence of black zone (Rf =0.19)) [100]
Coriander (Coriandrum sativum L.) Addition of linalool HRGC-P-IRMS (Linalool) [41,55]
Cornmint (Mentha arvensis L.) Addition of de Mentha X piperita L. oil Enantioselective GC ((+)-trans-sabinene: 1% in M. piperita, around 0% in M.
arvensis)
[24]
Damask rose (Rosa damascena Aut. Ou Mill.) Addition of citronellol Enantioselective GC ((S)(-)-citronellol, (2S,4R)(-)-cis, (-)-trans rose oxides are
specific indicators of genuine rose oils, (2S,5S)-trans linalol oxides, (2S,5R)-cis
linalool, and (S)-linalyl acetate are identified as unnatural enantiomers)
[29,41]
Addition of palmarosa oil (Cymbopogon martini (Roxb.) Will. Watson) GC/IR/MS (δ13C of geraniol) [28]
Addition of geraniol from Cymbopogon martini (Roxb.) Will. Watson,
or from Cymbopogon nardus (L.) Rendle
EA/IRMS, or GC/C/IRMS (δ13C of geraniol) [28,41]
Addition of geranyl acetate from Cymbopogon citratus (DC.) Stapf or
from Cymbopogon martini (Roxb.) Will. Watson
EA/IRMS, or GC/C/IRMS (δ13C of geranyl acetate) [28]
Addition of linalool from Ocimum basilicum L. EA/IRMS, or GC/C/IRMS (δ13C of linalool) [28]
Eucalyptus (Eucalyptus globulus)Discrimination of eucalyptus oil from Australia with Chinese
eucalyptus oil
FT-Raman spectra, or ATR-IR (β-citronellol, 1,8-cineole, citronellal) [78]
Geranium (Pelargonium graveolens L’Her.
Ex Aiton)
Mixture of chemotypes Chemometric treatment with MIR & NIR (Citronellol, geraniol, linalool,
citronellyl formate, isomenthone, geranyl formate, guaia-6,9-diene)
[101]
Addition of Egyptian geranium oil in geranium Bourbon Enantioselective-GC (Egyptian geranium oil contain 10-epi–eudesmol
which is absent in geranium Bourbon)
[16,33]
Addition of citronella oil from Ceylon and java
(Cymbopogon winterianus) in Bourbon oil
Enantioselective-GC (Citronellol, the (-) enantiomer in geranium, (+)
enantiomer in citronella oil)
[33]
Addition of fraction of palmarosa oil in Bourbon oil Enantioselective-GC [33]
Addition of almond oil in Bourbon oil Put a drop of the sample an blotting paper, pure essential oils would
evaporate completely
[33]
Lavandin (Lavandula angustifolia P.
Mill. ×Lavandula latifolia (L.f.) Medikus)
Discrimination of origin Chemometric treatment by MID-IR spectroscopy (The main 13
hydrocarbons and oxygenated compounds)
[85]
Addition of linalool HRGC-P-IRMS (Linalool) [55]
lavender (Lavandula angustifolia Miller) Addition of synthetic linalool and linalyl acetate Enantioselective-GC ((R)(-)-linalol 94%, Detection of dihydrolinalool and
dehydrolinalool)
[24,29]
Enantioselective-GC (linalool and linalyl acetate) [29,102]
SNIF NMR (Linalool, linalyl acetate) [98]
HRGC-P-IRMS (Linalool, linalyl acetate) [55]
Addition of lavandin oil (Lavandula angustifolia Mill. X L. latifolia
Medik.)
Quantitative GC analysis (Presence of high amounts of 1,8-cineol and camphor) [55,102]
Addition of grapefruit oil TLC (Auraptene) [22,103]
(continued on next page)
154 T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
Table 4 continued
Latin name Kind of adulteration Analytical methods and target of the analysis Ref.
Lemon (Citrus limon L. Burm. F.) Addition of sweet orange oil (Citrus aurantium var. sinensis L.) GC ultra-Fast (presence of δ-3-carene) [42]
Addition of other origin (Ivory coast, USA, Argentina) in Italia HPLC (Presence of oxypeucedanine, oxypeucedanine oxide, byakangecol) [93]
Addition of synthetic (+)-(2R,4S)-cis-rose oxides, (+)-(2S,4S)-trans-rose
oxides
Enantio-MDGC ((+)-(2R,4S)-cis-rose oxides, (+)-(2S,4S)-trans-rose oxides) [29]
Lemon balm (Melissa officinalis L.) Addition of synthetic (-)-(S)-citronellal, (+)-(R)-citronellal, or (-)-(S)-
citronellol, (+)-(R)-citronellol
Enantio-MDGC ((-)-(S)-citronellal, (+)-(R)-citronellal, or (-)-(S)-citronellol,
(+)-(R)-citronellol)
[29]
Addition of lemon grass oil (Cymbopogon citratus (DC.) Stapf) or of
citronella species oil (Cymbopogon)
IRMS (Lemon balm is a C3 plant and citronella is a C4 plant and C3 plants
are much more depleted in their δ13CPDB levels than those from C4 source)
[29]
Addition of citronellal, or citral Enantioselective-GC (Citronellal or citral) [35]
Addition of citronella essential oil (Cymbopogon nardus (L.) Rendle) Enantioselective-GC (Citronellal) [59]
Addition of coconut oil Physical analysis (Noting the changes in the physical constants and
solubility in 70% alcohol)
[31]
Lemongrass (Cymbopogon citratus)Addition of synthetic citral Enantioselective-GC & IRMS (Citral) [35,41]
Lemony Litsea (Litsea cubeba (Lour.) Pers.) Addition of terpineol IRMS (δ13C of terpineol) [41,42]
Lime (Citruis aurantifolia (Christm.) Swingle) Addition of terpinolene IRMS (δ13C of terpinolene) [41,42]
Addition of methyl-N-methyl anthranilate GC-IRMS (δ13CPDB
15NAIR values of methyl-N-methyl anthranilate) [34,41]
Mandarin (Citrus reticulata Blanco) Addition of sweet orange oil terpenes in cold-pressed oil GC-IRMS (The content of Δ-3-carene (present only in traces in mandarin
oil), and the Δ -3-carene/camphene and Δ -3-carene/α-terpinene ratios)
[25]
Addition of distilled mandarin in cold-pressed oil GC-IRMS (Ratios between specific components, mainly terpinen-4-ol/
citronellal, or terpinene-4-ol/decanal)
[25]
Addition of synthetic methyl acetate HPTLC-enantio-GC coupling (Methyl acetate) [29]
Mint (Mentha L.) Addition of linalool HRGC-P-IRMS (Linalool) [55]
Neroli (Citrus aurantium L. spp. Amara L.
var. pumilia)
Addition of tea tree (Melaleuca alternifolia Cheel) HPTLC (Presence of purple zone (Rf =0.26)) [104]
Niaouli (Melaleuca quinquenervia (Cav.)
S. T. Blake)
Addition of cajeput oil (Melaleuca leucadendra L.) HPTLC (Presence of violet double zone (Rf =0.23, Rf =0.25)) [104]
Addition of furanone GC-MS (Furanone, 2-n-hexyl-5-methyl-3(2H)furanone) [41]
Onion (Allium cepa L.) Addition of turpentine oil in cold-pressed oil, or in flower oil UV spectrophotometry (Maximum absorption) [20]
Orange (Citrus sinensis Osbeck) Addition of cottonseed in cold-pressed oil, or in flower oil UV spectrophotometry (Maximum absorption) [20]
Addition of gurjum balsam GC-MS (The abnormal presence of α-gurjunene and alloaromadendrene) [16]
Patchouli (Pogostemon cablin Benth.). Addition of Mentha arvensis L. essential oil Enantioselective-GC (If level of (-)-isopulegol is around 1.2 to 2.0% it’s
indicative of M. arvensis L., average of M. piperita L. is 0.7%)
[24,41]
Peppermint (Mentha X piperita L.) Addition of racemic menthyl acetate Enantioselective-GC ((-)-menthyl acetate present at ~2–8%. Adulteration if
(+)-menthyl acetate) present
[24]
Addition of mineral oil Physical, and chemical techniques (Turbidity when oil is added to 60–80%
ethanolic solution)
[41]
Addition of fraction Enantio-MDGC ((1S)-(-)-borneol of high enantiomeric purity (>90%) is a
reliable indicator of genuine of rosemary oils)
[29,41]
Addition of synthetic borneol Enantio-MDGC ((1S)-(-)-borneol of high enantiomeric purity (>90%) is a
reliable indicator of genuine of rosemary oils)
[29]
Rosemary (Rosmarinus officinalis L.) Addition of synthetic linalool ESI-MS, or HRGC-P-IRMS (Linalool) [55,105]
Rosewood (Aniba rosaeodora Ducke) Addition of synthetic Sandalore GC-MS (Presence of Sandalore) [52]
Sandalwood (Santalum album L.) Addition of castor oil or cedarwood oil GC-MS, GC-FID (Specification content of compounds) [52]
Addition of Verdox, Santaliff, Vertofix Coeur, Ebanol MDGC–qMS/FID (Presence of Verdox, Santaliff, Vertofix Coeur, Ebanol) [53]
Addition of polyethylene glycol TLC (Polyethylene glycol) [32]
Addition of anethole 2H NMR spectrometry (Anethole) [41,106]
Addition of ajwain seeds oil (Trachyspermum amni L. GC-IRMS (δ13H of thymol) [39]
Star anise (Illicium verum L.) Addition of linalool HRGC-P-IRMS (Linalool) [55]
Thyme (Thymus vulgaris L.) Addition of vegetal oil HPTLC (Presence of zone (Rf =0.69)) [72]
155T.K.T. Do et al./Trends in Analytical Chemistry 66 (2015) 146–157
Acknowledgements
The authors are grateful to Elise Carenini (Albert Vieille, Vallau-
ris, France) and Jean-Philippe Paris (Payan Bertrand, Grasse, France)
for their relevant suggestions. TKTD is grateful to ANRT for a doc-
toral fellowship. This project was supported by the University Nice
Sophia Antipolis and the CNRS.
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... General quality and authenticity issues are addressed in a plethora of monographs, commercial standards, official guidelines or recommendations for production, and specific regulations for application areas. Except for regulatory authorities, national bodies, international trade standard organizations, pharmacopoeias, industry and consumer associations all over the world cooperate to ensure quality and outline specifications for uses [30][31][32]. Given the increased commercial interest for potential applications of EOs, it is of high priority to tackle issues related to the authentication of the botanical and geographical origin of herbs/spices and their products [31]. ...
... Currently, the EO market and e-commerce suffer from illegal practices such as mislabeling and adulteration. Partial substitution by (a) vegetable oils/carriers, alcohols (ethanol), synthetic oils, mineral oils, and (in some cases) water, used as diluents; (b) cheaper EOs from the same species but different geographical origin; (c) cheaper EOs extracted from another organ/part of the plant; (d) cheaper EOs from closely related species; (e) alcohols with high b.p. and (f) pure natural or (semi) synthetic compounds are some of the known fraudulent practices [30,33,34]. Evaluation of the botanical origin of the EOs (species and plant part) is of fundamental importance for their integrity studies and may attract the interest of researchers from plant biology, food, and pharmaceutical fields, which is not usually emphasized in the studies for bay laurel EOs [15]. ...
... Quality, especially the certification of EO authenticity, must be ensured through reliable objective methods of analysis. Many reviews and book chapters update the most widely applied quality assessment methods as well as recent analytical advancements [30,[35][36][37][38]. ...
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Essential oils (EOs) find application as flavoring agents in the food industry and are also desirable ingredients as they possess preservative properties. The Mediterranean diet involves the use of a lot of herbs and spices and their products (infusions, EOs) as condiments and for the preservation of foods. Application of EOs has the advantage of homogeneous dispersion in comparison with dry leaf use in small pieces or powder. Among them, Laurus nobilis (bay laurel) L. EO is an interesting source of volatiles, such as 1,8-cineole and eugenol, which are known for their preservative properties. Its flavor suits cooked red meat, poultry, and fish, as well as vegetarian dishes, according to Mediterranean recipes. The review is focused on its chemistry, quality control aspects, and recent trends in methods of analysis and activity assessment with a focus on potential antioxidant activity and applications to olive industry products. Findings indicate that this EO is not extensively studied in comparison with those from other Mediterranean plants, such as oregano EO. More work is needed to establish authenticity and activity methods, whereas the interest for using it for the preparation of flavored olive oil or for the aromatization and preservation of table oils must be further encouraged.
... A summary of the enantiomeric ratios of citrus essential oils has been provided by Do et al. [89]. If the requirement for enantiomeric purity is that one enantiomer is >94% of the other, then by comparison with α-pinene, the components β-pinene and limonene are more often enantiopure. ...
... A comprehensive review published in 2015 provided a significant summary of adulteration tactics that commonly occur in the industry for essential oils [89]. What is conveyed is that there is no detailed protocol to follow that is generic for all the kinds of adulteration. ...
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The current text provides a comprehensive introduction to essential oils, their biosynthesis, naming, analysis, and chemistry. Importantly, this text quickly brings the reader up to a level of competence in the authentication of essential oils and their components. It gives detailed descriptions of enantiomers and other forms of stereoisomers relevant to the study of natural volatiles and essential oils. The text also describes GC-MS work and provides tips on rapid calculation of arithmetic indices, how to interpret suggested names from the NIST mass spectral library, and what additional efforts are required to validate essential oils and defeat sophisticated adulteration tactics. In brief, essential oils are mixtures of volatile organic compounds that were driven out of the raw plant material in distillation, condensed into an oil that is strongly aroma emitting, and collected in a vessel as the top layer (uncommonly bottom layer) of two phase separated liquids: oil and water. Essential oils commonly include components derived from two biosynthetic groups, being terpenes (monoterpenes, sesquiterpenes and their derivatives) and phenylpropanoids (aromatic ring with a propene tail). The current text provides details of how terpenes and phenylpropanoids are further categorised according to their parent skeleton, then recognised by the character of oxidation, which may be from oxygen, nitrogen, or sulphur, or the presence/absence of a double bond. The essential oil’s science niche is an epicentre of individuals from diverse backgrounds, such as aromatherapy, pharmacy, synthetic and analytical chemistry, or the hobbyist. To make the science more accessible to the curious student or researcher, it was necessary to write this fundamentals-level introduction to the chemistry of essential oils (i.e., organic chemistry in the context of essential oils), which is herein presented as a comprehensive and accessible overview. Lastly, the current review constitutes the only resource that highlights common errors and explains in simplistic detail how to correctly interpret GC-MS data then accurately present the respective chemical information to the wider scientific audience. Therefore, detailed study of the contents herein will equip the individual with prerequisite knowledge necessary to effectively analyse an essential oil and make qualified judgement on its authenticity.
... Chapitre 1 : Etude Bibliographique 36 (Do et al., 2015). Les évaluations sensorielles, et les analyses physico-chimiques, permettent le contrôle rapide de la qualité des huiles essentielles. ...
... Cependant, comme montré dans le chapitre 2 avec l'exemple du salicylate de méthyle, et identifié par Culp sur le benzaldéhyde (Culp and Noakes, 1990), un marquage de la molécule de synthèse rend inefficace la mesure de l'activité du 14 C. Des méthodes isotopiques par GC-P-IRMS δ 2 H sont applicables pour mettre en évidence les ajouts de synthèse sur le benzaldéhyde (Ruff et al., 2000) et le (E)-cinnamaldéhyde (Sewenig et al., 2003), ainsi que la SNIF-RMN (G. . La synthèse du (E)-cinnamaldéhyde, à partir de benzaldéhyde, produit une impureté résiduelle, le 5-phénylpenta-2,4-diénal (Do et al., 2015), qui est identifiable par GC, si le produit n'a pas été suffisamment purifié. ...
Thesis
Les matières naturelles aromatiques, telles que les huiles essentielles, que l’on retrouve sur le marché, ne sont pas toujours authentiques, bien que ces produits soient vendus comme étant 100% purs et naturels. Certains fournisseurs fraudent leurs produits afin de réduire les coûts de production, d’améliorer la qualité des huiles essentielles ou encore pour augmenter artificiellement les volumes de production. Les huiles essentielles sont adultérées en ajoutant des produits à moindre coût, incluant des matières naturelles moins chères et des molécules d’origine pétrochimique. Des méthodes d’authentification appropriées sont nécessaires pour contrôler la naturalité et la pureté des huiles essentielles. La détermination des ratios isotopiques stables et l’analyse énantiosélective de composés spécifiques, associées à la recherche de traces de précurseurs de synthèses, permettent d’authentifier de nombreuses huiles essentielles (gaulthérie, alliacées, néroli, menthe crépue, cannelle et cypriol). Le contrôle de ces produits naturels requiert l’établissement de banques de données, constituées d’échantillons parfaitement tracés pour l’authenticité de leurs origines. La méthodologie mise en place a permis de développer de nouveaux outils pertinents pour l’authentification, comprenant le développement de l’analyse isotopique de composés ciblés pour la mesure du δ18O et du δ34S, et d’identifier de nouvelles fraudes, comprenant les ajouts de composés enrichis en 14C et les molécules issues d’hémisynthèses.
... Ensuring the correct enantiomer ratios not only confirms identity, but also other important consumer-desired traits such as aroma or health benefits. Relative area percentages from gas chromatography (GC) separation have traditionally Symmetry 2022, 14, 917 2 of 10 been used to confirm the chiral specifications of terpenes in essential oils [8,9]. However, these chiral GC methods have various limitations, such as time, complexity, and the need for standards for ongoing retention time confirmation when it comes to verifying the chirality of constituents in these complex essential oil mixtures. ...
Article
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The chiral analysis of terpenes in complex mixtures of essential oils, necessary for authentication, has been further developed using chiral tagging molecular rotational resonance (MRR) spectroscopy. One analyte that is of particular interest is linalool (3,7-dimethyl-1,6-octadien-3-ol), a common natural chiral terpene found in botanicals with its enantiomers having unique flavor, fragrance, and aromatherapy characteristics. In this MRR demonstration, resolution of the enantiomers is achieved through the addition of a chiral tag, which creates non-covalent diastereomeric complexes with distinct spectral signatures. The relative stereochemistry of the complexes is identified by the comparison of calculated spectroscopic parameters with experimentally determined parameters of the chiral complexes with high accuracy. The diastereomeric complex intensities are analyzed to determine the absolute configuration (AC) and enantiomeric excess (EE) in each sample. Here, we demonstrate the use of chiral tagging MRR spectroscopy to perform a quantitative routine enantiomer analysis of linalool in complex essential oil mixtures, without the need for reference samples or chromatographic separation.
... Refractive index was measured in ATAGO refractometer system at 20 • C (Do et al., 2015). An average value of five consecutive readings was reported for both the chemotypes (Table 1). ...
Article
Ocimum basilicum L., is most popular fragrant herb renowned for its immense application. However, a plethora of studies revealed terpenoids and phenylpropanoids as marker chemicals with known identities. We herein report two unique chemotypes developed in CSIR-CIMAP for their compositional variability and biological activities. Essential oils obtained from aerial parts of both the chemotypes were analyzed in capillary gas chromatography and mass spectrometry systems on 5% diphenyl- and cyclodextrin coated fused silica columns. The statistical analysis was carried out to validate the phytochemical data of consecutive years and also to calculate the variability. The phenylpropanoids dominated the volatile fractions of chemotype II (72.5–77.5%) in comparison to chemotype I (29.8–40.0%) essential oil. In the contrary, sesquiterpenoids (16.4–17.4%) and monoterpenoids (33.5–43.9%) contributed oil composition of chemotype I in diverse proportions. The presence of single images of R-(+)-camphor and R-(-)-linalool were established in both the oils analyzed on a ethyl substituted cyclodextrin-based column. Essential oils were tested for biological activities against C. albicans, S. aureus, and E. coli. meta-Eugenol, the marker compound isolated from chemotype I showed best inhibition against C. albicans. In conclusion, meta-eugenol-rich chemotype I with high essential oil yield (0.1–0.8%) was identified as an alternative source for meta-eugenol.
... Wintergreen oil is easily adulterated by adding synthetic methyl salicylate [9], which is detected by the presence of synthetic markers [10], but apart from synthetic markers, enantiomeric ratio determination is a powerful tool in authenticity establishment, especially when the enantiomeric forms are unchanged by the extraction processes and the acid index [8]. To the best of our knowledge, this is the first analysis of the enantiomeric distribution of chiral compounds present in wintergreen essential oils. ...
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A comparative analysis of Gaultheria fragrantissima (Ericaceae) essential oils based on geographical location, distillation time, and varying distillation conditions was carried out, and their compositions were evaluated by gas chromatography–mass spectrometry (GC–MS), chiral GC–MS, and gas chromatography–flame ionization detection (GC–FID). In addition, each of seven commercial wintergreen essential oil samples from Nepal and China were analyzed. The highest extraction yield was 1.48% and the maximum number of compounds identified in natural wintergreen oil was twenty-two. Based on distillation time, the maximum numbers of identified compounds are present in 120 min. Linalool, phenol, vetispirane, and ethyl salicylate were present in commercial wintergreen oils both from Nepal and China. The presence of compounds such as elsholtzia ketone and β�dehydroelsholtzia ketone in the China samples represented a significant difference in wintergreen oil between the two geographical sources. Dimethyl 2-hydroxyterephthalate is a well-known synthetic marker for wintergreen oil when synthesis is carried out using salicylic acid, but the synthetic marker was absent while using acetylsalicylic acid as a precursor during synthesis. Adulteration analysis of wintergreen oil showed an increase in the concentration of dimethyl 2-hydroxyterephthalate, whereas the concentrations of minor components decreased and methyl salicylate remained unchanged. To the best of our knowledge, this is the first report of the enantioselective analysis of wintergreen essential oil. Furthermore, three samples showed notable antibacterial activity against Staphylococcus epidermidis, with an MIC value of 156.3 µg/mL. Similarly, one sample showed effectiveness against Aspergillus niger (MIC = 78.1 µg/mL). Keywords: adulteration; dimethyl 2-hydroxyterephthalate; enantiomeric ratio; synthetic marker; Gaultheria
Article
Chiral analysis is central for scientific advancement in the fields of chemistry, biology, and medicine. It is also indispensable in the development and quality control of chiral compounds in the chemical and pharmaceutical industries. Here, we present the concept of absolute optical chiral analysis, as enabled by cavity-enhanced polarimetry, which allows for accurate unambiguous enantiomeric characterization and enantiomeric excess determination of chiral compounds within complex mixtures at trace levels, without the need for calibration, even in the gas phase. Our approach and technology enable the absolute postchromatographic chiral analysis of complex gaseous mixtures, the rapid quality control of complex mixtures containing chiral volatile compounds, and the online in situ observation of chiral volatile emissions from a plant under stress.
Article
Recent times have witnessed an upsurge of interest in hemp and hemp-derived products, as driven by the scientific findings specific to the pharmacological properties of Cannabis sativa L. and its constituents. There has been evidence that the terpene profile, along with the cannabinoid content, produces in humans the effects associated with different strains, beyond fragrance perception. A great deal of effort has been put into developing analytical approaches to strengthen the scientific knowledge on cannabis essential oil composition and provide effective tools for ascertaining the authenticity of commercial cannabis samples. For this concern, enantio-selective-GC-C-IRMS has proven to be effective for assessing the ranges characteristic of the genuine samples and detecting any fraudulent additions. This research aimed at providing for the first time the enantiomeric and isotopic ratios of target terpenes in cannabis essential oils, obtained from microwave-assisted hydro-distillation from the fresh and dried inflorescences of different cannabis varieties. Implementing multidimensional gas chromatography separation was mandatory prior to detection, in order to obtain accurate δ13C values and enantiomeric data from completely separated peaks. For this purpose, a heart-cut method was developed, based on the coupling of an apolar first dimension column to a secondary chiral cyclodextrin-based stationary phase. Afterwards, the data gathered from enantio-selective-MDGC-C-IRMS/qMS analysis of a set of genuine samples were used to evaluate the quality of nineteen commercial cannabis essential oils purchased from local stores. Remarkably, the data in some cases evidenced enantiomeric ratios and δ13C values outside the typical ranges of genuine oils. Such findings suggest the usefulness of the method developed to ascertain the genuineness and quality of cannabis essential oils.
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Essential oils (EOs) have a long tradition of use in the medical and cosmetic fields based on their versatile properties, including fungicidal, antiparasitic, and bactericidal effects. Nowadays, with the development of industry and electronics, EOs are increasingly being used in the agricultural and food industries; health industries, including pharmacy and dental medicine; and as cosmetic enhancements. The purpose of this study is to develop a compact and portable platform for the detection of EO type and the concentration levels using knitted silver threads. The method is based on measuring the variation in values of the electrical parameters of the silver threads using electrochemical impedance spectroscopy (EIS). The impedance of the solutions applied on the testing platform was measured in the frequency range from 1 Hz to 200 kHz. The platform was tested using three types of essential oils: tea tree; clary sage; and cinnamon bark oil. Increasing the concentration of essential oils resulted in increasing the electrical resistance of the platform, decreasing the capacitance, and consequently increasing the impedance. The proposed cost-effective platform can be used for the fast determination of the type and quality of essential oils.
Chapter
Nowadays, people all over the world are highly focused not only on health but also on beauty and looks. The obsession with looking younger is not confined to the older generation. It has been noticed that people in the age group of 25–40 are progressively using antiaging cosmetics to look youthful. This is the reason that the market is flooded with antiaging cosmetics claiming magical outcomes with a short-term application. Due to increased public awareness and demand for natural ingredients, the use of synthetic cosmetic ingredients is declining, and a large number of people prefer natural cosmetic ingredients. In cosmetics, essential oils (EOs) already play an important role as fragrance ingredients, but in recent years there has been an increased interest in the biological activities of EOs. However, because of the volatile nature of EOs, their cosmetic benefits are not entirely utilized. To protect the stability and to deliver the EO to the desired site to get maximum benefits, cosmetic manufacturers have been focusing on innovation and raising the efficiency of antiaging cosmetics. One of the possibilities for maintaining the stability and efficacy and increasing the penetration of EOs is the use of lipid vesicles. Lipid vesicles encapsulating EOs are promising carriers that can increase the antiaging potential of the EO to combat skin aging.
A gas chromatographic procedure was developed for identifying and detecting adulteration of several perfumery products from the bitter orange tree. Components present to the extent of about 1% or more were determined quantitatively in reference and commercial samples of petitgrain oil, petitgrain absolute from water, neroli oil, orange flower absolute from water, and orange flower absolute. About 20 major components were common to these materials. These compounds were identified by mass spectrometric analysis following chromatographic separation and included β-pinene, limonene, γ-terpinene, linalool oxide, linalool, linalylacetate, α-terpineol, neryl acetate, geranyl acetate, nerol, geraniol, phenethyl alcohol, benzyl cyanide, nerolidol, methyl anthranilate, farnesol, and indole.
Book
Today, flavor chemists can generate copious amounts of data in a short time with relatively little effort using automated solid phase micro-extraction, Gerstel-Twister® and other extraction techniques in combination with gas chromatographic (GC) analysis. However, more data does not necessarily mean better understanding. In fact, the ability to extract, isolate, and concentrate potential flavor-important chemicals from complex food systems has surpassed the ability to understand how the chemical data relates to flavor. Sensory-Directed Flavor Analysis helps chemists unlock the flavor secrets that may be hiding in their chromatograms by translating cold hard numbers into a better understanding of the sense of smell and taste. The author integrates the two disciplines of sensory science and analytical chemistry, encouraging sensory scientists to incorporate more analytical data while encouraging analytical chemists to include more sensory techniques. Using more ancillary techniques helps each discipline elucidate how various chemical constituents influence food flavor and appeal. The book discusses important enabling technologies and analytical methods including GC-olfactometry (GC-O), combination GC-O and multi-dimensional GC, the application of odor activity values (OAVs), and recombination studies, as well as solid-phase dynamic extraction and preseparation techniques. A broad array of applications, in addition to dozens of tables, graphs, gas chromatograms, and pictures, are included throughout the book. Highlighting the advantages and disadvantages and the appropriate circumstances for each method of analysis, Sensory-Directed Flavor Analysis offers flavor scientists an essential reference to deepen their understanding of the function of chemicals on the perception of taste.
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Commercially used for food flavorings, toiletry products, cosmetics, and perfumes, among others, citrus essential oil has recently been applied physiologically, like for chemoprevention against cancer and in aromatherapy. Citrus Essential Oils: Flavor and Fragrance presents an overview of citrus essential oils, covering the basics, methodology, and applications involved in recent topics of citrus essential oils research. The concepts, analytical methods, and properties of these oils are described and the chapters detail techniques for oil extraction, compositional analysis, functional properties, and industrial uses. This book is an unparalleled resource for food and flavor scientists and chemists.
Chapter
Quand les huiles essentielles nous livrent leurs secrets… Les huiles essentielles sont aujourd’hui omniprésentes dans des domaines aussi divers que la parfumerie, les cosmétiques, l’agro-alimentaire ou la recherche pharmaceutique. Un état des lieux s’imposait. À l’initiative de Xavier Fernandez et de Farid Chemat, chimistes, biologistes et biochimistes nous livrent ici un panorama complet de la recherche dans ce secteur et analysent en détail ses différents aspects scientifiques : • Biologie et chimie des huiles essentielles • Techniques d’extraction : entre innovation et tradition • Analyse chimique des huiles essentielles : vers une qualité et une traçabilité • Les applications des huiles essentielles Un livre de référence indispensable aux amateurs, étudiants et professionnels qui utilisent ou travaillent avec les huiles essentielles.
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an extensive review of the literature pertaining to seagrass was accomplished through a search of published literature and unpublished documents up to mid 1977. Braod scientific subject areas that relate to seagrass such as anatomy, ecology, morphology, taxonomy, and physiology were considered together with more specific factors such as substrate selectivity, water quality, productivity, colonization, effect of physical energy (waves, tidal currents, sediments transport), propagation, and tolerance to disturbance. The bibliography is divided into two main reference sections consisting of a bibliographic citations section and a keyword index section. Also, two supplementary reference sections cons isting of an author index section and a source index section appear as appendices in microfiche form. (A)