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Chemistry of Flavours and
Modern flavours and fragrances are complex formulated products, containing
blends of aroma compounds with auxiliary materials, enabling desirable flavours or
fragrances to be added to a huge range of products. From the identification and synthesis
of materials such as cinnamaldehyde and vanillin in the 19th Century to the current
application of advanced analytical techniques for identification of trace aroma compounds
present in natural materials, the flavour and fragrance industry has developed as a key
part of the worldwide specialty chemicals industry.
“The earliest recognizable chemists were women, the perfume-makers of Babylon,
who used the earliest known stills to produce their wares. The first individual
chemist known to history was “Tapputi, the perfume-maker”, who was mentioned
on a cuneiform tablet from the second millennium BCE in Mesopotamia”~ Paul
Strathern, Mendeleev’s Dream
Ancient people realized that there is a pleasure in the aroma of a flower.
People in the area of Indus, Nile and Tigris used herbs and spices for rituals.
The Classical world of Greece and Rome built knowledge of spices, herbs, oils, and
developed the process of distillation.
Since perfumes were still a very expensive product, until the 19th century they
were used mostly by the wealthiest groups of society.
After WWII the fragrance industry developed greatly with the production of
synthetic aromas. These new synthesis increased the variety of scents available
and decreased the cost of production, since obtaining odorants from natural
sources involves very expensive process.
After 1960 the economies of US, Western Europe, and Japan experienced upward
development. Accumulation of disposable income stimulated customer purchases.
Now more people could afford luxuries like perfumes. Consequently, perfumes
became a personal care product and a common present for family holidays.
Otto Wallach – Nobel Prize in Chemistry 1910
Helps elucidate many of the C10H16 group terpene structures
present in essential oils utilizing common reagents such as hydrogen
chloride and hydrogen bromide.
Leopold Ruzicka – Nobel Prize in Chemistry 1939
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Chemistry of Flavours and
In the perfumery and sesquiterpene domain- the total
syntheses of nerolidol and farnesol.
From Jasmine- established the structure of jasmine.
Elucidated the structures of the naturally occurring musk
perfumes, civetone and muscone thus replacing scents prized since
antiquity- but only available from endangered species
RyojiNoyori – Nobel Prize in Chemistry 2001
For chirally catalysed hydrogenation reactions.
In perfumery and flavors – the chiral (asymmetric) synthesis
menthol and many other fragrance and flavour compounds.
In the chiral synthesis of pharmaceutical and photochromic
Flavours are more or less volatile substances produced by fruit or vegetables
during different stages of ripening or during manipulation. In particular, ripening is the
main process through which fruit flavours are produced, while manipulation (like cutting
or chewing) is the main cause of vegetable flavours generation. In this paragraph,
chemical aspects will be illustrated, along with the mechanism of their generation. An
overlook of artificial flavorings will also be given.
A natural flavour is a combination of naturally derived aroma chemicals and/or essential
oils. Natural flavours are very often added to food stuff to enhance the taste of products
while avoiding the consistency problems involved with using fruit or other whole flavouring
ingredient. Furthermore, adding whole flavouring ingredients like fruit can be extremely
costly and is limited by its seasonal availability. All food containing added natural flavours
must carry the label declaration “natural flavour/aroma” among the ingredients.
Fruit flavorings are mainly generated during ripening process and are produced by
secondary metabolism and by the catabolism of small quantities of carbohydrates, lipids,
and amino acids. Also vegetables flavors are produced essentially by catabolic process but
most of these are not due to ripening rather manipulation.
Flavor—encompassing both aroma and taste—provides the defining characteristic of how
we experience food. Flavor has long been an enigma to scientists: Aristotle described two
categories of taste, sweet and bitter. Today we recognize five basic tastes in food:
sweetness, saltiness, sourness, bitterness and umami (savoury).
Sweetness is found in many types of molecules (not sugars), and relative
sweetness is normally compared to sucrose
 Natural sugars- sucrose(1.0), glucose(0.76), fructrose(1.52)
 Artificial sweeteners- sodium cyclamate(30); acesulpham K (140);
aspartame (200); saccharin (350); 1-n-propoxy-2-amino-4-nitrobenzene
Sourness is assumed to be linked in acidic solution however the presence of
unionized organic acids (i.e. RCO2H)is more important for the taste of sourness –
citric, malic, tartaric (grape), isocitric, oxalic, acetic, lactic
ChE 310 Industrial Chemistry
Chemistry of Flavours and
 In food: sourness of vinegar due to acetic acid, but also adds importantly
to aroma, such as with fish and chips
 Lactic acid in pickled foods such as sauerkraut comes from bacterial
fermentation of the sugars in the vegetables
 Sodium lactate is used in salt and vinegar flavored crisps
Bitterness is exhibited through several classes of compounds.
 KBr is both salty and bitter – halide salts with sum of their ionic diameters
greater than KBr are bitter, if the sum is less than they are salty.
 Many plants contain molecules we can perceive as very bitter. – nicotine,
atropine, emetine, quinine
 Role in plants is unknown but many have undesired pharmacological
properties like physostygmine (eserine)
 Animal’s ability to perceive these have undoubtedly evolved to avoid eating
these plants. – Quinine antiplasmodial agent is used to prevent and cure
malaria by consumption of tonic waters.
Umami is a Japanese word for “delicious taste,” umami is produced by certain
amino acids. It’s best described as “savory”—a taste rich in flavor released by
cooking, curing or aging.
 People taste umami through receptors for glutamate, commonly found in
its salt form as the food additive monosodium glutamate (MSG).
 Umami has a mild but lasting aftertaste that is difficult to describe. It
induces salivation and a sensation of furriness on the tongue, stimulating
the throat, the roof and the back of the mouth.
Saltiness is a taste produced primarily by the presence of sodium ions. Other ions
of the alkali metals group also taste salty, but the further from sodium, the less
salty the sensation is.
 In moderation, salty taste improves the flavor of food, improves digestion,
lubricates tissues, liquefies mucous, maintains mineral balance, aids in the
elimination of wastes, and calms the nerves. Due to its tendency to attract
water, it also improves the radiance of the skin and promotes overall
growth in the body.
The flavor creation is done by a specially trained scientist called a "flavorist". The
flavorist's job combines extensive scientific knowledge of the chemical palette with artistic
creativity to develop new and distinctive flavors. The flavor creation begins when the
flavorist receives a brief from the client. In the brief the client will attempt to communicate
exactly what type of flavor they seek, in what application it will be used, and any special
requirements (e.g., must be all natural). The communication barrier can be quite difficult
to overcome since most people aren't experienced at describing flavors. The flavorist will
use his or her knowledge of the available chemical ingredients to create a formula and
compound it on an electronic balance. The flavor will then be submitted to the client for
testing. Several iterations, with feedback from the client, may be needed before the right
flavor is found.
An aroma compound, also known as odorant, aroma, fragrance, or flavor, is
a chemical compound that has a smell or odour. A chemical compound has a smell or odor
ChE 310 Industrial Chemistry
Chemistry of Flavours and
when it is sufficiently volatile to be transported to the olfactory system in the upper part
of the nose.
fragrant essential
oils or
compounds, fixatives and solvents used to give the human body, animals, food, objects,
and living spaces "a pleasant scent. It is is defined as any mixture of pleasantly odorous
incorporated in suitable vehicle.
Vehicles or solvents- the majority of the perfume is ethanol that has been prefixed
for a long time (from months to years) using mentioned fixatives. It usually
consists about 60 to 95% of the perfume but most frequently around 85-90% of
the overall volume of product.
Fixatives- used to equalize the vapour pressures, and thus the volatilities, of the
raw materials in perfume oil, as well as to increase the tenacity.
Natural fixatives are resinoids (benzoin, labdanum, myrrh, olibanum, storax, tolu
balsam) and animal products (ambergris, castoreum, musk, and civet). Synthetic
(diphenylmethane, cyclopentadecanolide, ambroxide, benzyl
virtually odourless solvents with very low vapour pressures (benzyl
benzoate,diethyl phthalate, triethyl citrate).
Odoriferous elements- this usually includes several oils but has one or more of oils
of higher concentrations than the others. These give the perfume its scent and
distinguish it from other perfumes. The concentration of fragrance oil is as stated
earlier (2-40%), but most frequently around 10% of the overall volume of
Fragrances can be classified into several olfactive families, by the themes, or accords,
of these fragrances:
 Floral: Fragrances that are dominated by the scent of one or more types of
flowers. When only one flower is used, it is called a soliflore (as
in Dior's Diorissimo, with jasmine).
 Chypre:
of bergamot, oakmoss and labdanum. This family of fragrances is named after a
perfume by François Coty by the same name. Meaning “Cyprus” in French, the
term alludes to where this base was inspired. This fragrance family is characterized
by a scent reminiscent of apricot and custard.
 Aldehydic: Fragrances that incorporate the family of chemicals known as
aldehydes. Chanel No 5 was the first aldehydic perfume (created by the royal
Russian perfumer Ernest Beaux in 1921). Others include Je Reviens and Arpege.
Aldehydic perfumes have the characteristic "piquant" note produced by materials
like Aldehyde C12 MNA.
 Fougère: Fragrances built on a base of lavender, coumarin and oakmoss. Many
men's fragrances belong to this family of fragrances, which is characterized by its
sharp herbaceous and woody scent.
 Leather: A family of fragrances which features the scents honey, tobacco, wood,
and wood tars in its middle or base notes and a scent that alludes to leather.
ChE 310 Industrial Chemistry
Chemistry of Flavours and
Woody: Fragrances that are dominated by the woody scents, typically of
sandalwood and cedar. Patchouli, with its camphoraceous smell, is commonly
found in these perfumes.
Orientals or ambers: A large fragrance class featuring the scents of vanilla and
animal scents together with flowers and woods. Can be enhanced by camphorous
oils and incense resins, which bring to mind Victorian era imagery of the Middle
East and Far East.
Citrus: An old fragrance family that until recently consisted mainly of "freshening"
Eau de colognes due to the low tenacity of citrus scents. Development of newer
fragrance compounds has allowed for the creation of primarily citrus fragrances.
Perfumes oils, or the "juice" of a perfume composition, are diluted with a suitable
solvent to make the perfume more usable. This is done because undiluted oils (natural or
synthetic) contain high concentrations of volatile components that will likely result in
allergic reactions and possibly injury when applied directly to skin or clothing.
Although dilutions of the perfume oil can be done using solvents such as jojoba,
fractionated coconut oil, and wax, the most common solvents for perfume oil dilution
is ethanol or a mixture of ethanol and water. The percent of perfume oil by volume in a
perfume is listed as follows:
Perfume extract: 20%-40% aromatic compounds
Eau de parfum: 10-30% aromatic compounds
Eau de toilette: 5-20% aromatic compounds
Eau de cologne: 2-3% aromatic compounds
As the percentage of aromatic compounds decreases, the intensity and longevity
of the scent decrease. It should be noted that different perfumeries or perfume houses
assign different amounts of oils to each of their perfumes. As such, although the oil
concentration of a perfume in eau de parfum (EDP) dilution will necessarily be higher than
the same perfume in eau de toilette (EDT) form, the same trends may not necessarily
apply to different perfume compositions much less across different perfume houses.
To complicate matters more, some fragrances with the same product name but
having a different concentration name may not only different in their dillutions, but
actually use different perfume oil mixtures altogether. For instance, in order to make the
EDT version of a fragrance brighter and fresher then its EDP, the EDT oil may be
"tweaked" to contain slightly more top notes or less base notes. In some cases, words
such as "extrême" or "concentrée" appended to frangrance names might indicate
completely different frangrances that relates only because of a similar perfume accord.
An instance of this would be Chanel‘s Pour Monsieur and Pour Monsieur Concentrée.
Plant sources
Plants have long been used in perfumery as a source of essential oils and aroma
compounds. These aromatics are usually secondary metabolites produced by plants as
protection against herbivores, infections, as well as to attract pollinators. Plants are by far
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Chemistry of Flavours and
the largest source of fragrant compounds used in perfumery. The sources of these
compounds may be derived from various parts of a plant. A plant can offer more than one
source of aromatics, for instance the aerial portions and seeds of coriander have
remarkably different odors from each other. Orange leaves, blossoms, and fruit zest are
the respective sources ofpetit grain, neroli, and orange oils.
 Flowers and Blossoms: Undoubtedly the largest source of aromatics. Includes
of rose and jasmine,
as osmanthus, mimosa, tuberose, as well as the blossoms of citrus and ylangylang trees. Although not traditionally thought of as a flower, the unopened flower
buds of the clove are also commonly used. Orchid flowers are not commercially
used to produce essential oils or absolutes.
 Leaves and Twigs:
are lavender leaf, patchouli, sage, violets, rosemary,
and citrus leaves.
Sometimes leaves are valued for the "green" smell they bring to perfumes,
examples of this include hay and tomato leaf.
 Roots, rhizomes and bulbs: Commonly used terrestrial portions in perfumery
include iris rhizomes, vetiver roots, various rhizomes of the ginger family.
 Seeds:
include tonka
bean, coriander, caraway, cocoa, nutmeg, mace, cardamom, and anise.
 Fruits: Fresh fruits such as apples, strawberries, cherries unfortunately do not
yield the expected odors when extracted; if such fragrance notes are found in a
perfume, they are synthetic. Notable exceptions include litseacubeba, vanilla,
and juniper berry. The most commonly used fruits yield their aromatics from the
rind; they include citrus such as oranges, lemons, limes, and grapefruit.
 Woods: Highly important in providing the base notes to a perfume, wood oils and
distillates are indispensable in perfumery. Commonly used woods
include sandalwood, rosewood, agarwood,birch, cedar, juniper, and pine.
 Bark: Commonly used barks includes cinnamon and cascarilla. The fragrant oil
in sassafras root bark is also used either directly or purified for its main
constituent, safrole, which is used in the synthesis of other fragrant compounds
such as helional.
 Resins: Valued since antiquity, resins have been widely used
in incense and perfumery. Highly fragrant and antiseptic resins and resincontaining perfumes have been used by many cultures as medicines for a large
include labdanum, frankincense/olibanum, myrrh, Peru
balsam, gum
benzoin. Pine and fir resins are a particularly valued source of terpenes used in
the organic synthesis of many other synthetic or naturally occurring aromatic
compounds. Some of what is called amber and copal in perfumery today is the
resinous secretion of fossil conifers.
 Lichens: Commonly used lichen includes oakmoss and treemoss thalli.
Animal sources
 Musk: Originally derived from the musk sacs from the Asian musk deer, it has now
been replaced by the use of synthetic musks due to its price and ethical issues.
 Civet: Also called Civet Musk, this is obtained from the odorous sacs of the civets,
animals in the family Viverridae, related to the Mongoose.
 Castoreum: Obtained from the odorous sacs of the North American beaver.
 Ambergris: Lumps of oxidized fatty compounds, whose precursors were secreted
and expelled by the Sperm Whale. Ambergris is commonly referred as "amber" in
perfumery and should not be confused with yellow amber, which is used in jewelry.
ChE 310 Industrial Chemistry
Chemistry of Flavours and
Honeycomb: Distilled from the honeycomb of the Honeybee.
Synthetic sources
Synthetic aromatics are created through organic synthesis from various chemical
compounds that are obtained from petroleum distillates, pine resins, or other relatively
cheap organic feedstock. Synthetics can provide fragrances which are not found in nature.
For instance, Calone, a compound of synthetic origin, imparts a fresh ozonous metallic
marine scent that is widely used in contemporary perfumes. Synthetic aromatics are often
used as an alternate source of compounds that are not easily obtained from natural
sources. For example, linalool and coumarin are both naturally occurring compounds that
can be cheaply synthesized from terpenes. Orchid scents (typically salicylates) are usually
not obtained directly from the plant itself but are instead synthetically created to match
the fragrant compounds found in various orchids.
Before perfumes can be composed, the odorants used in various perfume
compositions must first be obtained. Synthetic odorants are produced through organic
synthesis and purified. Odorants from natural sources require the use of various methods
to extract the aromatics from the raw materials. The results of the extraction are either
essential oils, absolutes, concretes, or butters, depending on the amount ofwaxes in the
extracted product.
All these techniques will to a certain extent, distort the odour of the aromatic
compounds obtained from the raw materials. This is due to the use of heat, harsh solvents,
or through exposure to oxygen in the extraction process which will denature the aromatic
compounds, which either change their odour character or renders them odourless.
 Maceration/Solvent extraction: The most used and economically important
technique for extracting aromatics in the modern perfume industry. Raw materials
are submerged in a solvent that can dissolve the desired aromatic
compounds. Maceration lasts anywhere from hours to months. Fragrant
compounds for woody and fibrous plant materials are often obtained in this matter
as are all aromatics from animal sources. The technique can also be used to extract
odorants that are too volatile for distillation or easily denatured by heat.
Commonly used solvents for maceration/solvent extraction include hexane,
and dimethyl ether. The product of this process is call a "concrete".
 Supercritical fluid extraction: A relatively new technique for extracting fragrant
compounds from a raw material, which often employ supercritical CO2. Due to the
low heat of process and the relatively unreactive solvent used in the extraction,
the fragrant compounds derived often closely resemble the original odour of the
raw material.
 Ethanol extraction: A type of solvent extraction used to extract fragrant
compounds directly from dry raw materials, as well as the impure oily compounds
materials resulting from solvent extraction or enfluerage. Ethanol extraction is not
used to extract fragraNce from fresh plant materials since these contain large
quantities of water, which will also be extracted into the ethanol.
 Distillation: A common technique for obtaining aromatic compounds from plants,
such as orange blossoms and roses. The raw material is heated and the fragrant
compounds are re-collected through condensation of the distilled vapour.
 Steam distillation: Steam from boiling water is passed through the raw material,
which drives out their volatile fragrant compounds. The condensate from
distillation are settled in aFlorentine flask. This allows for the easy separation of
the fragrant oils from the water. The water collected from the condensate, which
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Chemistry of Flavours and
retains some of the fragrant compounds and oils from the raw material is
called hydrosol and sometimes sold. This is most commonly used for fresh plant
materials such as flowers, leaves, and stems.
Dry/destructive distillation: The raw materials are directly heated in a still
without a carrier solvent such as water. Fragrant compounds that are released
from the raw material by the high heat often undergo anhydrous pyrolysis, which
results in the formation of different fragrant compounds, and thus different
fragrant notes. This method is used to obtain fragrant compounds from
fossil amber and fragrant woods where an intentional "burned" or "toasted" odour
is desired.
Expression: Raw material is squeezed or compressed and the oils are collected.
Of all raw materials, only the fragrant oils from the peels of fruits in the citrus
family are extracted in this manner since the oil is present in large enough
quantities as to make this extraction method economically feasible.
Enfleurage: Absorption of aroma materials into wax and then extracting the
odorous oil with alcohol. Extraction by enfleurage was commonly used
when distillation was not possible due to the fact that some fragrant
compounds denature through high heat. This technique is not commonly used in
the present day industry due to its prohibitive cost and the existence of more
efficient and effective extraction methods.
Wolfgang Sturm; Klaus Peters (2007), "Perfumes", Ullmann's Encyclopedia of Industrial
Chemistry (7th ed.), Wiley, pp. 2–3
"Perfume – Definition and More from the Free Merriam-Webster Dictionary". merriamwebster.com.
ChE 310 Industrial Chemistry
Chemistry of Flavours and
Flavor Chemistry Research at the USDA Western Regional Research Center
National Historic Chemical Landmark
Designated August 29, 2013, at the U.S. Department of Agriculture, Agricultural
Research Service, Western Regional Research Center in Albany, California.
ChE 310 Industrial Chemistry