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- Herausgeber: Wiley-VCH
- Kategorie: Fachliteratur
- Sprache: Englisch
This 6th edition is thoroughly revised and updated, and now additionally includes all commercially important flavor and fragrance materials that entered the market over the past 10 years.
In one handy and up-to-date source, this classic reference surveys those natural and synthetic materials that are commercially available, produced, and used on a relatively large scale, covering their properties, manufacturing methods employed, and areas of application.
For this new edition the chapter on essential oils has been completely revised with regard to production volumes, availability, and new product specifications, while new legal issues, such as REACH regulation aspects, are now included. Finally, the CAS registry numbers and physicochemical data of over 350 single substances and 100 essential oils have been updated and revised.
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Seitenzahl: 613
Veröffentlichungsjahr: 2016
Ähnliche
Table of Contents
Cover
Related Titles
Title Page
Copyright
Preface to the Sixth Edition
Preface to the Fifth Edition
Preface to the Fourth Edition
Preface to the Third Edition
Preface to the Second Edition
Preface to the First Edition
Chapter 1: Introduction
1.1 History
1.2 Definition
1.3 Physiological Importance
1.4 Natural, Nature-Identical, and Artificial Products
1.5 Sensory Properties and Chemical Structure
1.6 Volatility
1.7 Threshold Concentration
1.8 Sensory Properties
Chapter 2: Individual Fragrance and Flavor Materials
2.1 Aliphatic Compounds
2.2 Acyclic Terpenes
2.3 Cyclic Terpenes
2.4 Other Cycloaliphatic Compounds
2.5 Aromatic Compounds
2.6 Phenols and Phenol Derivatives
2.7
O-
,
O,S
- and
S,S
-Heterocycles
2.8
N
- and
N,S
-Heterocycles
Chapter 3: Natural Raw Materials in the Flavor and Fragrance Industry
3.1 Introduction
3.2 Isolation of Natural Fragrance and Flavor Concentrates
3.3 Survey of Natural Raw Materials
Chapter 4: Analytical Methods/Quality Control
Chapter 5: Safety Evaluation and Regulatory Aspects
5.1 Flavoring Substances
5.2 Fragrance Ingredients
References
Further Reading
Formula Index: CAS Registry Number Index
Subject Index
End User License Agreement
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Guide
Cover
Table of Contents
Preface to the Sixth Edition
Begin Reading
List of Tables
Chapter 3: Natural Raw Materials in the Flavor and Fragrance Industry
Table 3.1 Specifications for qualities of lemon oils of different origins
Table 3.2 Specifications of geranium oils
Table 3.3 Specifications of dementholized cornmint oils
Table 3.4 Characteristic components of Scotch and native spearmint oils
Table 3.5 Specifications of turpentine oils
Table 3.6 Specifications of Vetiver oils of different origins [1455]
Table 3.7 Specifications of ylang-ylang oils from the Comoro Islands (C) and Madagascar (M)
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Horst Surburg
Johannes Panten
Common Fragrance and Flavor Materials
Preparation, Properties and Uses
6 completely revised and updated Edition
Authors
Dr. Horst Surburg
Meiernberg 9
37603 Holzminden
Germany
Dr. Johannes Panten
Symrise AG
RD Synthesis
Bldg. D 209
Mühlenfeldstr. 1
37603 Holzminden
Germany
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Cover Design Adam Design
Preface to the Sixth Edition
Since its first publication 31 years ago, “Common Fragrance and Flavor Materials” became an indispensable tool for all people in the fragrance and flavor chemistry world. Also, in all parts of our life, things are moving ahead in this exciting field and, therefore, make it necessary to publish a new edition.
Traditionally, the concept of this book was not changed; however, several updates were added.
These are, among others, a revision of the sensorial descriptions in Chapter 1. In Chapter 2, several new and commonly available compounds were added. In addition, new production processes were introduced. Citations of Food Chem Tox as well as the commercial names were revised. Chapter 3 was amended by new raw materials and the citation and publication list was updated. As the registration and legislation situation especially in Europe has changed, it became necessary to revise Chapter 5. New references on safety data sheets and an updated citation list of patents complete this revision.
It is, however, not possible to review and to cite every new development in the field of fragrance and flavor raw materials. We decided, for example, not to include the development of precursor systems as this will go beyond the scope of this book.
The responsible authors for the sixth edition are still Horst Surburg and Johannes Panten, both of whom were or are still working in the synthesis department of the corporate research division of Symrise AG in Holzminden.
Both authors are indebted to many colleagues for their support and to the management of Symrise AG for the opportunity to prepare the sixth edition of this book.
Holzminden, July 2015
Horst SurburgJohannes Panten
Preface to the Fifth Edition
In the last two decades, “Common Fragrance and Flavor Materials” has developed to become probably the most cited standard work in the field of fragrance and flavor chemistry, and continual demand has now made it necessary to publish a new edition.
With regard to the contents, an update was required for several reasons, as some remarkable changes in the compositions of perfume oils – increasing use of macrocyclic musk materials has been observed, for example – have occurred since the publication of the 4th edition. Consequently, chapter 2 has had to be extended with some new monographs.
Some other trend-setting materials have also had to be included, whilst other materials that had lost their importance have had to be eliminated.
The changes in the landscape of fragrance and flavor materials producers also required corresponding adjustments.
The class of cooling agents – materials that create a cold sensation on skin or mucosa – has been admitted for the first time. Although known in principle for a long time, cooling agents have recently acquired increasing importance.
Chapter 3 has been partly revised and updated with regard to recent literature. Since it is impossible to cite the whole literature comprehensively, it was decided to refer to current review literature where possible. Otherwise, some of the very recent original references have been cited.
In general, the successful conception of this book, established about 20 years ago by Kurt Bauer and Dorothea Garbe, has been maintained. For a long time both of these authors worked in the research department of the flavor and fragrance company Haarmann & Reimer in Holzminden, Germany, Kurt Bauer as director of research and Dorothea Garbe as head of the department for scientific literature and documentation. Both retired some years ago and are therefore no longer engaged in the preparation of the 5th edition.
The responsible authors are now Horst Surburg and Johannes Panten, both of whom work in the synthesis department of the corporate research division of “Symrise”, the company formed by the merger of the flavor and fragrance houses “Dragoco” and “Haarmann & Reimer” in Holzminden.
Both authors are indebted to many colleagues for their support and to the management of Symrise for the opportunity to prepare the 5th edition of this book.
Holzminden, December 2005
Horst SurburgJohannes Panten
Preface to the Fourth Edition
The constant interest in “Common Fragrance and Flavor Materials” has encouraged us to proceed with the publication of a new edition within a relatively short period of time. The proven concept of the book has remained unchanged because of positive feedback from readers.
After a critical examination of the text, some material that has lost significance has been removed. A certain amount of new material, mainly components that have influenced modern fragrance trends over the past few years, have been added. The literature references in the chapter on “Natural Raw Materials” have been updated and the newest international standards for the characterization of materials have been included.
The authors would like to point out particularly that the present book can only provide a selection of the many commercially available fragrance and flavor materials. Also not included are compounds with exclusive uses that are not commonly/ generally available (“captives”) as well as substances that are too new to be judged as to whether they will find a successful place in the market. Analytical data on natural raw materials that can be obtained by means of new analytical techniques are not explicitly mentioned if the analytical techniques have not yet reached international standardization. However, reference is made to this in the corresponding literature and in the chapter on “Quality Control.”
We thank our critics for numerous suggestions and we especially thank our colleagues, who prompted our work on the new edition through their kind support.
Holzminden, June 2001
K. BauerD. GarbeH. Surburg
Preface to the Third Edition
Twelve years after its first publication comes the third edition of “Common Fragrance and Flavor Materials”. The content has been updated in many respects while retaining the proven concept.
In the case of the single-component fragrance and flavor materials, those compounds have been included which have become established on the market, as well as those which have attracted considerable interest on account of their outstanding organoleptic properties and have contributed to the composition of new fragrance types. The production processes for all fragrance and flavor materials described in the book have been critically reviewed. New processes have been taken into account, and those that are clearly outdated have been eliminated. A few compounds that have declined in importance or whose use is now restricted for toxicological reasons have been removed from the text, as have several essential oils. The latest publications and standards concerning essential oils and natural raw materials have been included in the new edition, making it an up-to-date reference work. For the first time references are cited for all essential oils, giving newcomers to the field a quick overview of the original literature. The chapters on quality control and product safety have been expanded and brought up to date.
The authors wish to thank all the colleagues whose specialist advice assisted us in revising the book.
Holzminden, February 1997
K. BauerD. GarbeH. Surburg
Preface to the Second Edition
Within three years of publication the first edition of “Common Fragrance and Flavor Materials” was out of print and is now followed by this second edition. As in the case of the first edition this book is based mainly on a chapter on “Flavors and Fragrances” which has since been published in English in Ullmann's Encyclopedia of Industrial Chemistry.
We would like to thank our readers for their suggestions for improvement and further development of the contents which were contained in several book reviews. We have not followed up all the suggestions for the simple reason that we did not wish to change the character of the book, which is expressly aimed at a general audience interested in commonly used fragrance and flavor materials, and not at experts in the field.
The chapter on “Single Fragrance and Flavor Compounds” has been updated to include new developments, production methods have been brought up-to-date and CAS registry numbers have been added to all single compounds described. The former chapters “Essential Oils” and “Animal Secretions” have been grouped together under the heading “Natural Raw Materials in the Flavor and Fragrance Industry” and thoroughly revised to include new literature references.
Holzminden, February 1990
K. BauerD. GarbeH. Surburg
Preface to the First Edition
Fragrance and flavor materials are used in a wide variety of products, such as soaps, cosmetics, toiletries, detergents, alcoholic and non-alcoholic beverages, ice cream, confectioneries, baked goods, convenience foods, tobacco products, and pharmaceutical preparations. This book presents a survey of those natural and synthetic fragrance and flavor materials which are produced commercially on a relatively large scale, or which are important because of their specific organoleptic properties. It provides information concerning their properties, methods employed in their manufacture, and areas of application. Therefore, the book should be of interest to anyone involved or interested in fragrance and flavor, e.g., perfumers, flavorists, individuals active in perfume and flavor application, food technologists, chemists, and even laymen.
The book is, essentially, a translation of the chapter on fragrance and flavor materials in Ullmanns Encyklopädie der technischen Chemie, Volume 20, 4th Edition, Verlag Chemie GmbH, Weinheim (Federal Republic of Germany), 1981. The original (German) text has been supplemented by inclusion of recent developments and of relevant information from other sections of the Encyclopedia. The present English version will make the information available to a wider circle of interested readers.
The condensed style of presentation of “Ullmann's” has been maintained. A more detailed treatment of various items and aspects was considered but was believed to be outside the scope of this book. Additional information, however, can be obtained from the literature cited.
To improve its usefulness, the book contains
a formula index, including CAS registry numbers;
an alphabetical index of single fragrance and flavor compounds, essential oils, and animal secretions.
Starting materials and intermediates are not covered by these indexes. The authors wish to express their gratitude to:
Haarmann & Reimer Company, in particular to its General Manager, Dr. C. Skopalik, who suggested the publication of this book in English and who, at an earlier stage, provided time and facilities for writing the chapter on fragrance and flavor materials in Ullmanns Encyklopädie der technischen Chemie (1981), and to Dr. Hopp, Vice President Research, for valuable additions to his book;
all others who provided information and suggestions for the chapter in Ullmann's Encyclopedia and thereby for this book.
The authors are most grateful to Dr. J. J. Kettenes-van den Bosch and Dr. D. K. Kettenes for translating the original German text into English and for their suggestions and help in shaping the present book. Drs. Kettenes thank Mr. W. S. Alexander, Hockessin, Delaware (USA), for critically reviewing the English.
Holzminden, June 1984
K. BauerD. Garbe
Chapter 1Introduction
1.1 History
Since early antiquity, spices and resins from animal and plant sources have been used extensively for perfumery and flavor purposes and to a lesser extent for their observed or presumed preservative properties. Fragrance and flavor materials vary from highly complex mixtures to single chemicals. Their history began when people discovered that component characteristic of the aroma of natural products could be enriched by simple methods. Recipes for extraction with olive oil and for distillation have survived from pre-Christian times to this day.
Although distillation techniques were improved, particularly in the ninth century A.D. by the Arabs, the production and application of these concoctions remained essentially unchanged for centuries. Systematic development began in the thirteenth century, when pharmacies started to prepare the so-called remedy oils and later recorded the properties and physiological effects of these oils in pharmacopoeias. Many essential oils currently used by perfumers and flavorists were originally prepared by distillation in pharmacies in the sixteenth and seventeenth centuries.
Another important step in the history of natural fragrance materials occurred in the first half of the nineteenth century, when the production of essential oils was industrialized due to the increased demand for these oils as perfume and flavor ingredients. Around 1850, single organic compounds were also used for the same purposes. This development resulted from the isolation of cinnamaldehyde from cinnamon oil by Dumas and Pèligot in 1834, and the isolation of benzaldehyde from bitter almond oil by Liebig and Wöhler in 1837. The first synthetic “aroma oils” were introduced between 1845 and 1850. These consisted of lower molecular mass fatty acid esters of several alcohols and were synthesized by the chemical industry for their fruity odor. Methyl salicylate was introduced in 1859 as “artificial wintergreen oil” and benzaldehyde in 1870 as “artificial bitter almond oil.” With the industrial synthesis of vanillin (1874) and coumarin (1878) by Haarmann & Reimer (Holzminden, Germany), a new branch of the chemical industry was founded.
The number of synthetically produced fragrance and flavor chemicals has since expanded continually as a result of the systematic investigation of essential oils and fragrance complexes for odoriferous compounds. Initially, only major components were isolated from natural products; their structure was then elucidated and processes were developed for their isolation or synthesis. With the development of modern analytical techniques, however, it became possible to isolate and identify characteristic fragrance and flavor substances that occur in the natural products in only trace amounts. The isolation and structure elucidation of these components require the use of sophisticated chromatographic and spectroscopic techniques. Interesting products can then be synthesized.
1.2 Definition
Fragrance and flavor substances are comparatively strong-smelling organic compounds with characteristic, usually pleasant odors. They are, therefore, used in perfumes and perfumed products, as well as for the flavoring of foods and beverages. Whether a particular product is called a fragrance or a flavor substance depends on whether it is used as a perfume or a flavor. Fragrances and flavors are, similar to taste substances, chemical messengers, their receptors being the olfactory cells in the nose [1, 2].
1.3 Physiological Importance
Chemical signals are indispensable for the survival of many organisms which use chemoreceptors to find their way, to hunt for and inspect food, to detect enemies and harmful objects, and to find members of the opposite sex (pheromones). These functions are no longer vitally important for humans. The importance of flavor and fragrance substances in humans has evolved to become quantitatively and qualitatively different from that in other mammals; this is because humans depend to a greater extent on acoustic and optical signals for orientation. However, humans have retained the ability to detect odors, and human behavior can undoubtedly be affected by fragrances and aromas.
Sensory information obtained from the interaction of fragrance and flavor molecules with olfactory and taste receptors is processed in defined cerebral areas, resulting in perception. During the past 15 years, much research was done concerning sensory perception, and the results have been published in, for example, [2–23].
Although food acceptance in humans is determined mainly by appearance and texture, flavor is nevertheless also important. For example, spices are added to food not for their nutritional value but for their taste and flavor. Furthermore, aromas that develop during frying and baking enhance the enjoyment of food. Unlike flavoring substances, fragrances are not vitally important for humans. The use of fragrances in perfumery is primarily directed toward invoking pleasurable sensations by shifting the organism's emotional level. Whereas “naturalness” is preferred in aromas (generally mixtures of many compounds), the talent and imagination of the perfumer are essential for the creation of a perfume.
1.4 Natural, Nature-Identical, and Artificial Products
Natural compounds are obtained directly from natural sources by physical or biotechnological (enzymatic, microbial) procedures. As a result of the rapid development and expansion of biotechnology in the past two decades, far more than 100 natural flavoring substances are available from biocatalytic processes today [24–26]. Nature-identical compounds are produced synthetically but are chemically identical to their natural counterparts. Artificial flavor substances are compounds that have not yet been identified in plant or animal products for human consumption [27]. Alcohols, aldehydes, ketones, esters, and lactones are classes of compounds that are represented most frequently in natural and artificial fragrances.
Nature-identical aroma substances are, with very few exceptions, the only synthetic compounds used in flavors besides natural products. The primary functions of the olfactory and taste receptors, as well as their evolutionary development, may explain why artificial flavor substances are far less important. A considerable proportion of compounds used in fragrances are those identified as components of natural products, for example, constituents of essential oils or resins. The fragrance characteristics of artificial compounds nearly always mimic those of natural products.
1.5 Sensory Properties and Chemical Structure
Similarity between odors arises because dissimilar substances or mixtures of compounds may interact with receptors to create similar sensory impressions in the sensory centers of the brain. The group of musk fragrances (comprising macrocyclic ketones and esters as well as aromatic nitro compounds and polycyclic aromatics), for example, are compounds with similar odors but totally different structures [28, 29]. Small changes in the structure (e.g., the introduction of one or more double bonds in aliphatic alcohols or aldehydes) may, however, alter a sensory impression or intensify an odor by several orders of magnitude. Increasing knowledge of the structure and functioning of olfactory receptors provides a better scientific basis for the correlation of odor and structure in fragrance and flavor substances and facilitates the more accurate prediction of the odors of still unknown compounds [30–52].
1.6 Volatility
Fragrances must be volatile to be perceived. Therefore, in addition to the nature of the functional groups and the molecular structure of a compound, the molecular mass is also an important factor. Molecular masses of about 200 occur relatively frequently; masses over 300 are an exception.
Since fragrance materials differ in volatility, the odor of a perfume composition changes during evaporation and is divided into the top note, the middle note or body, and the end note or dry-out, which consists mainly of less volatile compounds. Odor perception also depends largely on odor intensity. Therefore, the typical note is not determined only by the most volatile compounds.
In some cases, substances (fixatives) are added to perfumes to prevent the more volatile components from evaporating too rapidly [53].
1.7 Threshold Concentration
Due to the specificity of olfactory receptors, some compounds can be perceived in extremely low concentrations and significant differences in threshold concentrations are observed. The threshold concentration is defined as the lowest concentration at which a chemical compound can be distinguished with certainty from a blank under standard conditions.
For the compounds described in Chapter 2, threshold concentrations vary by a factor of 106–107. This explains why some fragrance and flavor materials are manufactured in quantities of a few kilograms per year, others in quantities of several thousands of tons.
The relative contribution of a particular compound (its odor or flavor value) to the odor impression of a composition can be expressed as the ratio between the actual concentration of the compound and its threshold concentration [54, 55].
1.8 Sensory Properties
The sensory properties of single aroma chemicals are extremely difficult to describe unequivocally. Complex mixtures are often impossible to describe unless one of the components is so characteristic that it largely determines the odor or flavor of the composition. Although a classification is always subjective, sensory properties can be described by adjectives such as flowery, fruity, woody, hay-like, which relate the fragrances or flavors to natural or other known products with similar sensory impressions [56]. However, such terms are not strictly defined and run into each other. In most cases, sensory properties of one and the same material can only be described by using more than one term.
1.8.1 Fragrance Ingredients
In accordance with the evolution of its fragrance properties, a perfume composition can formally be divided into three categories: top note, heart note (body; bouquet), and base note (fond).
In classic perfumes of feminine and masculine types, the heart note consists of fragrance materials with a floral character. It is enveloped by materials that are perceived immediately (top notes) and materials that are perceived mainly in the dry-out and impart tenacity to the composition (base notes). In a striking illustration of a “fragrance circle,” a circular central body is ringed by segments of top notes in the upper part and by base notes in the lower part [57]. The segments contain the most important fragrance categories that determine the character of a perfume.
Typical top notes are as follows:
Citrus
Fresh, stimulating odor of citrus fruits such as lemon, lime, orange, bergamot
Aldehydic
Odor note of the long-chained fatty aldehydes: fatty-sweaty, ironed laundry, metallic, fresh seawater, ozone-like, marine fragrances
Fruity
Light fruity notes: typical notes of aliphatic esters: found, for example, in odors of apples, pears, melons
Dark (heavy, sweet) fruity notes: found, for example, in odors of strawberries, raspberries, lactone odor of peaches and coconuts
Green
Typical odor of green vegetation: green leaves and freshly cut grass
Herbaceous/Herbal
Odor of green herbs and spices, for example, sage, mint, eucalyptus; camphoraceous such as rosemary; coniferous such as fir needles; earthy agrestic
Examples of floral notes (heart notes; body) are as follows:
Floral light
Rose
Floral green, clean
Lily of the Valley (muguet)
Floral fresh, herbal
Geranium, lavender
Floral fruity
For example, damascones
Floral heavy
Narcotic flower fragrances such as jasmine, tuberose
Floral woody (powdery)
For example, methylionones
Typical base notes are as follows:
Aromatic
Sweet aromatic to aromatic spicy odors, for example, of honey, almond, aniseed, woodruff, nutmeg, clove. This segment also contains the so-called gourmand notes having pronounced culinary properties, for example, vanilla, tonka, lovage
Balsamic
Heavy sweet odors, such as chocolate and vanilla, cinnamon with resinous elements
Moss
Dry, algae-like, tar-like, phenolic, oak moss
Leather, animalic
Odor of cresol, isobutyl quinoline, and so on; fecal such as indole
Musk
Warm soft odor reminding of freshly washed and ironed laundry, often with skin-like and animalic-erogenous facets
Amber
Warm, slightly earthy-camphoraceous woody note, reminding natural ambergris, represented typically by amber oxide
Wood
Clear cool radiant odor found in natural materials such as cedarwood (pencil note), patchouli, sandalwood, and vetiver
In addition to these generic properties, a number of specific terms are used to characterize fragrance material more in detail, for example, fatty, waxy, burnt, phenolic, fishy, sulfurous, musty, medicinal, [57].
1.8.2 Flavoring Substances
Sensory properties of flavoring substances can simply be illustrated when arranged in segments of a circle, “flavor wheel” [58], containing the following descriptors:
Green, grassy; herbaceous; spicy; fruity, ester-like; tropical; blackcurrant; vegetable; nutty; caramel; smoky; roast, burnt; beefy; pork, lamb, chicken; savory, bouillon; fatty; rancid, cheesy; mushroom, earthy; truffle; garlic; onion.
Chapter 2Individual Fragrance and Flavor Materials
Fragrance and flavor materials of commercial interest are arranged according to the Beilstein system of functional groups, not according to their sensory properties, since relationships between odor and structure are difficult to establish. However, the Beilstein system has been abandoned in a few cases for practical reasons. In each class of parent compounds, hydrocarbons and oxygen-containing compounds are described first. Nitrogen- and sulfur-containing compounds are treated at the end of each of these sections under the heading Miscellaneous Compounds. Aliphatic compounds are discussed in Section 2.1, followed by the terpenes. The terpenes constitute a very important group of compounds and are subdivided into acyclic terpenes (Section 2.2) and cyclic terpenes (Section 2.3). Nonterpenoid cycloaliphatics are described in Section 2.4. Aromatic compounds are discussed in Section 2.5. Phenols and phenol derivatives are described under a separate heading (Section 2.6) on account of their biogenetic and odor relationships. Methylenedioxyphenyl derivatives are also described under this heading for the same reason even though, systematically, they belong to the oxygen-containing heterocycles (Section 2.7). Materials that are only produced in small quantities, but which are important due to their high odor intensity, are mentioned but not described in detail.
When available, trade names are given for individual fragrance and flavor materials. The names of the suppliers are given as follows:
Agan
=
Agan Aroma, Israel
Aromor
=
Aromor Flavors & Fragrances Ltd, Israel
BASF
=
BASF SE, Germany
DRT
=
Les Derives Resiniques et Terpeniques, France
Firmenich
=
Firmenich International S.A., Switzerland
Givaudan
=
Givaudan S.A., Switzerland
Huaian Wangbang
=
Huaian Wangbang Aromatic Chemicals Industry Co., China
Hangzhou
=
Hangzhou Grascent Co., China
IFF
=
International Flavors & Fragrances, USA
Innospec
=
Innospec Inc., UK
KalpSutra
=
KalpSutra Chemicals Pvt. Ltd.
Kao
=
Kao Corp., Japan
Renessenz
=
Renessenz LLC, USA
Nippon Zeon
=
Nippon Zeon Co., Ltd, Japan
PFW
=
PFW Aroma Chemicals B.V., Netherlands
Rhodia
=
Solvay/Rhodia, Belgium
Soda Aromatic
=
Soda Aromatic Co., Ltd., Japan
Symrise
=
Symrise AG, Germany
Takasago
=
Takasago International Corporation, Japan
YingHai
=
YingHai Aroma Chemical Group Tianjin, China
Monographs on fragrance materials and essential oils that have been published by the Research Institute for Fragrance Materials (RIFM) in “Food and Chemical Toxicology” are cited below the individual compounds as “FCT” with year, volume, and page of publication.
2.1 Aliphatic Compounds
The acyclic terpenes are discussed separately in Section 2.2. Some of the cycloaliphatic fragrance and flavor materials are structurally related to the cyclic terpenes and are, therefore, discussed in Section 2.4 after the cyclic terpenes.
2.1.1 Hydrocarbons
Saturated and unsaturated aliphatic hydrocarbons with straight as well as branched chains occur abundantly in natural foodstuffs, but they contribute to the odor and taste only to a limited extent and have not, therefore, gained commercial importance. The only exception is the highly unsaturated hydrocarbon (E,Z)-1,3,5-undecatriene and its synthetic precursor 1,3-undecadien-5-yne.
2.1.1.1 (E,Z)-1,3,5-Undecatriene [51447-08-6]
C11H18, Mr 150.26, is a colorless liquid with a strong green, galbanum-like odor. It occurs naturally in galbanum oil (see p. 207) and is the odor-determining constituent of the oil. The commercial qualities also contain some all-trans-isomer and are offered only in dilution due to better stability.
Numerous synthetic routes for the production of 1,3,5-undecatrienes have been developed. Typical routes are described in [59–62].
FCT 1988 (26) p. 415.
Trade Names. Galbanolene Super (Firmenich), Undecatriene 10% (Givaudan).
2.1.1.2 1,3-Undecadien-5-yne [166432-52-6]
C11H16, Mr 148.24, 1.44–1.444, 0.845–0.855, is a colorless liquid with a nice fruity, green, strong violet-leaf note. It is recommended as an alternative to methyl octynoate and methyl nonynoate [63].
Trade Name. Violettyne MIP (Firmenich).
2.1.2 Alcohols
Free and esterified, saturated primary alcohols occur widely in nature, for example, in fruits. Since their odor is relatively weak, their use as components in fragrance compositions is limited. Their use in aroma compositions, especially for fruit flavors, is by far more important (e.g., straight-chain C4–C10 alcohols, isoamyl alcohol). Unsaturated alcohols are most important (e.g., leaf alcohol with its intensely green odor) and may impart characteristic notes to compositions. Naturally occurring fatty alcohols used in the fragrance industry are produced principally by reduction of the methyl esters of the corresponding carboxylic acids, which are obtained by transesterification of natural fats and oils with methanol. Industrial reduction processes include catalytic hydrogenation in the presence of copper–chromium oxide catalysts (Adkins catalysts) and reduction with sodium (Bouveault–Blanc reduction). Unsaturated alcohols can also be prepared by the latter method. Numerous alcohols for use as natural ingredients in flavor compositions are, in the meantime, produced by biotechnological processes [27] [64]. Alcohols are the starting materials for aldehydes and esters.
2.1.2.1 3-Octanol [589-98-0]
C8H18O, Mr 130.23, bp97.6 kPa 176–176.5 °C, 0.8264, 1.4252, may occur in its optically active form. It is a colorless liquid that has a mushroomy–earthy odor and occurs in mushrooms. 3-Octanol can be obtained by hydrogenation of 3-octanone; it is used in lavender compositions and for imparting mushroom-like odors.
FCT 1979 (17) p. 881.
2.1.2.2 2,6-Dimethyl-2-heptanol [13254-34-7]
C9H20O, Mr 144.26, bp101.3 kPa 170–172 °C, 0.8186, 1.4248, which has not yet been found in nature, is a colorless liquid with a delicate, floral odor reminiscent of freesias. It is synthesized from 6-methyl-5-hepten-2-one and methylmagnesium chloride by a Grignard reaction, followed by hydrogenation, and is used in floral perfume compositions.
FCT 1992 (30) p. 30; FCT 2010 (48, suppl. 4) pp. S110–S114.
Trade Name. Dimetol® (Givaudan).
2.1.2.3 (E)-2-Hexen-1-ol [928-95-0]
C6H12O, Mr 100.16, bp101.3 kPa 155 °C, 0.8459, 1.4382, occurs in many fruits and has a fruity, green odor, which is sweeter than that of the isomeric (Z)-3-hexen-1-ol and is, therefore, preferred in aroma compositions.
FCT 1974 (12) p. 911.
2.1.2.4 (Z)-3-Hexen-1-ol [928-96-1], Leaf Alcohol
C6H12O, Mr 100.16, bp101.3 kPa 156–157 °C, 0.8459, 1.4384, is a colorless liquid with the characteristic odor of freshly cut grass. In small quantities, leaf alcohol occurs in the green parts of nearly all plants. The volatile flavor constituents of green tea contain up to 30%.
A stereospecific synthesis of (Z)-3-hexen-1-ol starts with the ethylation of sodium acetylide to 1-butyne, which is reacted with ethylene oxide to give 3-hexyn-1-ol. Selective hydrogenation of the triple bond in the presence of palladium catalysts yields (Z)-3-hexen-1-ol [65]. Biotechnological processes have been developed for its synthesis as a natural flavor compound, for example, [64] [66, 67].
Leaf alcohol is used to obtain natural green top notes in perfumes and flavors. In addition, it is the starting material for the synthesis of (2E,6Z)-2,6-nonadien-l-ol (see p. 11) and (2E,6Z)-2,6-nonadien-l-al.
FCT 1974 (12) p. 909.
2.1.2.5 1-Octen-3-ol [3391-86-4]
C8H16O, Mr 128.21, bp94.6 kPa 175–175.2 °C, 0.8383, 1.4378, may occur in the optically active form. It is found, for example, in lavender oil and is a steam-volatile component of mushrooms. l-Octen-3-ol is a liquid with an intense mushroom, forest–earthy odor that can be prepared by a Grignard reaction from vinylmagnesium bromide and hexanal. It is used in lavender compositions and in mushroom aromas.
FCT 1976 (14) p. 681.
Trade Name. Matsutakeol (Takasago).
2.1.2.6 9-Decen-1 (cipher)-ol [13019-22-2]
C10H20O, Mr 157.27, bp0.27 kPa 85–86 °C, 1.4480, has been identified as a trace constituent of cognac. It is a colorless liquid with a fresh, dewy, rose note that can be prepared by partial dehydration of 1,10-decanediol. It is used in rosy, floral soap perfumes.
FCT 1974 (12) p. 405.
Trade Names. Rosalva (IFF), Trepanol® (Takasago).
2.1.2.7 10-Undecen-1-ol [112-43-6]
C11H22O, Mr 170.29, bp2.1 kPa 133 °C, 0.8495, 1.4500, is a colorless liquid with a fatty, green, slightly citrus-like odor. It can be synthesized from 10-undecylenic acid and is used to give flower perfumes a fresh note.
FCT 1973 (11) p. 107.
2.1.2.8 3,4,5,6,6-Pentamethylheptan-2-ol [87118-95-4]
C12H26O, Mr 186.34, is a colorless to pale yellow liquid, 0.864–0.872, with an exquisite floral woody odor with dry, amber, vetiver, raisin nuances. Synthesis starts from 2-methyl-2-butene (isoamylene), which is dimerized, and the product acetylated to give the corresponding pentamethylhepten-2-ones (see p. 19). 3,4,5,6,6-Pentamethylheptan-2-ol is obtained by subsequent hydrogenation along with some isomers [68].
The material is used in perfume compositions, for example, for detergents.
FCT 2010 (48, suppl. 4) pp. S63–S66.
Trade Name. Kohinool® (IFF).
2.1.2.9 (2E,6Z)-2,6-Nonadien-1-ol [28069-72-9], Violet Leaf Alcohol
C9H16O, Mr 140.22, bp1.5 kPa 96–100 °C, 0.8622, 1.4631, occurs, for example, in cucumber oil, violet leaf oil, and violet blossom oil. It is a colorless liquid with an intense, heavy, fatty, green odor, reminiscent of violet leaves. The starting material for the synthesis of (2E,6Z)-2,6-nonadien-l-ol is (Z)-3-hexen-1-ol, which is converted via its halide into the corresponding Grignard reagent. The Grignard reagent is reacted with acrolein to give 1,6-nonadien-3-ol, which is converted into (2E,6Z)-2,6-nonadien-l-ol by allylic rearrangement.
Nonadienal is a powerful fragrance substance. It is used in fine fragrances to create refined violet odors and to impart interesting notes to other blossom compositions. In aroma compositions, it is used for fresh, green cucumber notes.
FCT 1982 (20) p. 771; FCT 2010 (48, suppl. 3) pp. S91–S92.
2.1.2.10 4-Methyl-3-decen-5-ol [81782-77-6]
C11H22O, Mr 170.30, 0.8420–0.8480, 1.449–1.454, is a colorless to pale yellow liquid with a powerful, rich, fresh, green, floral, violet-leaf-like odor. It is used in modern perfume oils as a substitute for the methyl alkynoates (see p. 25) and is found in perfume oils for nearly all applications.
4-Methyl-3-decen-5-ol is prepared by Grignard reaction of pentylmagnesium bromide and 2-methyl-2-pentenal [69].
FCT 2010 (48, suppl. 3) pp. S93–S96.
Trade Names. Figovert (Hangzhou), Undecavertol (Givaudan).
2.1.3 Aldehydes and Acetals
Aliphatic aldehydes are among the most important components used in perfumery. Although the lower fatty aldehydes C2–C7 occur widely in nature, they are – with the exception of hexanal – seldom used in fragrance compositions. The lower aldehydes (e.g., acetaldehyde, isobutyraldehyde, isovaleraldehyde, and 2-methyl-butyraldehyde) impart fruity and roasted characters to flavor compositions. Fatty aldehydes C8–C13, however, are used, singly or in combination, in nearly all perfume types and also in aromas. Their odor becomes weaker with increasing molecular mass, so that aldehydes >C13 are not important as perfume ingredients.
In addition to the straight-chain saturated aldehydes, a number of branched-chain and unsaturated aliphatic aldehydes are important as fragrance and flavoring materials. Branched-chain and aliphatic aldehydes bearing an alkyl group in α-position are used for perfuming difficult media such as soaps and detergents because they are much more stable than their unsubstituted counterparts.
The double unsaturated (2E,6Z)-2,6-nonadienal [557-48-2], “violet leaf aldehyde” (the dominant component of cucumber aroma), is one of the most potent fragrance and flavoring substances; it is, therefore, only used in very small amounts. (2E,4E)-2,4-Decadienal [25152-84-5] with its specifically fatty odor character is indispensable in chicken meat flavor compositions.
Acetals derived from aliphatic aldehydes have odor characteristics that resemble those of the aldehydes but are less pronounced. These acetals contribute to the aroma of alcoholic beverages, but can rarely be used in flavoring compositions because they are not sufficiently stable. Since they are resistant to alkali, a number of them (e.g., heptanal dimethyl acetal and octanal dimethyl acetal) are occasionally incorporated into soap perfumes.
Fatty aldehydes are generally produced by dehydrogenation of alcohols in the presence of suitable catalysts. The alcohols are often cheap and available in good purity. Aldehyde synthesis via the oxo process is less suitable since the resultant products are often not pure enough for flavor and perfume purposes. Specific syntheses for the branched-chain and unsaturated aldehydes that are important in perfumery and flavoring techniques are described under the individual compounds.
2.1.3.1 Hexanal [66-25-1], Caproaldehyde, Aldehyde C6
C6H12O, Mr 100.16, bp101.3 kPa 128 °C, 0.8139, 1.4039, occurs, for example, in apple and strawberry aromas as well as in orange and lemon oil. It is a colorless liquid with a fatty, green odor and, in low concentration, is reminiscent of unripe fruit.
Hexanal is used in fruit flavors and, when highly diluted, in perfumery for obtaining fruity notes.
FCT 1973 (11) p. 111.
2.1.3.2 Octanal [124-13-0], Caprylaldehyde, Aldehyde C8
C8H16O, Mr 128.21, bp101.3 kPa 171 °C, 0.8211, 1.4217, occurs in several citrus oils, for example, orange oil. It is a colorless liquid with a pungent odor, which becomes citrus-like on dilution. Octanal is used in perfumery in low concentrations, in eau de cologne, and in artificial citrus oils.
FCT 1973 (11) p. 113.
2.1.3.3 Nonanal [124-19-6], Pelargonaldehyde, Aldehyde C9
C9H18O, Mr 142.24, bp101.3 kPa 190–192 °C, 0.8264, 1.4273, occurs in citrus and rose oils. It is a colorless liquid with a fatty, rose-like odor and is used in floral compositions, particularly those with rose characteristics.
FCT 1973 (11) p. 115.
2.1.3.4 Decanal [112-31-2], Caprinaldehyde, Aldehyde C10
C10H20O, Mr 156.27, bp101.3 kPa 208–209 °C, 0.830, 1.4287, is a component of many essential oils (e.g., neroli oil) and various citrus peel oils. It is a colorless liquid with a strong odor, reminiscent of orange peel, which changes to a fresh citrus odor when diluted. Decanal is used in low concentrations in blossom fragrances (especially to create citrus nuances) and in the production of artificial citrus oils.
FCT 1973 (11) p. 477.
2.1.3.5 Undecanal [112-44-7], Aldehyde C11
C11H22O, Mr 170.29, bp2.4 kPa 117 °C, 0.8251, 1.4325, occurs in citrus oils. It is a colorless liquid with a floral, waxy odor that has aspects of freshness. Undecanal is the prototype of the perfumery aldehydes and is widely used in perfume compositions for imparting an “aldehydic note.”
FCT 1973 (11) p. 481.
2.1.3.6 Dodecanal [112-54-9], Lauraldehyde, Lauric Aldehyde, Aldehyde C12
C12H24O, Mr 184.32, bp13.3 kPa 185 °C, 0.8352, 1.4350, is a colorless liquid with a waxy odor; in high dilution, it is reminiscent of violets. Dodecanal occurs in several citrus oils and has been found in small amounts in essential oils obtained from several Pinus species. It is used in perfumery in conifer fragrances with fatty, waxy notes, but also in many other odor types. It is added to aroma compositions to obtain citrus notes.
FCT 1973 (11) p. 483.
2.1.3.7 Tridecanal [10486-19-8]
C13H26O, Mr 198.34, bp1.3 kPa 128 °C, 0.8356, 1.4384, occurs in lemon oil and has been identified as a volatile constituent of cucumber. It is a colorless liquid having a fatty, waxy, slightly citrus-like odor. Addition of tridecanal to fragrance compositions imparts fresh nuances in the top note as well as in the dry-out.
2.1.3.8 2-Methyldecanal [19009-56-4], Methyloctylacetaldehyde, Aldehyde MOA
C11H22O, Mr 170.29, bp98.8 kPa 119–120 °C, 0.8948, 1.4205. It is a colorless liquid with an aldehydic, citrus-peel-like, waxy, green odor. 2-Methyldecanal is obtained as a by-product in the manufacture of 2-methylundecanal by hydroformylation of 1-decene (see 2-methylundecanal). It is used in perfumery to refresh green and citrus nuances.
FCT 1976 (14) p. 609.
2.1.3.9 2-Methylundecanal [110-41-8], Methylnonylacetaldehyde, Aldehyde MNA
C12H24O, Mr 184.32, bp1.3 kPa 114 °C, 0.830, 1.4321, is reported as being found in nature. It is a colorless liquid, with an odor markedly different from that of the isomeric dodecanal. It has a fatty odor with incense and ambergris notes.
2-Methylundecanal is produced by two routes:
1.
2-Undecanone is converted into its glycidate by reaction with an alkyl chloroacetate. Saponification of the glycidate, followed by decarboxylation, yields 2-methylundecanal.
2.
The second synthesis is based on the conversion of undecanal into 2-methyleneundecanal by reaction with formaldehyde in the presence of catalytic amounts of amines [70]. Hydrogenation of 2-methyleneundecanal yields methylnonylacetaldehyde (MNA). A convenient process starts from 1-decene: hydroformylation gives a mixture consisting mainly of undecanal and 2-methyldecanal. Reaction of the crude product with formaldehyde in the presence of dibutylamine yields a mixture containing over 50% 2-methyleneundecanal. After hydrogenation of the double bond, pure 2-methylundecanal is separated from the by-products by fractional distillation [71].
In comparison with other fatty aldehydes, 2-methylundecanal is used in perfumery in rather large amounts to impart conifer notes, particularly fir impressions, but frequently also in fantasy compositions.
FCT 1973 (11) p. 485.
2.1.3.10 (E)-2-Hexenal [6728-26-3], Leaf Aldehyde
C6H10O, Mr 98.14, bp101.3 kPa 146–147 °C, 0.8491, 1.4480, is the simplest straight-chain unsaturated aldehyde of interest for perfumes and flavors. It occurs in essential oils obtained from green leaves of many plants.
(E)-2-Hexenal is a colorless, sharp, herbal-green-smelling liquid with a slight acrolein-like pungency. Upon dilution, however, it smells pleasantly green and apple-like. The aldehyde can be synthesized by reacting butanal with vinyl ethyl ether in the presence of boron trifluoride, followed by hydrolysis of the reaction product with dilute sulfuric acid [72].
Biosynthetic methods for its production as natural flavor material have been developed [64] [67].
(E)-2-Hexenal has an intense odor and is used in perfumes to obtain a green-leaf note and in fruit flavors for green nuances.
FCT 1975 (13) p. 453.
2.1.3.11 (Z)-4-Heptenal [6728-31-0]
C7H12O, Mr 112.17, bp1.33 kPa 41 °C, 1.4343, is a widespread volatile trace constituent of food flavors. It is a colorless, oily liquid with a powerful, fatty, somewhat fishy, and, in high dilution, creamy odor. It can be prepared by several ways, for example, by starting from (Z)-3-hexenol (see p. 10) [73].
(Z)-4-Heptenal is used in cream, butter, and fat flavors.
2.1.3.12 2,6-Dimethyl-5-hepten-1-al [106-72-9]
C9H16O, Mr 140.23, bp2 kPa 79–80 °C, 0.848, 1.4492 was identified in ginger. It is a yellow liquid with a powerful, green, cucumber-like, and melon odor. It can be prepared by Darzens reaction of 6-methyl-5-hepten-2-one with ethyl chloroacetate. The intermediate glycidate is saponified and decarboxylated to yield the title compound.
It is used in many fragrance types and is invaluable in the creation of melon and cucumber notes.
Trade Names. Melonal (Givaudan), Melomor (Aromor).
2.1.3.13 (E)-4-Decenal [65405-70-1]
C10H18O, Mr 154.25, 1.4421–1.4432, is a pale yellow liquid with a powerful aldehydic, orange-like, green, floral odor. It is used in fragrances to create fresh, natural, citrus-like notes.
The material can be produced by the reaction of 1-octen-3-ol with ethyl vinyl ether [74].
2.1.3.14 10-Undecenal [112-45-8]
C11H20O, Mr 168.28, bp0.4 kPa 103 °C, 0.8496, 1.4464, was identified, for example, in coriander leaf extract [75]. It is a colorless liquid with a fatty, green, slightly metallic, heavy, floral odor. The aldehyde can be synthesized from undecylenic acid, for example, by hydrogenation of the acid chloride (Rosenmund reduction) or by reaction with formic acid in the vapor phase in the presence of titanium dioxide. In perfumery, 10-undecenal is one of the aldehydes essential for creating the “aldehydic note.”
Mixtures containing undecenals with the double bond in other positions (9-, 8-, 7-) are also marketed and used in fragrances, for example, Aldehyde C11 Iso (Givaudan), Intreleven aldehyde (IFF).
FCT 1973 (11) p. 479.
2.1.3.15 2-Dodecenal [20407-84-5]
C12H22O, Mr 182.30, 0.8390–0.8490, is a colorless liquid with a powerful aldehydic, mandarin, citrus-like odor. It may be prepared as described earlier, see 2-hexenal, [72]. 2-Dodecenal is used in flavors and fragrances to create orange-mandarin-like citrus notes.
FCT 1983 (21) p. 849.
Trade Name. Mandarin Aldehyde (Firmenich).
2.1.3.16 2,6,10-Trimethyl-5,9-undecadienal [24048-13-3] and [54082-68-7]
C14H24O, Mr 208.34, 0.870–0.877, 1.468–1.473, not found in nature, is a clear, colorless to pale yellowish liquid. It has an aldehydic, floral odor reminiscent of nerolidol, with fruity nuances. It can be prepared from geranylacetone (see p. 47) by Darzens reaction with ethyl chloroacetate through the corresponding glycidic ester, which is hydrolyzed and decarboxylated.
2,6,10-Trimethyl-5,9-undecadienal is used to modify perfume compositions for soaps, detergents, and household products.
Trade Name. Profarnesal (Symrise).
2.1.3.17 1,1-Dimethoxy-2,2,5-trimethyl-4-hexene [67674-46-8]
C11H22O2, Mr 186.30, bp1.6 kPa 82 °C, 1.441, is a colorless to pale yellow liquid with a fresh, fruity, citrus grapefruit-peel-like odor. It has not been found in nature. It is prepared by reaction of 2,2,5-trimethyl-4-hexenal (from isobutyraldehyde and prenyl chloride) with methanol in the presence of calcium chloride [76].
Due to its alkali stability, it is used in citrus compositions for soaps and detergents.
Trade Names. Methyl Pamplemousse (Givaudan), Amarocit® (Symrise).
2.1.4 Ketones
Aliphatic monoketones are of minor importance as fragrance and aroma substances. 2-Alkanones (C3–C15) have been found in the volatile fractions of many fruits and foodstuffs, but they do not contribute significantly to their aroma. The odd-numbered methyl ketones C7, C9, C11 are an exception, which possess a characteristic nutty note; they are used, for example, in cheese flavor compositions. In perfumery, aliphatic ketones are used for accentuation, for example, 3-octanone [106-68-3] for lavender notes. The hydroxyketone acetoin and the diketone 2,3-butanedione are commercially important aroma substances.
2.1.4.1 3-Hydroxy-2-butanone [52217-02-4], Acetoin
C4H8O2, Mr 88.11, bp101.3 kPa 148 °C, 1.0062, 1.4171, has a pleasant buttery odor, and both of its optical isomers occur widely in nature. It is synthesized by partial oxidation of 2,3-butanediol and is obtained as a by-product in the fermentation of molasses. It is used for flavoring margarine.
FCT 1979 (17) p. 509.
2.1.4.2 2,3-Butanedione [431-03-8], Diacetyl
C4H6O2, Mr 86.09, bp 88 °C, 0.9831, 1.3933, is a constituent of many fruit and food aromas and well-known as a constituent of butter. Many methods are known for its manufacture, for example, dehydrogenation of 2,3-butanediol with a copper chromite catalyst [77]. Biotechnological production on an industrial scale is referred [78]. It is used mainly in aromas for butter and roasted notes. Large quantities are used for flavoring margarine; small amounts are used in perfumes.
FCT 1979 (17) p. 765.
2.1.4.3 (2E)-5-Methyl-2-hepten-4-one [81925-81-7]
C8H14O, Mr 126.20, has a fruity, hazelnut, and green odor reminding of dried fruits and a characteristic, nutty, roasted, and nougat-like hazelnut flavor. It was identified as the character compound of natural hazelnut flavor [79]. Preparation is possible, for example, by Grignard reaction of 2-butyl magnesium chloride with crotonaldehyde and subsequent oxidation or by reaction of 2-methylbutanoyl chloride with propene [80].
The material is used in fragrances as top-note booster in exotic fruit and citrus notes and in nut, cocoa, coffee, and so on, flavors.
Trade Name. Filbertone (Symrise).
2.1.4.4 3,4,5,6,6-Pentamethyl-3-hepten-2-one [81786-73-4]
Also contains other double bond isomers [81786-74-5], [81786-75-6], [81786-76-7], [81786-77-8].
C12H22O, Mr 182.30, 0.861–0.870, 1.453–1.461, is a mixture of double bond isomers. It is a colorless to slightly yellow liquid with a complex wood, floral note with amber and violet nuances and is used in perfume oils for a wide range of applications, especially in perfume oils for soaps, shower gels, and shampoos.
The material is prepared by acetylation of diisoamylene with acetic anhydride or acetyl chloride under boron trifluoride etherate catalysis [81].
Trade Names. Koavone® (IFF), Mulantone (YingHai).
2.1.4.5 2,4,4,7-Tetramethyl-6-octen-3-one [74338-72-0]
C12H22O, Mr 182.31, 0.846–0.850, 1.444–1.450, is a clear, colorless liquid with a fresh, green, and citrus herbal top note. It is reminiscent of the natural fruity freshness of grapefruit and clary sage oil and is used to create fresh top notes in a broad range of fragrance types. The material is prepared by alkylation of diisopropylketone with prenyl chloride [82].
Trade Name. Claritone® (Symrise).
2.1.5 Acids and Esters
Straight-chain, saturated aliphatic acids are found in many essential oils and foods. These acids contribute to aromas, but are not important as fragrance substances. In flavor compositions, aliphatic acids up to C10 are used to accentuate certain aroma characteristics (C3–C8 for fruity notes; C4, C6–C12 for cheese flavors). However, straight-chain and some branched-chain aliphatic acids are of considerable importance as starting materials in the manufacture of esters, many of which are valuable fragrance and flavor materials. Aliphatic esters contribute to the aroma of nearly all fruits and many foods. Some are responsible for a particular fruit aroma, or for the smell of a particular flower; however, many of these esters possess a nonspecific fruity odor.
Most of the esters used are acetates, and ethanol is the most common alcohol component. In nature, most esters are derived from alcohols and acids with an even number of carbon atoms. In addition to straight-chain saturated compounds, branched-chain compounds such as isoamyl esters and unsaturated compounds such as hexenyl esters are important.
Although the odor of aliphatic esters with a small number of carbon atoms is strictly fruity, it changes to fatty and soapy and even metallic as the number of carbon atoms increases.
Esters are usually prepared by esterification of carboxylic acids with alcohols. Industrial procedures depend on the physical properties of the esters concerned. Biosynthetic methods may be applied to produce natural esters for flavor purposes [27] [67, 83].
In perfumery, acetates are the most important aliphatic esters; formates do not keep well. Animal and fatty notes become more pronounced in esters of higher fatty acids. Acetates of alcohols up to C6 are used principally for fruity notes, whereas the acetates of C8, C10, and C12 alcohols are employed for blossom fragrances and for flower notes in general. Lauryl acetate in particular is also used for conifer notes.
In flavor compositions, aliphatic esters are preferred for artificial fruit aromas; as in nature, acetates and ethyl esters prevail.
2.1.5.1 2-Methyl-2-pentenoic Acid [3142-72-1]
C6H10O2, Mr 114.14, is a yellow liquid, 0.979–0.987, 1.457–1.462, with a dry acid note, found in the odor of strawberries. The acid can be prepared from the corresponding saturated one by α-bromination followed by dehydrobromination.
It is used in fragrances to enhance fruity notes and in strawberry flavors [84].
FCT 2000 (38, suppl. 3) p. S151.
2.1.5.2 Ethyl Formate [109-94-4]
C3H6O2, Mr 74.08, bp101.3 kPa 54.5 °C, d20 0.9168, 1.3598, occurs widely in fruits. It is a liquid with a slightly pungent, fruity, ethereal odor and is used in fruit flavors.
FCT 1978 (16) p. 737.
2.1.5.3 (Z)-3-Hexenyl Formate [33467-73-1]
C7H12O2, Mr 128.17, bp101.3 kPa 155 °C, 0.908, 1.4270, has been identified in tea. It possesses a green, fruity odor and is used in perfumery and flavor compositions to impart fruity, green notes.
FCT 1979 (17) p. 797.
2.1.5.4 Ethyl Acetate [141-78-6]
C4H8O2Mr 88.11, bp101.3 kPa 77.1 °C, 0.9003, 1.3723, is a fruity-smelling liquid with a brandy note and is the most common ester in fruits. It is used in fruit and brandy flavors.
FCT 1974 (12) p. 711.
2.1.5.5 Butyl Acetate [123-86-4]
C6H12O2, Mr 116.16, bp101.3 kPa 126.5 °C, 0.882, 1.3942, is a liquid with a strong fruity odor. It occurs in many fruits and is a constituent of apple aromas.
FCT 1979 (17) p. 515.
2.1.5.6 Isoamyl Acetate [123-92-2]
C7H14O2, Mr 130.19, bp101.3 kPa 142.5 °C, 0.868–0.878, 1.4017, is a strongly fruity-smelling liquid and has been identified in many fruit aromas. It is the main component of banana aroma and is, therefore, also used in banana flavors.
FCT 1975 (13) p. 551.
2.1.5.7 Hexyl Acetate [142-92-7]
C8H16O2, Mr 144.21, bp101.3 kPa 171.5 °C, 0.8779, 1.4092, is a liquid with a sweet-fruity, pear-like odor. It is present in a number of fruits and alcoholic beverages and is used in fruit aroma compositions.
FCT 1974 (12) p. 913.
2.1.5.8 3,5,5-Trimethylhexyl Acetate [58430-94-7], Isononyl Acetate
C
