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Sensory-Directed Flavor Analysis. Edited by Ray Marsili

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Angewandte
Books
Chemie
Sensory-Directed Flavor Analysis
Edited by Ray Marsili. CRC Press/
Taylor & Francis,
Boca Raton 2006.
288 pp., hardcover
$ 189.00.—ISBN
978-157-444568-8
When asked the popular examination
question: “which is the better analytical
method, GC or HPLC?”, the smart
student answers: “this depends on the
scientific context, on the analytes, and
on the matrix, and sometimes you might
even require both techniques”. Ray
Marsili, in his introduction to the new
multi-author book Sensory-Directed
Flavor Analysis, compares sensory and
analytical methods for flavor analysis,
thereby posing the even more challenging question: “which is the better detector when analyzing flavor compounds—
the human nose or mass spectroscopy?”.
And from the outset, the authors agree
with the smart student on that point: “it
depends on the problem—sometimes
you need the complementarity of these
detectors”. This question leads directly
to one of the essential problems in
aroma, flavor, and perfume chemistry:
among the numerous molecular constituents of a food or natural product, which
of them do actually contribute to the
product,s flavor? A possible way of
finding an answer is to compare aromagrams and chromatograms. The latter
give the response of a physical detector
over time, whereas aromagrams trace
the response of a sensorial detection
Angew. Chem. Int. Ed. 2008, 47, 31 – 32
over time, both preceded by chromatographic separation.
Recognizing that it is impossible to
cover the entire analytical process of
flavor analysis, from sampling, through
the analysis, to data treatment, the
authors take care to mention most of
the crucial points (especially head-space
sampling methods such as SPME and
SPDE, and in the analysis stage not only
one-dimensional GC but also multidimensional GC and HPLC), and give
extensive literature references so that
one can dig deeper. An entire chapter is
dedicated to preseparation techniques
such as fractionation. The signal-tonoise increase that can be achieved
with such techniques in some cases
must not be overlooked, despite the
advantages of various other methods
that may be more convenient and capable of automation. Little information is
given about the extraction of foodstuffs
constituents. However, that is a very
difficult task because of the chemical
complexity of food and the choice
between the many techniques that are
available, e.g., steam distillation, liquid–
liquid and solid–liquid extraction using
not only conventional organic solvents
but also supercritical fluids and fluorinated solvents, and activation methods
such as microwave-assisted extraction,
ultrasonic extraction, pressurized solvent extraction, and various head-space
techniques.
Ray Marsili,s book gives an insight
into a highly topical field of research and
a clear and useful overview, as well as
many interesting ideas on the various
ways to solve flavor research problems
and how to efficiently (if possible) link
analytical and sensorial data. Although
the book does not introduce anything
new in the field of flavor research, it is a
very technically competent and wellwritten r3sum3 of the state of the art. In
order to understand its content, knowledge of analytical chemistry is
required—but despite the large amount
of information given, the book is easy
and pleasant to read.
The book,s merit is that the authors
strongly encourage researchers to not
merely produce tons of data, but to
recognize the importance of adapting
one,s analytical choices to the specific
problem. They do not gloss over the
difficulty and complexity of certain
tasks, and they cite numerous examples
for illustration. The graphics (in logical
diagram form) for experiment planning
or choice of methods are explicit and
provide a quick overview. The table of
contents is clear, and since there is no
direct link between chapters, one can
enter the book from the table of contents, or alternatively from the carefully
compiled index. The authors also
emphasize the value of statistical analysis in data processing, a tool that might
sometimes still be insufficiently appreciated. The main statistical methods are
presented in an easily comprehensible
way, illustrated by graphics. Literature
references are given for further information.
The authors manage not to get lost
in the jungle of information. This might
be due to the fact that three of the
book,s nine chapters have been written
by Ray Marsili himself. The chapters
differ in their writing style and pedagogic approach, explaining crucial
points in different ways. This might
also explain the heterogeneous presentation of cited literature and graphics.
For a research article, homogeneity of
graphics is required by journal standards—this rule should also be respected
for a book. Thus, the reproduction of
screen images of old computer programs
should be avoided. Since apparently no
instructions about the presentation of
chromatograms were given, some have
poor image resolution and are difficult
to interpret. It is also a pity that
apparently the authors of several chapters did not know that the book was to
be printed in black and white. Some
graphics that were originally colored
have turned out with only gray tones,
and have therefore become of no interest for the reader. In several cases,
chromatograms with organoleptic properties written on top of the peaks are
incorrectly called “aromagrams”.
The last chapter is a compilation of
data on flavor compounds found in
different natural matrices, listing their
occurrence, organoleptic properties,
structures, and odor thresholds. The
latter are presented in a very heterogeneous way, covering all possible imaginable units, ranging from mg/L to ng/L,
ppm, ppb, ppt, pg/g, and mg/kg. To
achieve consistency within the chapter
and to facilitate data comparison, it
- 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
31
Books
would have been preferable to use only
one or two directly comparable units for
the whole chapter. When using the
“parts-per” notation, the appropriate
unit should be chosen to avoid values
such as 0.005 ppt or 105 ppt, and the
matrix (solvent or air) and the way of
measuring (volume, mass, particles)
should be specified. Also, 0.3 ppm
cannot be called an “extremely low
detection threshold”.
Despite these criticisms, SensoryDirected Flavor Analysis is a “should
have” for flavor researchers and definitely worth reading! It gives the reader
a good overview, combined with numerous examples. It also provides literature
for refreshing one,s knowledge of general aspects of the subject. Being somewhere between textbook and research
paper, its contents easily enter the reader,s mind and provide food for thought.
Katharina Breme, Xavier Fernandez,
Uwe J. Meierhenrich
Facult7 des Sciences
Universit7 de Nice Sophia Antipolis
Nice (France)
DOI: 10.1002/anie.200685540
The Way of Synthesis
Evolution of Design
and Methods for
Natural Products.
By Tom%š Hudlický
and Josephine W.
Reed. Wiley-VCH,
Weinheim 2007.
1004 pp., softcover
E 69.00.—ISBN
978-3-527-31444-7
Tom>š Hudlický and Josephine Reed
take the reader of The Way of Synthesis
on an intellectual and scholarly journey
through highlights of total synthesis
during the last five decades. The book
discusses the beginnings of total synthesis, and describes classic examples of
the synthesis of terpenes (juvenile hormones, cedrenes, vernolepin, isocomene, retigeranic acid, taxol, and many
more) and alkaloids (quinine, reserpine,
32
www.angewandte.org
Lycopodium alkaloids, Daphniphyllum
alkaloids, Amaryllidaceae constituents,
and several others). The overview of
total synthesis is concluded by a discussion of various more recent examples of
the synthesis of natural products, such as
those of brevetoxin and indinavir.
As stated by the authors in the
preface to The Way of Synthesis, the
idea of writing this book was born after
composing an article for Chemical
Reviews (Chem. Rev. 1996, 96, 3),
which served as an introduction for a
special issue on “Frontiers in Organic
Synthesis”. The Chemical Reviews article is of a rather philosophical nature,
and critically examines general aspects
of organic synthesis. As that review
provided the framework for this book,
The Way of Synthesis can also be viewed
as a philosophical treatise, and a good
part of the book is devoted to analyzing
current trends and to explaining and
elaborating ideas that are thought-provoking and stimulating. The introductory part includes a discussion of the
history and purpose of synthesis, followed by references to historically
important milestones in structure elucidation (glucose, morphine, aspidospermine, Patchouli alcohol). A whole chapter is dedicated to the concepts of
strategy and tactics in total synthesis.
Brevity of execution, efficiency, and the
benefits of incorporating new technologies are explained in detail, followed by
discussions of dimensional analysis, pattern recognition, symmetry, connectivity, topology, computer-assisted design,
regio- and stereocontrol, modifications
of ring size, and protecting group operations.
Several books have been published
within the last few years reviewing
classics and highlights in total synthesis.
Therefore, every new addition to this
ever growing collection of compendia
needs a justification and a special purpose. This is especially true if the main
focus of a book is on summarized
descriptions of the preparation of
target compounds and of syntheses that
were published several decades ago and
have already been reviewed on numerous occasions. In fact, most of the target
compounds discussed are mature examples, and the chemistry reflects the state
of the art as it existed in the mid-1980s
rather than that of today.
- 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
A novelty in The Way of Synthesis,
compared to other books on the market
is the direct comparison of different and
independent approaches for every single
synthetic target described. Key steps of
syntheses are clearly explained and
highlighted in schemes in a different
color. The syntheses of target compounds chosen in this book were not
only the most important contributions
to total synthesis at the time, they also
serve as examples that validate general
ideas and concepts outlined in the
introductory chapters. The most important difference compared with other
textbooks is the inclusion of personal
reflections of the authors and others, as
well as anecdotes from people who were
directly involved in the research described. These descriptive and narrative
passages are of great value to a reader
and a scientist interested in learning
about the personal experiences, opinions, doubts, and thoughts of colleagues
in the field of organic chemistry and
masters of total synthesis. Such anecdotes of well-known members of the
synthetic community, as well as the
historical aspects, can easily become
lost over the years, and The Way of
Synthesis helps to preserve individual
experiences for future generations.
However, the quite unusual style of
the book, together with the philosophical, anecdotal, opinionated, and often
lengthy and self-centered sections might
distract a reader whose main focus is on
learning organic chemistry in a more
conventional way. It makes difficult
reading for a student who is looking
for a textbook on organic reactions and
reagents.
In summary, The Way of Synthesis
provides much information for its price.
It can be recommended for academic
researchers in the field of organic
chemistry who are interested in the
historical and philosophical aspects of
total synthesis, and for students who
want to get an overview of classics in
total synthesis of the second half of the
last century.
Uwe Rinner, Johann Mulzer
Department of Organic Chemistry
University of Vienna (Austria)
Angew. Chem. Int. Ed. 2008, 47, 31 – 32
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