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The 11th Wartburg Symposium on Flavor Chemistry & Biology, held at the hotel “Auf der Wartburg” in Eisenach, Germany, from June 21 to 24 in 2016, ...
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Symposium Introduction

Current Status and Future Perspectives in Flavor Research: Highlights of the 11th Wartburg Symposium on Flavor Chemistry & Biology Thomas Hofmann, Dietmar Krautwurst, and Peter Schieberle J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b06144 • Publication Date (Web): 03 Jan 2018 Downloaded from http://pubs.acs.org on January 3, 2018

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Journal of Agricultural and Food Chemistry

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Current Status and Future Perspectives in Flavor Research: Highlights of

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the 11th Wartburg Symposium on Flavor Chemistry & Biology

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Thomas Hofmann1,2*, Dietmar Krautwurst2, and Peter Schieberle2,3

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Chair of Food Chemistry and Molecular and Sensory Science, Technische

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Universität München, Lise-Meitner-Str. 34, D-85354 Freising, Germany, and

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Leibniz-Institute for Food Systems Biology at the Technical University of Munich

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(formerly: Deutsche Forschungsanstalt für Lebensmittelchemie), Lise-Meitner-Str. 34,

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D-85354 Freising, Germany 3

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Lehrstuhl für Lebensmittelchemie, Technische Universität München, Lise-Meitner Strasse 34, D-85354 Freising

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*

To whom correspondence should be addressed

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PHONE

+49-8161/71-2902

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FAX

+49-8161/71-2949

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E-MAIL

[email protected]

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ACS Paragon Plus Environment

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ABSTRACT

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The 11th Wartburg Symposium on Flavor Chemistry & Biology, held at the hotel “Auf

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der Wartburg” in Eisenach, Germany, from June 21 to 24 in 2016, offered a venue for

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global exchange on cutting-edge research in chemistry and biology of odor and taste.

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The focus areas were (1) Functional Flavor Genomics and Biotechnology, (2) Flavor

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Generation and Precursors, (3) New Approaches and Precursors, (4) New

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Approaches

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Relationships, (6) Food-Borne Bioactives and Chemosensory Health Prevention, and

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(7) Chemosensory Reception, Processing, and Perception. Selected from more than

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250 applicants, 160 distinguished scientists and rising stars from academia and

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industry from 24 countries participated in this multidisciplinary event. This special

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issue comprises a selection of 33 papers from oral presentations and poster

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contributions, and is prefaced by this introduction paper to carve out essential

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achievements in odor and taste chemistry and to share future research perspectives.

and

Technologies,

(5)

New

Molecules

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KEYWORDS

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Wartburg symposium, flavor, taste, aroma, chemoreceptors

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Structure/Activity

Journal of Agricultural and Food Chemistry

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History of the Wartburg Symposium. Scientific exchange on flavor research at the

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historical Wartburg Castle in Eisenach, Germany, dates back to 1978, when political

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conflicts between Eastern and Western Europe reached their maximum. At this time,

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Cornelius Weurman, a pioneer of flavor research who later organized the first

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Weurman Symposium in 1975, had the idea to bring together all existing European

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research groups. But he neglected that contacts between East and West European

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scientists were rather difficult at that time and were hindered by the Eastern political

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situation. As most Eastern European scientist did not have the chance to participate

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in meetings organized outside Eastern Europe, Martin Rothe, who introduced the

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consideration of odor thresholds in the evaluation of a compound’s odor contribution,1

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followed the idea to establish a separate Aroma Symposium in Eastern Europe. The

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Wartburg was selected for this symposium because of its historical background as

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well as the central geographic position in Germany. But the political problems could

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not be overcome. The organizers of the 1st Wartburg Aroma Symposium were clearly

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asked by the East German government, not only to select participants under

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scientific, but also political aspects. Considering this difficult situation, the organizers

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were proud about the active participation of eight well-known West European

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scientists, among them Werner Grosch, one of the inventors of the aroma extract

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dilution analysis (AEDA) and the odor activity value (OAV) concept,2 which was later

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further refined by Peter Schieberle,3,4 one of the organizers of the Wartburg

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symposium. In the past 40 years, the Wartburg Symposium has convened every

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three years and is today internationally respected as one of the most influential

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international symposia on flavor chemistry with firmly established bridges to biology

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and neurophysiology of smell and taste.

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Achievements in Flavor Research. Primarily driven by the introduction of

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gas chromatography in the nineteen sixties, the primary objective in the early days of ACS Paragon Plus Environment

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flavor research was to characterize as many volatiles in foods as possible. This led to

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the identification of about 8,000 volatiles and supported the prediction of a total of

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~10,000 volatiles to occur in foods.5,6 However, dose/activity considerations fed

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increasing doubts that the typical aroma of a given food is caused by a huge number

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of volatiles, and Martin Rothe, the founder of the Wartburg symposium, was one of

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them.1-3 This induced a paradigm shift in flavor research, fueled by the birth of GC-

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olfactometry (GC-O), enabling the localization of aroma-relevant odorants among the

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bulk of sensorially inactive volatiles in the chromatographic effluent by human

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“sniffing” detection.7-10 By repeated GC-O analysis of serially diluted aroma distillates,

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charm analysis10 or aroma extract dilution analysis (AEDA)2-4,10 even allowed the

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ranking of the odorants detected with respect to their sensory impact, and helped to

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focus the laborious identification experiments on the most intense food odorants. As

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the GC-O screening of key odorants is based on their threshold in air and not in the

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respective food matrix, researchers then started to study the contribution of individual

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odorants to a given food aroma on the basis of “odor activity values” (OAV) defined

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as the ratio of the concentration of an odorant in the food and its odor threshold in an

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appropriate matrix.1-4,12-14 This concept demonstrated that the rather unlimited

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variations in food flavors are due to a “combinatorial chemosensory code” (Figure

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1A), comprising a surprisingly small center group of 3-40 volatile key food odorants

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among the several ten thousands of non-odor active food constituents.

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In the early years of the new millennium, flavor chemistry was expanded by

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applying the principle of bioresponse-guided identification of odorants to non-volatile

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taste-active compounds. In particular, the application of the taste dilution analysis

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(TDA)15 and the comparative taste dilution analysis (cTDA)16 have led to the

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discovery of previously unknown key taste molecules and taste modulators in

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thermally processed foods like chicken broth,17 beef juice,18 hazelnuts,19 cooked ACS Paragon Plus Environment

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crustaceans,20 roasted coffee,21 fermented foods like Gouda and Parmesan

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cheese,22-25 red wine,26 beer and hops,27,28 black tea,29 fish sauce,30 balsamic

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vinegar,31 and yeast extracts,32 and plant-derived products like cocoa,33 Tasmanian

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pepper,34 carrots,35 and asparagus,36 respectively. Very recently, for the first time,

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odorants have been discovered to exhibit taste modulatory function, e.g. (R)-

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citronellal has been reported to attenuate caffeine bitterness by inhibiting the bitter

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receptors TAS2R43 and TAS2R46.37

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Counteracting analytical challenges in accurate quantitation of odorants and

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tastants, which are largely differing in concentration, volatility, and chemical stability,

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the so-called stable isotope dilution analysis (SIDA) was introduced in flavor

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research, using stable isotope (13C, 2H)-labeled twin molecules of the odorants and

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tastants as most suitable internal standards for GC-MS and LC-MS analysis.2-4,10,38-40

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Most impressively, minimal chemosensory recombinates of 3 to 40 key odorants and

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15-40 key tastants have been demonstrated to be truly necessary and sufficient for

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“synthesizing” the authentic percept of a specific food’s odor such as, e.g. black tea41

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and red wine (Figure 1B),39 although the overall flavor quality was not represented

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by any of the single ingredients alone.42 Therefore, the key mechanism by which the

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brain encodes perceptual representations of behaviorally relevant food items is

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through the synthesis of combinatorial chemosensory inputs into a unique perceptual

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experience (“flavor object”), rather than through individual molecules.42 In

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contradiction to traditional views, the sheer unlimited variations in food flavors is

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today accepted to be due to a “combinatorial chemosensory code” (Figure 1A)

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comprising a surprisingly small center group of 3-40 volatile key food odorants and

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10-40 non-volatile key food tastants among the several ten thousands of food

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constituents.31,39,42

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The hedonic differentiation and evaluation of these food flavor signatures is

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due to the high discriminatory power of the olfactory and gustatory system.42,43 A

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food’s chemical flavor profile is translated into specific receptor activity patterns

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elicited by the interaction of the mixture of chemosensory key molecules with their

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best cognate receptors out of the ~400 olfactory und ~30 taste receptors, among

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which sweet and umami tastes are mainly mediated by TAS1R receptor

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heterodimers44-46 while the perception of bitterness is mediated by 25 G-protein-

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coupled TAS2R receptors.47-49 Although these flavor objects enable us to make food

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choice decisions, surprisingly little is known about the human receptor activation

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patterns for single food odorants and tastants, and nothing is known about receptor

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codes for chemosensory mixtures as recently exemplified for the odorant receptor

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code of cultured butter (Figure 1C).50 Moreover, knowledge is rather limited on the

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complementation as well as co-activation of bitter taste receptors by the various

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bitter-tasting molecules present in foods and beverages such as, e.g. beer,51

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cheese,52 stevia extract,53 carrots, and coffee (unpublished data), respectively

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(Figure 2). In consequence, the minimal chemosensory recombinates, rather than

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individual stimuli, seem to be most promising “molecular probes” for future research

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to decode the mechanisms triggering food preference and aversive behaviors.

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Scientific Challenges and Future Perspectives. Today’s challenges in

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flavour research are multifold: To overcome flavor defects in healthy food products,

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reduced in salt, sugar, monosodium glutamate (MSG), and fat, respectively, the food

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and nutrition sector relies on new solutions and technologies capable of fine-tuning

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aroma deviations as well as the use of natural and/or biosynthetic, high-potency taste

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modulation systems for the delivery of truly authentic flavor signatures.

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Independent from their sensory quality, most food-borne key odorants/tastants

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are generated from precursors in the raw materials upon processing and/or ACS Paragon Plus Environment

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fermentation of foods and their generation is strongly dependent on the processing

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conditions. Representing the molecular blueprint of our food’s chemosensory

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signature, the population of key flavor compounds, coined “sensometabolome”,24

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may be used as a molecular target for visualizing the changes in odor and taste

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profiles from the raw materials through the various manufacturing process

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intermediates all the way up-stream to the consumer’s plate by high-precision and

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high-throughput mass spectrometric profiling. This will open new avenues for a more

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scientifically directed taste improvement of foods by tailoring processing parameters

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(“molecular food engineering”); for example, targeted food-borne generation of high-

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potency salt, sweet, umami, or mouthfullness (kokumi) enhancers will help to

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overcome taste defects in salt, sugar, and MSG-reduced food products without

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artificial ingredients. Also the efficient control of bitter off-tastes of food products and

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phytochemical supplemented products might be possible by suppressing bitter taste

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perception by means of controlled generation of food-borne bitter inhibitors.

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Molecular knowledge of the odor code of crops and vegetables holds promise

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for major improvements in future breeding strategies, which in the past have been

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targeted primarily towards field performance, yield, and storage characteristics, while

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ignoring quality traits such as aroma and taste. The analytical assessment of the key

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odorants and tastants would greatly facilitate the accurate evaluation of a large

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number of progeny, thus moving the selection of flavor earlier in the selection

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sequence and increasing the chance of finding truly superior new cultivars for a wide

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cross-section of food crops. Therefore, advances in flavor chemistry and biology hold

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promise to become truly a game-changer helping to transform the incremental

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product improvement approaches of our today’s industry into a consumer-centric re-

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engineering strategy, more effectively targeting food development to consumers’

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preference, acceptance, and needs. ACS Paragon Plus Environment

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To achieve all this, we need modern analytical technologies to speed up the

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discovery of unknown chemosensory active molecules in nature’s unlimited box of

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molecules and to understand their physico-chemical interactions with food matrix

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constituents on a molecular level. We need to learn how to optimize the gene

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computer of plants and to utilize the biosynthetic power of plants and microorganisms

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to produce target flavor molecules in high yields and also high enantioselectivity. In

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addition, we should use our knowledge on the combinatorial chemosensory codes for

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a targeted navigation of breeding and post-harvest processing parameters to support

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plant breeders in the development of premium tasty plant materials.

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New research is required to increase our knowledge on the molecular

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alterations of salivary composition upon stimulation with odorants and tastants,54,55 as

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well as the receptor proteins involved in sensing of odorants, tastants, and additional

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stimuli such as fat. We need to understand how our foods’ combinatorial

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chemosensory codes are translated into food-specific chemosensory receptor

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activation patterns and how this can be modulated to develop premium tasty and

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healthy food products with reduced levels of, e.g., salt, sugar, and fat.

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More fundamental knowledge is urgently needed from the secretion of

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neurotransmitters to the induction of neural activity that is conveyed to the cerebral

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cortex to represent the distinct odor and taste qualities. As food preferences and

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aversions have been reported to develop across life stages and individual differences

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in chemosensory receptor genotypes to affect flavor experience and food selection,56-

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genotypic differences with respect to sensory preference for and aversion against

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food flavors. Intriguingly, the conditioned aversion for odorants in mice has been

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shown to be maintained over two generations60, indicating epigenetic modification to

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play a key role not only in mono-allelic odorant receptor gene activation,61 but also in

we need to entangle individual age-dependent chemosensory pheno- and

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sensory programming and development of nutritional preferences/aversions across

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life stages.62 Last but not least, we have to furtherance our knowledge on the

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biotransformation of odorants and tastants in the nasal and oral cavity, but also on

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the biological response induced upon their ingestion.

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Without any doubt, advancement in these fields will crucially depend on how

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consequently scientists will dare to leave the trampling paths of their own disciplines,

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and will learn to live up their science in a interdisciplinary environment, striving to

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generate synergies by bundling the different expertise and technology know-how of

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research in food and natural product chemistry, psychophysics and sensory science,

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nutrition and health sciences, biotechnology, plant biology and genetics, human

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biology, genetics and neurophysiology, respectively. Exactly this profile rounds out

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the Wartburg Symposium’s characteristic signature as a fruitful retreat to discuss

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emerging cross-disciplinary challenges in a relaxing atmosphere.

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The 11th Wartburg Symposium on Flavor Chemistry & Biology. To tackle

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these truly cross-disciplinary research challenges, top-tier flavor chemistry and

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biology once more returned back to the “Hotel on the Wartburg” in Eisenach,

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Germany. Between June 21 and 24 in 2016, this symposium offered a venue for

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global exchanges and knowledge calibration of the state of the art research in flavor

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chemistry and biology and for the presentation and discussion of latest advances and

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future research opportunities. Compared to its infant days, flavor research has

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embarked on a journey beyond its traditional core disciplines in chemistry and

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sensory analysis, and has begun to valorize the sweet spots emerging at the

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intersection with biotechnology, human biology, and neurophysiology.

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Selected from more than 250 applicants, 160 distinguished scientists and

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rising stars from academia and industry from 24 countries and 4 continents

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participated in this highly multidisciplinary event on the historic castle (Figure 3). ACS Paragon Plus Environment

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Experts from analytical and natural product chemistry, psychophysics and sensory

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science, nutrition and health sciences, biotechnology, plant biology and genetics,

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human biology and neurophysiology, and imaging technologies shared expertise and

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new insights, calibrated their knowledge, and exchanged on future perspectives.

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This special issue presents a selection of 33 papers from oral and flash poster

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presentations and poster contributions shown in the thematic symposium sessions

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(1) Functional Flavor Genomics and Biotechnology, (2) Flavor Generation and

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Precursors, (3) New Approaches and Precursors, (4) New Approaches and

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Technologies, (5) New Molecules and Structure/Activity Relationships, (6) Food-Born

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Bioactives and Chemosensory Health Prevention, and (7) Chemosensory Reception,

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Processing and Perception, and demonstrates the depth and broad scope of the

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science presented at the Wartburg symposium. The former idea of bringing together

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people from Eastern and Western Europe was replaced in favour of building

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multinational bridges between different scientific disciplines – and this will also shape

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the unique signature of future Wartburg Symposia.

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The 12th Wartburg Symposium in 2019. The next Wartburg Symposium on

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Flavor Chemistry & Biology will be held from May 21 to May 24, 2019 at the historic

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Wartburg Castle. If you want to see the latest developments at the intersection of

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chemistry and biology of flavors, make your plans to be there.

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ACKNOWLEDGEMENT

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The organizers are grateful to all the sponsors for their generous support, which

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helped to offset the travel expenses of invited speakers and other costs to run the

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symposium: the Gold sponsors, namely, PepsiCo, Mars, Nestle, Altria, General Mills, ACS Paragon Plus Environment

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DSM, and Philip Morris; the Silver sponsors, namely Döhler, Hasegawa, Givaudan,

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Lucta, Takasago, Symrise, Gerstel, and Mondelez; and the Bronze sponsors, namely

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Ajinomoto, Aromalab, Wakunaga, Bell Flavors, Flavologic, and the American

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Chemical Society (ACS). In addition, we thank the German Research Center for

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Food Chemistry, and the Technical University of Munich for supporting the

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organization of the symposium with staff and expertise, in particular, Corinna Dawid

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for planning and organization of the symposium and Andreas Dunkel for the technical

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support. We also would like to thank the Wartburg Stiftung and, in particular, Andreas

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Volkert, for making it again possible to use the stimulating historic place with the

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knights hall for that symposium, and the hotel staff for creating a friendly and warm

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atmosphere in the hotel “Auf der Wartburg”.

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LITERATURE CITED

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Rothe, M.; Thomas, B. Odorants in bread – a study on chemical flavor analysis

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using threshold concentrations (in German). Z. Lebensm.-Unters. Forsch. 1975,

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aroma models and omission. Chem. Senses 2001, 26, 533-545.

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Grosch, W. Evaluation of the key odorants of foods by dilution experiments,

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Schieberle, P. New developments on methods for analysis of volatile flavor

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compounds and their precursors. In: Characterization of food-emerging

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methods (A. G. Gaonkar, Ed.), 1995, Elsevier, Amsterdam, 1995, pp. 403-433.

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Hofmann, T.; Schieberle, P. Elucidation of the chemosensory code of foods by means of a sensomics approach. Flavour Science - Proceedings of the XIV

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Weurman Flavour Research Symposium (Taylor A.J., Mottram

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2015, pp. 3-12.

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eds),

VCF Volatile Compounds in FOOD, database version 14.1 (Eds.: L. M. Nijssen, C. A. Ingen-Visscher, J. J. H. van Donders), TNO Triskelion, Zeist, 2013.

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Rijkens, F.; Boelens, M.H. The future of aroma research; In: Aroma Research

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T. E. Acree, GC/olfactometry Anal. Chem. 1997, 69, 170A-175A.

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Frank, D.; Ball, A.; Hughes, J.; Krishnamurthy, R.; Piyasiri, U.; Stark, J.;

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Watkins, P.; Warner, P. Sensory and flavor chemistry characteristics of

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Australian beef: influence of intramuscular fat, feed, and breed. J. Agric. Food

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W. Grosch, Detection of potent odorants in foods by aroma extract dilution analysis. Trends Food Sci. Technol. 1993, 4, 68-73.

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10. Schieberle, P.; Hofmann, T. Evaluation of the character impact odorants in fresh

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strawberry juice by quantitative measurements and sensory studies on model

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mixtures. J. Agric. Food Chem. 1997, 45, 227-232.

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11. Acree, E.; Barnard, J.; Cunningham, D.G. A procedure for the sensory analysis of gas chromatographic effluents. Food. Chem. 1984, 14, 273-286.

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12. Buttery, R.G. Quantitative and sensory aspects of flavior of tomato and other

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vegetables and fruits. In: Flavor Science. Sensible Principles and Techniques

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(Eds.: T. E. Acree, R. Teranishi), American Chemical Society, Washington DC,

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1993, 259-286.

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13. Wagner, J.; Granvogl, M.; Schieberle, O. Characterization of the key aroma

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compounds in raw licorice (Glycyrrhiza glabra L.) by means of molecular

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sensory science. J. Agric. Food Chem., 2016, 64, 8388–8396. ACS Paragon Plus Environment

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14. Xiao, Z.; Wu, Q.; Niu, Y.; Wu, M.; Zhu, J.; Zhou, X.; Chen, X.; Wang, H.; Li, J.;

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Kong, J. Characterization of the key aroma compounds in five varieties of

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mandarins by gas chromatography-olfactometry, odor activity values, aroma

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recombination, and omission analysis. J. Agric. Food Chem. 2017, 65, 8392-

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8401.

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15. Frank O., Ottinger H., Hofmann T. (2001) Characterization of an Intense Bitter-

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tasting 1H,4H-Quinolizinium-7-olate by Application of the Taste Dilution

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Analysis, A Novel Bioassay for the Screening and Identification of Taste-active

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Compounds in Foods. J. Agric. Food Chem., 49, 231-238.

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16. Ottinger H., Soldo T., Hofmann T.

(2003) Discovery and Structure

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Determination of a Novel Maillard-Derived Sweetness Enhancer by Application

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of the Comparative Taste Dilution Analysis (cTDA). J. Agric Food Chem., 51,

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1035-1041.

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17. Dunkel, A.; Hofmann, T., Sensory-directed identification of beta-alanyl

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dipeptides as contributors to the thick-sour and white-meaty orosensation

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induced by chicken broth. J. Agric. Food Chem. 2009, 57, 9867-77.

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18. Ottinger, H.; Hofmann, T., Identification of the taste enhancer alapyridaine in

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beef broth and evaluation of its sensory impact by taste reconstitution

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experiments. J. Agric. Food Chem. 2003, 51, 6791-6796.

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19. Singldinger, B.; Dunkel, A.; Hofmann, T. The cyclic diarylheptanoid asadanin as

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the main contributor to the bitter off-taste in hazelnuts (Corylus avellana L.). J.

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Agric. Food Chem. 2017, 65, 1677-1683.

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20. Meyer, S.; Dunkel, A.; Hofmann, T., Sensomics-Assisted Elucidation of the

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Tastant Code of Cooked Crustaceans and Taste Reconstruction Experiments.

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J. Agric. Food Chem. 2016, 64, 1164-75.

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21. Frank, O.; Zehentbauer, G.; Hofmann, T. Bioresponse-guided decomposition of

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roast coffee beverage and identification of key bitter taste compounds, Eur.

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Food Res. Technol. 2005, 222, 492-508.

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22. Toelstede, S.; Dunkel, A.; Hofmann, T., A Series of Kokumi Peptides Impart the

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Long-Lasting Mouthfulness of Matured Gouda Cheese. J. Agric. Food Chem.

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2009, 57, 1440-1448.

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23. Toelstede, S.; Hofmann, T., Quantitative studies and taste re-engineering

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experiments toward the decoding of the nonvolatile sensometabolome of Gouda

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cheese. J. Agric. Food Chem. 2008, 56, 5299-5307.

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24. Toelstede, S.; Hofmann, T., Sensomics mapping and identification of the key

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bitter metabolites in Gouda cheese. J. Agric. Food Chem. 2008, 56, 2795-2804.

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25. Hillmann, H.; Hofmann, T. Quantitation of key tastants and re-engineering the

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taste of Parmesan cheese. J. Agric. Food Chem. 2016, 64, 1794-805. 26. Hufnagel, J. C.; Hofmann, T., Quantitative reconstruction of the nonvolatile sensometabolome of a red wine. J. Agric. Food Chem. 2008, 56, 9190-9199.

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27. Intelmann, D.; Haseleu, G.; Dunkel, A.; Lagemann, A.; Stephan, A.; Hofmann,

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T. Comprehensive sensomics analysis of hop-derived bitter compounds during

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storage of beer. J. Agric. Food Chem. 2011, 59, 1939-1953.

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28. Dresel, M.; Vogt, Ch.; Dunkel, A.; Hofmann, T. The bitter chemodiversity of hops (Humulus lupulus L.). J. Agric. Food Chem., 2016, 64, 7789–7799.

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29. Scharbert, S.; Holzmann, N.; Hofmann, T. Identification of the astringent taste

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compounds in black tea infusions by combining instrumental analysis and

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human bioresponse, J. Agric. Food Chem. 2004, 52, 3498–3508.

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30. Schindler, A.; Dunkel, A.; Stähler. F.; Backes, M.; Meyerhof, W.; Hofmann, T.

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Discovery of salt taste enhancing arginyl dipeptides in protein digests and

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fermented fish sauces by means of a sensomics approach. J. Agric Food

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Chem. 2011, 59, 12578-12588.

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31. Hillmann, H.; Mattes, J.; Brockhoff, B.; Dunkel, A.; Meyerhof, W.; Hofmann, T.

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Sensomics analysis of taste compounds in balsamic vinegar and discovery of 5-

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acetoxymethyl-2-furaldehyde as a novel sweet taste modulator. J. Agric. Food

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Chem. 2012, 60, 9974–9990.

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32. Festring, D.; Hofmann, T., Discovery of N(2)-(1-carboxyethyl)guanosine 5'-

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monophosphate as an umami-enhancing maillard-modified nucleotide in yeast

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extracts. J. Agric. Food Chem. 2010, 58, 10614-22.

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33. Stark, T.; Hofmann, T. Isolation, structure determination, synthesis, and sensory

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activity of N-phenylpropenoyl-L-amino acids from cocoa (Theobroma cacao), J.

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Agric. Food Chem. 2005, 53, 5419–5428.

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34. Mathie, K.; Lainer, J.; Spreng, S.; Dawid, C.; Andersson, D.A.; Bevan, S.;

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Hofmann, T. Structure–pungency relationships and TRP channel activation of

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drimane sesquiterpenes in Tasmanian pepper (Tasmannia lanceolata). J. Agric.

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Food Chem., 2017, 65, 5700–5712.

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35. Czepa, A.; Hofmann, T. Structural and sensory characterization of compounds

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contributing to the bitter off-taste of carrots (Daucus carota L.) and carrot puree,

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J. Agric. Food Chem. 2003, 51, 3865–3873.#

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36. Dawid, C.; Hofmann, T. Structural and sensory characterization of bitter tasting

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steroidal saponins from Asparagus apears (Asparagus officinalis L.), J. Agric.

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Food Chem. 2012, 60, 11889–11900.

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37. Suess, B.; Brockhoff, A.; Meyerhof, W.; Hofmann, T. The odorant (R)-citronellal

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attenuates caffeine bitterness by inhibiting the bitter receptors TAS2R43 and

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TAS2R46. J. Agric. Food Chem. 2017, DOI: 10.1021/acs.jafc.6b03554

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38. Kiefl, J.; Pollner, G.; Schieberle, P. Sensomics analysis of key hazelnut

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odorants (Corylus avellana L. 'Tonda Gentile') using comprehensive two-

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dimensional gas chromatography in combination with time-of-flight mass

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spectrometry (GC×GC-TOF-MS). J. Agric. Food Chem. 2013, 61, 5226-5235.

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39. Frank, S.; Wollmann, N.; Schieberle, P.; Hofmann, T. Reconstitution of the

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flavor signature of Dornfelder red wine on the basis of the natural

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concentrations of its key aroma and taste Compounds. J. Agric. Food Chem.

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2011, 59, 8866-8874.

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40. Stark T., Justus H., Hofmann T. Quantitative analysis of N-phenylpropenoyl-L-

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amino acids in roasted coffee and cocoa powder by means of a stable isotope

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dilution assay. J. Agric. Food Chem. 2006, 54, 2859-2867.

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41. Schieberle P., Hofmann T. In: Food Flavors - Chemical, Sensory and

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Technological Properties (H. Jelen, ed.); CRC Press, Taylor and Francis Group,

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2011, pp. 411-437.

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42. Dunkel, A.; Steinhaus, M.; Kotthoff, M.; Nowak, B.; Krautwurst, D.; Schieberle,

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P.; Hofmann, T. Nature’s chemical signatures in human olfaction: a foodborne

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perspective for future biotechnology. Angew. Chem. Int. Ed. 2014, 53, 7124-714

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43. Olender, T.; Waszak, S.; Viavant, M.; Khen, M.; Ben-Asher, E.; Reyes, A.;

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Nativ, N.; Wysocki, C.J., Ge, D.; Lancet, D. Personal receptor repertoires:

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olfaction as a model BMC Genomics 2012, 13, 414.

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44. Li, X.; Staszewski, L.; Xu, H.; Durick, K.; Zoller, M.; Adler, E. Human receptors

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for sweet and umami taste. Proc. Natl. Acad. Sci USA 2002, 99, 4692-4696.

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45. Behrens, M.; Meyerhof, W.; Hellfritsch, C.; Hofmann, T. Sweet and umami

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taste: natural products, their chemosensory targets, and beyond. Angew. Chem.

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Int. Ed. 2011, 50, 2220-2242.

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46. Nelson, G.; Chandrashekar, J.; Hoon, M.A.; Feng, L.; Zhao, G.; Ryba, N.J.P.; Zuker, C.S. An amino-acid taste receptor. Nature 2002, 416, 199-202. 47. Adler, E.; Hoon, M.A.; Mueller, K.L.; Chandrashekar, J.; Ryba, N.J.; Zuker, C.S. A novel family of mammalian taste receptors. Cell 2000, 100, 693-702.

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48. Chandrashekar, J.; Mueller, K.L.; Hoon, M.A.; Adler, E.; Feng, L.; Guo, W.;

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Zuker, C.S.; Ryba, N.J. T2Rs function a bitter taste receptors. Cell 2000, 100,

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703-711.

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49. Matsunami, H.; Montmayeur, J.P.; Buck, L.B. A family of candidate taste receptors in human and mouse. Nature 2000, 404, 601-604.

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50. Geithe, C.; Andersen, G.; Malki, A., Krautwurst, D. A butter aroma recombinate

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activates human class-I odorant receptors. J. Agric. Food Chem. 2015, 63,

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9410-9420.

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51. Intelmann, D.; Batram, C.; Kuhn, Ch.; Haseleu, G.; Meyerhof, M.; Hofmann, T.

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Three TAS2R bitter taste receptors mediate the psychophysical responses to

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bitter compounds of hops (Humulus lupulus L.) and beer, Chem. Percept. 2009,

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2, 118-132.

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52. Kohl, S.; Behrens, M.; Dunkel, A.; Hofmann, T.; Meyerhof, W. Amino acids and

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peptides activate at least five members of the human bitter taste receptor

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family. J. Agric. Food Chem. 2013, 61, 53-60.

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53. Hellfritsch, C.; Brockhoff, A.; Staehler , F.; Meyerhof, W.; Hofmann, T. Human

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psychometric and taste receptor responses to steviol glycosides. J. Agric. Food

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Chem. 2012, 60, 6782-6793.

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54. Delius, J.; Médard, G.; Kuster, B.; Hofmann, T. Effect of astringent stimuli on

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salivary

protein

interactions

elucidated

by

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approaches. J. Agric. Food Chem. 2017, 65, 2147-2154.

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55. Stolle, T.; Grondinger, F.; Dunkel, A.; Meng, C.; Médard, G.; Kuster, B.;

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Hofmann, T. Salivary proteome patterns affecting human salt taste sensitivity. J.

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56. Doty, R.L.; Kamath, V. The influences of age on olfaction: a review. Front Psychol. 2014, 5, 20. eCollection 2014 57. Mennella, J.A.; Finkbeiner, S.; Reed, D.R. The proof is in the pudding: children prefer lower fat but higher sugar than do mothers. Int. J. Obes. 2012, 36, 1285.

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58. Mennella, J.A., Pepino, M.Y.; Duke, F.F.; Reed, D.R. Age modifies the

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genotype-phenotype relationship for the bitter receptor TAS2R38. BMC Genet.

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2010, 11, 60

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59. Jaeger, S.R.; McRae, J.F.; Bava, C.M.; Beresford, M.K.; Hunter, D.; Jia, Y.;

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Chheang, S.L.; Jin, D.; Peng, M.; Gamble, J.C.; Atkinson, K.R.; Axten, L.G.;

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Paisley, A.G.; Tooman, L.; Pineau, B.; Rouse, S.A.; Newcomb, R.D. A

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mendelian trait for olfactory sensitivity affects odor experience and food

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selection. Curr. Biol. 2013, 23, 1601-1605.

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60. Dias, B.G.; Ressler, K.J. Parental olfactory experience influences behavior and

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neural structure in subsequent generations. Nat. Neurosci. 2014, 17, 89-96.

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61. Reinsborough, C.; Chess, A. An epigenetic trap involved in olfactory receptor

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gene choice. Dev. Cell. 2013, 26, 120-121. 62. Langley-Evans, S.C. Nutrition in early life and the programming of adult disease: a review. J. Hum. Nutr. Diet. 2015, 28, 1-14.

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Figure Legend

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Figure 1.

(A) Heatmap displaying odor activity values (OAVs) of the 226 key food

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odorants (KFOs) characterized in 227 food samples.42 (B) Sensory

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profile of an authentic red wine vs. a minimal biomimetic flavor

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recombinate comprising 28 key food odorants and 35 key food

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tastants.39 (C) EC50-based odorant receptor activation barcodes elicited

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by a minimal recombinant exemplified with a 3-compound recombinate

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of cultured butter aroma.50

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Figure 2.

tastants in beer, coffee, carrots, cheese, and Stevia.

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Bitter taste receptor complementation and co-activation by bitter

Figure 3.

The global science community met at the hotel “Auf der Wartburg” in

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Eisenach, Germany, from June 21 to 24 in 2016, to participate in the

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11th Wartburg Symposium on Flavor Chemistry & Biology.

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Figure 1 (Hofmann et al.)

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Figure 2 (Hofmann et al.)

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Figure 3 (Hofmann et al.)

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