Reflections on a Half Century of Flavor Chemistry SFC 50th Anniversary Flavor Symposium October 7, 2004 John C. Leffingwell Leffingwell & Associates

Or is it??? Mold Dicoumarol (Coumadin) Coumarin Major metabolite in man Is it hepatoxic? 1954 – FDA BANS COUMARIN

Reflections on a Half Century of Flavor Chemistry television screens were small round and black & white 1954 – the first transistor radio (The Regency) is introduced in October 1954 (transistors were developed at Bell Labs in 1948 by Shockley, Brattain & Bardeen for which they received the Nobel Prize in Physics 1956) Tom Watson, Jr., at IBM gave Regency radios to his engineers and told them to put transistors in computers.

By 1954 over a million people a year were deserting the big cities for affordable homes in suburbia

Major Advances in Instrumentation

Major Advances in Instrumentation - NMR

 Gas Chromatography – Mass Spectrometry e e e e+07 Time--> Abundance GC-MS Analysis of a Meat Flavor Peak Identified as Furfuryl Mercaptan Powerful Coffee Aroma Peaks are 2-Methyl-2,3-dihydrofuran-3-thiol isomers Powerful meat-like aroma Major Advances in Instrumentation

1958 – Food Additives Amendment Food Additives Amendment enacted, requiring manufacturers of food additives to establish safety. FEMA begins process for establishment of a GRAS list for flavorings in cooperation with the FDA – FEMA publishes first “tentative” list of GRAS flavorants – FEMA publishes first “expert committee peer reviewed” list of GRAS flavorants (662 items) – FEMA publishes expanded GRAS list (1124 items) – FEMA GRAS lists now contain ~2066 items

Butter Flavor and the delta-lactones By the mid-50’s margarine was poised to overtake butter as the table spread of choice About 1955 it was recognized that delta-dodecalactone was an important butter flavor and combinations of delta-decalactone & delta-dodecalactone would soon be the key to improved acceptability

In 1926, Reichstein & Staudinger patented the use of furfuryl mercaptan and other coffee isolates including a series of alkyl pyrazines for use in artificial coffee flavor But the value of pyrazines as flavorants was overlooked until the mid 50’s when they were rediscovered as important contributors to cocoa by Dietrich, et al., at Firmenich. Subsequently many hundreds of publications have appeared on the flavor properties of pyrazines. In coffee, cocoa and tea alone, 100 monocyclic pyrazines, 15 bicyclic pyrazines and 12 quinoxalines have been identified. Advances in Flavoring Materials Pyrazines

Advances in Flavoring Materials Green, Bell pepper, Galbanum Roasted peanut, hazelnut Popcorn, nutty, bready Cocoa, dark chocolate, nutty Earthy, raw potato; aroma of damp black earth Nutty, brown, roasted, earthy and musty 1950’s –1960’s - Pyrazines Today about 60 different pyrazines are employed in flavor creation

Advances in Flavoring Materials 2-acetylthiazole Nutty, popcorn, bread, toasted cereal 2-isobutylthiazole Green tomato aroma and taste; tomato leaf aroma Sulfurol meaty-beef like with nutty note 2,4-Dimethyl-5-vinylthiazole Nutty, meat like notes 1950’s – 1970’s – Thiazoles Today about 45 different thiazoles are employed in flavor creation.

Advances in Flavoring Materials 1950’s – Mushroom alcohol (1-octen-3-ol) Although first isolated from Armillaria matsutake in 1937 and Later (in 1944) from lavender, this material was virtually unknown to most Flavorists until the late 1950’s. Natural mushroom odor, slightly fruity Herbaceous, green, musty Today, we know that the racemates odor is dominated by the olfactively more powerful (-)-(R)- enantiomer.

Advances in Flavoring Materials beta-Pinene Myrcene Linalool GeraniolCitronellolCitronellal Menthol Linalyl Acetate 1959 – Bain & Webb – Turpentine into Fragrance & Flavor

1959 – Roche Process for Linalool & Citral via Acetylene Advances in Flavoring Materials

1959 – Discovery of Methyl Dihydrojasmonate Hedione ® First synthesis of pure "(+)-cis-Hedione ® " the olfactively most active stereoisomer of Hedione ® 1971 – Introduction of Hedione ® "

Advances in Flavoring Materials 1959 – Discovery of Rose Oxide

1960 – Safrole Banned Root Beer manufacturers shudder. Key ingredient banned. Manufacturers and flavor companies scramble to reformulate. Solution: Methyl salicylate with other items such as methyl chavicol and anethole. Methyl salicylateAnetholeMethyl chavicol Safrole

Leaf Alcohol Although the exact structure of leaf alcohol was established in 1938, it was not widely available until Bedoukian’s process in Leaf alcohol was essential for the development of many fruit flavors, especially strawberry The esters are important in many tropical flavors Advances in Flavoring Materials

Discovered in 1937, the First Publication on Raspberry Ketone appears in 1961 Advances in Flavoring Materials

1962 – First publications appear on Methyl Jasmonate & Methyl Dihydrojasmonate 1R,2R-(-)-Z-methyl jasmonate 1S,2S-(+)-Z-methyl jasmonate 1R,2S-(+)-Z-methyl epijasmonate 1S,2R-(-)-Z-methyl epijasmonate Methyl Jasmonate – odorant, insect pheromone, plant growth regulator

Advances in Flavoring Materials Chirality & Odor - Methyl Jasmonate & Methyl Dihydrojasmonate ConfigurationOdor DescriptionOdor Threshold (in PPB) Methyl jasmonates 1R,2R-(-)-Weak odor >70* 1S,2S-(+)-Odorless Odorless 1S,2R-(-)-epi-Odorless Odorless 1R,2S-(+)-epi-Strong odor; floral, true jasmin-like 3* Ref: T.E. Acree et. al., J.Agric.Food.Chem Methyl dihydrojasmonates 1R,2R-(-)-Floral, sweet, jasminelike 240** 1S,2S-(+)-Floral, fatty, cis-jasmone, hay character, 15,360** tea note, slightly lemon peellike (weak) 1S,2R-(-)-epi-Herbal, fatty, tea-like, tobacco, 12,500** β-damascone, cis-jasmone 1R,2S-(+)-epi-Intensely floral, jasmine-like, bright, cis- 15** jasmone, slightly fatty, woody, β-ionone-like, extremely long lasting Ref: Werkhoff, P., et. al., Food Reviews International, 2002 * detection threshold **recognition threshold

1964 – Introduction of Furaneol ® 1965 – First publications on isolation of Furaneol ® from strawberry and pineapple Advances in Flavoring Materials

– α - & β- Sinensal isolated from orange oil Advances in Flavoring Materials

1950’s - 60’s – Synthetic Carvones Advances in Flavoring Materials By 1957 a commercially viable route to l-carvone was available and in the 1960’s both synthetic l-carvone and d-carvone were items of commerce. But only in 1971 was it unequivocally proven that the odor differences were due to the enantioselective odor perception of the differing chiral forms.

Advances in Flavoring Materials 1960’s – Nootkatone First isolated in 1962, it’s importance to citrus flavor was unknown until it’s isolation from grapefruit by Mcleod in In 1966, Coca-Cola introduced Fresca. By 1970, Nootkatone was GRAS and became a key ingredient in Fresca. Coca-Cola manufactured Nootkatone for many years and soon made it available to the flavor industry. (+)-Nootkatone strong grapefruit odor, bitter in taste (-)-Nootkatone weak woody (vetiver note); no grapefruit character; virtually no taste Threshold: 60,000 ppb 800 ppb

1968 – Pfizer patents Ethyl maltol Ethyl maltol (Veltol Plus ® ) was touted to be about 6X stronger than maltol and an important substitute for Coumarin. Well, at least it is stronger than maltol. Advances in Flavoring Materials

1960’s-80’s – Important meaty compounds 2-methylthiophene-3-thiol Cooked meat Ortho-toluenthiol Meaty, liver 2-methylfuran-3-thiol Cooked meat 2-methyl-4,5-dihydrofuran-3-thiol Cooked meat Decadienal Meat & poultry fat 2-pentylpyridine Tallow flavor

Advances in Flavoring Materials 1970’s-80’s – Other Furanones Sotolon (caramel furanone) & Maple furanone identified in cane sugar – powerful caramel maple notes Sotolon Maple Furanone (Abhexone) Threshold: ppb ppb Sotolon – key flavorant of fenugreek, sake, sherry wine

Advances in Flavoring Materials Introduction of α -Damascone and β- Damascone 1982 – Introduction of Damascenone 1970 – Discovery Damascenone & β-Damascone

Advances in Flavoring Materials 1965 – Haarmann & Reimer begins study on synthesis of (-)-menthol from m-cresol/thymol 1973 – H&R menthol plant begins production in Holzminden 1978 – H&R’s Bushy Park, SC menthol plant on stream Haarmann & Reimer (-)-Menthol Synthesis

Advances in Flavoring Materials 1974 – Thiomenthones identified in Buchu oil Key component for black currant and the “fuzzy” peach skin note

1970’s - Wilkinson Sword’s - “Cool without Menthol” In the 1970's Wilkinson Sword Ltd. designed and evaluated about 1200 compounds for their cooling activity. Two of these, WS-3 and WS-23 were commercialized with limited success. Upon expiration of the Wilkinson Sword patents in the late 90’s, a flurry of activity resulted in expanded interest in these and related “sensate” compounds (such as Takasago’s Coolant Agent 10 and Symrise’s Frescolat ® series). WS-3 WS-23 Advances in Flavoring Materials

1980 – Patent on Oxane ® Winter identifies 2-methyl-4-propyl-1,3-oxathiane as a character impact compound in Passionfruit 1984 – Pickenhagen determines that (-)- cis- 2-methyl-4- propyl-1,3-oxathiane is the important diastereomer Advances in Flavoring Materials (-)-(2R,4S)-2-methyl-4-propyl-1,3-oxathiane Odor: powerful sulfury, tropical fruit Threshold: 2 ppb (+)-(2S,4R)-2-methyl-4-propyl-1,3-oxathiane Odor: flat, estery, camphoraceous, floral, less sulfury Threshold:4 ppb

Advances in Flavoring Materials 1981 – BASF Citral Plant comes on stream 2004 – BASF opens new continuous process citral plant with 40,000 metric tons capacity

1982 – 1-p-Menthene-8-thiol Demole identifies 1-p-Menthene-8-thiol as a character impact compound in Grapefruit Juice Very powerful with an odor threshold of ppb, it also requires stabilization as it tends to rapidly cyclize to the thio analog of dihydropinol. Advances in Flavoring Materials

1983 – Takasago’s new Enantioselective Method For producing (-)-menthol

Advances in Flavoring Materials 1986 – H&R Patents Filbertone The Character Impact Compound of Hazelnut (-)-(E,R)-Filbertone - hazelnut, soft, butter, chocolate, metallic, weaker impact (at 25 ppb in water) Odor Threshold of (-)-(E,R)-Filbertone is about 10 times higher than for (+)- (E,S)-Filbertone (+)-(E,S)-Filbertone - hazelnut, metallic, fatty, pyidine, stronger impact (at 25 ppb in water) Odor Threshold of (+)-(E,S)-Filbertone is about 10 times lower than for (-)- (E,R)-Filbertone

Advances in Flavoring Materials 3-mercapto-2-methyl-pentane-1-ol diastereosomers broth-like, sweaty, leek-like 2000 – The 3-mercapto-2-methyl-pentane-1-ols

Advances in Flavoring Materials ,4,6-trithiaheptane Character impact compound of white truffles Odor: Leek, onion, cress, horseradish; mushroom-like, earthy, green tinge

Advances in Flavoring Materials 2001 – Takasago’s Professor Ryoji Noyori wins the 2001 Nobel Prize for Chemistry

Advances in Flavoring Materials Advances in an Ambergris Compound Synthesis 1950 – Synthesis of (-)-Ambrox ® from Sclareol via Sclareolide (~90% (-)-Ambrox) 1988 – Introduction of DL-Ambrox (purely synthetic) (>50% (+/-)-Ambrox + <50% diastereomers) 1993 – Intoduction of Cetalox ® (purely synthetic) (~96% (+/-)-Ambrox) 2004 – Introduction of (-)-Cetalox Leavo (purely synthetic) (99% (-)-Ambrox) presumably via resolution of racemic Sclareolide acid with a pseudoephedrine enantiomer

Advances in Flavoring Materials Mintlactone (1983) Dihydromintlactone (1995)Wine lactone (1996) GRAS No Odor:Vinous, lactonic Minty, coumarinic, Coumarinic, hay, (coconut) tenacious lactonic, tonka Flavor:Lactonic, sweet, herbal Coumarinic, fatty, Coumarinic, herbal lactonic, coconut Threshold*: ppb ppb ppb *In air Ref: Frerot, et. al., Flavour Fragr. J., 2002; 17: 218–226; Gaudin, Tetrahedron, 2000, 56: Coumarinic p-Menthane Lactones

A 5 th taste sensation called “Umami” (aka Umani) is now accepted. Most common example is MSG (Monosodium glutamate) which enhances meat & savory flavors. The Fifth Taste Until only 4 taste sensations were generally recognized: Sweet – e.g. Sucrose, Aspartame Sour – e.g. Citric acid, Phosphoric acid (H + ions) Bitter – e.g. Quinine Salty – Sodium Chloride

Biotechnology & the Future In 1955, Artificial flavorings comprised the vast majority of flavors produced. As consumer marketing became more important, a dramatic shift to “natural” flavorings occurred requiring new and improved methods for the production of natural flavor chemicals. Biotechnology in the production of many materials is now commonplace. But, this was only the beginning. The Future is upon us.

2000/2001 – Identification of complete set of human olfactory genes (Lancet, et. al. [Weizmann Institute] & Zozulya et. al. [Senomyx]) March cloning and characterization of TRPM8 & CMR1 (cold and menthol receptors) (McKemy et. al. [UCSF] & Peier et. al. [Novartis]) 2002/2003 – characterization of heterodimeric receptors T1R2/T1R3 (sweet receptors) and T1R1/T1R3 (umami receptors) (Li et. al. [Senomyx]) 2004 – Efficacy and Potency of cooling sensates demonstrated with TRMP8 cold receptor using the (FLIPR) assay (Behrendt et. al. [Grünenthal]) Biotechnology & the Future

WATCH Identifying Taste Enhancers by taste receptor screening of lead compounds Savory – Sweet – Salt

Biotechnology & the Future October 4, Richard Axel and Linda Buck honored with the 2004 Nobel Prize in Physiology or Medicine for pioneering studies that clarify how the olfactory system works.