Flavor Chemistry - American Chemical Society

Downloaded by UNIV ILLINOIS URBANA-CHAMPAIGN on March 26, 2017 | http://pubs.acs.org Publication Date: February 21, 1989 | doi: 10.1021/bk-1989-0388.ch016

Chapter 16

New Trends in Black Truffle Aroma Analysis T. Talou, M. Delmas, and A. Gaset Laboratoire de Chimie des Agroressources, Ecole National Supérieure de Chimie, I.N.P.T., 118, route de Narbonne 31077 Toulouse Cedex, France The volatile compounds in the atmosphere of cold stored Black Perigord Truffles (Tuber Melanosporum) were adsorbed onto a Tenax trap by means of a vacuum pump. The efficiency of the sampling method was sensorially validated. The volatiles eluted from the trap by heat desorption were analysed by capillary gas chromatography - mass spectrometry. A total of 26 compounds was identified. Their contribution to the final aroma impression was discussed. The i s o l a t i o n o f v o l a t i l e f l a v o r compounds from foods r e p r e s e n t s a major problem i n a n a l y t i c a l studies of food flavor. Headspace methods are e s p e c i a l l y a t t r a c t i v e s i n c e they a r e r a p i d , s i m p l e and measure what i s t y p i c a l l y p r e s e n t e d t o the n o s e . We have p r e v i o u s l y used a Dynamic Headspace method, optimized with E x p e r i m e n t a l D e s i g n (1), f o r the i s o l a t i o n o f the volatiles from Black P e r i g o r d T r u f f l e s (Tuber Melanosporum). T r u f f l e s are underground mushrooms t h a t grow i n s y m b i o s i s w i t h certain trees, especially oaks. One f i n d s them i n s e v e r a l regions of Europe, p a r t i c u l a r l y i n France, where t h e i r f l a v o r i s v e r y much a p p r e c i a t e d by gourmets. Our s t u d i e s , c a r r i e d out on t r u f f l e f l e s h (2,3) » and entire t r u f f l e s (Talou, T . et a l l , S c i Food A g r i c . , i n p r e s s ) , a l l o w e d us t o i d e n t i f y the major v o l a t i l e compounds. Due to the low sampling weight, however, the method appeared to be i n e f f e c t i v e f o r i s o l a t i n g compounds e x t r e m e l y low i n c o n c e n t r a t i o n . The atmosphere of c o l d stored Black T r u f f l e s is particularly rich in volatile compounds which i m p a r t the truffle aroma. We therefore d e v e l o p e d a m o d i f i e d gas headspace s a m p l i n g p r o c e d u r e f o r their isolation. The aims o f t h i s s t u d y were to e v a l u a t e the e f f i c i e n c y o f our sampling method f o r t r a p p i n g v o l a t i l e components i m p o r t a n t t o the aroma o f Black Perigord Truffles, and the analysis of minor v o l a t i l e s v i a t h e i r i d e n t i f c a t i o n w i t h c a p i l l a r y gas chromatographymass s p e c t r o m e t r y . 0097-6156/89/0388-0202$06.00/0 © 1989 American Chemical Society

Teranishi et al.; Flavor Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

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Experimental P l a n t m a t e r i a l F r e s h B l a c k P e r i g o r d T r u f f l e s (Tuber Melanosporum) f o r a n a l y s i s were p u r c h a s e d by Pebeyre L t d . , a company s p e c i a l i z i n g in t r u f f l e m a r k e t i n g . C o l l e c t e d e s s e n t i a l l y i n the South East of France, they were f u l l y r i p e (4) and r e l e a s e d t h e i r c h a r a c t e r i s t i c aroma. R e c e i v e d the day a f t e r g a t h e r i n g i n w i c k e r - b a s k e t s , . t r u f f l e s were h a n d - p i c k e d and then s t o c k e d i n a c o l d s t o r a g e o f 15 m . V o l a t i l e c o l l e c t i o n was g e n e r a l l y begun the day a f t e r r e c e i v i n g the packages. 1000 kg o f unbrushed t r u f f l e s were i n s t o r a g e when atmosphere c a p t u r e was c a r r i e d o u t . Three i s o l a t i o n s were carried out i n d u p l i c a t e d u r i n g F e b r u a r y 1987. Preparation o f Tenax tubes and Blank Tenax chromatogram Tenax GC (60-80 mesh) was c o n d i t i o n n e d by h e a t i n g 10 g a t 250 C f o r 24 h i n a dry Helium flow o f 50 mL/min. C o n d i t i o n e d Tenax (0,2 g) was packed i n t o a 6 cm l o n g s t e e l tubes (6 mm o.d., 4 mm i . d . ) and p l u g g e d w i t h glass wool. A blank Tenax gas chromatogram was o b t a i n e d by heat desorbing the tube i n t o a gas chromatograph (GC) column u s i n g the p r o c e d u r e d e s c r i b e d under Heat D e s o r p t i o n o f Aroma v o l a t i l e s s e c t i o n , Additional c l e a n i n g o f Tenax tubes was s t a n d a r d i z e d by heat desorption a t 200°C f o r 30 min i n the oven o f the D.C.I. System. Headspace sampling method An i d e a l i z e d diagram o f the sampling system i s shown i n F i g u r e 1. I t c o n s i s t e d o f a vacuum pump, a needle valve, a f l o w meter and 2 a u x i l i a r y Tenax t u b e s . C o n n e c t i o n s were made by Swagelock T e f l o n u n i o n s . C o l d s t o r a g e atmosphere was passed through the two " i n - s e r i e " ambient Tenax tubes by a p p l y i n g suction t o the o u t l e t o f the tube by means o f the vacuum pump. Preliminary experiments, the r e s u l t s o f which are summarized b r i e f l y under R e s u l t s and D i s c u s s i o n , l e d t o the f o l l o w i n g o p t i m i z e d sampling method. V o l a t i l e c o l l e c t i o n was c a r r i e d out f o r 30 min at the c o l d s t o r a g e temperature (4°C) and w i t h a vacuum pump f l o w r a t e o f 50 mL/min. Then, the sampled Tenax tubes were removed, capped and ready f o r GC a n a l y s i s the same day. Heat D e s o r p t i o n o f Aroma v o l a t i l e s The gas c h r o m a t o g r a p h i c method employed a D.C.I. System ( D e s o r p t i o n - C o n c e n t r a t i o n - GC Introduction), a v a i l a b l e from D e l s i I n s t r u m e n t s ( 5 ) . A schematic diagram o f t h i s a p p a r a t u s i s g i v e n i n F i g u r e 2. One of the a u x i l i a r y Tenax tubes (1) was placed inside the desorption oven ( 2 ) , l o c a t e d upstream o f the f i x e d Tenax t r a p (3) (0,2 g Tenax GC, 60-80 mesh, packed i n t o a 7 cm by 2 mm i.d. stainless steel tube). At c o n t r o l l e d temperature (lOO'C) and low pressure (1,5 p s i ) the oven was f l u s h e d by a 25 mL/min f l o w of Helium f o r 10 min. Desorbed and d i l u t e d i n s c a v e n g i n g gas ( a ) , the volatiles were then c o n c e n t r a t e d and t r a p p e d i n the Tenax trap, cooled t o - 3 0 ° C by c i r c u l a t i o n o f l i q u i d n i t r o g e n . By s w i t c h i n g a rotary valve (4), carrier gas (b) flowed through the trap (backflush) and towards the GC column ( 6 ) . By rapid thermal d e s o r p t i o n a t 240°C, aroma v o l a t i l e s were d i r e c t l y t r a n s f e r r e d onto the GC column. F i g u r e 3 shows the c h r o n o l o g i c a l sequence for cryogenic volatile adsorption and thermal desorption, and chromatographic s e p a r a t i o n .



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F i g u r e 1. Schematic diagram o f the s a m p l i n g apparatus 1) f l o w m e t e r ; 2) a u x i l i a r y Tenax tube; 3) needle v a l v e ; 4) pump.



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INTRODUCTION F i g u r e 2. Schematic diagram o f the D.C.I, system a) scavenger gas; b) c a r r i e r gas 1) a u x i l i a r y Tenax tube; 2) d e s o r p t i o n oven; 3) f i x e d Tenax t r a p ; 4) s w i t c h i n g v a l v e ; 5) gas v e n t ; 6) GC column;7) mass s p e c t r o m e t e r


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F i g u r e 3. C h r o n o l o g i c a l sequences o f GC a n a l y s i s A) temperature sequence; B) time sequence.



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Combined C a p i l l a r y Gas Chromatography - Mass S p e c t r o m e t r y A GIRDEL 31 gas chromatograph equipped w i t h a D.C.I. System was c o u p l e d by means o f a g l a s s lined tubing i n t e r f a c e t o a NERMAG R10-10B quadrupole mass f i l t e r s p e c t r o m e t e r . The system was c o n n e c t e d online t o a d e d i c a t e d d a t a p r o c e s s i n g system c o n s i s t i n g o f a D i g i t a l Equipment Co. PDP8 Computer, u s i n g SIDAR s o f t w a r e i n c l u d i n g t h e l i b r a r y o f mass s p e c t r a l d a t a NIH/EPA (6). The capillary column used was a 50 m X 0,32 mm (i.d.) fused silica UCON 75H 90000 w a l l c o a t e d column. The column oven temperature was programmed from 30 t o 180°C a t a r a t e o f 3°C/min with a 10-min p o s t i n j e c t i o n h o l d and a 10-min h o l d at a final limit. Column i n l e t p r e s s u r e o f Helium was 7 p s i and t h e s p l i t 30 mL/min. Significant Mass S p e c t r o m e t r y o p e r a t i o n a l parameters were as follows : ionization voltage, 70 eV; i o n i z a t i o n c u r r e n t , 200 uA; source temperature, 200°C; e l e c t r o n m u l t i p l i e r t e n s i o n , 1,9 kV; integration time, 1 ms/u.m.a.. F o r optimum sample t r a n s f e r , an i n t e r f a c e temperature o f 200°C was adopted. Reagents Helium was p u r i f i e d by passage through charcoal, molecular s i e v e and an O x i s o r b t r a p . Tenax a d s o r b a n t was o b t a i n e d from A l l t e c h A s s o c . I n c . C h e m i c a l compounds f o r comparisons o f mass s p e c t r a and GC r e t e n t i o n times were o b t a i n e d from commercial s o u r c e s (Aldrich). S e c - b u t y l and i s o p r o p y l formates were synthesized a c c o r d i n g t o Dimicky (7). Sensory Validation o f Sampling and GC T e c h n i q u e s The s e n s o r y e v a l u a t i o n was c a r r i e d o u t by a p a n e l o f t h r e e judges (employees o f Pebeyre L t d . ) . F o r t h i s s t u d y , an e x t e r n a l odor p o r t was a t t a c h e d t o the gas vent (5) o f t h e D.C.I. System and t h e r o t a r y v a l v e (4) was not s w i t c h e d ( a n a l y s i s u s i n g t h e D e s o r p t i o n - C o n c e n t r a t i o n mode). Thus, after the thermal d e s o r p t i o n o f the v o l a t i l e s from t h e trap, the r o t a r y v a l v e was p o s i t i o n e d so t h a t t h e u n r e s o l v e d aroma isolate went t o o u r s n i f f i n g p o r t . The response was measured as s i m i l a r i t y o r d i s s i m i l a r i t y t o B l a c k T r u f f l e aroma. Sensory Evaluation o f t h e c o n t r i b u t i o n o f i d e n t i f i e d compounds t o the aroma I n o r d e r t o i d e n t i f y those compounds m a i n l y c o n t r i b u t i n g to t h e c h a r a c t e r i s t i c f l a v o r o f t h e B l a c k T r u f f l e , t h e odor o f the individual components o f t h e headspace a n a l y s i s were t e s t e d by a panel o f e i g h t judges ( t r a i n e d i n s e n s o r y e v a l u a t i o n o f t r u f f l e s ) . The compounds t e s t e d were d i l u t e d i n v e g e t a b l e o i l , i n a range o f c o n c e n t r a t i o n s from 30 t o 300 ppm. 5 p o i n t s c a l e s (5 = e x c e p t i o n a l l y good f u l l t r u f f l e aroma, 1 = n o t d i f f e r e n t from s o l v e n t ) were used f o r f l a v o r i m i t a t i o n and i n t e n s i t y . R e s u l t s and D i s c u s s i o n s Optimization o f t h e s a m p l i n g and a n a l y t i c a l t e c h n i q u e s P r e l i m i n a r y trials were used t o determine t h e o p t i m a l a d s o r b e n t . Tenax GC was chosen due t o i t s h i g h a f f i n i t y f o r o r g a n i c compounds which i t adsorbs r e v e r s i b l y , and i t s r e l a t i v e l y h y d r o p h o b i c c h a r a c t e r . This point i s important i n view o f t h e l a r g e volume o f water vapor present i n t h e c o l d s t o r a g e atmosphere. For this same reason,


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subambient traps appeared t o be i n n e f e c t i v e due t o the risk of physical blockage of the Tenax by s o l i d i f i c a t i o n o f atmospheric water v a p o r . The o p t i m i z a t i o n o f the s a m p l i n g c o n d i t i o n s was necessary to avoid breakthrough from the Tenax, i . e . elution of volatiles partially through the trap during atmosphere capture. Indeed, sampling e f f i c i e n c y decreased with sampling time, b r e a k t h r o u g h then occurring, but t h i s was not s i g n i f i c a n t l y d e c r e a s e d by u s i n g lower sampling f l o w r a t e s . Under our o p t i m i z e d s a m p l i n g c o n d i t i o n s , the heat d e s o r p t i o n o f the second Tenax t r a p which was n e a r e s t to the vacuum pump i n the s a m p l i n g system gave a b l a n k chromatogram, showing t h a t t h e r e were no l o s s e s o f v o l a t i l e s from the f i r s t trap d u r i n g the c a p t u r e . The conditions of chromatographic analysis (desorption of volatiles from the Tenax tube and t h e i r a d s o r p t i o n on the Fixed Tenax t r a p ) have a l s o been o p t i m i z e d i n o r d e r i ) t o o b t a i n a total d e s o r p t i o n o f v o l a t i l e s t r a p p e d on the a u x i l i a r y tube ( c o n f i r m e d by a b l a n k chromatogram f o r a second heat desorption), i i ) to avoid losses of volatiles during the adsorption phase (sensorially v e r i f i e d a t the odor p o r t ) . One particular volatile isolate desorbed and assessed sensorially at our odor p o r t was d e s c r i b e d as typical of Black T r u f f l e , showing t h a t the Tenax had a d s o r b e d and d e s o r b e d (under the analytical conditions used) v o l a t i l e components t h a t impart Black T r u f f l e aroma. The aroma i s o l a t i o n method and heat d e s o r p t i o n t e c h n i q u e s were therefore validated. Identification o f v o l a t i l e s compounds A t y p i c a l t o t a l i o n current chromatogram o f the Tenax t r a p p e d B l a c k T r u f f l e (Tuber Melanosporum) v o l a t i l e s i s shown i n F i g u r e 4. The compounds i d e n t i f i e d by GC-MS a r e l i s t e d i n T a b l e I, in order of elution from the GC column w i t h their observed characteristic mass s p e c t r a l data. The i d e n t i f i c a t i o n of these compounds i s based on comparison o f t h e i r r e s p e c t i v e mass spectra obtained with those s t o r e d i n the NIH/EPA l i b r a r y and then with those of a u t h e n t i c compounds. Moreover, an a d d i t i o n a l s e a r c h of published s t a n d a r d mass s p e c t r a t o c o n f i r m the i d e n t i t y o f unknown was u n d e r t a k e n ( 8 ) . The i s o l a t i o n o f the major v o l a t i l e compounds, i . e . low b o i l i n g point a l c o h o l s , and t h e i r r e l a t i v e aldehydes, 2 k e t o n e s and one major s u l f u r compound was c o n s i s t e n t w i t h p r e v i o u s reports (2,3) » Although alcohols remained the major constituents of headspace volatiles, d i m e t h y l s u l f i d e was p r e s e n t i n g r e a t e r p r o p o r t i o n than i n our e a r l i e r s t u d i e s . The similarity of the c h r o m a t o g r a p h i c p r o f i l e s of headspace v o l a t i l e s of brushed (^2) and unbrushed t r u f f l e s ( o b t a i n e d i n this study) allowed us to give s c i e n t i f i c support to the informal s u b j e c t i v e o b s e r v a t i o n t h a t unbrushed and brushed t r u f f l e aroma are not s i g n i f i c a n t l y d i f f e r e n t . Nevertheless, we noticed t h a t the r e l a t i v e c o n c e n t r a t i o n of alcohols increased during the p e r i o d o f cold storage. But the experts (employees o f Pebeyre L t d . ) r e p o r t e d t h a t the aroma o f the analysed t r u f f l e s were not r e a l l y a l t e r e d by t h i s modification of


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I

I

I

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I

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2600 SCAN NUMBER

F i g u r e 4. Reconstructed c a p i l l a r y GC-total i o n current chromatogram o f the Tenax t r a p p e d B l a c k T r u f f l e (Tuber Melanosporum) headspace v o l a t i l e s .


»

3000

210



T a b l e I . V o l a t i l e s i d e n t i f i e d i n atmosphere o f c o l d s t o r a g e f o r B l a c k T r u f f l e s (Tuber Melanosporum)

peak number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

compound (a) acetaldehyde dimethyl s u l f i d e propanal acetone 2-methylpropanal i s o p r o p y l formate ethyl acetate 2-butanone 2-methylbutanal 3-methylbutanal ethanol s e c - b u t y l formate chloroform 2-butanol 1-propanol toluene dimethyl d i s u l f i d e 2-methyl-l-propanol e t h y l benzene xylene 2-methyl-l-butanol 3-methyl-l-butanol anisole acetic acid benzaldehyde 2-formyl thiophene

mass s p e c t r a l data (b) 29,44,43,42 42,62,45,46 29,28,27,58 43,58,42,39 43,41,72,27 45,42,43,73 43,29,61,45 43,72,29,27 41,57,29,58 44,41,43,29 31,45,46,29 45,41,56,29 83,85,47,48 45,31,59,29 31,29,42,27 91,92,65,51 94,45,79,46 43,33,42,41 91,106,51,28 91,106,105,77 41,29,57,56 41,29,42,55 108,78,65,39 45,43,60,28 105,106,77,51 111,112,39,45

identification GC,MS GC,MS GC,MS GC,MS GC,MS GC,MS GC,MS MS GC,MS GC,MS GC,MS GC,MS GC,MS MS GC,MS GC,MS MS MS GC,MS MS MS GC,MS GC,MS GC,MS MS GC,MS MS

a) The peak numbers c o r r e s p o n d t o numbers i n F i g u r e 4; b ) The f o u r most i n t e n s e peaks a r e r e p o r t e d .



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concentrations. This result showed that a short period of cold s t o r a g e d i d n o t a f f e c t the o r g a n o l e p t i c q u a l i t y o f t r u f f l e s . The major advantage o f the sampling t e c h n i q u e developed, was that some t r a c e c h e m i c a l s c o u l d be t r a p p e d and d e s c r i b e d f o r the f i r s t time as B l a c k T r u f f l e aroma c o n s t i t u e n t s . I n p a r t i c u l a r , some compounds, important f l a v o r c o n t r i b u t o r s , g e n e r a l l y appearing in s m a l l c o n c e n t r a t i o n s , such as b e n z a l d e h y d e , p r o p a n a l , e t h y l a c e t a t e , anisole or dimethyl d i s u l f i d e - p r e v i o u s l y i d e n t i f i e d i n Shiitake mushrooms (9) - c o u l d be c h a r a c t e r i z e d . T h i s was a l s o the case f o r t h r e e a r o m a t i c compounds, toluene, x y l e n e and e t h y l benzene, well known as raw v e g e t a b l e constituents (10). I n a d d i t i o n , two a l i p h a t i c e s t e r s , i s o p r o p y l and s e c - b u t y l f o r m a t e s , and one c y c l i c sulfur compound (2-formyl thiophene) previously reported respectively i n plums and a p p l e s (10) and i n c o f f e e and bread p r o d u c t s (11) were i d e n t i f i e d . C h l o r o f o r m was c e r t a i n l y an a r t i f a c t where the t r u f f l e s were h a r v e s t e d .

due t o t r e a t m e n t o f t h e s o i l

R e l a t i v e odor c o n t r i b u t i o n o f components Considered individually, none o f the compounds i d e n t i f i e d d u p l i c a t e d the f l a v o r o f the B l a c k Truffle. However, according t o the j u d g e s , dimethyl s u l f i d e was d e t e r m i n e d t o have a g r e a t importance t o the f i n a l aroma i m p r e s s i o n . In the same way, 2-butanone and a n i s o l e were found t o be responsible f o r an o f f - f l a v o r characteristic of over-mature truffles. When m i x t u r e s o f two and/or t h r e e compounds were t e s t e d , the panel scores remained low e x c e p t f o r the m i x t u r e of dimethyl sulfide/2-methylbutanal. A synosmic e f f e c t , which has been d e f i n e d by S c h u t t e (12) as being due t o two o r more compounds combining t o g e t h e r t o g i v e a flavor s e n s a t i o n v e r y d i f f e r e n t from t h a t o f any s i n g l e component, seemed e v i d e n t . T h i s was c o n f i r m e d by the h i g h s c o r e o b t a i n e d by a mixture o f a l l compounds. T h i s o i l s o l u t i o n was j u d g e d t o be very s i m i l a r t o f r e s h b l a c k t r u f f l e aroma by t h e p a n e l ( T a l o u , T. Ph.D. Thesis, i n p r e p a r a t i o n ) : t h i s i n d i c a t e d t h a t the t y p i c a l f l a v o r f o r black P e r i g o r d T r u f f l e was the r e s u l t o f an i n t e g r a t e d r e s p o n s e t o the c o n t r i b u t i o n o f a l l the i d e n t i f i e d compounds. An i n d u s t r i a l a p p l i c a t i o n o f t h i s r e s u l t was the e l a b o r a t i o n o f the first N a t u r e - I d e n t i c a l Black Truffle aromatizer (13). This p r o d u c t was t e s t e d w i t h s u c c e s s d u r i n g one y e a r by w e l l known f r e n c h cooks i n their restaurant. Culinary t e s t s confirm t h e good organoleptic q u a l i t y o f the f l a v o r e d p r o d u c t s obtained, both f o r c o l d o r hot d i s h e s .

Conclusions The headspace s a m p l i n g t e c h n i q u e d e v e l o p e d i n t h e p r e s e n t s t u d y to collect volatiles from cold stored Black Truffles performed adequately. Indeed, t h e aroma i s o l a t e o b t a i n e d was d e s c r i b e d as typical, and 11 minor compounds c o u l d be d e s c r i b e d f o r the first time as B l a c k T r u f f l e aroma c o n s t i t u e n t s . Moreover, these r e s u l t s a l l o w e d the f o r m u l a t i o n o f the f i r s t N a t u r e - I d e n t i c a l B l a c k Truffle aromatizer.


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Acknowledgments T h i s r e s e a r c h was c o n d u c t e d i n p a r t i a l f u l f i l l m e n t o f t h e r e q u i r e m e n t s o f t h e Ph.D. degree by T. T a l o u . The a u t h o r s thank Dr. 0. M o r i n o f t h e department o f A n a l y t i c a l C h e m i s t r y o f ITERG (Bordeaux, F r a n c e ) f o r t h e GC-MS a n a l y s i s , and Ms. Suzanne Harington and S y l v i e Bourdarie f o rtheir contributions i n the preparation o f t h i s paper. T h i s s t u d y was a p a r t o f a Research Program sponsored by Pebeyre L t d . (Cahors, France), the French M i n i s t r y o f A g r i c u l t u r e and t h e Midi-Pyrénées R e g i o n a l C o u n c i l .

Literature Cited 1. Talou, T.; Rigal, L. and Gaset, A. Proc. 1st Colloquium Chemiometricum Mediteraneum, 1987, p18. 2. Talou, T.; Delmas, M. and Gaset, A. J. Agric. Food Chem., 1987, 35, 774. 3. Talou, T.; Delmas, M. and Gaset, A. Proc. 5th International Flavor Conference, 1987, p 14. 4. Kulifaj, M. Ph.D. Thesis, University of Paul Sabatier, Toulouse, France, 1984. 5. Gregoire, J. and Samoun, A.M. Proc. 33rd Pittsburg Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, 1982, p 768. 6. Heller, S.R. and Milne, G.W.A., EPA/NIH Mass spectra data base ; US Government printing office: Washington, DC, 1978; Vol 1-4. 7. Dimicky, M. Organic Preparations and Procedures Int. 1982, 14, 177 8. Stenhagen,E.; Abrahamsson, S. and MacLafferty, K.W. Registry of Mass Spectra data ; Willey: New York, 1974. 9. Chu-Chin, C.; Su-Er, L.; Chung-May, W. and Chi-Tang,H. ACS Symp. Ser.317 ; Parliment, T.H. and Croteau, R. Ed:,ACS Washington DC, 1986 ; p 14. 10. Teranishi, R. Flath, R.A. and Sugisawa,H. Flavor Research Recent Advances ; Marcel Dekker : New York, 1981. 11. Fenaroli, G. HandBook of Flavor Ingredients, 2nd Ed; CRC : Cleveland,OH, 1975 ; Vol 2. 12. Schutte, L.,ACS Symp. Ser.26 ; Charalambous, G. and Katz, I., Ed:, ACS : Washington DC, 1976 ; p 96. 13. Talou, T.; Delmas, M.; Gaset, Α.; Montant, C. and Pebeyre, P.J. European Patent 87201148.1, 1987 ; Japaneese Patent 62.183242, 1987 ; U.S. Patent 077.276, 1987. RECEIVED

August 8, 1988


Flavor Chemistry - American Chemical Society

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