Volatile Compounds in Ginger Oil Generated by Thermal Treatment

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Chapter 34

Volatile Compounds in Ginger Oil Generated by Thermal Treatment 1

Chu-Chin Chen and Chi-Tang Ho Department of Food Science, New Jersey Agricultural Experiment Station, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903

Ginger oils from steam distillation and liquid carbon dioxide extraction (600 - 700 psi) were fractionated into hydrocarbons and oxygenated hydrocarbons by s i l i c a gel column chromatography. Volatile hydrocarbons and oxygenated hydrocarbons were analyzed by capillary GC and GC-MS. Monoterpenes, sesquiterpenes, aliphatic aldehydes, 2-alkanones, c i t r a l , monoterpene alcohols and sesquiterpene alcohols were major categories of ginger components which were affected or generated by thermal induced degradation during steam d i s t i l l a t i o n . Steam d i s t i l l a t i o n i s the most common p r o c e s s f o r the e x t r a c t i o n o f e s s e n t i a l o i l s from p l a n t s ( 1 - 3 ) . I t p r o v i d e s a f a s t and s i m p l e way t o o b t a i n a r o m a t i c components w h i c h bear the c h a r a c t e r i s t i c odor o f t h a t s p e c i e s . However, " s t i l l n o t e s " o r "burnt n o t e s " are f r e q u e n t l y found i n f r e s h l y d i s t i l l e d o i l . The o f f - f l a v o r r e s u l t s i n most cases from t h e r m a l l y induced h y d r o l y t i c o r d e g r a d a t i v e r e actions (4). V o l a t i l e g i n g e r o i l o b t a i n e d from steam d i s t i l l a t i o n has been the s u b j e c t o f many r e s e a r c h s t u d i e s ( 5 - 1 2 ) . However, t h e t h e r m a l d e g r a d a t i v e e f f e c t s o f steam d i s t i l l a t i o n upon v o l a t i l e and n o n v o l a t i l e components o f g i n g e r were seldom d i s c u s s e d . R e c e n t l y , M o y l e r (1) compared the advantages o f l i q u i d carbon d i o x i d e e x t r a c t i o n over c o n v e n t i o n a l methods such as s o l v e n t e x t r a c t i o n o r steam d i s t i l l a t i o n by showing r e c o n s t r u c t e d GC chromatograms w h i c h c l e a r l y d i s p l a y e d the d i f f e r e n c e s . H o w e v e r , q u a n t i t a t i v e r e s u l t s showing the d i f f e r e n c e s were not mentioned. The p r e s e n t study compares the c a p i l l a r y GC a n a l y s i s o f v o l a t i l e compounds d e r i v e d from steam d i s t i l l a t i o n o f g i n g e r w i t h those e x t r a c t e d by l i q u i d carbon d i o x i d e . V o l a t i l e components a f f e c t e d by t h e r m a l treatment d u r i n g p r e p a r a t i o n were o f major c o n c e r n . 1

Current address: Food Industry Research and Development Institute, Hsinchu, Taiwan, 30099, Republic of China 0097-6156/89/0409-0366S06.00/0 ο 1989 American Chemical Society In Thermal Generation of Aromas; Parliment, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

34.

CHEN AND HO

Volatile Compounds in Ginger Oil

367

M a t e r i a l s and Methods


Reagents. The s o l v e n t s (n-pentane, d i e t h y l e t h e r ) were reagent grade and g l a s s d i s t i l l e d . η-Aldehydes (C6-C14) were o b t a i n e d from A l l t e c h A s s o c i a t e s ( D e e r f i e l d , I L ) . 2-Heptanone, 2-nonanone and 2undecanone were o b t a i n e d from A l d r i c h (Milwaukee, W l ) ; 2 - t r i d e c a n o n e was o b t a i n e d from Caro (Tokyo, J a p a n ) . U n l e s s o t h e r w i s e s t a t e d , a l l o t h e r c h e m i c a l s were o f reagent grade. Z i n g e r o n e was o b t a i n e d from ICN B i o c h e m i c a l ( P l a i n v i e w , NY). L i q u i d Carbon D i o x i d e E x t r a c t i o n . Mature g i n g e r (Z. o f f i c i n a l e Roscoe) rhizomes were o b t a i n e d from a s u p p l i e r i n H s i n c h u ( T a i w a n ) . The rhizomes were washed, s l i c e d , f r e e z e - d r i e d , ground and s i e v e d (200 mesh). About 110 g o f f r e e z e - d r i e d g i n g e r powder was p l a c e d i n a glass Soxhlet e x t r a c t o r i n s t a l l e d i n a s t a i n l e s s s t e e l l i q u i d car bon d i o x i d e e x t r a c t o r . O p e r a t i n g p r o c e d u r e s were d e s c r i b e d p r e v i o u s l y ( 1 3 ) . A g o l d e n brown o i l m a t e r i a l (3.44%) was o b t a i n e d by the l i q u i d carbon d i o x i d e e x t r a c t i o n . F r a c t i o n a t i o n o f V o l a t i l e Compounds by Column Chromatography. Steamd i s t i l l e d g i n g e r o i l (0.96 g) and l i q u i d carbon d i o x i d e - e x t r a c t e d g i n g e r o i l (1.71 g) were a p p l i e d s e p a r a t e l y t o a g l a s s column (40 cm χ 2.0 cm) packed w i t h s i l i c a g e l (50 g, 60/200 mesh; M a l l i n c k r o d t ) . The h y d r o c a r b o n f r a c t i o n was e l u t e d w i t h pentane (1 L, A l d r i c h ) and the oxygenated h y d r o c a r b o n f r a c t i o n was e l u t e d w i t h e t h y l e t h e r (1L, E. M e r c k ) . The pungent g i n g e r o l compounds were not e l u t e d under t h e s e c o n d i t i o n s . Tetradecane (Matheson, 7.60 mg) and e t h y l decanoate (Lachat C h e m i c a l , 3.8 mg) were added t o the h y d r o c a r b o n and oxygenated h y d r o c a r b o n f r a c t i o n s , r e s p e c t i v e l y , as i n t e r n a l s t a n d ards . GC and GC-MS A n a l y s i s o f V o l a t i l e Components. The two f r a c t i o n s o f g i n g e r o i l e x t r a c t e d by l i q u i d carbon d i o x i d e were s u b j e c t e d t o gas c h r o m a t o g r a p h i c a n a l y s e s on a V a r i a n 3400 gas chromatograph. A fused s i l i c a column w i t h a s t a t i o n a r y phase e q u i v a l e n t t o Carbowax 20M (DB-WAX+, 60 m χ 0.32 mm; J&W S c i e n t i f i c ) was used. The oven tem p e r a t u r e was programmed l i n e a r l y from 50 t o 225°C a t 1.5 C/min and was h e l d at 225°C f o r 80 min. Other o p e r a t i n g c o n d i t i o n s were as f o l l o w s : i n j e c t o r and d e t e c t o r t e m p e r a t u r e s , 250°C; makeup h e l i u m f l o w , 30 mL/min; d e t e c t o r hydrogen f l o w , 30 mL/min; d e t e c t o r a i r f l o w , 30 mL/min. The samples were i n j e c t e d i n the s p l i t mode w i t h a s p l i t r a t i o o f 1/100. The l i n e a r v e l o c i t y o f the h e l i u m c a r r i e r f l o w was 22 cm/s. Q u a n t i t a t i v e d e t e r m i n a t i o n s were made w i t h a V a r i a n 4270 i n t e g r a t o r . L i n e a r r e t e n t i o n i n d i c e s f o r the v o l a t i l e components were c a l c u l a t e d by u s i n g η-paraffins (C8-C25; A l l t e c h A s s o c i a t e s ) as r e f e r e n c e s ( 1 4 ) . C a p i l l a r y gas chromatography-mass s p e c t r o m e t r y was c a r r i e d out on a H e w l e t t - P a c k a r d 5985 Β system equipped w i t h a H e w l e t t - P a c k a r d 5840A gas chromatograph. A fused s i l i c a c a p i l l a r y column (Carbowax 20M) was used. A n a l y t i c a l c o n d i t i o n s were as f o l l o w s : temperature program, 50 - 200°C, 1.5 C/min, i s o t h e r m a l a t 200°C, 50 min; i n j e c t o r t e m p e r a t u r e , 250°C; h e l i u m c a r r i e r v e l o c i t y , 30 cm/s; i o n source t e m p e r a t u r e , 200°C; i o n i z a t i o n v o l t a g e , 70 eV; e l e c t r o n m u l t i p l i e r v o l t a g e , 2600 V.

In Thermal Generation of Aromas; Parliment, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

368

THERMAL GENERATION OF AROMAS


R e s u l t s and D i s c u s s i o n In o r d e r t o i n v e s t i g a t e the t h e r m a l d e g r a d a t i v e r e a c t i o n d u r i n g t h e p r e p a r a t i o n o f v o l a t i l e g i n g e r o i l , f r e e z e - d r i e d g i n g e r powder e x t r a c t e d by c o n v e n t i o n a l steam d i s t i l l a t i o n was compared w i t h low temperature e x t r a c t i o n u s i n g l i q u i d carbon d i o x i d e . Both e x t r a c t s were f u r t h e r f r a c t i o n a t e d i n t o hydrocarbon and oxygenated h y d r o c a r bon f r a c t i o n s . GC and GC-MS i d e n t i f i c a t i o n s o f v o l a t i l e compounds were a c c o m p l i s h e d by comparing w i t h p r e v i o u s r e p o r t ( 1 5 ) . T e t r a decane and e t h y l dodecanoate, r e s p e c t i v e l y , were added as i n t e r n a l standards. F i g u r e s 1 and 2 show the c a p i l l a r y gas chromatographic a n a l y s e s of the hydrocarbon and the oxygenated hydrocarbon f r a c t i o n s . I n t h e hydrocarbon f r a c t i o n , 13 s e l e c t e d monoterpene compounds and s e s q u i terpene compounds were compared. I n the oxygenated hydrocarbon f r a c t i o n , 22 v o l a t i l e components, which i n c l u d e a l i p h a t i c a l d e h y d e s , 2-alkanones, c i t r a l , monoterpene a l c o h o l s and s e s q u i t e r p e n e a l c o h o l s , were compared. T a b l e I . Comparison o f S e l e c t e d Hydrocarbon Compounds i n Steam D i s t i l l e d and LCO2 E x t r a c t e d G i n g e r O i l

% (w/w) Peak No.

3

Compound

Monoterpenes a-pinene camphene β-pinene myrcene 3-phellandrene 1imonene terpinolene Sesquiterpenes 8 β-elemene 9 Zingiberene 10 γ-bisabolene 11 β-bisabolene 12 3-sesquiphellandrene 13 ar-curcumene Number r e f e r s t o F i g . 1 1 2 3 4 5 6 7

Dist.

LC0

0.16 0.40 0.02 0.08 0.09 0.31 0.11

0.98 3.08 0.16 0.90 0.89 2.75 0.11

0.29 14.19 3.47 6.37 10.62 16.30

0.31 24.15 8.40 5.60 10.14 7.96

2

a

T a b l e I shows the q u a n t i t a t i v e comparison o f s e l e c t i v e compounds i n the hydrocarbon f r a c t i o n . The t o t a l amount o f monoterpenes i n the steam d i s t i l l e d sample was l e s s than t h a t i n the l i q u i d carbon d i o x i d e e x t r a c t . These compounds c o u l d have been l o s t d u r i n g d i s tillation. The s i g n i f i c a n t decrease i n z i n g i b e r e n e and the con c o m i t a n t i n c r e a s e i n ar-curcumene c o n f i r m e d t h a t z i n g i b e r e n e was c o n v e r t e d t o ar-curcumene ( 1 6 ) . 3 - S e s q u i p h e l l a d r e n e , another com pound which c o u l d be c o n v e r t e d t o ar-curcumene, decreased s l i g h t l y . The scheme o f o x i d a t i v e c o n v e r s i o n o f z i n g i b e r e n e and 3 " s e s q u i p h e l -



F i g u r e 1. C a p i l l a r y gas c h r o m a t o g r a p h i c a n a l y s e s o f h y d r o c a r b o n f r a c t i o n s o f l i q u i d c a r b o n d i o x i d e e x t r a c t e d and steam d i s t i l l e d oils.

(min)


U S


Ο

10

30

40

50

60

70

80

90

100

110

120

(min) F i g u r e 2. C a p i l l a r y gas c h r o m a t o g r a p h i c a n a l y s e s o f oxygenated h y d r o c a r b o n f r a c t i o n s o f l i q u i d carbon d i o x i d e e x t r a c t e d and steam d i s t i l l e d o i l s .

20

130


34.

CHEN AND HO

371


l a n d r e n e t o ar-curcumene i s shown i n F i g . 3. Such changes w i l l l e a d to d i m i n u t i o n o f f r e s h f l a v o r o f g i n g e r o i l . Table I I shows the q u a n t i t a t i v e comparison o f s e l e c t e d com pounds i n the oxygenated h y d r o c a r b o n f r a c t i o n . Table I I . Comparison o f S e l e c t e d Oxygenated Hydrocarbon Compounds i n Steam D i s t i l l e d and L C 0 E x t r a c t e d G i n g e r O i l 2


% Peak No.

a

(w/w)

Compound Dist.

Aldehydes/Alkanones 1 hexanal 2 2-heptanone 3 octanal 5 2-nonanone 6 decanal 8 2-undecanone 11 dodecanal 16 2-tridecanone 24 zimgerone Citral 4 2-methyl-2-heptene-6-one 9 neral 13 geranial Monoterpene A l c o h o l s 7 linalool 15 citronellol 17 nerol 18 geraniol Sesquiterpene Alcohols 19 nerolidol 20 β-sesquisabinenhydrate 21 zingiberenol 22 3-eudesmol 23 t-3-sesquiphellandrol Number r e f e r s t o F i g . 2.

0.05 0.01 0.03 0.01 0.04 0.29 0.01 0.04

-

LC0

2

+ 0.01 0.01 0.04

+ 0.13 _

0.02

+

0.24 1.54 2.58

0.17 2.32 4.62

0.26 1.25 0.22 1.74

0.35 0.79 0.08 1.02

0.03 0.90 1.42 0.90 0.21

0.45 0.93 0.57 0.48

+

a

G i n g e r o l compounds, the dominant pungent p r i n c i p l e s o f g i n g e r , are t h e r m a l l y l a b i l e due t o t h e p r e s e n c e o f a β-hydroxy k e t o m o i e t y i n t h e i r s t r u c t u r e (17, 1 8 ) . I n our p r e v i o u s r e p o r t (19, 2 0 ) , two homologous s e r i e s o f g i n g e r o l compounds, i . e . , 6-, 8-, 10-, 12-, 14g i n g e r o l s and m e t h y l - 6 - , m e t h y l - 8 - , m e t h y l - 1 0 - , m e t h y l - 1 2 - g i n g e r o l s have been i d e n t i f i e d ( F i g . 4 ) . I t was found t h a t upon i n j e c t i o n o f g i n g e r o l compounds i n t o a gas chromatograph, s t r a i g h t c h a i n a l d e hydes (C6, C8, C10, C12 and C14) and 2-alkanones (2-heptaone, 2nonanone, 2-undecanone and 2 - t r i d e c a n o n e ) were g e n e r a t e d due t o t h e r m a l d e g r a d a t i v e r e a c t i o n s ( r e t r o - a l d o l and r e t r o - C l a i s e n Schmidt r e a c t i o n ) (20, 2 1 ) . I t i s a l s o i n t e r e s t i n g t o n o t e t h a t the p r e s ence o f h e x a n a l , o c t a n a l , d e c a n a l , 2-heptanone, 2-nonanone and 2undecanone i n steam d i s t i l l e d o i l o f g i n g e r has been w e l l docu mented ( 7 - 9 , 11-12). I t i s n o t known whether t h e s e compounds a r e r e l a t e d t o the n o n v o l a t i l e g i n g e r o l compounds.



372


ar-Curcumene F i g u r e 3. O x i d a t i v e c o n v e r s i o n o f z i n g i b e r e n e and β - s e s q u i p h e l l a n d r e n e i n t o ar-curcumene.

Zingerone CH (CH ) CHO 2

2

CH3CO ( C H ) „ C H

N

2

3

n=4,6,8,10 F i g u r e 4. S t r u c t u r e o f g i n g e r o l compounds and t h e i r degradation products.

thermal



34.

CHEN AND HO


373

I n T a b l e I I , the s i g n i f i c a n t l y h i g h e r c o n c e n t r a t i o n o f a l i p h a t i c aldehydes (C6, C8, CIO, C12) and 2-alkanones, (2-heptanone, 2undecanone and 2 - t r i d e c a n o n e ) i n the steam d i s t i l l e d o i l suggested t h a t t h e r m a l d e g r a d a t i o n o f g i n g e r o l compounds d u r i n g steam d i s t i l l a t i o n may cause such changes. W i t h the e x c e p t i o n o f 2-nonanone, a l i p h a t i c aldehydes and 2-alkanones were i n lower c o n c e n t r a t i o n i n the l i q u i d carbon d i o x i d e e x t r a c t than i n steam d i s t i l l e d o i l . This i s a good i n d i c a t i o n o f l e s s severe t h e r m a l t r e a t m e n t d u r i n g the l i q u i d carbon d i o x i d e e x t r a c t i o n . A l s o , the f i n d i n g o f a t r a c e amount o f z i n g e r o n e (peak 24) i n the l i q u i d carbon d i o x i d e e x t r a c t shows t h a t i t i s p o s s i b l e t h a t t r a c e amounts o f g i n g e r o l compounds may appear i n v a r i o u s f r a c t i o n s . These t r a c e amounts o f g i n g e r o l compounds may e x p l a i n the d e t e c t i o n o f a l i p h a t i c aldehydes and 2alkanones d u r i n g gas chromatographic a n a l y s i s . F i g u r e 5 shows the t h e r m a l l y induced h y d r o l y t i c d e g r a d a t i o n o f c i t r a l ( g e r a n i a l and n e r a l ) i n t o 2-methyl-2-hepten-6-one and a c e t a l d e h y d e . I t i s s i m i l a r t o the r e a c t i o n mechanism as proposed by Josephson and L i n d s a y (22, 23). The r e l a t i v e l y h i g h e r amount o f 2-methyl-2-hepten-6-one and the concomitant lower amount o f g e r a n i a l and n e r a l i n steam d i s t i l l e d o i l c o n f i r m e d a g a i n a p r e v i o u s r e p o r t (24). I n v e g e t a b l e s , f r u i t s and p l a n t s , i t has become well-known t h a t some o f the t e r p e n o i d a l c o h o l s o r i g i n a t e d from n o n v o l a t i l e t e r p e n o i d g l y c o s i d e s through the a c t i o n o f enzymes, a c i d and/or h e a t . Vege-

Neral

Geranial

CHO

CHO

+

CH CHO 3

F i g u r e 5. T h e r m a l l y induced h y d r o l y t i c d e g r a d a t i o n o f c i t r a l ( g e r a n i a l and c i t r a l ) i n t o 2-methyl-2-hepten-6-one and acetaldehyde.




374

t a b l e s , f r u i t s and p l a n t s r e p o r t e d i n such c a t e g o r i e s i n c l u d e tomato (25, 2 6 ) , t e a shoot ( 2 7 ) , grape (28-30), p a s s i o n f r u i t (31) and papaya ( 3 2 ) . R e c e n t l y , Sakamura (33) r e p o r t e d t h a t the amounts o f monoter pene a l c o h o l s i n young rhizomes were l e s s than those i n mature rhizomes. Whether enzymic a c t i v i t y i s i n v o l v e d d u r i n g the growth p e r i o d was not mentioned. In the present r e p o r t , the amount o f most monoterpene a l c o h o l s and s e s q u i t e r p e n e a l c o h o l s i n d i s t i l l e d o i l was h i g h e r than those e x t r a c t e d by l i q u i d carbon d i o x i d e . I t i s p o s s i b l e t h a t the d i f f e r e n c e s were due t o the thermal d e g r a d a t i v e e f f e c t o f steam d i s t i l l a t i o n upon the n o n v o l a t i l e g l y c o s i d e s o f monoterpene a l c o h o l s and/or s e s q u i t e r p e n e a l c o h o l , as i n the case o f tomato. Conclusion Thermal t r e a t m e n t , such as steam d i s t i l l a t i o n d u r i n g sample p r e p a r a t i o n , w i l l cause c o n s i d e r a b l e d e g r a d a t i v e r e a c t i o n to both v o l a t i l e and n o n v o l a t i l e compounds o f g i n g e r . To the c o n t r a r y , however, p r e p a r a t i o n under low t e m p e r a t u r e , such as l i q u i d carbon d i o x i d e e x t r a c t i o n , can e f f e c t i v e l y e l i m i n a t e t h e r m a l l y induced d e g r a d a t i v e reactions. Acknowledgments The t e c h n i c a l a s s i s t a n c e of Dr. Chung-May Wu, May-Chien Kuo, Su-Er L i o u and Ming-Ching Wang, Food I n d u s t r y Research and Development I n s t i t u t e , i s appreciated. T h i s r e s e a r c h was supported i n p a r t by the N a t i o n a l S c i e n c e C o u n c i l (NSC74-0406-E080-003), R e p u b l i c o f China. Literature Cited 1. 2. 3. 4.

Moyler, D. A. Perfum. Flavor. 1984, 9, 109. Stahl, E.; Gerard, D. Perfum. Flavor. 1985, 10, 29. Meyer-Warnod, B. Perfum. Flavor 1984, 9, 93. Ohloff, G.; Flament, I.; Pickenhagen, W. Food Rev. Int. 1985, 1, 99. 5. Masada, Y. Analysis of Essential Oils by Gas Chromatography and Mass Spectrometry; Wiley: New York, 1976. 6. Sakamura, F.; Hayashi, S. Nihon Nogei Kagakkaishi 1978, 52, 207. 7. Smith, R. M.; Robinson, J. M. Phytochemistry 1981, 20, 203. 8. Lawrence, Β. M. Paper presented at 9th International Essential Oil Congress, Singapore, March. 13-17, 1983, 4, 69. 9. Lawrence, Β. M. Perfum. Flavor. 1984, 5, 1. 10. MacLeod, A. J.; Pieris, Ν. M. Phytochemistry 1984, 23, 353. 11. van Beek, T. Α., Posthumus, Μ. Α.; Lelyveld, G. P.; Phiet, H. V.; Yen, B. T. Phytochemistry 1987, 26, 3005. 12. Erler, J.; Vostrowsky, O.; Strobel, H.; Knobloch, K. Z. Lebensm Unters Forsch 1988, 186, 231.


34. CHEN AND HO 13. 14. 15. 16.


17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33.


375

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