Parameter Effects on the Thermal Reaction of Cystine and 2,5

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on April 29, 2016 | http://pubs.acs.org Publication Date: October 3, 1989 | doi: 10.1021/bk-1989-0409.ch021

Chapter 21

Parameter Effects on the Thermal Reaction of Cystine and 2,5-Dimethyl-4-hydroxy-3(2H)-furanone 1

Chi-Kuen Shu 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

The thermal reaction of cystine and DMHF is important for the generation of meat flavors. The products of this reaction, their flavor compounds, aroma profiles and yields, however, vary according to the reaction parameters. This study focused on determining the ef fect of the reaction medium, duration, water content, temperature, pH and oxygen on the products of this re action. The M a i l l a r d r e a c t i o n commonly o c c u r s i n food p r o d u c t s and d u r i n g food p r o c e s s i n g . A t y p i c a l o r pure M a i l l a r d r e a c t i o n i s s i m p l y t h e r e a c t i o n o f a sugar and an amino a c i d . S t r i c t l y s p e a k i n g , t h e sugar must be a r e d u c i n g c a r b o h y d r a t e and t h e amino a c i d can be e i t h e r f r e e o r bound, as a p e p t i d e o r p r o t e i n . The r e a c t i o n gener a t e s not o n l y v o l a t i l e compounds, w h i c h p r o v i d e odor, but a l s o odor l e s s n o n v o l a t i l e compounds, some o f which a r e c o l o r e d . The M a i l l a r d r e a c t i o n i s a complex system. Sugars and amino a c i d s f i r s t condense i n t o Amadori o r Heyns compounds, which t h e n , through a s e r i e s o f β-elimination and e n o l i z a t i o n can be c o n v e r t e d i n t o α-dicarbonyls. These α-dicarbonyls p l a y t h e key r o l e i n f u r t h e r r e a c t i o n s t o generate t h e d i f f e r e n t types o f f l a v o r compounds. The sugar and amino a c i d r e a c t not o n l y t o g e t h e r , b u t a l s o s e p a r a t e l y and i n d i v i d u a l l y . The t h e r m a l d e g r a d a t i o n o f s u g a r , o r c a r a m e l i z a t i o n , g e n e r a t e s α-dicarbonyls and, s u b s e q u e n t l y , f l a v o r com pounds. With amino a c i d s v a r i o u s a c t i v e p r i m a r y p r o d u c t s a r e formed ( 1 - 4 ) . These p r i m a r y p r o d u c t s r e a c t f u r t h e r t o produce a l a r g e number o f a d d i t i o n a l f l a v o r compounds. The y i e l d o f f l a v o r compounds from t h e M a i l l a r d r e a c t i o n i s v e r y low compared t o t h e y i e l d o f n o n v o l a t i l e s . T h e r e f o r e , i t i s v e r y d i f f i c u l t t o use t h e t y p i c a l / p u r e M a i l l a r d r e a c t i o n t o s y n t h e s i z e f l a v o r compounds f o r commercial use o r t o s t u d y i t s c h e m i s t r y . 1

Current address: R. J. Reynolds Tobacco Company, Bowman Gray Technical Center, WinstonSalem, N C 27102 0097-6156/89/0409-0229$06.00/0 o 1989 American Chemical Society Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


230

THERMAL GENERATION OF AROMAS

To overcome the problems a s s o c i a t e d w i t h t h e i n h e r e n t l y low y i e l d amino a c i d d e g r a d a t i o n p r o d u c t s , α-dicarbonyls have been used i n p l a c e o f amino a c i d s and s u g a r s , r e s p e c t i v e l y ( 5 - 1 0 ) . I t i s u s e f u l t o c a t e g o r i z e the M a i l l a r d r e a c t i o n s i n t o pure M a i l l a r d r e a c t i o n s and m o d i f i e d M a i l l a r d r e a c t i o n s . The former i n c l u d e s o n l y sugar and amino a c i d ; t h e l a t t e r i n c l u d e s (a) sugar and amino a c i d d e g r a d a t i o n p r o d u c t s , o r (b) α-dicarbonyls and amino a c i d or ( c ) α-dicarbonyls and amino a c i d d e g r a d a t i o n p r o d u c t s . The t h e r m a l r e a c t i o n o f c y s t i n e and 2,3-dimethyl-4-hydroxy-3 (2H)-furanone (DMHF), a m o d i f i e d M a i l l a r d r e a c t i o n i s i m p o r t a n t f o r the g e n e r a t i o n o f meat f l a v o r s . The r e a c t i o n p r o d u c t s , t h e i r f l a v o r compounds, aroma c h a r a c t e r and y i e l d v a r y , a c c o r d i n g t o t h e r e a c t i o n parameters. These parameters i n c l u d e t h e r e a c t i o n medium, d u r a t i o n , water c o n t e n t , t e m p e r a t u r e , pH and presence o r absence o f oxygen. C y s t i n e and o t h e r s u l f u r - c o n t a i n i n g amino a c i d s a r e r e c o g n i z e d as i m p o r t a n t p r e c u r s o r s o f food f l a v o r s , e s p e c i a l l y meat f l a v o r s (3, 11-12). DMHF, a c y c l i c - a - d i c a r b o n y l , possesses a sweet, caramel and f r u i t y aroma ( 1 3 ) . I t i s found i n many food sources (14-17) and i s used e x t e n s i v e l y i n many f l a v o r a p p l i c a t i o n s (18-19). DMHF can be formed from sugar v i a e i t h e r sugar e n o l i z a t i o n ( c a r a m e l i z a t i o n ) by a M a i l l a r d r e a c t i o n then c y c l i z a t i o n ( 2 0 ) . R e c e n t l y , we r e p o r t e d on the t h e r m a l d e g r a d a t i o n o f c y s t i n e (21) and a l s o the t h e r m a l d e g r a d a t i o n o f DMHF (22) as background f o r the t i t l e r e a c t i o n . Experimental Section M a t e r i a l s Employed. 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) o f h i g h p u r i t y was p r o v i d e d by I n t e r n a t i o n a l F l a v o r s and F r a g r a n c e s ( I F F ) . L - c y s t i n e , i n j e c t a b l e grade, was purchased from Ajinomoto Company, Tokyo, Japan. Reagent grade methylene c h l o r i d e was pur chased from A l d r i c h Chemical Company, and was f r e s h l y d i s t i l l e d p r i o r t o use. S p e c t r a l grade g l y c e r o l was o b t a i n e d from a commer c i a l source. Sample P r e p a r a t i o n . A m i x t u r e o f c y s t i n e , DMHF (0.05 mole e a c h ) , and 500 g o f d i s t i l l e d water o r g l y c e r o l was p l a c e d i n a 2 - l i t e r Paar Bomb (Paar I n s t r u m e n t s Co., M o l i n e , I L ) equipped w i t h a magnet i c s t i r r e r , an i n t e r n a l c o o l i n g c o i l and a temperature c o n t r o l l e r . The r e a c t i o n m i x t u r e was heated t o the s p e c i f i c temperature and h e l d at t h a t temperature f o r a s p e c i f i c time f o r each experiment. After c o o l i n g t o room t e m p e r a t u r e , a r e a c t i o n mass was o b t a i n e d . The r e a c t i o n time and temperature f o r each parameter s t u d i e d i s o u t l i n e d below. The procedures used f o r the i s o l a t i o n , e x t r a c t i o n , a n a l y s i s and i d e n t i f i c a t i o n o f v o l a t i l e s have been d e s c r i b e d elsewhere ( 2 1 ) . S p e c i f i c C o n d i t i o n s f o r Parameter

Study

1. Medium E f f e c t : C y s t i n e and DMHF were r e a c t e d i n both aqueous and nonaqueous s o l v e n t s . G l y c e r o l was chosen as the nonaqueous medium f o r two r e a s o n s : ( i ) g l y c e r o l has a h i g h b o i l i n g p o i n t so t h a t i t was n o t r e a d i l y d i s t i l l e d under the c o n d i t i o n s o f vacuum steam d i s t i l l a t i o n and ( i i ) g l y c e r o l i s m i s c i b l e w i t h water so t h a t

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


21. SHU AND HO

Cystimand2,5'Dimeihyl-4'hydroxy-3(2H)-furanone 231

an i n v e s t i g a t i o n on the e f f e c t o f the water c o n t e n t was p o s s i b l e . R e a c t i o n s s t u d y i n g the e f f e c t o f the r e a c t i o n medium were c a r r i e d out a t 160°C f o r a h a l f hour. 2. D u r a t i o n E f f e c t : The r e a c t i o n was c a r r i e d o u t i n water and i n g l y c e r o l a t 160°C and stopped a f t e r one h a l f , one and two h o u r s . 3. Water Content E f f e c t : Water and g l y c e r o l were combined t o p r e pare r e a c t i o n m i x t u r e s c o n t a i n i n g 10%, 25%, 5 0 % and 75% w a t e r . These r e a c t i o n s were r u n f o r one h a l f hour a t 160°C. 4. Temperature E f f e c t : Three temperatures (100°C, 160°C and 200°C) were s e l e c t e d t o r e p r e s e n t b o i l i n g , r o a s t i n g and f r y i n g c o n d i t i o n s . The temperature s t u d i e s were r u n f o r a h a l f hour i n 75% w a t e r . 5. pH E f f e c t : R e a c t i o n s were c a r r i e d o u t a t t h r e e d i f f e r e n t pH's: a t below and above t h e i s o e l e c t r i c p o i n t o f c y s t i n e . The pH was a d j u s t e d w i t h 10% Na C03 ° P v a l u e s o f 2.4, 4.7 and 7.0, which were chosen f o r the s t u d y . 6. Oxygen E f f e c t : The r e a c t i o n o f c y s t i n e and DMHF was s t u d i e d i n the presence and absence o f oxygen. P r i o r t o s t a r t i n g the r e a c t i o n i n the absence o f oxygen, the r e a c t i o n m i x t u r e i n the Paar Bomb was degassed by a stream o f n i t r o g e n . Both r e a c t i o n s i n t h i s s t u d y were c a r r i e d out a t 160°C f o r a h a l f hour. a

n

d

l7

H

C

1

t

o

t

h

e

H

2

R e s u l t s and D i s c u s s i o n The v o l a t i l e components i d e n t i f i e d from the r e a c t i o n o f c y s t i n e and DMHF i n aqueous medium a r e shown i n Table I . 2,4-Hexanedione, 3,5d i m e t h y l - l , 2 , 4 - t r i t h i o l a n e s and t h i o p h e n e s a r e the major compounds. The m e c h a n i s t i c r e l a t i o n s h i p o f the t h r e e thiophenones produced has been p o s t u l a t e d ( 2 3 ) . The major groups o f v o l a t i l e components i d e n t i f i e d from the r e a c t i o n i n the g l y c e r o l medium a r e 1 , 3 - d i o x o l a n e s and t h i a z o l e s ( T a b l e I I ) . 1,3-Dioxolanes a r e formed by the r e a c t i o n o f g l y c e r o l and the degraded c a r b o n y l s by k e t a l o r a c e t a l format i o n s . Comparison o f the r e a c t i o n o f c y s t i n e and DMHF i n water and i n g l y c e r o l i s o u t l i n e d i n Table I I I . The e f f e c t o f r e a c t i o n time on the major components o f the r e a c t i o n o f c y s t i n e and DMHF i n water i s shown i n Table IV. I t i s noteworthy t h a t amounts o f 2,4-hexanedione, 3 , 5 - d i m e t h y l - l , 2 , 4 t r i t h i o l a n e s and thiophenones were found a t a maximum a f t e r one hour. I t was a l s o found t h a t the amount o f 2 - a c e t y l t h i a z o l e i n c r e a s e d w i t h time and t h a t a c e t o l a c e t a t e d e c r e a s e d w i t h time as exp e c t e d . I n the g l y c e r o l medium, the e f f e c t o f r e a c t i o n time on t h e major components i s shown i n Table V. A p p a r e n t l y , t h e 1,3-dioxol a n e , which i s a k e t a l formed from g l y c e r o l and a c e t o n e , d e c r e a s e d o v e r t i m e . A l s o , l o n g r e a c t i o n time f a v o r s t h e f o r m a t i o n o f c y c l i c compounds, i n c l u d i n g 2 , 5 - d i m e t h y l - 2 - h y d r o x y - 3 ( 2 H ) - t h i o p h e n e , c y c l o pentenones and 4 , 5 - d i m e t h y l - l , 2 - d i t h i o l e n o n e . The samples were r e a c t e d f o r one h a l f , one and 2 hours and y i e l d e d 392, 585 and 565 mg v o l a t i l e s , r e s p e c t i v e l y . The aroma was judged b e s t a f t e r one h a l f hour where r o a s t e d , p o t - r o a s t e d and b u r n t notes were produced. A f t e r one hour, the aroma was b u r n t , r o a s t e d and b i t i n g , w h i l e a f t e r two h o u r s , the aroma was c o n s i d e r e d b i t i n g , b u r n t and p h e n o l i c . I n the g l y c e r o l medium the y i e l d was 310, 410 and 438 mg a f t e r one h a l f , one and 2 h o u r s . I n c o n t r a s t t o the aqueous medium where the b e s t aroma was produced a f t e r one h a l f



232


Table I . The V o l a t i l e Components I d e n t i f i e d from the R e a c t i o n o f C y s t i n e and DMHF i n Water Compounds Aldehydes/Ketones Acetaldehyde Acetone M e t h y l e t h y l ketone 2-Pentanone 3-Hexanone 1-Hydroxy-2-butanone 2,4-Pentanedione 3-Hydroxy-2-pent anone 2-Hydroxy-3-pentanone 2,4-hexanedione 2-Ethyl-5-methyl-2-cyclopenten-l-one Esters Acetol acetate 2-0xobutyl acetate Furanones 2,5-Dimethyl-4,5-d ihydrο-3(2H)-furanone 2,5-Dimethy1-4,5-dihydro-3(2H)-furanone 2,5-Dimethy1-3(2H)-furanone 2,4,5-Trimethy1-3(2H)-furanone 2,4-Dimethyl-5-ethyl-3(2H)-furanone Thiolanes/Thianes 3,5-Dimethyl-1,2,4-trithiolane 3,5-Dimethyl-l,2,4-trithiolane 3-Methy1-1,2,4-trithiane 4,6-Dimethyl-l,2,3,5-tetrathiane 4,6-Dimethyl-l,2,3,5-tetrathiane 3,6-Dimethyl-l,2,4,5-tetrathiane 2-Methy1-1,3-dithiolane

GC A r e a , % Τ Τ 1.2 1.5 Τ Τ Τ 4.2 1.3 16.4 Τ 1.1 Τ Τ Τ Τ Τ Τ 3.7 4.9 Τ Τ Τ Τ Τ

Continued on next page



21. SHU AND HO

Cystine and 2,5-Dimethyl-4-hydroxy-3(2B)-furanone233

Table I. Continued Compounds Thiazoles/Isothiazoie-Thiazoline Thiazole 3-Methylisothiazole 2,5-Dimethylthiazole 2-Acetylthiazole 2 - T h i a z o l y l e t h y l ketone 2-Methylthiazole 2,4,5-Trimethylthiazole 2-n-Propylthiazole 2.4- D i m e t h y l - 3 - t h i a z o l i n e 2.5- D i m e t h y 1 - 4 - e t h y l t h i a z o l e 2- M e t h y l - 5 - e t h y l t h i a z o l e Thiols 1- Mercapto-2-propanone 3- Mercapto-2-pentanone Pyrazine 2,5-Dimethylpyrazine Thiophenes 2- A c e t y l - 5 - m e t h y l t h i o p h e n e 3- M e t h y 1 - 2 - ( 2 - o x o p r o p y l ) t h i o p h e n e 4,5-Dimethyl-2-acetylthiophene 2- A c e t y l t h i o p h e n e 3- M e t h y l - 2 - t h i o p h e n e c a r b o x a l d e h y d e Thiophenones 2,5-Dimethyl-4-hydroxy-3(2H)-thiophenone 2,5-Dimethyl-2-hydroxy-3(2H)-thiophenone 2,5-Dimethyl-2,4-dihydroxy-3(2H)-thiophenone

GC A r e a , % Τ Τ Τ 1·9 1.0 Τ Τ Τ Τ Τ Τ Τ Τ Τ Τ Τ Τ Τ Τ

22.5

Τ = t r a c e , l e s s than 1%



234


T a b l e I I . The V o l a t i l e Components I d e n t i f i e d from t h e R e a c t i o n o f C y s t i n e and DMHF i n G l y c e r o l Compounds GC A r e a , % Thiazoles/Isothiazoles Thiazole Τ 2- M e t h y l t h i a z o l e 2.5 3- M e t h y l i s o t h i a z o l e Τ 5-Methylthiazole Τ 2.4- D i m e t h y l t h i a z o l e Τ 2-Ethylthiazole 1.3 2.5- D i m e t h y l t h i a z o l e 1.4 2-n-Propylthiazole 1.1 2,4,5-Trimethylthiazole 1.5 4- M e t h y l - 5 - e t h y l - t h i a z o l e Τ 2,5-Dimethy1-4-ethy1-thiazole 2.1 2.4- D i m e t h y 1 - 5 - e t h y l - t h i a z o l e 3.0 4.5- D i m e t h y l t h i a z o l e Τ 2-(2'Thienyl)thiazole Τ 2-Methyl-5-ethylthiazole 2.6 1,3-Dioxolanes 2,2-Dimethyl-4-hydroxymethy6.1 l,3-dioxolane >k 2-Methyl-2-ethyl-4-hydroxy2.0 methy1-1,3-dioxolane 2,2-Diethyl or (2-methyl-2-propyl)-41.9 hydroxymethyl-1,3-dioxolane » 2-Me thy1-4-hydroxyme t hy 1 l,3-dioxolane Aldehyde/Ketones Acetaldehyde Acetone M e t h y l e t h y l ketone 2-Pentanone 2.3- pentanedione 3.4- D i m e t h y l - 2 - c y c l o p e n t e n - l - o n e 2-Ethy1-5-methy1-2-cyclopenten-l-one 3-Hexanone 3.4 Other Compounds 2.5- D i m e t h y l p y r a z i n e 2.6- D i m e t h y l p y r a z i n e Τ 2-Ethyl-3,6-dimethylpyrazine Τ 2.4- D i m e t h y l - 5 - e t h y l p y r r o l e Τ Ethyl disulfide 1-6 2.5- D i m e t h y l - 2 - h y d r o x y - 3 ( 2 H ) - t h i o p h e n o n e 6.9 4,5-Dimethy1-1,2-dithiole-3-one 2.3 2-Acetyl-4,5-dimethylthiophene Τ γ-Thiovalero l a c tone Τ Formed from t h e r e a c t i o n between g l y c e r o l and degraded c a r b o n y l s . a

a

a

b

a

T

a

b Glycerol

impurity.


21. SHU AND HO

Cystine and 2,5^imethyl-4-hydroxy-3(2R)-furanone


T a b l e I I I . Comparison o f the R e a c t i o n o f C y s t i n e and DMHF i n Water and i n G l y c e r o l Characteristics Components Trithiolanes 2,4-Hexanedione Thiophenones Furanones Thianes Thiazoles Pyrazines Aroma Roasted/Meaty Burnt Biting Strength Smoothness Yield

in

i n Water

Glycerol

-

+ + ++ ++ ++ + +

+ + + ++ 4-+

+ ++

++ + + ++ ++

•f+

+ + +

-H-

T a b l e IV. The E f f e c t o f D u r a t i o n on the M a j o r Components o f the R e a c t i o n o f C y s t i n e and DMHF i n Water

Compounds M e t h y l e t h y l ketone 2-Pentanone 3-Hydroxy-2-pentanone 2-Hydroxy-3-pentanone 2,4-Hexanedione Acetolactate 2-Acetylthiazole 3,5-Dimethyl-l,2,4-trithiolane 2,5-Dimethyl-4-hydroxy-3(2H)thiophenone 2,5-Dimethyl-2-hydroxy-3(2H)thiophenone 2,5-Dimethyl-2,4-dihydroxy-3(2H)thiophenone

1/2 Hr. 4.7 5.9 16.5 5.1 64.3 4.3 7.4 33.7

86.6

(mg) 1 Hr. 7.6 8.2 17.0 8.2 80.1 1.2 13.5 36.3

129.9


2 Hr. 9.6 7.9 10.2 12.4 66.7

125

Φ

100

75

Η

50

Η

Thiophenones

1 1 1 1 1 60 80 100 % Moisture Thiophenones Include: 2,4-Dimethyl-4-Hydroxy-3(2H)-Thiophenone 2,4-Dimethyl-2-Hydroxy-3(2H)-Thiophenone 2,4-Dimethyl-2.4-Dihydroxy-3(2H)-Thiophenone

0

1

1

20

1

1

1

40

F i g u r e 4. The e f f e c t o f w a t e r c o n t e n t on t h e f o r m a t i o n o f t h i o p h e n e s from t h e r e a c t i o n o f c y s t i n e and DMHF.



21. SHU AND HO

Cystine and 2,5-Dimethyl-4-hydroxy-3(2YL)-furanone 239

200°C, no e s t e r s and furanones a r e found, b u t t h i a z o l e s , c y c l o p e n tenones and o t h e r h e t e r o c y c l i c compounds dominate. These d a t a i m p l y t h a t e s t e r s and furanones a r e s t a b l e a t m i l d temperatures w h i l e t h e f o r m a t i o n o f t h i a z o l e s , c y c l o p e n t e n o n e s and o t h e r h e t e r o c y c l i c compounds r e q u i r e a h i g h e r t e m p e r a t u r e . A l s o a t 160°C, t r i t h i o l a n e s , thiophenones and 2,4-hexanedione predominate, i n d i c a t i n g that form a t i o n o f such compounds i s f a v o r e d by a medium t e m p e r a t u r e . Bread, c r u s t y and caramel aromas were found i n the 100°C sample, p o t r o a s t e d , r o a s t e d , meaty and c l e a n aromas were found a t 160°C, and r o a s t e d , roasted-meat, c h e m i c a l and o f f - n o t e s were produced a t 200°C. pH has a l e s s d r a m a t i c e f f e c t on the y i e l d and aroma from t h e r e a c t i o n . The h i g h e s t y i e l d was o b t a i n e d a t pH 4.7 (523 mg) compared t o 392 a t pH 2.4 and 329 mg a t pH 7.0. The b e s t aroma was found a t pH 2.4 where i t was r o a s t e d , b u r n t and b i t i n g . A t pH 4.7, the aroma was t o a s t e d , o n i o n - l i k e w h i l e a t pH 7.0 t h e aroma was cooked o n i o n and s u l f u r y . T a b l e V I shows t h a t the major components formed from the r e a c t i o n v a r y q u a n t i t a t i v e l y a t the d i f f e r e n t pH v a l u e s . The g r e a t e s t q u a n t i t y o f t r i t h i o l a n e s , t h i o p h e n e s , 2-hydroxy -3-pentanone and 3-hydroxy-2-pentanone i s formed a t pH 4.7, w h i c h i s t h e i s o e l e c t r i c p o i n t o f c y s t i n e . F o r m a t i o n o f 2,4-hexaned i o n e s h a r p l y d e c r e a s e d w i t h i n c r e a s e d pH. T a b l e V I I a d d r e s s e s the e f f e c t o f oxygen on the y i e l d and aroma o f the r e a c t i o n o f c y s t i n e and DMHF. I n g e n e r a l , oxygen a f f e c t s the y i e l d r a t h e r than the types o f v o l a t i l e s g e n e r a t e d . A h i g h e r y i e l d o f v o l a t i l e s was o b t a i n e d i n the absence o f oxygen. I t may be t h a t oxygen promotes p o l y m e r i z a t i o n o f v o l a t i l e s i n t o nonv o l a t i l e compounds. T h i s may be a p p l i c a b l e t o i n c r e a s i n g the y i e l d o f o t h e r model systems. I t i s noteworthy t h a t t h e l e v e l o f the t r i t h i o l a n e s formed was h i g h e r when oxygen was a b s e n t . The presence o r absence o f oxygen d i d not g r e a t l y i n f l u e n c e t h e aroma c h a r a c t e r o f the r e a c t i o n p r o d u c t s . The o p t i m a l c o n d i t i o n s f o r g e n e r a t i n g the major p r o d u c t s formed from c y s t i n e and DMHF a r e as f o l l o w s : 3,5-dimethyl-l,2,4-trithiol a n e , thiophenones and 2,4-hexanedione are a l l found p r e f e r e n t i a l l y i n an aqueous medium h e a t e d t o 160°C. The t r i t h i o l a n e and t h i o p h e none a r e o p t i m i z e d a t 75% H 0 and pH 4.5, w h i l e 2,4-hexanedione f o r m a t i o n i s b e t t e r a t 100% H 0 and lower pH. T h i a z o l e s , on t h e o t h e r hand, r e q u i r e a h i g h e r temperature and a nonaqueous medium. 2

2

Table V I . The E f f e c t o f pH on the Major Components from the R e a c t i o n o f C y s t i n e and DMHF (mg) 4 .7 pH=2.4 27 .2 16.5 8.9 5.1 64.3 31 .9 14 .1 7.5 50 .7 33.7 104 .6 101.0 * I n c l u d i n g 2,5-Dimethyl-4-hydroxy--3(2H)-thioph< anone 2,5-Dimethyl-2-hydorxy-3(2H)-thiophenone 2,5-Dimethy1-2,4-dihydroxy-3(2H)-thiophenone

Compounds 3-Hydroxy-2-pentanone 2-Hydroxy-3-pentanone 2,4-Hexanedione 2-Acetylthiazole 3,5-Dimethyl-l,2,4-trithiolane Thiophenones*


7.0 8.2 4.3 4.3 24.7 33.9 23.7

240

THERMAL GENERATION OF AROMAS T a b l e V I I . The E f f e c t o f Oxygen on the M a j o r Components from the R e a c t i o n o f C y s t i n e and DMHF


Major Peaks 3-Hydroxy-2-pentanone 2,4-Hexanedione 3,5-Dimethyl-l,2,4-trithiolane Thiophenones^ Yield

a

In Presence o f Oxygen mg 16.5 60.1 35.7 101.5 392

Aroma

Roasted, Burnt Biting

I n Absence o f Oxygen mg 10.1 74.6 80.0 98.1 533 Roasted, B u r n t , Warmed

- c i s / t r a n s Isomers b

- Including

2,5-Dimethyl-4-hydroxy-3(2H)-thiophenone 2,5-Dimethyl-2-hydroxy-3(2H)-thiophenone 2,5-Dimethy1-2,4-dihydroxy-3(2H)-thiophenone

Conclusions As a r e s u l t o f t h e r e a c t i o n parameter s t u d y , t h e p r o d u c t s , aromas and c h e m i s t r y o f t h e r e a c t i o n between c y s t i n e and DMHF i s more c l e a r l y u n d e r s t o o d . The major v o l a t i l e components g e n e r a t e d by t h i s r e a c t i o n are 3 , 5 - d i m e t h y l - l , 2 , 4 - t r i t h i o l a n e s , thiophenones, t h i a z o l e s and 2,4-hexanedione. The f i r s t t h r e e groups o f compounds c o n t r i b u t e g r e a t l y t o t h e q u a l i t y o f t h e o v e r a l l aroma w h i c h i s r o a s t e d , meaty and b u r n t . F u r t h e r v a r i a t i o n s i n aromas may depend on t h e p r o p o r t i o n s o f t h e s e components p r e s e n t a s r e a c t i o n p r o d u c t s . O p t i m a l c o n d i t i o n s f o r p r o d u c i n g the major components o f i n t e r e s t from the t i t l e r e a c t i o n have been d e t e r m i n e d . I t i s hoped t h a t t h e d a t a p r e s e n t e d may prove u s e f u l as a g u i d e l i n e f o r o t h e r r e a c t i o n f l a v o r s t u d i e s where maximation o f f l a v o r compounds i s d e s i r e d . Acknowledgement s New J e r s e y A g r i c u l t u r a l Experiment S t a t i o n P u r b l i c a t i o n No. D10205-7-88, s u p p o r t e d by S t a t e Funds and R e g i o n a l P r o j e c t NE-116. We thank James Shaw f o r r e v i e w i n g the m a n u s c r i p t and Mrs. Joan B. Shumsky f o r h e r s e c r e t a r i a l h e l p .

Literature Cited 1. 2. 3. 4.

Lien, Y. C. and Nawar, W. W. J . Food Sci. 1974, 39, 911-913. de Rijke, D.; van Dort, J . M. and Boelens, H. In Flavor '81; Schreier, P., Ed.; Walter de Gruyter and Co., Berlin, 1981; p 417-431. Fujimaki, M.; Kato, S. and Karata, T. Agric. Biol. Chem. 1969, 33, 1144-1151. Boelens, H . ; van der Linde, L.M.; de Valois, P . J . ; van Dort, J.M. and Takken, H.J. Proc. Inst. Symp. on Aroma Res; Zeist, Prodoc, Wageningen, 1975, p 95-10.


21. SHU AND HO Cystine and 2,5-Dimethyl-4-hydroxy-3(2H)-furanone 241 5. 6. 7. 8.


9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Shibamoto, T. and Russell, G. F. J. Agric. Food Chem. 1976, 24, 843-846. Kato, S.; Kurata, T. and Fujimaki, M. Agric. Biol. Chem. 1973, 37, 539-544. Kobayashi, N. and Fujimaki, M. Agric. Biol. Chem. 1965. 19, 698-699. Piloty, M. and Baltes, W. Z. Lebensm-Unters, Forsch. 1979, 168, 374-380. Shibamoto, T.; Nishimura, O. and Mihara, S. J. Agric. Food Chem. 1981, 29, 643-646. van der Ouweland, G. A. M. and Peer, H. G. J. Agric. Food Chem. 1975, 23, 501-505. Hurrell, R. J. In Food Flavor, Part A. Introduction; Morton, I. D.; MacLeod, A.J., Eds.; Elsevier Publi. Co.: Amsterdam, 1982; p 339. Ching, J. C.-Y. Ph.D. Thesis, University of Missouri, Colum bia, Missouri, 1979. Ohloff, G. and flament, I. Fortschr. Chem. Org. Naturst. 1878, 36, 231-283. Rodin, J. O.; Himl, C. M. J.; Silverstein, R. M.; Leeper, R. W. and Gortner, W. A. J. Food Sci. 1965, 30, 280-285. Re, L.; Maurer, B. and Ohloff, G. Helv. Chem. Acta. 1973, 56, 1882-1888. Tonsbeek, C. H. T.; Plancken, A. J. and Werdhof, V. d. J. Agric. Food Chem. 1968, 16, 1016-1021. Takei, Y. and Yamanishi, T. Agric. Biol. Chem. 1974, 38, 2329-2336. Hirvi, T.; Honkanen, E. and Pyysalo, T. Lebensm.-Wiss. u.Technol. 1980, 13, 324-325. Re, L. and Ohloff, G. Swiss Patent 540 650, 1974. Hodge, J. E. and Osman, Ε. M. In Principles of Food Science, Part I.; Fennema, O., Ed.; Marcel Dekker:New York and Basel, 1980, p 41. Shu, C.-K.; Hagedorn, M. L.; Mookherjee, B. D. and Ho, C.-T. J. Agric. Food Chem. 1985, 33, 438-442. Shu, C.-K.; Mookherjee, B. D. and Ho, C.-T. J. Agric. Food Chem. 1985 , 33, 446-448. Shu, C.-K.; Hagedorn, M. L.; Mookherjee, B. D. and Ho, C.-T. J. Agric. Food Chem. 1985 , 33, 638-641.

RECEIVED May 11, 1989


Parameter Effects on the Thermal Reaction of Cystine and 2,5

Recommend Documents