Formation of Amino Acid Specific Maillard Products ... - ACS Publications

Chapter 15

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on April 19, 2016 | http://pubs.acs.org Publication Date: October 3, 1989 | doi: 10.1021/bk-1989-0409.ch015

Formation of Amino Acid Specific Maillard Products and Their Contribution to Thermally Generated Aromas R. Tressl, B. Helak, N. Martin, and E. Kersten Institut für Biotechnologie, Forschungsinstitut für Chemisch-technische Analyse, Technische Universität Berlin, Seestrasse 13, D-1000 Berlin 65, Federal Republic of Germany In model experiments L-proline, hydroxyproline, cysteine and methionine were heated with monosaccharides for 1 - 1.5 h at 150 °C. Amino acid specific Maillard products were isolated from the extracts by preparative GC or HPLC and identified by MS-, IR-, H- and C-NMR-spectroscopy. Proline derived components are important constituents in bread, malt and beer. More than 120 proline specific Maillard products were characterized. Cysteine and methionine derived components were predominant in roasted coffee and meat flavors. Thirty cysteineand twenty methionine-specific Maillard products were identified for the first time. 1

13

Proline

Specific Maillard

Products

As d e m o n s t r a t e d i n p r e v i o u s p u b l i c a t i o n s , model r e a c t i o n s o f L - p r o l i n e and m o n o s a c c h a r i d e s r e s u l t i n complex m i x t u r e s o f p r o l i n e s p e c i f i c compounds (J_-4^ . D u r i n g t h e M a i l l a r d r e a c t i o n o f L - p r o l i n e and r e d u c i n g s u g a r s more t h a n 120 p r o l i n e s p e c i f i c compounds were i d e n t i f i e d b y MS-, IR-, H - and 3 c - N M R - s p e c t r o s c o p y (among them: 2,3-dihydro-1H-pyrrolizines, p y r r o l i d i n e s , 2 - a c e t y l - and 2 - f u r y l p i p e r i d i n e s and - p i p e r i d e i n e s , d i - and t e t r a h y d r o - 1 H - a z e p i n e s ) . The r e a c t i o n c o n d i t i o n s d e t e r m i n e t h e s p e c t r u m o f p r o l i n e s p e c i f i c compounds. We a t t e m p t e d t o s e l e c t c o n d i t i o n s , s o we c o u l d t r a c e t h e r o u t e s by w h i c h i m p o r t a n t c o n s t i t u e n t s a r e formed w i t h o u t s p l i t t i n g C - c h a i n s o f t h e s u g a r s b y p y r r o l y s i s . Under m i l d r e a c t i o n c o n d i t i o n s (100 °C; H2O; pH 3 - 7; 1 - 2 h) o n l y a few compounds a r e f o r m e d ( F i g u r e 1 ) . I t c a n b e s e e n t h a t a l l c o n s t i t u e n t s ( e x c e p t 2_5) c o n t a i n s i x C-atoms from g l u c o s e . In 1 982 we i s o l a t e d 6 0 ^ as a main component f r o m m a l t and named t h e new t r i c y c l i c compound m a l t o x a z i n e ( J _ ) . 1

1

0097-6156/89/0409-0156$06.00/0 ο 1989 American Chemical Society

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


15.

TRESSLETAL.

Figure

Formation ofAmino Acid Specific Maillard Products

1 : Main components f r o m p r o l i n e / g l u c o s e s y s t e m , d e p e n d i n g on p H - v a l u e

model


157


158

THERMAL GENERATION OF AROMAS

Components 2J5 and j_2 were f i r s t d e t e c t e d i n w o r t , w h i c h was h e a t e d above 140 °C. B e e r , p r o d u c e d by t h i s p r o c e s s , p o s s e s s e d a b i t t e r a f t e r t a s t e . Compound 30^ was r e c e n t l y i d e n t i f i e d as a r e a c t i v e i n t e r m e d i a t e , w h i c h decomposed v e r y s o o n even by s t o r a g e a t -20 °C. On h e a t i n g L - p r o l i n e and m o n o s a c c h a r i d e s a t 150 °C f o r 1.5 h a l l compounds i n c r e a s e d t e n t o f i f t y f o l d and 2,3-dihydro-1H-pyrrolizines and d i - and t e t r a h y d r o - 1 H - a z e p i n e s were c h a r a c t e r i z e d as major components. On r o a s t i n g L - p r o l i n e and monosaccha r i d e s ( o r s u c r o s e ) p y r r o l i d i n e s and a z e p i n o n e s p r e d o m i n a t e among t h e M a i l l a r d p r o d u c t s . These compounds were a l s o f o r m e d by h e a t i n g p y r r o l i d i n e and g l u c o s e a t 100 °C. A z e p i n o n e s and c e r t a i n p y r r o l i n - d e r i v a t i v e s p o s s e s s e x t r e m e b i t t e r t a s t e and t h r e s h o l d s o f 5 - 10 ppm (3^5.)· The s i g n i f i c a n t r o l e o f L - p r o l i n e i n t h e f o r m a t i o n o f s p e c i f i c p r o d u c t s can be e x p l a i n e d by i t s S t r e c k e r d e g r a d a t i o n (_3 ) . As shown i n model e x p e r i m e n t s , L - p r o l i n e r e a c t s w i t h α - d i c a r b o n y l s t o y i e l d 1 - p y r r o l i n e and α - h y d r o x y k e t o n e , p y r r o l i d i n e and α - d i k e t o n e . H y d r o x y p r o l i n e i s t r a n s f o r m e d i n t o p y r r o l e and d i k e t o n e and p y r r o l y l d e r i v a t i v e s , d e p e n d i n g on t h e s u g a r and r e a c t i o n c o n d i t i o n s . P r i m a r y amino a c i d s form p y r a z i n e s and p y r r o l e s w h i c h a r e not p r o d u c e d i n t h e p r o l i n e s y s t e m . Under e l e v a t e d t e m p e r a t u r e s r e t r o a l d o l r e a c t i o n s p r e dominate forming α - d i c a r b o n y l s and α-hydroxyketones c o n t a i n i n g two t o f o u r C-atoms. In a model e x p e r i m e n t o f e r y t h r o s e ( g l u c o s e ) and L - p r o l i n e , 5 - ( 3 - h y d r o x y p r o p i o n y l ) - 2 , 3 - d i h y d r o - 1 H - p y r r o l i z i n e and 1,2,3,4,5,6h e x a h y d r o c y c l o p e n t a ( b ) p y r i d i n e - 7 ( 1 Η)-one were i d e n t i f i e d . B o t h compounds a r e f o r m e d by 3 - d e o x y o s o n e s and t h e i r r e t r o a l d o l p r o d u c t s , r e s p e c t i v e l y (_2). D u r i n g t h i s r e a c t i o n 2 - a c e t y l t e t r a h y d r o p y r i d i n e s a r e f o r m e d as f l a v o r components p o s s e s s i n g c r a c k e r - l i k e aromas and t h r e s h o l d s a t 1 t o 2 ppb. A z e p i n o n e - d e r i v a t i v e s a r e f o r m e d u n d e r e l e v a t e d temperatures i n proline/monosaccharide experi ments. As d e m o n s t r a t e d , c y c l i c α - d i c a r b o n y l s a c t as p r e c u r s o r s i n c r e a s i n g t h e p r o d u c t s 1000 f o l d compared t o m o n o s a c c h a r i d e s . F i g u r e 2 p r e s e n t s a scheme w h i c h may e x p l a i n t h e r e a c t i o n w h i c h f o r m s components w i t h e x t r e m e b i t t e r t a s t e q u a l i t i e s . In m a l t and b e e r L - p r o l i n e i s t h e major f r e e amino a c i d and i s t r a n s f o r m e d i n t o f l a v o r c o n t r i b u t i n g compounds d u r i n g k i l n i n g , wort b o i l i n g , p a s t e u r i z a t i o n , and e l e v a t e d s t o r a g e c o n d i t i o n s . F i g u r e 3 shows a pathway w h i c h i s o p e r a t i v e u n d e r m i l d r e a c t i o n c o n d i t i o n s and l e a d s t o m a l t o x a z i n e . The p r o d u c t s f o u n d i n model e x p e r i m e n t s and i n f o o d s t u f f s a r e n o t c o m p a r a b l e . The c o n c e n t r a t i o n s o f i n d i v i d u a l c o n s t i t u e n t s v a r y c o n s i d e r a b l y between b o t h s y s t e m s . F i g u r e 4 summarizes p r o l i n e s p e c i f i c components d e t e r m i n e d i n w o r t and b e e r p r o d u c e d u n d e r d i f f e r e n t r e a c t i o n c o n d i t i o n s . Beer I r e p r e s e n t s a German p a l e b e e r , p r o d u c e d f r o m p a l e m a l t by a c o n v e n t i o n a l wort



TRESSL ET AL.

Figure

Formation of Amino Acid Specific Maillard Products

2: R e a c t i o n scheme o f h e x a - and t e t r a h y d r o - 1 a z e p i n o n e s from p r o l i n e and c y c l i c a - d i carbonyls




Figure

3: P a t h w a y l e a d i n g t o m a l t o x a z i n e 3-deoxyglucosone and p r o l i n e

from


15.

TRESSL ET AL.


120*C


Wfiri*

1 Bi«r 1

8 0 min

Wtiri* Il Bi«r II

120°C

3 min

140 C e

3min

Wiirs* III Bier III W i i r i . IV Bi«r IV

60 170

(X H

11 12 9

9? 9* Qo

10

1130

1300

240

220

180

170

0.5

1

2

3

0.1

2

4

2

1

4

9

10

0.2

5

11

4

5

35

10

180

39

73

43

50

7

4.5

150

100

4.6

7.6

5.4

4.1

0.8

0.6

32

35

0.1

2

0.1

2

5

5

11

9

14

18

15

13

4

3

4

70

6

76

6

70

-

-

3

•

6

•

5

•

1

4

18

32

14

11

26

15

0

Çr 25

600

H

Figure

4:

T y p i c a l p r o l i n e s p e c i f i c c o n s t i t u e n t s i n wort and b e e r d e p e n d i n g on d i f f e r e n t b o i l i n g c o n ditions


161



162

b o i l i n g p r o c e s s , w h i c h p o s s e s s e d d e s i r a b l e f l a v o r . Beer I I was p r o d u c e d from t h e same m a l t by a w o r t b o i l i n g p r o c e s s o f 120 °C. T h i s b e e r p o s s e s s e d a s t r o n g b r e a d y o f f f l a v o r and an u n d e s i r a b l e b i t t e r a f t e r t a s t e . I t c a n be s e e n t h a t some t e t r a h y d r o p y r i d i n e s and a z e p i n o n e s i n c r e a s e d d u r i n g t h i s p r o c e s s ( 6_) . The c o n c e n t r a t i o n s o f f l a v o r c o n t r i b u t i n g components were n o t c o m p a r a b l e t o o u r model e x p e r i m e n t s . R e c e n t l y we d e m o n s t r a t e d t h a t t h e compounds w i t h h i g h f l a v o r v a l u e s a r e m e t h y l e n e a c t i v e c o n s t i t u e n t s and r e a c t w i t h c a r b o n y l s t o form c y c l o p e n t a ( b ) p y r i d i n o n e - d e r i v a t i v e s w h i c h a r e l e s s v o l a t i l e and p o s s e s s h i g h t h r e s h o l d s . By t h i s r e a c t i o n , f l a v o r c o n t r i b u t i n g p r o l i n e d e r i v a t i v e s may be bound t o t h e m a t r i x of m e l a n o i d i n e s . A z e p i n o n e s w i t h e x o c y c l i c d o u b l e bonds a r e t r a n s f o r m e d i n t o n o n v o l a t i l e compounds and may cause t h e b i t t e r a f t e r t a s t e o f t h e p r o d u c t s . F i n a l l y , we i d e n t i f i e d 3 - f u r y l i d e n e - 1 - p y r r o l i n e s and 3 - f u r f u r y l p y r r o l s by h e a t i n g L - p r o l i n e w i t h f u r a n a l d e h y d e s and monosacchar i d e s (_7, 8) . * Cysteine

Specific

Maillard

Products

Figure 5 presents t y p i c a l Strecker degradation products from c y s t e i n e , w h i c h were i d e n t i f i e d i n a x y l o s e model system. During S t r e c k e r d e g r a d a t i o n the l a b i l e mercaptoa c e t a l d e h y d e i s f u r t h e r decomposed t o a c e t a l d e h y d e and H S. 3 , 5 - D i m e t h y l - 1 , 2 , 4 - t r i t h i o l a n e s and t h i a l d i n e a r e f o r m e d by t h i s r e a c t i o n as w e l l as 3 , 6 - d i m e t h y l - 1 ,2 , 4 , 5tetrathiane. 1,2,3-Trithia-5-cycloheptene, f i r s t i d e n t i f i e d by Shu e t a l . {9_) , i s o b v i o u s l y formed by c o n d e n s a t i o n of mercaptoacetaldehyde and a c e t a l d e h y d e . Mercaptoacetaldehyde i s transformed into 1,2,4-trithiane and 2 - m e t h y l - 1 , 3 - d i t h i o l a n e . T h i a z o l i d i n e s a r e formed f r o m t h e S t r e c k e r amine w h i c h u n d e r g o e s f u r t h e r r e a c t i o n s w i t h c a r b o n y l s . 3 - M e t h y l - 1 , 2 - d i t h i o l a n - 4 - o n e , a main p r o d u c t i n t e t r o s e model s y s t e m s , i s o b v i o u s l y f o r m e d from t h e c o r r e s p o n d i n g 1 - d e o x y t e t r o s o n e (also detected i n g l u c o s e / c y s t e i n e e x p e r i m e n t s ) . S i m i l a r r e s u l t s were o b t a i n e d by Shu e t a l . (9_) on h e a t i n g c y s t i n e a t d i f ferent pH-values. 2

Cysteine/Pentose

Model

System

Main components i n t h e c y s t e i n e / x y l o s e s y s t e m (180 °C; H^O I pH - 5) a r e 2- and 3 - m e r c a p t o p r o p i o n i c - , f u r a n - , and t h i o p h e n e c a r b o x y l i c a c i d s , w h i c h amount t o 40 t o 80 % o f t h e v o l a t i l e M a i l l a r d p r o d u c t s . The f u r a n - and t h i o p h e n e c a r b o x y l i c a c i d s a r e f o r m e d v i a 3-deoxyosone and t h e m e r c a p t o a c i d s v i a 1-deoxyosone ( F i g u r e 6 ) . By d e h y d r a t i o n , a d d i t i o n o f H«0 ( o r by S t r e c k e r d e g r a d a t i o n of Cys) and r e d u c t i o n o f t h e c a r b o n y l g r o u p , f u r f u r y l m e r c a p t a n ( t h e i m p a c t component o f r o a s t e d c o f f e e ) r e s u l t s . 2-Hydroxymethyl-4-thiolanone, w h i c h may be f o r m e d by t h e same r o u t e , was i d e n t i f i e d f o r t h e f i r s t



15.

TRESSL ET AL.

Figure

5:


Strecker degradation products formed from a c e t a l d e h y d e , H S ?

of c y s t e i n e and c y s t e a m i n e


163

164



Figure

6: Main components o f t h e c y s t e i n e / x y l o s e system formed v i a 3-deoxypentosone


model

15.

TRESSLETAL.



t i m e as a c y s t e i n e - s p e c i f i c M a i l l a r d p r o d u c t . I t was i s o l a t e d from t h e model e x p e r i m e n t by p r e p a r a t i v e GC and i d e n t i f i e d by IR- and H - N M R - s p e c t r o s c o p y . The r a t i o s f o r f u r f u r y l a l c o h o l t o f u r a n c a r b o x y l i c a c i d (and t h e c o r r e s p o n d i n g t h i o p h e n e s ) were d e t e c t e d a t 90 ppm t o 1300 and 80 ppm t o 2100, r e s p e c t i v e l y . T h e r e f o r e , d i s p r o p o r t i o n a t i o n o f f u r f u r a l c a n be e l i m i n a t e d . As a p o s s i b l e i n t e r m e d i a t e we i d e n t i f i e d 3 - h y d r o x y - 2 - p y r a n o n e w h i c h i s o b v i o u s l y t r a n s f o r m e d i n t o t h e c o r r e s p o n d i n g a c i d s . In t h e c y s t e i n e / r h a m n o s e model e x p e r i m e n t s a l l homologous components were i d e n t i f i e d i n a s i m i l a r r a n g e . At p H - v a l u e s o f 5 - 7 t y p i c a l c y s t e i n e / p e n t o s e p r o d u c t s are formed v i a 1-deoxypentosone ( F i g u r e 7 ) . 2M e t h y l - 3 - t h i o l a n o n e i s a f l a v o r c o n t r i b u t i n g component i n r o a s t e d c o f f e e ( w i t h a t h r e s h o l d o f 50 ppb) and 2m e t h y l - 3 - m e r c a p t o t h i o p h e n e i s a component o f r o a s t e d / c o o k e d b e e f ( 1_0) . Two t h i a n o n e s were i d e n t i f i e d f o r t h e f i r s t t i m e as c y s t e i n e s p e c i f i c M a i l l a r d p r o d u c t s . 2-Met h y l - 4 - t h i a n o n e and 4 - t h i a n o n e ( n o t shown i n F i g u r e 7) were a l s o d e t e c t e d i n t h e g l u c o s e , e r y t h r o s e and a s c o r b i c acid experiments. F i g u r e 8 o u t l i n e s p o s s i b l e r o u t e s l e a d i n g to cysteine s p e c i f i c p r o d u c t s v i a 1 - d e o x y p e n t o s o n e . Under t h e c h o s e n r e a c t i o n c o n d i t i o n s , (180 °C; H~0) n o r f u r a n e o l i s f u r t h e r transformed v i a 4-hydroxy-5-metnyl-3-(2H)-thiophenone and 2-methyl-3-(2H)-thiophenone, i n t o 2-methyl-3-mercaptot h i o p h e n e and 2 - m e t h y l t h i o p h e n e , r e s p e c t i v e l y . N o r f u r a n e o l i s a m e t h y l e n e a c t i v e compound, w h i c h u n d e r g o e s a l d o l c o n d e n s a t i o n w i t h c a r b o n y l s f o r m i n g c o l o r e d nonv o l a t i l e p r o d u c t s . 2 - M e r c a p t o p r o p i o n i c a c i d may be formed from t h e m e r c a p t o k e t o n e by o x i d a t i v e c l e a v a g e . By t h i s r o u t e 2 - m e t h y l - 3 - t h i o l a n o n e and 2 - m e t h y l - 4 , 5 - d i h y d r o t h i o p h e n e may r e s u l t . C y s t e i n e / H e x o s e Model

System

In t h e c y s t e i n e / g l u c o s e model e x p e r i m e n t s g l u c o s e r e d u c t o n e , a c e t y l f o r m o i n , f u r a n e o l and c y c l o t e n e were d e t e c t e d as major c o n s t i t u e n t s i n d i c a t i n g t h a t t h e 1-deoxyosone r o u t e i s o p e r a t i v e a t p H - v a l u e s oj^ 5 t o 7. As main component we i d e n t i f i e d by MS, IR- and H-NMR-spectroscopy 4-hydroxy-2,5-dimethyl-3(2H)thiophenone. O b v i o u s l y t h i s compound i s l e s s r e a c t i v e t h a n t h e c o r r e s p o n d i n g n o r f u r a n e o l d e r i v a t i v e . T h i o f u r a n e o l i s a l s o formed from g l u c o s e / r e d u c t o n e , a c e t y l f o r m o i n and f u r a n e o l as demons t r a t e d i n model e x p e r i m e n t s . S u r p r i s i n g l y , i t i s n o t f o r m e d i n c y s t e i n e / r h a m n o s e e x p e r i m e n t s , where f u r a n e o l i s a major compound. In a d d i t i o n 2 - a c e t y l - 4 - t h i o l a n o n e and 5 - h y d r o x y m e t h y l - 2 - m e t h y l - 3 - t h i o l a n o n e were i d e n t i f i e d f o r t h e f i r s t t i m e as c y s t e i n e s p e c i f i c p r o d u c t s . 2- A c e t y l - 4 - t h i o l a n o n e i s formed a t pH 3, i n d i c a t i n g 3- d e o x y h e x o s o n e i s a p o s s i b l e p r e c u r s o r . Under t h i s


165


Figure

7: F o r m a t i o n o f t y p i c a l c y s t e i n e / p e n t o s e p r o d u c t s v i a 1-deoxysone d e p e n d i n g on p H - v a l u e



15.

TRESSLETAL.

Figure

8:


P o s s i b l e routes leading to 2-mercaptopropionic a c i d , and s e v e r a l t h i o p h e n o n e s and t h i o p h e n e s v i a 1-deoxypentosone


167

168


c o n d i t i o n 2 - ( 1 - h y d r o x y e t h y l ) - 4 - t h i o l a n o n e c o u l d a l s o be c h a r a c t e r i z e d . T h e s e compounds a r e formed a n a l o g o u s l y t o the c y s t e i n e / x y l o s e system. 5-Hydroxymethylfurfurylmerc a p t a n c o u l d n o t be d e t e c t e d i n our model e x p e r i m e n t s .


F i g u r e 9 p r e s e n t s r o u t e s l e a d i n g t o major p r o d u c t s i n t h e c y s t e i n e / g l u c o s e e x p e r i m e n t s a t pH v a l u e s o f 5 - 7. T h i o f u r a n e o l and 2,4-dihydroxy-2,5-dimethyl-3(2H)-thiophenone were f o r m e d as major components a t a r a t i o o f 10 : 1. A l l o t h e r t h i o p h e n e s were m i n o r c o n s t i t u e n t s .

Figure

9:

R e a c t i o n scheme l e a d i n g t o t h e major p r o d u c t s o f t h e c y s t e i n e / g l u c o s e model e x p e r i m e n t s


15. TRESSLETAL.


In t h e c y s t e i n e / r h a m n o s e s y s t e m 2 - h y d r o x y - 2 , 5 - d i m e t h y l 3 ( 2 H ) - t h i o p h e n o n e and 2 , 5 - d i m e t h y l - 3 - t h i o l a n o n e were c h a r a c t e r i z e d as major compounds. On h e a t i n g c y s t e i n e and f u r a n e o l , p r o d u c t s were f o r m e d c o m p a r a b l e t o t h o s e f o u n d by Shu e t a l . under m i l d e r r e a c t i o n c o n d i tions .


E x p e r i m e n t a l c o n d i t i o n s and s p e c t r o s c o p i c d a t a o f t h e new c h a r a c t e r i z e d c y s t e i n e / s u g a r r e a c t i o n p r o d u c t s w i l l be p u b l i s h e d i n d e t a i l . Methionine

M o n o s a c c h a r i d e Model

Systems

M a i l l a r d p r o d u c t s w h i c h were i d e n t i f i e d i n m e t h i o n i n e / r e d u c i n g s u g a r model e x p e r i m e n t s , r e s u l t p r e d o m i n a n t l y from t h e S t r e c k e r a l d e h y d e ( m e t h i o n a l ) and m e t h y l m e r captan, respectively. F i g u r e 10 summarizes compounds

0 0 H II

-CO,

^S^^COOH

-c-cH C-SH • 3

^S^-s^S-CHj S-CH

O^S-CH

^CHO

Ν

3

3

^S-CH /Sv^

"

S

^ C H 0

—-S-CH,

3

CH -0-C-CH 2

„

S-CH

C H r 0 H

3

Q^CHO

5

Λ^ ^ OH „

/Γ rCH,

OH

OHC^N^ ^-S-CH,

S-CH, ^O^^CHO

O^K^s-cHj 0

N

0^^S'

0 x"s^S-CH

3

S-CH A

COOH

(

0HC^N^CH 0H 2

^Sv^v^COOH

F i g u r e 10: S t r e c k e r d e g r a d a t i o n p r o d u c t s i d e n t i f i e d i n m e t h i o n i n e / r e d u c i n g s u g a r model s y s t e m s u n d e r elevated temperatures


169

170


c h a r a c t e r i z e d i n m e t h i o n i n e / r e d u c i n g s u g a r model e x p e r i ments ( r e a c t i o n c o n d i t i o n s : 180 °C; H 0 , pH 5; 1 1/2 h ) . S i m i l a r r e s u l t s were o b t a i n e d b y R i j k e e t a l . ( 1 2 ) . 3 - M e t h y l t h i o p r o p a n a l i s more s t a b i l e t h a n t h e c o r r e s p o n d i n g m e r c a p t o a c e t a l d e h y d e from c y s t e i n e . I t i s o b v i o u s l y f u r t h e r degraded t o methylmercaptan and a c r o l e i n . The m e r c a p t a l s from 3 - m e t h y l t h i o p r o p a n a l and a c r o l e i n were c h a r a c t e r i z e d as major compounds. M e t h i o n a l u n d e r g o e s a l d o l c o n d e n s a t i o n w i t h f u r a n a l d e h y d e s and i s t r a n s formed i n t o 3 - m e t h y l t h i o m e t h y l p y r i d i n e as w e l l as i n t o s e r i e s o f a l k y l s u b s t i t u t i e d 3 - ( t h i a b u t y l ) - and 4 - ( t h i a pentyl)pyrazines w h i c h were i d e n t i f i e d f o r t h e f i r s t t i m e as m e t h i o n i n e s p e c i f i c p r o d u c t s . The p r e s e n c e o f f u r f u r y l m e t h y l s u l f i d e s i n d i c a t e t h a t t h e s e compounds a r e formed from 3 - d e o x y o s o n e s as w e l l as from a l d o l r e a c t i o n s . Methylmercaptan i s the r e a c t i v e i n t e r m e d i a t e as d e m o n s t r a t e d w i t h t h e c o r r e s p o n d i n g p r e c u r s o r s . The S t r e c k e r amine i s t r a n s f o r m e d i n t o p y r r o l e s as s p e c i f i c compounds. More t h a n 20 compounds were i d e n t i f i e d f o r t h e f i r s t t i m e i n t h i s s t u d y . The r e s u l t s w i l l be p u blished in detail.


2

Acknowledgments T h i s work was s u p p o r t e d b y t h e D e u t s c h e Forschungsg e m e i n s c h a f t , Bonn-Bad G o d e s b e r g , and A r b e i t s g e m e i n s c h a f t i n d u s t r i e l l e r F o r s c h u n g s v e r e i n i g u n g e n e.V., Koln, (West Germany).

LITERATURE CITED 1. 2.

3. 4. 5. 6. 7. 8. 9.

Tressl, R.; Helak, B. Helv. Chim. Acta 1982, 65, 483-489 Tressl, R.; Rewicki, D.; Helak, B.; Kamperschröer, H.; Martin, N. J. Agric. Food Chem. 1985, 33, 919-923 Tressl, R.; Rewicki, D.; Helak, B.; Kamperschröer,H. J. Agric. Food Chem. 1985, 33, 924-928 Tressl, R.; Helak, B.; Spengler, Κ.; Schröder, Α.; Rewicki, D. Liebigs Ann. Chem. 1985, 2017-2027 Pabst, H.M.E.; Ledl, F.; Belitz, H.-D. Z. Lebensm. Unters. Forsch. 1984, 178, 356-360 Tressl, R.; Grünewald, K.G.; Silwar, R.; Helak, B. Proc. 18th EBC Congress 1981, 391-403 Helak, B.; Spengler, K.; Tressl, R.; Rewicki, D. J. Agric. Food Chem. 1989, 37, 400-404 Helak, B.; Kersten, E., Spengler, K.; Tressl, R.; Rewicki, D. J. Agric. Food Chem. 1989, 37, 405-410 Shu , C.-K.; Hagedorn, M.L.; Mookherjee, B.D.; Ho, C.-T. J. Agric. Food Chem. 1985, 33, 438


15. TRESSL ET AL. 10. 11. 12.


van den Ouweland, D.A.M.; Peer, H.G. J. Agric. Food Chem. 1975, 23, 501 -505 Shu, C.-K.; Hagedorn, M.L.; Mookherjee, B.D.; Ho, C.-T. J. Agric. Food Chem. 1985, 33, 638-641 de Rijke, D.; van Dort, J.M.; Boelens, H. Flavour '81, 3. Weurman Symposium (1981), p. 417


RECEIVED July 10, 1989


171

Formation of Amino Acid Specific Maillard Products ... - ACS Publications

Recommend Documents