bk-1983-0215.ch012

12 Sensory Properties of Volatile Maillard Reaction Products and Related Compounds A Literature Review SUSAN FORS

Downloaded by EMORY UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch012

SIK-The Swedish Food Institute, Box 5401, S-402 29 Göteborg, Sweden

V o l a t i l e c o m p o u n d s f o r m e d by n o n - e n z y m a t i c b r o w n i n g r e a c t i o n s are of g r e a t i m p o r t a n c e f o r the sensory p r o p e r t i e s of h e a t - t r e a t e d f o o d s . L i t e r a t u r e i n f o r m a t i o n about the sensory p r o p e r t i e s f o r n e a r l y 450 M a i l l a r d r e a c t i o n p r o d u c t s has b e e n c o m p i l e d in a s u r v e y . It i n c l u d e s q u a l i t a t i v e a r o m a and f l a v o r d e s c r i p t i o n s as w e l l as sensory t h r e s h o l d values in d i f f e r e n t m e d i a f o r the c o m p o u n d s , c l a s s i f i e d a c c o r d i n g to t h e i r c h e m i c a l s t r u c t u r e .

In r e c e n t d e c a d e s a l a r g e n u m b e r of papers and r e v i e w s about r e s e a r c h on f o o d a r o m a and f l a v o r have been p u b l i s h e d , and this r e s e a r c h f i e l d c o n t i n u e s to e x p a n d . T h e e x p a n s i o n is r e f l e c t e d in the r a p i d i n c r e a s e in the n u m b e r of v o l a t i l e c o m p o u n d s i d e n t i f i e d in v a r i o u s f o o d s . N o n - e n z y m a t i c b r o w n i n g r e a c t i o n s play a c e n t r a l role in the f o r m a t i o n of f o o d a r o m a and f l a v o r , e s p e c i a l l y in h e a t - t r e a t e d f o o d s . T h e purpose of this work is to present sensory d a t a , s c a t t e r e d in the l i t e r a t u r e , f o r v o l a t i l e n o n - e n z y m a t i c browning r e a c t i o n p r o d u c t s a n d r e l a t e d c o m p o u n d s . T h e c o m p i l a t i o n has no p r e t e n s i o n s to c o m p l e t e n e s s and only a s m a l l p a r t of the e x t e n s i v e p a t e n t l i t e r a t u r e has been c o v e r e d . A n y h o w , it is f e l t t h a t a c o m p i l a t i o n of this k i n d , w h i c h has not b e e n a v a i l a b l e h i t h e r t o , w o u l d be u s e f u l to w o r k e r s in the f i e l d . T h e m a j o r i t y of the c o m p o u n d s in this c o m p i l a t i o n are M a i l l a r d r e a c t i o n p r o d u c t s and l i k e w i s e r e c o g n i z e d as i m p o r t a n t a r o m a and f l a v o r s u b s t a n c e s in f o o d s . T h e sensory p r o p e r t i e s , p r e s e n t e d in t a b u l a r f o r m , i n c l u d e the following •

T h e q u a l i t a t i v e odor a n d / o r f l a v o r d e s c r i p t i o n of the c o m p o u n d . T h e c o n c e n t r a t i o n m a y h a v e a s t r o n g i n f l u e n c e on the odor or f l a v o r q u a l i t y ; one c o m p o u n d s t r o n g l y d i l u t e d w i l l not h a v e the sensory c h a r a c t e r i s t i c s of the s a m e c o m p o u n d in a m o r e c o n c e n trated f o r m .

0097-6156/83/0215-0185$21.20/0 © 1983 American Chemical Society

In The Maillard Reaction in Foods and Nutrition; Waller, G., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

MAILLARD REACTIONS

186 •

T h e t h r e s h o l d values d e t e r m i n e d in d i f f e r e n t liquids ( w a t e r , o i l , o r a n g e j u i c e , b e e r , sugar s o l u t i o n e t c . ) or less f r e q u e n t l y , in a i r . T h e m a j o r i t y of the t h r e s h o l d values g i v e n are d e t e c t i o n r a t h e r than r e c o g n i t i o n t h r e s h o l d s , although in m a n y cases the type of t h r e s h o l d d e t e r m i n e d is not i n d i c a t e d in the o r i g i n a l p a p e r .


The t h r e s h o l d values g i v e n by d i f f e r e n t i n v e s t i g a t o r s vary c o n s i d e r ably depending on the c h o i c e of solvent(s), the m e t h o d used f o r the d e t e r m i n a t i o n , and the p u r i t y of the c o m p o u n d . T h e r e f o r e , the s a m e a r o m a or f l a v o r c o m p o u n d may have as many t h r e s h o l d values as t h e r e are i n v e s t i g a t o r s . C a r e must be e x e r c i s e d when t h r e s h o l d values f r o m the l i t e r a t u r e are u s e d , and the m e n t i o n e d s o u r c e s of d i s c r e p a n c i e s must a l w a y s be borne in m i n d . O d o r t h r e s h o l d v a l u e s , e x p r e s s e d as c o n c e n t r a t i o n in the gaseous p h a s e , have the d i s t i n c t a d v a n t a g e of being independent of the s o l v e n t used. M a j o r c l a s s e s of f l a v o r c o m p o u n d s in g e n e r a l The v o l a t i l e c o m p o u n d s f o r m e d by the M a i l l a r d r e a c t i o n are only one group of f l a v o r c o m p o u n d s in f o o d s . S c h u t t e (1) presents a b r i e f s u m m a r y of the m a j o r classes and t h e i r modes of f o r m a t i o n f r o m p r e c u r s o r s . S o m e of t h e m can be f o r m e d by d i f f e r e n t p a t h w a y s . A n e x a m p l e is the f u r a n s , w h i c h c a n be f o r m e d by n o n - e n z y m a t i c b r o w n i n g r e a c t i o n but also by b i o t r a n s formation. C l a s s i f i c a t i o n of M a i l l a r d r e a c t i o n p r o d u c t s S i n c e this c o m p i l a t i o n c o n c e r n s v o l a t i l e M a i l l a r d r e a c t i o n p r o d u c t s , a b r i e f p r e s e n t a t i o n o f d i f f e r e n t t y p e s of s u b s t a n c e s in this group is j u s t i f i e d . T h e c l a s s i f i c a t i o n s y s t e m g i v e n by N u r s t e n (1980-1981) (2) has b e e n a v a l u a b l e t o o l . T h e v o l a t i l e s may be c l a s s i f i e d into t h r e e groups 1)

' S i m p l e ' sugar d e h y d r a t i o n / f r a g m e n t a t i o n p r o d u c t s : Furans Pyrones Cyclopentenes Carbonyl compounds Acids

2)

'Simple' amino a c i d degradation products: Aldehydes Sulfur compounds V o l a t i l e s p r o d u c e d by f u r t h e r i n t e r a c t i o n s : Pyrroles Pyridines Imidazoles Pyrazines Oxazoles Thiazoles C o m p o u n d s ex aldol c o n d e n s a t i o n s

3)


12.

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Sensory Properties: Literature

Review

187

A s seen a b o v e , the v o l a t i l e M a i l l a r d c o m p o u n d s h a v e v e r y d i v e r s e c h e m i c a l s t r u c t u r e s . T h e m o s t i m p o r t a n t groups w i l l now be p r e s e n t e d one by o n e .


T h e i m p o r t a n c e of h e t e r o c y c l i c c o m p o u n d s A m o n g the known c o n s t i t u e n t s of f o o d a r o m a , h e t e r o c y c l i c c o m p o u n d s deserve particular attention. T h e s e are f o r m e d in l a r g e n u m b e r s during p r e p a r a t i o n of the f o o d , e . g . , by c o o k i n g , baking or r o a s t i n g . O w i n g to t h e i r c h a r a c t e r i s t i c o d o r s , h e t e r o c y c l e s c o n t r i b u t e s i g n i f i c a n t l y to the f l a v o r of p r o c e s s e d f o o d s . T h e s e h e t e r o c y c l i c s do not a l w a y s a r i s e by n o n - e n z y m a t i c M a i l l a r d r e a c t i o n s ; e n z y m a t i c (including m i c r o b i o l o g i c a l ) p r o c e s s e s are also i m p o r t a n t r o u t e s of f o r m a t i o n . D e g r a d a t i o n by p y r o l y s i s of c e r t a i n c o m p o u n d s (sugars, a m i n o a c i d s , t h i a m i n , t r i g o n e l l i n e , e t c . ) , also r e l e a s e s a r o m a c o m p o u n d s (3). A m o n g the h e t e r o c y c l i c s t h e r e is one group w h i c h w i l l be t h o r o u g h l y e x a m i n e d : the p y r a z i n e s . T h e c o m p o u n d s b e l o n g i n g to this f a m i l y play a v e r y i m p o r t a n t r o l e as c o n t r i b u t o r s of d e s i r a b l e f o o d f l a v o r p r o p e r t i e s . S t r u c t u r a l l y , p y r a z i n e s are h e t e r o c y c l i c n i t r o g e n c o m p o u n d s a n d t h e i r f o r m a t i o n is a quite c o m p l i c a t e d p r o c e s s . M a g a and S i z e r (4) p r e s e n t a s u m m a r y of these f o r m a t i o n p a t h w a y s . N o n - h e t e r o c y c l i c compounds T h e r e are other c o m p o u n d s than h e t e r o c y c l i c s that also d e s e r v e a t t e n t i o n : S u l f u r c o m p o u n d s and other c l a s s e s of a l i p h a t i c s . S c h u t t e (1) lists s u b s t a n c e s c o n t a i n i n g s u l f u r and t h e i r m o d e of f o r m a t i o n . ( N o t e that t h i a z o l e s , t h i o p h e n e s , and o t h e r c y c l i c c o m p o u n d s c a n be c l a s s i f i e d also in the p r e c e d i n g g r o u p , the h e t e r o c y c l i c s ) . O t h e r groups of a l i p h a t i c substances ( a l d e h y d e s , k e t o n e s , e s t e r s , e t c . ) m a y also c o n t r i b u t e to a g r e e a b l e f o o d s e n s a t i o n s . A r o m a and f l a v o r p r o p e r t i e s of i m p o r t a n t s u b s t a n c e groups T h i s c h a p t e r g i v e s b r i e f g e n e r a l d e s c r i p t i o n s of the sensory p r o p e r t i e s of the most i m p o r t a n t s u b s t a n c e groups. It is i n t e n d e d as an i n t r o d u c t i o n to the m o r e d e t a i l e d sensory i n f o r m a t i o n in the f o l l o w i n g t a b l e s . P y r a n o n e s , f u r a n o n e s , and r e l a t e d c o m p o u n d s (6, 7). Structurally these s u b s t a n c e s are g e n e r a l l y c y c l i c e t h e r s , m a i n l y f u r a n o i d c o m p o u n d s . T h e y are found in c o n d e n s a t e s f r o m c a r b o h y d r a t e s t h a t have been s u b j e c t e d to browning r e a c t i o n s . A s a rule f u r a n d e r i v a t i v e s are c o n s i d e r e d i m p o r t a n t a r o m a c o n s t i t u e n t s f r o m a sensory point o f v i e w . T h e y are m a i n l y a s s o c i a t e d w i t h s w e e t , f r u i t y , n u t t y or c a r a m e l - l i k e o d o r - i m p r e s s i o n s . T h e furans h a v e no m e a t y c h a r a c t e r i s t i c s , but it s e e m s possible that they c o n t r i b u t e to the o v e r a l l odor of b r o i l e d and r o a s t e d m e a t . F u r a n d e r i v a t i v e s w i t h s e v e r a l f u n c t i o n a l groups h a v e i n c r e a s e d odor i n t e n s i t y as c o m p a r e d with l o w e r h o m o l o g u e s .


188

MAILLARD REACTIONS

Pyrroles (5 - 8). About fifty members of this group have b e e n d e t e c t e d in various f o o d s t u f f s , though it appears t h a t p y r r o l e s are not present in f r e s h , raw f o o d s . P y r r o l e s have not r e c e i v e d m u c h a t t e n t i o n as f l a v o r - c o n t r i b u t i n g c o m p o n e n t s , but they s e e m to c o n t r i b u t e an u n d d e s i r a b l e odor to c o o k e d m e a t .


P y r i d i n e s (6, 9). P y r i d i n e s have been found in c o f f e e , b a r l e y and r o a s t e d l a m b . T h e i r i m p o r t a n c e as a r o m a c o n s t i t u e n t s is l i m i t e d . P y r a z i n e s (4, 6, 10, 11). The pyrazines constitute a very i m p o r t a n t class a m o n g f l a v o r c o m p o u n d s . T h e y have b e e n i d e n t i f i e d in v a r i o u s f o o d s y s t e m s , and they are a s s o c i a t e d w i t h p l e a s a n t and d e s i r a b l e f o o d f l a v o r p r o p e r t i e s . A s a r u l e , the a l k y l d e r i v a t i v e s p r o d u c e r o a s t e d - n u t l i k e sensory i m p r e s s i o n s . T h e a c e t y l p y r a z i n e s also have an e s s e n t i a l p l a c e a m o n g f l a v o r i n g a g e n t s . T h e y have a c h a r a c t e r i s t i c r o a s t e d n o t e , r e m i n i s c e n t of p o p c o r n . Sulfur compounds S u l f u r - c o n t a i n i n g v o l a t i l e s c o n t r i b u t e to both p l e a s a n t and unpleasant o v e r a l l f l a v o r s in m a n y f o o d s . • T h i o l s (7, 12) The t r a d i t i o n a l n a m e f o r this group is m e r c a p t a n s ; n o w a d a y s , the t e r m t h i o l s is m o r e c o m m o n . T h e y have been i d e n t i f i e d in m o r e t h a n s i x t y different foodstuffs. M a g a (12) g i v e s an e x p l a n a t i o n f o r t h e i r i m p o r t a n c e as a r o m a and flavor components: a) they have o b j e c t i o n a b l e sensory p r o p e r t i e s (although t h e r e a r e e x c e p tions) b) the t h r e s h o l d s f o r most t h i o l s are in the low p a r t s - p e r - m i l l i o n r a n g e or l o w e r . • T h i o p h e n e s (13) The m a j o r i t y of the thiophenes has b e e n i d e n t i f i e d as c o n s t i t u e n t s of m e a t - b a s e d p r o d u c t s . T h i s group of f l a v o r c o m p o u n d s is r e l a t i v e l y n e w , t h e r e f o r e sensory d a t a are s o m e w h a t l a c k i n g . • O x a z o l e s and O x a z o l i n e s (14, 15) T h e i r p r e s e n c e has only been r e p o r t e d in a l i m i t e d n u m b e r of f o o d s : c o f f e e , c o c o a , m e a t p r o d u c t s , b a r l e y and soy s a u c e . V e r y f e w sensory p r o p e r t i e s have b e e n r e p o r t e d f o r o x a z o l e s and o x a z o l i n e s . • T h i a z o l e s (6, 16) T h i a z o l e s are in a c e r t a i n way unique; they c o n t a i n a h e t e r o c y c l i c r i n g c o n t a i n i n g b o t h n i t r o g e n and s u l f u r . M o s t of the t h i a z o l e s h a v e b e e n i s o l a t e d f r o m c o f f e e and m e a t . T h e a l k y l d e r i v a t i v e s a r e most c o m m o n ; t h e y g e n e r a l l y have g r e e n , n u t t y , and v e g e t a b l e - l i k e o d o r s .


12.

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Sensory Properties: Literature Review

189

Sensory d a t a f o r c o m p o u n d s E x p l a n a t o r y notes N o t a t i o n , s y m b o l s and a b b r e v i a t i o n s used in the f o l l o w i n g t a b l e s : Names T h e n o m e n c l a t u r e is i n t e n d e d to f o l l o w I U P A C 1979 R u l e s , " N o m e n c l a t u r e of O r g a n i c C h e m i s t r y " . Synonyms


S y n o n y m s are at t i m e s g i v e n , e s p e c i a l l y when a c c e p t e d t r i v i a l n a m e s exist a n d / o r to a v o i d doubt. Descriptions T h e sensory p r o p e r t i e s of e a c h c o m p o u n d s are d e s c r i b e d . F

s i g n i f i e s F l a v o r , i.e. odor and taste t o g e t h e r (the senses of s m e l l and t a s t e ) , w h i c h is the c a s e when the i t e m is t a k e n into the m o u t h .

Ο

s i g n i f i e s O d o r , i.e. a p r o p e r t y p e r c e i v e d through the sense o f s m e l l only.

L e a v i n g out one or both of these l e t t e r s s i g n i f i e s l a c k of such i n f o r m a t i o n , for example: green note, characteristic. T h r e s h o l d values T h e s e values are usually e v a l u a t e d through the sense of s m e l l ; they are m a r k e d w i t h Ο = O d o r t h r e s h o l d v a l u e . S o m e values are e v a l u a t e d through the sense of t a s t e ; Τ F

= T a s t e t h r e s h o l d value = F l a v o r t h r e s h o l d v a l u e , i.e. odor and t a s t e t o g e t h e r .

T h e s o l v e n t used is m e n t i o n e d a f t e r the t h r e s h o l d v a l u e : Examples: Ο

0.05 p p b / w a t e r

the

odor threshold of an a r o m a c o m p o u n d

is m e a s u r e d (dissolved) in w a t e r Τ

150 p p m / w a t e r

the t a s t e threshold of a c o m p o u n d in b e e r

*

F o r further values,

see r e f e r e n c e s N o s . 23, 141, and 142.

Remarks U n d e r this h e a d i n g , place(s) of o c c u r r e n c e of e a c h c o m p o u n d is g i v e n . F

f o r F o o d s , i.e. the c o m p o u n d s has been i d e n t i f i e d in a f o o d b e v e r a g e , such as m e a t , v e g e t a b l e s , c o f f e e , c o c o a , and t e a .

M

f o r M o d e l S y s t e m , i.e. the c o m p o u n d has been i d e n t i f i e d non-food milieu. Example: glucose-cysteine model system.

S

f o r S y n t h e t i c , i.e. the c o m p o u n d has been s y n t h e s i z e d .


in

or a

190

MAILLARD REACTIONS

FURANS

NAME

/

(SYNONYM)

R

2

R

3

Furan


2-Methylfuran

CH^

C

H

25

2-Ethylfuran

2-Propylfuran

Π"Ο^Η

7

2-Butylfuran

U-

9

2-Pentylfuran

-" 5 11

C 4

C

H

H

2-Vinylfuran (2-Furylethylene)

CH=CH, 2

2-Acetylfuran (2-Furyl methyl ketone)

COChL

2-Furyl-2-propanone (2-Furfuryl methyl ketone)

2-Furfuryl methyl ether (2-(Methoxymethyl)furan)

CHJiZOCH

ChLOCH


R^

12.

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R


Review

191

3 W « 2

2Λ DESCRIPTION

THRESHOLD VALUE

O: Peculiar spice-smoky, slightly cinnamon-like O: Ethereal Ο of GC eluates: Sickly, nasty

REM.

REF

F,M,S,

17 18 19 20

Ο 4.5 ppm/water


O: Ethereal Ο of GC eluates: Sickly Ο Ο

F,S

17 21

Ο

8 ppm/oil

Ο

6 ppm/oil

Ο

10 ppm/oil

O: Fruity Ο of GC eluates: Green, sweet pungent O: Sweet, pungent F in vegetable oil at concentration up to 10 ppm: Beany, grassy

18 19 20 21

3.5 ppm/water 27 ppm/oil

O: Powerful sweet, burnt; when dilute, warm, sweet F: Caffeine-like

O: Weak, noncharacteristic

F,M,S,

F

21

F

22 21

F,S

23 19

Ο Ο

6 ppb/water 2 ppm/oil

24 21

Ο

1 ppm/oil

22 21

O: Phenolic, coffee-grounds O: Pleasant, ketonic F: Burning, sweetish O: Powerful balsamic-sweet with a tobacco-like, almost narcotic pungence. Floral undertones of balsamic-cinnamic character F in beer: Almonds, rubber, burnt/ /phenolic, pyrazole

F,M

18 17

80 ppm/beer

25

Τ F

26 27

O: Mild, sweet, fruity-caramellic, somewhat spicy F: Sweet, fruity-spicy, slightly nut- like F: Suggestive of radish O: Rum-like

110 ppm/orange juice 80 ppm/water F,S

17 23 6 22

O: Mustard-like

C o n t i n u e d on n e x t page


MAILLARD REACTIONS

FURANS (cont.)


NAME

/

(SYNONYM)

R

l

2

R

R

2-Furfuryl methyl sulfide

CH SCH

2-Furfuryl acetate

CH OCOCH

2-Furfuryl propionate

CH OCOC H

2-Ethyl furoate (2-Furancarboxylic acid, ethyl ester)

COOC H

2-Furoic acid (2-Furancarboxylic acid)

2-Furfuryl alcohol (2-Furylmethanol, 2-(Hydroxymethyl)furan)

2

R

4

3

2

2

2

2

3

3

5

5

COOH

CH OH 2

2-(Hydroxyacetyl)furan (2-Furyl hydroxymethyl ketone)

COCH OH

2-Propionylfuran (Ethyl 2-furyl ketone)

COCJ-L

2-Furaldehyde (Furfural, 2-Furancarbaldehyde)

CHO

2,5-Dimethylfuran

CH

2

3


CH

3

12.

FORS



DESCRIPTION

Review

193

REM.

REF

O: Coffee-like

F,M

28

O: Nut-like

F

29

O: Bitter, nut-like

F

22

O: Burnt, buttery, vanilla-like

F

6

Ο: F: Ο: F:

THRESHOLD VALUE

Stinging Sour Practically odorless Clear acid, mildly caramellic note

F,M,S

17

O: F: O: F:

"Characteristic" F,M,S Bitter Very mild, warm-oily, "burnt" Warm, slightly caramellic, in higher concentration burning, yet some what creamy O: Mild sweet F in beer: Sugar cane, woody > 3000 ppm/beer Τ 30 ppm/orange juice F 5 ppm/water O: Burnt F,M

O: None F: Burning, sweetish O: Sweet, caramellic O: Pungent, but sweet, bread-like caramellic, cinnamon-almond-like of poor tenacity Sweet bread-like, caramellic in proper dilution O: "Characteristic" F: Sweet F: Bitter F in beer: Paper, husk

O: Ethereal

18

Τ >200 ppm/ orange juice

18 17 22 25 26 27 30 18 26

F,M

28

F,M,S

17

18

F Τ Ο

29 25 27 26 24

150 ppm/beer 5 ppm/water 80 ppm/orange juice 3000 ppb/water F,M

28



194

MAILLARD REACTIONS

FURANS (cont.)


NAME

(SYNONYM)

5-Methyl-2-furaldehyde (5-Methylfurfural)

CHO

5-Hydroxymethyl-2-furaldehyde (HMF, 5-(Hydroxymethyl)furfural)

CHO

CH OH

2,5-Diformylfuran (2,5-Furandicarbaldehyde)

CHO

CHO

2-Acetyl-3-hydroxyfuran (Isomaltol)

COCH

2-Acetyl-5-methylfuran

COCH,

2-Butyl-5-methylfuran

2

3

OH

H

n-c 9

CH

7

CH

7

4

2-(2-Hydroxybutyl)-5-methylfuran

CH CH(OH)C H

2-(l,2-Dioxopropyl)-5-methylfuran

COCOCH^

2-(2,3-Dioxobutyl)-5-methylfuran

CH COCOCH

2-Cyano-5-methylfuran (5-Methyl-2-furonitrile)

CN

2

2

2

5

CH, CH,

3

CH, CH,


12.

FORS

Sensory Properties:

Literature

DESCRIPTION

195

THRESHOLD VALUE

O: Sweet-spicy, warm and slightly caramellic F: Sweet-caramellic, warm O: Burnt, caramel-like, slightly meaty F in beer: Almonds, burnt/phenolic, pyrazole


Review

REM.

REF

F,M,S

17 y

O: None F: Bitter, astringent O: Warm-herbaceous, winy-ethereal remotely resembling Hungarian chamomile (matricaria oil). A natural sweetness common; similarity to hay, caramel, tobac co, etc. often perceptible F: Sweet, herbaceous-hay-like, mildly tobacco-like F2 Bitter F in beer: Aldehyde, stale, vegetable oil

20 ppm/beer

6 25

10 ppm/orange juice

26 F,M,S

18

17

29 25

1000 ppm/beer

26 27

Τ >200 ppm/orange juice F 100 ppm/water F > 100 ppm/water

Ο: Burnt, pungent, fruity F: Sour, sweet, fruity O: Caramellic-sweet, but rather pungentjof good tenacity F: First sour, then sweet, caramellic-fruity, bread-like, depending upon the concentration used. Sour taste mostly noticed in high concentration! of the material.

M,S

27

F,M,S

18

17

O: Caramel-like

F,M

28

O: Green

S

31

O: Green

S

31

M,S

27

O: Like roasted rye bread

F

22

O: Nut-like, bitter almond-like

F

22

O: Caramel

F

2 ppm/water

Continued on next page


196

MAILLARD REACTIONS

FURANS (cont.)


NAME

/

(SYNONYM)

R

R

x

2-Methyl-3-furanthiol (5-Mercapto-2-methylfuran)

CH

3

2-Methyl-4-furanthiol (4-Mercapto-2-methylfuran)

CH

3

2,5-Dimethyl-3-furanthiol (3-Mercapto-2,5-dimethylfuran)

CH

3

S-Methyl 2-thiofuroate (2-Thiofuroic acid, methyl ester)

COSCH

5-Methylthio-2-furaldehyde (5-Methylthiofurfural)

CHO

2-(Mercaptomethyl)furan (2-Furylmethanethiol, Furfuryl mercaptan)

CH SH

S-2-Furfuryl thioacetate

R

£

R

3

4

SH SH SH

CH

3

3

SCH

2

CH SCOCH 2

3

2-Methyl-5-(methylthio)furan (2-Methyl-5-furyl methyl sulfide)

CH

SCH

2- ((Methyldithio)methyDfuran (Furfuryl methyl disulfide)

CH SSCH

2-Furfurylfuran

CH ~furan

Difurfuryl sulfide

CH SCH ~furan

3

2

3

2

2

2


3

12.

FORS



DESCRIPTION

THRESHOLD VALUE

197

REM.

REF

F: Sweetish, fried meat, beef broth

32

O: Green, meaty, herbaceous

31

F: Strongly roasted meat

32

O: Mercaptan-like O: Cabbage-like

F,M

22 28

O: Meaty

F,S

33

F,M,S

17

O: Extremely powerful and diffusive, penetrating, only in proper dilution agreeable, coffee-like, caramellic-burnt, sweet F: Dilution < 5 ppm: Pronounced caramellic-coffee-like O: Characteristic, unpleasant O: Strong like roasted coffee F: Coffee

23 22 34 0.04 ppb/water 0.04 ppb/2% protein-hydrolysate solution 0.003 ppb/skim milk

32

O: Coffee-like

F

22

O: Very strong sulfurated

F,M,S

23

O: Fresh white bread crust O: Roasted bread crust O: Freshly baked bread

0.04 ppb/water

6,7 35 36

O: Caramellic

F,M

O: Toasted

F,M

37 37



MAILLARD REACTIONS

198

4,5-DIHYDROFURANS


NAME

/

(SYNONYM)

R

R

2-Methyl-4,5-dihydrofuran-3-thiol

CH

2-Methyltetrahydrofuran-3-ol

CH,

3

R

2

R

3

SH OH

FURANONES

2

3-Hydroxy-4,5-dimethyl-2(5H)-furanone

CH

CH

3-Hydroxy-4-ethyl-5-methyl-2(5H)-furanone

OH

C H

3-Hydroxy-4-methyl-5-ethyl-2(5H)-furanone

OH

C H

2

3

$

3

/

CH

3

CH

3

C

2 5 H

4 - Hydroxy - 5 - methyl - 3(2H)- f uranone

OH

CH,

4-Mercapto-5-methyl-3(2H)-f uranone

SH

CH, CH

2,5-Dimethyl-3(2H)-furanone

CH,

2,5-Dimethyl-4-methoxy-3(2H)-furanone

CH

3

OCH

4-Hydroxy-2,5-dimethyl-3(2H)-furanone^ (Furaneol )

CH

3

OH

3

7

CH

3

CH,


\

12.

FORS

Sensory Properties:

Literature

199

Review

TETRAHYDROFURANS


DESCRIPTION

THRESHOLD VALUE

REM.

REF

O: Roasted meat

31

O: Fatty

31

R

R

3\/^ 1

F: Burnt

38 29

O: Typically caramel O: Typically caramel

29 Τ Ο

0.005-0.01 ppm/ water 0.5-1 ppm/water

39

O: Maple-like, curry-like O: Intense caramel and curry-like

38 7

O: Caramel-like O: Roasted chicory root O: Reminiscent of roasted chicory root with an unmistakable undertone of maple sirup

F,M

O: Sweet, meat-like

40 38

31

O: Strong odor of freshly baked bread but not very reminiscent of bread aroma O: Reminiscent of sherry Ο

7 41

0.03 ppb/water

O: Fragrant, fruity, caramel, burnt pineapple F: Burning, sweet O: Caramel, burnt sugar-like O: Sweet, cotton-candy O: Caramel-like, burnt pineapple which turns into a strawberrylike note as dilution increases

F,M

18 30 42

Ο F Ο Τ

0.04 ppb/water 1 ppm/water 0.1-0.2 ppm/water 0.03 ppm/water

41 27 39



200

MAILLARD REACTIONS

FURANONES (cont.)


NAME

/

(SYNONYM)

R,

R,.

2-Hydroxymethyl-4-hydroxy- 5- methyl - 3(2H)- f uranone

CH OH

OH

CH,

2-Ethyl-4-hydroxy-5-methyl-3(2H)-furanone

C H

OH

CH,

2

2

5

DIHYDROFURAN-3-ONES

4-Hydroxy-5-methyl-2,3-dihydrofuran-3-one

OH

CH,

TETRAHYDROFURAN-3-ONES

2-Methyltetrahydrofuran-3-one

CH^

4-Mercaptotetrahydrofuran-3-one (4-Mercapto-3-oxotetrahydrofuran)

SH

4-Mercapto-5-methyltetrahydrofuran-3-one (4-Mercapto-5-methyl-3-oxotetrahydrofuran)

SH

CH,


12.

FORS


REM.

REF

O: Unpleasant odor of charred paper

M

42

O: Sweet, reminiscent of shortcake F: Intensely sweet O: Caramel-like

F

7 38 40

F: Pleasant, maltol-like

M

43

Ο: Sweet, roasted

F,M

28

O: Green, meaty, "Maggi-like"

S

31

O: Meaty, "Maggi-like"

S

31

DESCRIPTION


201

Review

THRESHOLD VALUE



MAILLARD REACTIONS

202

4H-PYRAN-4-ONES


NAME

/

(SYNONYM)

R

R

x

2-Methyl-3-hydroxy-4H-pyran-4-one (Maltol)

CH,

OH

2-Ethyl-3-hydroxy-4H-pyran-4-one (Ethylmaltol)

C H,-

OH

2-Methyl-3,5-dihydroxy-4H-pyran-4-one (5-Hydroxymaltol)

CH

OH

2-Ethyl-3-hydroxy-6-methyl-4H-pyran-4-one

C ^

2,3-Dihydro-3,5-dihydroxy-6- methyl-4H-pyran-4-one (5-Hydroxy-5,6-dihydromaltol) 3- Hydroxy -2H-py ran-2-one (3-Hydroxy-2-pyrone)

Methyl 4,5-dimethyl-3,6-dihydro2H-pyran-2-carboxylate

?

3

O

R

£

R^

?

OH

H

C H

Ô H O v ^ \ OH fj j ^ J 3 Ό v

.OH

O ^^3\ S)

I " c

OOCH

3


3

12.

FORS

Sensory Properties:

Literature

Review

203

Ο


DESCRIPTION

THRESHOLD VALUE

O: Warm-fruity, caramellic-sweet with emphasis on the caramellic note in the dry state, while solu tions show a pronounced fruity, jam-like odor of pineapple, straw berry type O: Fragrant, caramel F: Bitter, sweetish O: Warm, sweet, fruity; jam-like in solution O: Coffee, malt, caramel

REM.

REFE

F,M,S

17

18 23 34 27 44

20 ppm/water 7.1 ppm/water 35 ppm/water 13 ppm/water

39

O: Intensely sweet, fruity-bread like, pleasant, of immense ten acity F: Sweet, fruity-jam-like, remini scent of pineapple, strawberry, vanilla and heavy fruit-preserve or syrup, depending upon concen tration O: Very sweet, caramel-like, of immense tenacity F: Sweet, fruity with initial bittertart flavor

17

23

40

O: Caramel-like

7

O: Preserved tang boiled down in soy sauce O: Not reminiscent of maltol O: Odorless

Ο: Interesting green note

29 F,S Τ > 200 ppm/orange juice

18 26

Τ

26

30 ppm/orange juice F

F,S

45



MAILLARD REACTIONS

204

PYRROLES


NAME

/

(SYNONYM)

R

R

±

R

2

R

3

Pyrrole

H

1-Methylpyrrole (N-Methylpyrrole)

CH

2 - Pyrrolecar baldehy de

H

1-Acetonylpyrrole (l-Pyrrolyl-2-propanone)

CH COCH

2-Acetylpyrrole (Methyl 2-pyrrolyl ketone)

H

COCH

3

2-Acetyl-5-chloropyrrole

H

COCH

3

Cl

2-Acetyl-5-bromopyrrole

H

COCH

3

Br

2-Formyl-5-methylpyrrole (5-Methylpyrrole-2-carbaldehyde)

H

CHO

l-Ethyl-2-formylpyrrole (N-Ethylpyrrole-2-carbaldehyde)

C H

l-(2-Furfuryl)pyrrole (N-Furfurylpyrrole)

furfuryl

4

3

CHO 2

2

5

3

CH

'3

CHO

PYRROLIDINES (TETRAHYDROPYRROLES)

Pyrrolidine

H

1-Acetylpyrrolidine

COCH

1-Pyrroline


12.

FORS

Sensory Properties:

Literature

205

Review

REM.

REF

F,S

17

O: Powerful and penetrating smoky-tarry, in extreme dilution sweet, woody-herbaceous, slightly animal.

F,S

17

O: Corny, pungent

F,M

37

DESCRIPTION

THRESHOLD VALUE


O: Sweet and warm-ethereal, slightly burnt-nauseating, resembling that of chloroform

O: Bready green O: Cookie- or mushroom-like

Ο

10 ppb/water

M

46 7

Τ

200 ppm/orange juice F

26

O: Strong almond aroma

F,S

47

O: Strong almond aroma

F,S

48

Τ

110 ppm/orange juice F,M,S

26 37

τ

2 ppm/orange juice

F,M

26

F

29

O: Penetrating amine-type remini scent of ammonia and piperidine, nauseating and diffusive, of very poor tenacity, repulsive

F,S

17

O: Bread-like

M

46

O: Corn-like

M

49

O: Pungent

O: Green, hay-like

Ο 1



206

MAILLARD REACTIONS

2,3-DIHYDRO-lH-PYRROLIZINES


NAME

/

(SYNONYM)

R

R

1

5-Acetyl-2,3-dihydro-lH-pyrrolizine

COCH

3

5-Acetyl-6-methyl-2,3-dihydro-lH-pyrrolizine

COCH

3

5-Formyl-6-methyl-2,3-dihydro-lH-pyrrolizine

CHO

R

2

CH

3

CH

3

3

R

4

TETRAHYDROINDOLIZIN-8-ONES

5,6,7,8-Tetrahydroindolizin-8-one

H

2-Methyl-5,6,7,8-tetrahydroindolizin-8-one

CH

3


12.

FORS

Sensory Properties:

Literature

Review

207

*1


DESCRIPTION

REM.

REF

O: Smoky, amine-like F: Sweet

F,M

30

O: Smoky, medicine-like F: Bitter

M

30

F,M

30

Ο: Mild smoky, weak amine-like

M

30

Ο: Mild smoky, weak amine-like

M

30

Ο: Smoky F: Sweet, cinnamic

THRESHOLD VALUE

r9



208

MAILLARD REACTIONS

PYRIDINES

NAME

/

(SYNONYM)

R^

R

R

2

R^

?


Pyridine

3-Methylpyridine (P -Picoline) 2-Ethylpyridine

CH, C H 2

5

3-Ethylpyridine

C H 2

3-Propylpyridine 2-Isopropylpyridine

n-C H 3

i-C H

7

2 - Isobu tylpy ridine

irC H

9

2-Pentylpyridine (2-Amylpyridine)

n-C H

2-Methoxypyridine

OCH,

2-Ethoxypyridine

OC H

2-Pyridinecarbaldehyde (2-Pyridylmethanal)

CHO

2-Acetylpyridine (Methyl 2-pyridyI ketone)

COCH,

2-Acetylpyridin-3-ol

COCH

3

5

?

2-Butylpyridine

3,4-Dimethylpyridine

4

5

2

n

5

3

OH CH

3

CH

3


12.

FORS

N

Sensory Properties:

Literature

Review

209

R

" V 1


R

4^f DESCRIPTION

THRESHOLD VALUE

REM.

REF

O: Burnt, pungent, diamine O: Pungent, penetrating and diffusive, generally de scribed as nauseating, but in extreme dilution, warm, "burnt", smoky, of very poor tenacity F: ( * Ί ppm): Rather sharp, burnt

Ο

F

50

21 ppb/air

17

Ο

0.82 ppm/water

51

F: Green

F,S

52

F: Green F: Green, smoky

F,S

52 53

F: Tobacco

F

23 53

F; Sweet, musty, beany F: Green, vegetable

S

52

F: Sweet, green

F,S

52

F: Green pepper

S

52

F

54

O: Fatty or tallowy-like

Ο

0.6 ppb/water

F: Phenolic

52

F: Phenolic

52

Ο: Pungent bitter almond-like, poor tenacity. In extreme dilution quite pleasant, sweet, bitter almond and nut-like O: O: O: O:

Popcorn Bready Tobacco-like Cracker-like

17

Ο

6 46 23 55

19 ppb/water

53

F: Cereal-like F: Green

F,S

52



MAILLARD REACTIONS

210

PYRIDINES (cont.)

NAME

/

(SYNONYM)

R

R

4-Ethyl-3-methylpyridine 2- Isobutyl-3-methoxypyridine


3- Isobutyl-2-methoxypyridine

R

2

C

CH^ i-C^H^

R

3

4

H

25

OCH^

OCH, i-C-H

g

1,4,5,6-TETRAHYDROPYRIDINES

2-Acetyl-l,4,5,6-tetrahydropyridine

COCH

PYRIMIDINES

4,6-Dimethylpyrimidine 4-Acetyl-2-methylpyrimidine

CH CH

3

3

COCH

3


12.

FORS

Sensory Properties:

Literature

DESCRIPTION

REM.

REF

F: Sweet, nutty

S

52

F: Green pepper

S

52

S

56

F,S

57 55

Ο: Not very characteristic, but perhaps somewhat camphoraceous


111

Review

THRESHOLD VALUE

Ο

11 ppb/water

Ο

1.6 ppb/water

Ο Ο: Distinct odor of crackers O: Cracker-like

"2 O: Similar to alkyl-substituted pyrazines (i.e. roasted, nut-like)

F

6

Very interesting grilled note

F

6



212

MAILLARD REACTIONS

PYRAZINES

NAME

/

(SYNONYM)

R

Η

χ

£

R

3

R^


Pyrazine

2-Methylpyrazine

CH^

2-Ethylpyrazine

C

2 5 H

2-Propylpyrazine

D" 3 7

2-Isopropylpyrazine

i-C^H^

2-Isobutylpyrazine

i-C^H^

2-Pentylpyrazine

-" 5 11

2,3-Dimethylpyrazine

C

C

H

H

CH^

CH^


12.

FORS

213


XT R X^R 3

2

DESCRIPTION

THRESHOLD VALUE

REM.


O: Pungent, sweet, in dilution floral F,S with remote resemblance to helio trope. Very diffusive, poor tenacity O: Strong, sweet (slightly ammoniacal) Ο: Cornlike with bitter note Ο 50 χ 10 gpb/water F: Roasted hazelnuts Ο 17.5 χ 10 ppb/water F >100 ppm/beer F: Chocolate, roasted peanuts, grilled chicken Ο: Nutty, roasted Ο: Nutty, green Ο: Strong basic role; in dilution chocolate character Ο: Grassy

F,S

REF 17 58 70 59 35 60 35 52 46 58 70 59 61

10 χ 10 ppb/water 105 ppm/water \ 27 ppm/oil 100 pprn/beer 6 χ 10 ppb/water 1

O: Nutty, roasted O: Buttery, rum

60 62 F,S

22 ppm/water 17 ppm/oil 6000 ppb/water 10 ppm/beer

62 60

Green, vegetable

F,S

Green, nutty

F,S

Green, fruity

F,S 400 ppb/water 1 ppm/water 9 ppm/oil

O: Pungent; in dilution chocolate type O: Nutty, green O: New leather, linseed oil

52 65 61

S F,S

400 ppm/water 2500 ppb/water 35 ppm/water 50 ppm/beer

C o n t i n u e d on n e x t


52 52 52 63 61 58 52 65 59 62 64 60

page

MAILLARD REACTIONS

214

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

R

±


CH^


CH^

2,3-Diethylpyrazine

C

2 5 H

2.5- Diethylpyrazine

^2^5

2.6- Diethylpyrazine

^2^5

2-Ethyl-3-methyIpyrazine (3-Ethyl-2-methylpyrazine)

C

2 5 H

2-Ethyl-5-methylpyrazine (5-Ethyl-2-methylpyrazine)

2-Ethyl-6-vinylpyrazine 2-Methyl-6-propylpyrazine

R

£

CH

2 5 H

CH

3

4

3

CH^

C

2 5 H

^2^5 ^2^5 C

^3

CH

C

R

3

3

CH=CH

2

D'^H^


12.

FORS

Sensory Properties:

Literature

DESCRIPTION


F: Characteristic, reminiscent of potato chips F: Chocolate, grilled chicken, roasted peanuts O: Grassy, "cornnuts" O: Roasted F in oil: Earthy raw potato

O: Sweet, "fried", resembling | fried potatoes, but not as typical odor as the 2,5-isomer O: Nutty, roasted F: Chocolate O: Ether-like with corn note

215

Review

THRESHOLD VALUE

23

70 66 67 63 62 61 60 F,S

Ο

200 ppb/water

Ο

54 ppm/water \ 8 ppm/oil ' 9 ppm/water 1500 ppb/water 3 ppm/beer

17 46 35 70 61 64 62 60

F,S

35

Ο

20 ppb/water 270 ppb/oil

F,S

62

Ο

6 ppb/water

F,S

62

F,S

68 52 65 69 62 60

F,S

46 70 62

Raw potato Nutty, roasted Butterscotch, nutty Pleasant earthy, nutty Ο F

130 ppb/water 2 ppm/beer

Ο

50 ppb/oil

Ο

100 ppb/water \ 320 ppb/oil ' 1 ppm/beer

F O: Buttery, baked, potatolike Ο: Burnt, butterscotch

F,S

Ο 800 ppb/water Ο 1 ppm/water ι 2 ppm/oil ' Ο 1800 ppb/water Ο 2600 ppb/oil Ο 35 ppm/water » 17 ppm/oil * F 25 ppm/beer

F: Roasted hazelnuts

O: Nutty, roasted O: Grassy

REF

35

Ο Ο F

O: O: O: O:

REM.

Ο 27 ppm/oil f 1 ppm/beer

0

1 ppb/water

Ο

5 ppb/water

Ο

43 ppm/water 24 ppm/oil 0.4 ppb/water 24 ppb/oil 25 ppb/beer

ο F O: Nutty, roasted F: Walnut, steak O: Nutty, roasted

REF

F,S

Ο Ο

F: Chocolate, sweet O: Nutty, roasted

REM.

58 70 59 61 60 F,S

53 46

F,S

66 46 35 69 61

ι ' ι /

62 60 F,S

Ο

ο F

52 23 35

1 ppb/water 15 ppm/water ι 24 ppm/oil ' 5 ppb/beer

52 34 46 61 60

O: Nutty, roasted

F,S

52

O: Grassy

F

70

O: Sweet, earthy

F

69

O: Sweet, smoked, caramel-like

S

71

O: Caramel-like, coffee, sweet

S

71

O: Honey-like, sweet

S

71



MAILLARD REACTIONS

218

PYRAZINES (cont.)

NAME

/

(SYNONYM)

R

R

2

3

R

4

2,3-Dimethyl-5-(2-methylbutyl)pyrazine

CH

3

CH

3

C H CH(CH )CH -

2,3-Dimethyl-5-(l,2-dimethylpropyl)pyrazine

CH

3

CH

3

(CH ) CHCH(CH )-

2,3-Dimethyl-5-(2,2-dimethylpropyl)pyrazine (2,3-Dimethyl-5-neopentylpyrazine)


R

l

2,3-Dimethyl-5-(l-ethylpropyl)pyrazine 2,3-Dimethyl-5-(l,5-dimethyl-4-hexenyl)pyrazine R

3

2

3

CH

3

(CH ) CCH -

CH

3

CH

3

(C H ) CH-

CH

3

CH

3

3

2

3

5

2

2

3

2

2

2

3

3

3

CH

3

3

CH(CH ):=CHCH C H C H ( C H ) C H C H -

3,6-Diethyl-2,5-dimethylpyrazine (2,5-Diethyl-3,6-dimethylpyrazine)

CH^

2

2

3

CH

CH

3

C

H 2

i-C^H^

3

2

2-Acetylpyrazine

COCH-^

2-Acetyl-3-methylpyrazine

COCH

2-Acetyl-5-methylpyrazine

COCH,

6-Acetyl-2-methylpyrazine (2-Acetyl-6-methylpyrazine)

CH,

2-Acetyl-3-ethylpyrazine

COCH

3

C H

5

CH

CH

3

CH

3

2-(2-MethylbutyI)-3,5,6-trimethylpyrazine C H CH(CH )CH lCH 5

2

3

2,3,5,6-Tetramethylpyrazine

2

3

CH

CH

2-Isobutyl-3,5,6-trimethylpyrazine

5

( C H ) C :=CHCH C H C H ( C H ) -

2,3-Dimethyl-5-(3,7-dimethyl-6-heptenyl)pyrazine R

2

2

CH

3

3

2

3

2 5

C

H

3

CH

3

CH

3

3

CH

3

CH

3

3

CH, COCH,

3

C H 2

5


12.

FORS

Sensory Properties:

Literature


DESCRIPTION

Review

219

THRESHOLD VALUE

REM.

REF

O: Sweet, smoked, caramel-like

S

71

Ο

S

71

Ο: Brown sugar-like, roasted

S

71

Ο: Honey-like, sweet

S

71

Ο: Roasted nut

S

71

Sweet, caramel-like

Ο: Roasted nut O: Fermented soybeans F: Lard O: Similar to trimethylpyrazine but without the odor intensity

5

7

F,S Ο

1000 ppb/water

Ο

10 ppm/water 38 ppm/oil F > 100 ppm/beer

F

100 ppm/beer

ι '

1

4 55 58 61 60

F,S

60

O: Roasted nut, sweet

S

71

Ο: Sweet, roasted

F,S

71

F: O: F: O:

F,S

72 52 55 64

Popcorn-like Popcorn, nutty Chocolate, popcorn Breadcrust-like, nutty, no green notes, reminiscent of acetamide

F: Cereal, roast grain O: Nutty, vegetable

Ο

62 ppb/water

Ο

4 ppb/water

55 F,S

53 46

F: Popcorn-like

S

72

Ο: Popcorn F: Popcorn-like

F,S

52 72

F: Potatoes F: Reminiscent of slightly roasted potatoes

F,S

35 7 C o n t i n u e d on n e x t page


MAILLARD REACTIONS

220

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

l

R

2

R

2-Methoxypyrazine

OCH

2-Ethoxypyrazine

OC H

2-Butoxypyrazine

OC H -n

2 - (Methoxy met hy l)py raz i ne

CH OCH

3

2-Methoxy-3-methylpyrazine (3-Methoxy-2-methylpyrazine)

OCH

CH

2-Methoxy-5-methylpyrazine (5-Methoxy-2-methylpyrazine)

OCH,

2-Ethyl-3-methoxypyrazine (3-Ethyl-2-methoxypyrazine)

C H 2

5

2-Ethyl-5-methoxypyrazine (5-Ethyl-2-methoxypyrazine)

C H

5

n-C H

y

2- Propyl-3-methoxypyrazine (3-Propyl-2-methoxypyrazine) 3- Isopropyl-2-methoxypyrazine (2-Isopropyl-3-methoxypyrazine)

4

4

5

9

2

3

R

3

2

2

3

OCH

3

3

CH,

OCH

OCH

3

i-C H 3

3

OCH

3

OCH

3

3

?

2-Isopropyl-5-methoxypyrazine (5-Isopropyl-2-methoxypyrazine)

i-C-jH^

2-Butyl-3-methoxypyrazine

n-C^H^

OCH

2-Isobutyl-3-methoxypyrazine

i-C^H^

OCH

3

(3-Isobutyl-2-methoxypyrazine)



12.

FORS

Sensory Properties:

Literature

221

Review

DESCRIPTION

THRESHOLD VALUE

REM.

REF

O: Sweet, nutty Ο: Not very characteristic

Ο

S

52 63

O: Sweet, nutty

S

52

Ο: Green, vegetable

S

52

F: Nutty, earthy Ο: Ethereal character

S

73 58 59

F,S

23

Ο

700 ppb/water

150 ppb/water

O: Reminiscent of hazelnut, almond and peanut O: Roasted peanuts, nutty, earthy O: in concentration vegetably; in dilution popcorn/potato

4 Ο Ο

58 63 59

4 ppb/water 3 ppb/water

F: Hazelnuts, almonds, peanuts Ο: Green vegetably character Ο O: Raw potato, earthy, bell pepper F: Earthy, bell pepper

Ο

F: O: O: O:

Ο

F,S

4 73 63

F,S

66

S

73 63

F,S

73

0.4 ppb/water

0.006 ppb/water

Bell pepper, earthy Potato-like Earthy, bell pepper, raw potato Strong galbanum note

7

Ο Ο Ο

10 ppb/water 0.002 ppb/water 0.001 ppb/water

Ο

10 ppb/water

O: Strong galbanum note F: Bell pepper Ο: Strongly green (bell pepper-like) O: (Green) bell pepper

35 58 59

15 ppb/water

O: Bread-like/mousy F: Bell pepper Ο: Very similar to bell pepper

S

Ο Ο Ο

0.016 ppb/water 0.002 ppb/water 10 ppb/water

4 58 59 63 74 S

58 -59

S

73

F,S

64 24 59



MAILLARD REACTIONS

222

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

R

x


i-C^H^


i-C H 4

R

2

R^

3

OCH^

OCH

9

3 - sec.Buty 1 - 2 - metho xy pyraz ine (2-sec.Butyl-3-methoxypyrazine, 2-Methoxy-3-(l-methylpropyl)pyrazine)

OCH

3

s-C H

2-Methoxy-3-(l-methylbutyl)pyrazine

OCH

3

CH(CH )C H -n

2-Isopentyl-3-methoxypyrazine

i-C H

2-Hexyl-3-methoxypyrazine (3-Hexyl-2-methoxypyrazine)

-~ 6 13

5

C

4

g

3

OCH

1 1

H

0

C

3

?

3

3

H

2-Methoxy-3-(2-methyloctyl)pyrazine

OCH

3

2-Methoxy-3-isononylpyrazine

OCH

3

2-Methoxy-3-acetylpyrazine

OCH

3

2-Methoxy-3,5-dimethylpyrazine

OCH

3

CH

3

2-Methoxy-3,6-dimethylpyrazine

OCH

3

CH

3

2-Methoxy-3-isopropyl-5-methylpyrazine

OCH

3

" 3 7

2-Methoxy-3-isopropyl-6-methylpyrazine

OCH

3

i-C H

2-Methoxy-3-(DC-hydroxyisopropyl)-5-methylpyrazine

OCH

3

2-Methoxy-3-(cC-hydroxyisopropyl)-6-methylpyrazine

OCH

3

CH CH(CH )C H 2

i-C H 9

3

C

3

CH

H

3

1 3

1 9

COCH

i

6

3

?

3

3

CH

3

CH

3

3

C H

C(OH)(CH )

CH

CH

2

C(OH)(CH ) 3

2

3


3

12.

FORS

223


DESCRIPTION

THRESHOLD VALUE

REM.

REF

S

58 59 35

S

73

S

73 74

F: Bell pepper

S

73

F: Bell pepper

S

73

S

73 63

F: Earthy, bell pepper

S

73

F: Bell pepper

S

73

Ο: Weak breadcrust-like, green and nutty notes

S

64

F,S

46

S

73

O: Strong green bell pepper note Ο

10 ppb/water

F: Coffee F: Bell pepper F: Bell pepper


Ο

F: Bell pepper Ο: Very similar to bell pepper

O: Bready/mousy

Ο

Ο

0.001 ppb/water

0.001 ppb/water

4 ppb/water

F: Medicinal, earthy Ο: Strongly green (green bean-like), floral and ethereal undertone, no nutty notes

Ο

0.05 ppb/water

S

64

O: Strongly green (green bean-like), no nutty or floral notes

Ο

0.045 ppb/water

S

64

O: Weak, green (bell pepper-like), earthy undertone, chimney soot

F,S

64

O: Weak, green (bell pepper-like), earthy undertone, chimney soot, nutty note

S

64

C o n t i n u e d on n e x t


page

MAILLARD REACTIONS

224

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

1

2-Isobutyl-3-methoxy-5-methylpyrazine

i-C^H^ OCH^


i-C^H^

OCH^

2-Methoxy-3,6-diisobutylpyrazine

OCH,

-C H

2-Methoxy-3-acetyl-5-methylpyrazine

OCH

3

2-Methoxy-3-acetyl-6-methylpyrazine

OCH

3

COCH


OCH

3

CH

5-(2-Methylbutyl)-2-methoxy-3-methylpyrazine

OCH

3

5-Isopentyl-2-methoxy-3-methylpyrazine

OCH

3

5-(2-Methy Ipent yl)- 2 - methoxy -3-methylpyrazine

OCH

3

2-Ethoxy-5-isobutyl-3-methylpyrazine

OC H

5-Isobutyl-2-isopropoxy-3-methylpyrazine

2

4

COCH

CH

CH

5

OC H -i 3

CH

7

SCH

3

5-(2-Methylpentyl)-3-methyl-2-(methylthio)pyrazine

SCH

3

5-Isobutyl-3-methyl-2-(phenylthio)pyrazine

SC^H^

CH

2-Isobutyl-3-methoxy-5,6-dimethylpyrazine

'~ ^

OCH

2,5-Dimethoxy-3,6-dimethylpyrazine

OCH

l

5

3

9

3

5

CH CH(CH )C H 2

3

i-C,H

i-C^H

9

CH

3

i-C H

9

4

CH CH(CH )C H

3

2

3

i-C H

3

3

3

4

3

CH

3

OCH

3

y

9

i-C H 4

5

9

3

CH

2

1 1

CH

CH

c

3

-C H

3

5-Isobutyl-3-methyl-2-(methylthio)pyrazine

6

3

2

3

OC H

9

CH CH(CH )C H

3

5-Isobutyl-3-methyl-2-phenoxypyrazine

CH

3

4

3

CH

i-C,H

9

i-C H

3

3

CH

CH^

3

9

CH

3

CH

?


7


12.

FORS


Review

225

DESCRIPTION

THRESHOLD VALUE

O: Similar to bell pepper but with some minty notes

Ο

0.3 ppb/water

56

O: Minty camphoraceous in character Ο with slight bell pepper undertone

2.6 ppb/water

56

REM.

REF

F: Earthy, low bell pepper

S

73

O: Weak, breadcrust-like, green musky note, chimney soot

F,S

64 64

O: Weakly green, unpleasant, no nutty notes, chimney soot O: Licorice-woody

Ο

0.7 ppm/water

75

O: Licorice-woody, slightly green

Ο

1 ppm/water

75

O: Licorice-woody, walnut-like

Ο

1 ppm/water

75

O: Burdock, bell pepper

Ο

0.5 ppm/water

75

O: Burdock-like brownish, slightly bell pepper, galbanum green

Ο

0.2 ppm/water

75


Ο

1 ppm/water

75

O: Bell pepper, cacao bean

Ο

1 ppm/water

75


Ο

0.8 ppm/water

75

O: Burdock-like, slightly earthy

Ο

1 ppm/water

75

O: Nutty, macadamia-like

Ο

0.7 ppm/water

75

O: Minty-camphoraceous

Ο

315 ppb/water

56

O: Green (bell pepper-like), nutty Ο notes, floral and ethereal undertone

180 ppb/water

S

64



MAILLARD REACTIONS

226

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

R

2

3

2,5-Dimethoxy-3,6-diisopropylpyrazine

OCH

3

i-C H

7

OCH

3

i-C H.

2,5-Dimethoxy-3-isopropyl-6-methylpyrazine

OCH

3

i-C H

7

OCH

3

CH

3

2.5- Dimethoxy-3-acetyl-6-methylpyrazine

OCH

3

COCH

OCH

3

CH

3

2.6- Dimethoxy-3-isopropyl- 5- methy lpy razine

OCH

3

i-C H

2-Ethoxy-3-methylpyrazine

OC H

5

2-Ethoxy-6-methy lpy razine (6-Ethoxy-2-methylpyrazine)

OC H

5

2-Ethoxy-3-ethylpyrazine

OC H

5

C H

2-Ethoxy-3-isobutylpyrazine

OC H

5

i-C H

°C H

9

2-Butoxy-3-propylpyrazine

OC H

9

2-Methylamino-3-methylpyrazine

NHCH

2-Butoxy-3-methylpyrazine

2

2

2

2

4

2-Dimethylamino-3-methylpyrazine

4

3

3

3

CH

3

2

2

2-Dimethylamino-3-isobutylpyrazine

N(CH )

2

2-Dimethylamino-6-isobutylpyrazine

N(CH,)

2-(Methy lthiomethyl)py razine

CH SCH

2-Methylthio-3-methylpyrazine (2-Methyl-3-methylthiopyrazine)

SCH

5-Methylthio-2-methylpyrazine

CH

3

3

3

3

3

CH

3

9

n-C H 3

3

5

4

N(CH ) C H

2

OCH

3

3

2

CH

3

CH

7

CH

N(CH )

2-Dimethylamino-6-methy lpy razine

3

3

7

3

3

CH

3

i-C^ i-C H

?

4

3

CH

3

SCH

3


9

12.

FORS

Sensory Properties:

Literature

Review

227

DESCRIPTION

THRESHOLD VALUE

REM.

REF

O: Green (bell pepper-like), nutty notes, weakly sweet

Ο

670 ppb/water

S

64

O: Green (bell pepper-like), nutty notes

Ο

250 ppb/water

S

64

S

64

F,S

64

F: Earthy, nutty F: Hazelnuts, almonds, peanuts

S

73 35

F: Pineapple

S

35

S

56

F: Earthy, bell pepper

S

73

F: Floral, medicinal

S

73

F: Medicinal, earthy

S

73

Ο: Weak, reminds of roasted peanuts, green and cocoa notes

S

64


O: Unpleasant, weakly green, earthy notes, chimney soot O: Nutty, green (bell pepper-like) woody bynote

Ο: Raw potato

Ο

70 ppb/water

0 11 ppb/water

O: Like 2-methylamino-3-methylpyrazine but more green and peanut-like, less cocoa notes

Ο

180 ppb/water

S

64

O: Reminds of unburnt coffee, peanut-like and sweet notes, no cocoa notes

Ο

1200 ppb/water

S

64

O: Strong cocoa note, reminds of Ο fusel oil, green and burnt undertone

1600 ppb/water

S

64

O: Weakly green, cocoa note, no peanut note

Ο

5000 ppb/water

S

64

O: Weak sulfide note

Ο

20 ppb/water

S

58

S

73 58 59

S

58

F: Nutty, cracker Ο: Cooked meat, vegetable O: Meaty, vegetably

Ο

1 ppb/water

Ο

4 ppb/water



MAILLARD REACTIONS

228

PYRAZINES (cont.)


NAME

/

(SYNONYM)

R

l

R

2

R

2-Methylthio-3-isobutylpyrazine

SCH

2-Methylthio-6-isobutylpyrazine

SCH^

2-(Furfurylthiomethyl)pyrazine

CH -S-furfuryl

2-Methyl-3-(furfurylthio)pyrazine

CH,

2-Methyl-5-(furfurylthio)pyrazine

CH,

3

i-C H 4

3

R

4

9

i-C H 4

2

S-furfuryl S-furfuryl

w

5-Methylcyclopenta [b jpyrazine

Co CH

3

6,7-Dihydro-5H-cyclopenta [ b] pyrazine

2-Methyl-6,7-dihydro-5H-cyclopenta[ î>] pyrazine

5-Methyl-6,7-dihydro-5H-cyclopenta[ b] pyrazine

3,5-Dimethyl-6,7-dihydro-5H-cyclopenta [ b ] pyrazine 5,7-Dihydro-5,7-dimethylfuro[ 3,4-bpyrazine

5,7-Dihydrothieno [ 3,4-b ] pyrazine

3

CH, υπ,

CΝ Oι

CH

3

Co


9

12.

FORS

Sensory Properties:

Literature

DESCRIPTION

THRESHOLD VALUE

REM.

REF

F: Bell pepper Ο: Weakly green, roasted peanuts, cheese-like (Camembert) note

Ο

S

73 64

S

73

1 ppb/water

S

58

F: Roasted coffee-like Ο: Powerful coffee, cooked meat note Ο \ ^ ^ •

CH

3

N


12.

FORS



DESCRIPTION

Review

231

THRESHOLD VALUE

REM.

REF

O: Roasted nut-like

S

76

Ο: Bready, nut-like

S

77

Ο: Intense popcorn

S

77

Ο: Earthy, baked, potato-like

F

69

Ο: Cedar wood, tobacco, buttery

S

77

Ο: Sweet, tobacco-like fragrance note

S

77

F: Nut-like, fatty

S

77

Ο: Roasted bean-like

M

78



232

MAILLARD REACTIONS

THIOPHENES

NAME

/

(SYNONYM)

R

R

±

R

2

R^

3

Thiophene


2-Methylthiophene

CH

3

CH-j

3-Methylthiophene 2-Ethylthiophene

C

H

2.4- Dimethylthiophene

CH

3

2.5- Dimethylthiophene

CH

3

2 5 CH

3

CH CH

3,4-Dimethylthiophene 2-Thienyl alcohol (2-Hydroxythiophene)

OH

2-Acetylthiophene (Methyl 2-thienyl ketone)

COCH

2-Acetyl-3-methylthiophene (Methyl 3-methyl-2-thienyl ketone)

COCH

2-Acetyl-5-methylthiophene (Methyl 5-methyl-2-thienyl ketone)

COCH

2-Thiophenecarbaldehyde (2-Formylthiophene)

CHO

3

CH

3

3

3

CH

3

3


CH

3

12.

FORS

3\

S**2

R

Sensory Properties:

Literature

233

Review

«1 DESCRIPTION


Ο of GC eluates: Sickly, pungent

THRESHOLD VALUE

F F F

REM.

REF

F,M

19

8 ppb/water 300 ppb/skim milk 4 ppb/proteinhydrolysate solution 2%

32

19 31

Ο of GC eluates: Green, sweet Ο at GC exhaust: Onion-like, gasoline-like, paraffinic O: Heated onion or sulfury

F,M,S

O: Fatty, winey

F,M

28

O: Styrene-like

F,M

28

O: Fried onion

F,M

28

F,M

80 28

F,M

34 80

O: Burnt

F,M

28

O: Mustard-like Ο in syrup: 1 g/100 ml: Onion-like; ι Ο in coffee: Malty, roasted

F,M

28 6

O: Fried onions O: Greenish F: Fresh onion O: Fried onions

79

Ο

1.3 ppb/water

Ο

1.3 ppb/water

F F F

F: Mustard O: Nutty O: Sweet, flowery O: Nutty O: O: O: O:

Reminiscent of benzaldehyde Spicy meat Coconut-like Sharp, sweet-nutty, somewhat roasted grain-like

F F F

32

0.08 ppb/water 1 ppm/skim milk 0.3 ppb/proteinhydrolysate solution 2% F,M

34 28

F,M

28

F,M

81 6 33 28 82

200 ppb/water 8 ppm/skim milk 600 ppb/proteinhydrolysate solution 2%

32



MAILLARD REACTIONS

234

THIOPHENES (cont.)


NAME

/

(SYNONYM)

R

R

l

R

2

3

R

4

CH

5-Methyl-2-thiophenecarbaldehyde (5-Methyl-2-formylthiophene)

CHO

3 - Methyl - 2 - thiophenecar baldehy de (3- Methyl - 2- f or mylthiophene)

CHO

l-(2-Thienyl)-l-propanone (2-Propionylthiophene)

COC H

l-(2- or 3-Thienyl)-propane-l,2-dione

COCOCH

2-Methylthiophene-3-thiol

CH

3

2-Methylthiophene-4-thiol

CH

3

CH

2

3

3

5

3

SH SH

DIHYDROTHIOPHENES

2-Methyl-2,3(or 2,5)-dihydrothiophene

CH

3

2-Methyl-4,5-dihydrothiophene

CH

3

2-Methyl-2,3-dihydrothiophene-3-thiol

CH

3

2- Methyl-2,3-dihydrothiophene-4-thiol

CH

3

3- Mercapto-2-methyl-2,3-dihydrothiophen-4-ol

CH

3

SH


CH,

SH


CH,

2-Methyltetrahydrothiophene-3-thiol

CH,

2-Methyltetrahydrothiophene-4-thiol

CH,

2,3(4,5)

SH SH OH

SH SH SH


12.

FORS

Sensory Properties:

Literature

DESCRIPTION

THRESHOLD VALUE

REM.

REF

F,M

6 34 1

O: Reminiscent of saffron

F,M

6

Ο in syrup 1 g/100 ml: Creamy, caramel-like

F,M

6

Imparts a parline-like and woody note to coffee O: Woody

F,M

6

Ο at GC exhaust: Roasted meat

S

31

Ο at GC exhaust: Rubbery

S

31


O: Cherry-like F: Cherry, bitter almond

R

235

Review

3 N

IJ

,R

F 1 ppb/water

28

R

2

\

3y

' 2 R

TETRAHYDROTHIOPHENES

Ο at GC exhaust: Cabbage-like

S

31

O: Heated onion or sulfury

M

79

Ο at GC exhaust: Sweet, roasted meat

S

31

Ο at GC exhaust: Rubbery, meaty

S

31

Ο at GC exhaust: Meaty, savory, phenolic

S

31

Ο at GC exhaust: Meaty

S

31

Ο at GC exhaust: Roasted meat

S

31

Ο at GC exhaust: Cis-form, meaty; trans-form, meaty, savory

S

31

Ο at GC exhaust: Meat-like

S

31



MAILLARD REACTIONS

236

3_(2H-)-THIOPHENONES


NAME

/

(SYNONYM)

R

2

R

3

R

4

4-Hydroxy-5-methyl-3(2H)-thiophenone

=o

OH

CH

3

4 - Mer capto - 5 - methyl - 3(2H)-thiophenone

=o

SH

CH

3

4,5-Dihydro-3(2H)-thiophenone

=o

2-Methyl-4,5-dihydro-3(2H)-thiophenone

CH

3

=0

3,4-Dimethyl-2,5-dioxo-2,5-dihydrothiophene


12.

FORS

Sensory Properties:

Literature

Review

237

4,5-DIHYDRO-3(2H)-THIOPHENONES


DESCRIPTION

THRESHOLD VALUE

REM.

REF

Ο at GC exhaust: Popcorn-like

S

31

Ο at GC exhaust: Nutty

S

31

F: Garlic

F,M

F: Green, burnt, coffee Ο at GC exhaust: Acetylenic

F,M,S

7 31

O: Onion, a little H S

F

83

2

7



MAILLARD REACTIONS

238

AROMATIC SULFUR COMPOUNDS

NAME

/

(SYNONYM)


oC-Toluenethiol (Benzyl mercaptan, Phenylmethanethiol)

Benzyl methyl sulfide

2-Naphthalenethiol (2-Naphthyl mercaptan)


12.

FORS

Sensory Properties:

Literature

DESCRIPTION

O: Disagreeable, mercaptan-like

239

THRESHOLD VALUE

Ο


"Leek-like" (a more exact de scription than the older still common "onion-like"). Has the sharpness of leek odor, yet not lachrymatory O: Repulsive, garlic-like F: Reminiscent of the natural landcress off-flavor

Review

REM.

REF

F,S

17

23 F

1 ppb/milk

84

F F

10 ppb/milk \ F,M 100 ppb/butter oil '

84

F,S

23



MAILLARD REACTIONS

240

CYCLIC NON-AROMATIC SULFUR COMPOUNDS

NAME

/

(SYNONYM)

V

Ethylene sulfide (Thiirane)


ΓΛ 1,2-Dithiacyclopentene (3H-l,2-Dithiole)

\

3-Methyl-l,2-dithiolane

Ο

y$ S

Ρ** CH, /

3,5-Dimethyl-l,2-dithiolane

3

CH^X

S

3

-s 1,3-Dithiolane

^ ^ ^CH 2-Methyl-l,3-dithiolane

^S'

3

b

4-Methyl-l,3-dithiolane

CH,

S

2,4-Dimethyl-l,3-dithiolane

s—S

1,2,4-Trithiolane

3,5-Dimethyl-l,2,4-trithiolane

CH^g/'C^ S - S

3-Ethyl-5-methyl-l,2,4-trithiolane

C

H

3 ^ S ^

C

2 5 H

S—S

3,5-Diethyl-l,2,4-trithiolane

^'s^S

^ 5


12.

FORS



DESCRIPTION

241

Review

THRESHOLD VALUE

REM.

REF

O: Cooked cabbage Ο of GC eluates: Sickly, cooked cabbage, pungent

6 19

O: Pleasant smell like cooked asparagus

85

Τ

2 ppb

86

Cooked onion, cooked vegetable nutty note

Τ

10 ppb

86

Sweet, sulfury character, in high levels: reminiscent of degrading onions

Τ

2 ppb

T: Oniony metallic with cooked beef or braised and vegetable nuances

ppb/water

F,S

86

F,S

34

F: Onion and garlic roasted or boiled

20

T: Onion, root-vegetable-like

Τ

50 ppb

86

T: Onion-like with slight metallic background notes

Τ

20 ppb

86

O: Roast beef O: Sulfurous

M

78 28

Ο: Characteristic of boiled beef O: Onion-like

F,M,S

87 88 1

O: Garlicky

F,S

88

O: Garlicky

F,S

88

F

10 ppb/water



MAILLARD REACTIONS

242

CYCLIC NON-AROMATIC NAME

/

SULFUR COMPOUNDS (cont.)

(SYNONYM)

3,5-Di-(2-methylpropyl)-l,2,4-trithiolane

^

(CH ) CH CH 3

1,2-Dithiane

2

2

/ 2

\ /^CH CH (CH ) S

2

Q

2

S


S

3-Methyl-l,2-dithiane

S r

8

3,5-Dimethyl-l,2-dithiane S

2,6-Dimethyldithiin (2,6-Dimethyl-4H-dithiin)

1,3-Dithiane


"S

CH ^s

/ c H

3

3

Q C^CH

3

CH


2,4-Dimethyl-l,3-dithiane

3

Q α

S' Ν * 3 ÇH,

2,4,6-Trimethyl-l,3-dithiane

1,4-Dithiane

Ô


3

2

12.

FORS

Sensory Properties:

Literature

DESCRIPTION

Review

243

THRESHOLD VALUE

REM.

F at 1 ppm: Roasted, crisp bacon-like, pork rind-like


Garlic character with slight metallic nuance

REF 86

Τ

2 ppb

M,S

86

F: Onion and garlic, roasted or boiled

2 ppb/water

34

F: Onion and garlic, roasted or boiled

10 ppb/water

34

O: Fuel gas-like

F: Onion and garlic, roasted or boiled T: Onion, garlic-like with a metallic by-note

2 ppb/water

F,S

88

F,S

34

Τ

50 ppb

86

Onion-like character with metallic notes

Τ

20 ppb

86

Onion, garlic and tomato like character

Τ

50 ppb

86

Allium-onion like character with slight metallic notes

Τ

5 ppb

86

Root-vegetable-like character

Τ

10 ppb

86

Onion-like or garlic-like character Τ

50 ppb

F,S

86



244

MAILLARD REACTIONS

CYCLIC NON-AROMATIC SULFUR COMPOUNDS (cont.)

NAME

/

(SYNONYM)


1,3,5-Trithiane (s-Trithiane)

Ç H

3

S^S 2,4,6-Trimethyl-l,3,5-trithiane (2,4,6-Trimethyl-s-trithiane)

|^ J CH^^s^C^

C H 2

2,4,6-Triethyl-l,3,5-trithiane

I

S

J

C H;S^C H 2

2

5

6-Methyl-2,3-dihydrothieno [ 2,3-c ] furan (Kahweofuran)


12.

FORS

Sensory Properties:

Literature

245

REM.

REF

F,M

78 32

F dissolved in water: Dusty, earthy, nutty

F,M

89

F dissolved in water: Green, allium (onion, garden cress)

M

89

Ο in pure state: Violent, sulfury, but in high dilution develops a pleasant roasted and smoky note

F,S

DESCRIPTION

O: Sulfurous


Review

THRESHOLD VALUE

F F F

0.04 ppb/water 60 ppb/skim milk 0.08 ppb/proteinhydrolysate solution 2%



246

MAILLARD

REACTIONS

OXAZOLES

NAME

/

(SYNONYM)

2-Acetyloxazole

R

R

±

COCH

4-Butyloxazole

R

2

3

n-c

H 4

9

5-Butyloxazole

n-C H 4

n-C H


4-Heptyloxazole 2,4-Dimethyloxazole

?

7

9

1 5

CH

3

4,5-Dimethyloxazole

CH

3

4,5-Diethyloxazole

C H

4-Methyl-5-propyloxazole

CH

3

n-C H

?

4-Methyl-5-butyloxazole

CH

3

D-C H

9

4-Methyl-5-hexyloxazole

CH,

4-Ethyl-5-propyloxazole

C H 2

5

n-C H

7

4-Ethyl-5-butyloxazole

C H 2

5

D-C H

9

4-Ethyl-5-pentyloxazole

C H

5

n-C H

4-Propyl-5-methyloxazole

n-C H

7

CH

4-Propyl-5-ethyloxazole

n-C H

?

C H

4-Butyl-5-methyloxazole

0-C H

9

CH

4-Butyl-5-propyloxazole

n-C H

9

C H

4-Pentyl-5-methyloxazole

n-C H

4- Hexy 1 - 5 - methy loxazole

n-C H

CH

3

2

2

3

3

4

4

5

6

2,4-Diethyl-5-propyloxazole

CH

3

CH

3

2,4,5-Trimethyloxazole

CH

3

CH

3

CH

3

C H 2

5

3

4

5

2" 6 13 C

H

3

4

5

3

2

5

3

3

u

CH

3

1 3

CH

3

n-C H 3

CH

n

7

?

3


12.

FORS



DESCRIPTION

REM.

REF

O: Nutty, popcorn-like

F

90

O: Vegetable-like, green

S

91

O: Green, sweet, vegetable

F

90

O: Vegetable-like

S

91

O: Nutty, sweet

M

37

O: Green, sweet, vegetable

F

90

O: Green, vegetable-like

S

91


S

91


S

91


S

91


S

91


S

91


S

91

O: Green, weak bell pepper-like

S

91

O: Celery-like, green

S

91

O: Bell pepper-like

S

91

O: Bell pepper-like

S

91

O: Bell pepper-like

S

91


S

91

O: Nutty, sweet, green

F

90

F,S

6 92

F: Like boiled beef F: Nutty, sweet, green

THRESHOLD VALUE

247

F

5 ppb

American Chemical Society Library


1155 16th St. N. W. In The Maillard Reaction in Foods and 20031 Nutrition; Waller, G., et al.; Washington, 0. C. ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

MAILLARD REACTIONS

248

OXAZOLINES

NAME

/

(SYNONYM)


2-Ethyl-5-methyl-2-oxazoline

R

l

R

C H 2

2

R

3

5

CH

3

?

CH

3

CH

3

3

5 - Methyl - 2 - propyl - 2 - oxazoline

n-C H

5-Methyl-2-pentyl-2-oxazoline

n-C H

3

5

n

2-Methyl-3-oxazoline

CH

3

2,4-Dimethyl-3-oxazoline

CH

3

CH

3

2,4,5-Trimethyl-3-oxazoline

CH

3

CH

3

CH

2,4-Dimethyl-5-ethyl-3-oxazoline

CH

3

CH

3

C H

2,5-Dimethyl-4-ethyl-3-oxazoline

CH

3

C H 2

5

CH

2,4,5-Triethyl-3-oxazoline

C H

C H 2

5

C H

C

2

5

2

i-C H

7

C H

5

4,5-Dipropyl-2-isopropyl-3-oxazoline i - C H

7

n- C H 3

7

C H

5

4,5-Diethyl-2-isopropyl-3-oxazoline

3

3

2-s-Butyl-4,5-diethyl-3-oxazoline

2

2

5

3

2

5

2 5 H

n-C H 3

C H 2

?

5

2-Isopropyl-4,5,5-trimethyl-3-oxazoline

i-C H

7

CH

3

2xCH

3

2-Isobutyl-4,5,5-trimethyl-3-oxazoline

i-C H

9

CH

3

2xCH

3

2-t-Butyl-4,5,5-trimethyl-3-oxazoline

t-C H

CH

3

2xCH

3

3

4

4

9

BENZOXAZOLES

2-Methylbenzoxazole


12.

FORS


Η

η—N

R

Review

249

^ = N

DESCRIPTION

THRESHOLD VALUE

REF

O: Melon, fruity

35

F: Fresh mint

35

F: Mild, fruity

35

O: Nutty, sweet


REM.

F

90

F: Nutty, vegetable, not roasted O: Nutty, sweet

F 1.0 ppm/water

F,S

92 90

F: Woody, musty, green O: Characteristic boiled beef

F

1.0 ppm/water

F,S

92 87

F: Nutty, sweet, green, woody

F

0.5 ppm/water

F,S

92

F: Nutty, sweet

F

1.0 ppm/water

F,S

92

S

7 93

0 : Very reminiscent of fresh carrots O: Green

7

O: Cocoa O: Banana O: Cool, banana-like

S

35 93

O: Cocoa

s

93

Rum-like note O: Cool, menthol-like, unroasted cocoa

s

7 93

O: Earthy (fungal) with a butter-like green leaf-like note O: Earthy, diacetyl

s

7 93 35

O: Fresh mint and, depending on the concentration, fresh banana or buttery O: Cool, mint-like

O: Very sweet, of rather gassy-pungent character when undiluted, becoming floral-sweet, heavy, when diluted

93

F,S

17



MAILLARD REACTIONS

250

THIAZOLES

NAME

/

(SYNONYM)

R

R

2

3

Thiazole

2-Methylthiazole

CH, CH,


4-Methylthiazole C H

5

2-Propylthiazole

n-C H

7

2-Isopropylthiazole

i-C H

2-Butylthiazole

n-C H

2-Isobutylthiazole

i-C H

2-Ethylthiazole

2-Acetylthiazole (Methyl 2-thiazolyl ketone)

2

3

3

4

4

7

9

9

COCH

4- Acetylthiazole (Methyl 4-thiazolyl ketone)

2-Methoxy thiazole

5- Methoxy thiazole

COCH

OCH

3

3

OCH

3

2-Ethoxythiazole


12.

R

FORS


251

%—Ν

DESCRIPTION

THRESHOLD VALUE

REM.

REF

Τ

F,M

25 23 22

F: Green, vegetable

F,M,S

52

O: Green, nutty

F,M

23

F: Green, nutty

F,M,S

52

F: Green, herby, nutty

M,S

52

F: Green, vegetable

S

52

F: Raw, green, herby

S

52

F in water: Spoiled wine-like, slightly horseradish Ο 2 ppb/water F in canned tomato juice or tomato paste: More intense, fresh tomato-like O: Strong green, resembling that of tomato leaf Ο 3.5 ppb/water F 3 ppb/water

F,S

94

F: O: O: O:

F,M,S

F in beer: Sulfury, grainy, C S O: Pyridine-like O: Nutty, meaty


Review

2

23 ppm/beer

Nutty, cereal, popcorn Cereal bready Taco, grassy Popcorn-like, strong, nuttyroasted character F

F: Nutty, cereal O: Hazelnut, earthy | F: Nutty, steak with bitter aftertaste, baked bread, meat O: Cracker-like Ο

7 95 1

10 ppb/water

52 46 70 82 1

M,S

52 35

170 ppb/water

55

F: Sweet, roasted, phenolic F: Oatmeal, bread and caramel

M,S

52 35

F: Roasted, meaty, onion F: Braised vegetables, roast meat, fresh onions

M,S

52

F: Phenolic, burnt, nutty F: Roasted peanuts, roast meat

M,S

35 52 35



MAILLARD REACTIONS

252

THIAZOLES (cont.)

NAME

/

(SYNONYM)

R

R

2


5-Ethoxythiazole

OC H 2

2-Butoxythiazole

OC^H^-n

2.4- Dimethylthiazole

CH

3

4.5- Dimethylthiazole

2.4- Diethylthiazole

C

2 5

2.5- Diethylthiazole

C

2 5

H

C

CH

3

CH

3

CH

3

H

C

C H 2

5

2 5 H

C H 2

5

D'^-jH^ D'^-jH^

4.5- Dibutylthiazole

D- 4 9 Π-°4 9 C

5-Ethyl-4-methylthiazole

2-Acetyl-4-methylthiazole (Methyl 4-methyl-2-thiazolyl ketone)

H

CH

COCH

5-Acetyl-4-methylthiazole (Methyl 4-methyl-5-thiazolyl ketone)

3

CH

Η

C H

3

2

COCH.

CH^

C

4-Ethyl-5-butylthiazole

C H

2 5 H

2

5

n-CjH. n-C H, 4

4-Butyl-5-methylthiazole

n" 4 9

4-Butyl-5-ethylthiazole

n-- C H

4-Butyl-5-propylthiazole

n-CjH. n" 4 9

C

H

4

C

CH

3

5

3

4-Ethyl-5-propylthiazole

2-Methyl-5-methoxy thiazole

5

2 5

H

4,5-Diethylthiazole 2.4- Dipropylthiazole

3

9

CH

3

C H

5

2

H

OCH

3


12.

FORS

Sensory Properties:

Literature

253

REM.

REF

F: Cooked onion F: Cooked vegetables (sharp resembling nuts)

M,S

52 35

F: Green vegetable

S

52

F,M

55 34, 35

F,M,S

52 35

DESCRIPTION


Review

THRESHOLD VALUE

O: Skunky-oily O: Meat, cocoa

Ο Ο

18 ppb/water 0.1 ppb/water

F: Roasted, nutty, green F: Braised meat, hazelnut O: Meaty, boiled poultry

Ο

0.5 ppm

Ο

470 ppb/water

O: Ethereal, musty, earthy

Ο

6.5 ppb/water

F

55

O: Slightly skunky and green peppery

Ο

0.09 ppb/water

F

55

Ο

5.1 ppb/water

S

96

O: Sweet, fruity, minty

Ο Ο

F: Nutty, green, earthy O: Green vegetables, unroasted hazelnuts

Ο

96

55

26 ppb/water 0.19 ppb/water

S

96

F,M,S

52 35

0.02 ppm

F: Very sharp, dry and earthy parsley] F: Anthranilic, burnt F: Roasted, nutty, sulfury O: Peanut, earthy F: Roasted nuts, sulfury, bitter metallic and earthy

F

F,M

7 1

M,S

52

300 ppb/water

35

Ο

0.05 ppm

O: Bell pepper

O

0.06 ppb/water

S

96

O: Bell pepper

O

0.12 ppb/water

S

96

O: Bell pepper

O

0.01 ppb/water

S

96

O: Bell pepper

O

0.02 ppb/water

S

96

O: Bell pepper

O

0.003 ppb/water

S

96

S

52

F: Cabbagy, sulfury, vegetable



MAILLARD REACTIONS

254

THIAZOLES (cont.)


NAME

/

(SYNONYM)

R

R

2

3

4-Isobutyl-5-methoxy thiazole

i-C H

9

OCH

4-Isobutyl-5-ethoxy thiazole

i-C H

9

OC H

4

4

3

2

5

2,4,5-Trimethylthiazole

CH

3

CH

3

CH

2,4-Dimethyl-5-ethylthiazole

CH

3

CH

3

C H

4-Acetyl-2,5-dimethylthiazole

CH

3

COCH

5-Acetyl-2,4-dirnethylthiazole

CH

3

CH

3

COCH

2,4-Dimethyl-5-vinylthiazole

CH

3

CH

3

CH=CH

2,5-Dimethyl-4-butylthiazole

CH

3

2,5-Diethyl-4-methylthiazole

C H 2

2-Isopropyi-4,5-dimethylthiazole

i-C H

2-Propyl-4,5-diethylthiazole

B- 3

3

C

2

0-C H 4

5

?

H 7

3

9

3

CH

CH

3

3

C H

CH

3

CH

2

2 5 H

3

C H 2

5

CH

3

i-C H

9

OCH

4-Isobutyl-5-ethoxy-2-methylthiazole

CH

3

i-C H

9

OC H

i-C H

9

OCH

2-Butyl-4-isobutyl-5-methoxy thiazole

4

4

2

5

4-Isobutyl-5-methoxy-2-methylthiazole

4

3

3

CH

C

5

3

2

5

3


12.

FORS


REM.

REF

F: Green pepper O: Vegetable soup (minestrone) F: Pepper, onion, celery and green vegetables (peas and haricot beans)

M,S

52

F: Cucumber, green potato

M,S

52 35

F,M,S

52

DESCRIPTION

F: Cucumber, green pepper, onions


255

Review

THRESHOLD VALUE

35

Ο

F: Cocoa, nutty O: Cocoa, hazelnut, dark chocolate, 1 green vegetables (haricot beans) j Ο F: Nutty, roasted, meaty O: Hazelnut, steak, meat, liver, Ο green vegetables, "Buccu" leaf and black currant Ο F: Nuts, meat, steak

0.02 ppm 34, 35 0.05 ppm/water

52 F,M,S

0.02 ppm

35 34

0.002 ppm

F: Roasted, meaty, sulfury

S

52

F: Roasted, nutty, meaty O: Sulfury as in meat F: Boiled beef, chicken and turkey

M,S

52

O: Strong, characteristic, nut-like

F

7

O: Sweet, earthy

F

69

F: Green, nutty

S

52

O: Pleasant, nutty

F

90

O: Pleasant, nutty

F

90

35

52

F: Green, vegetable O: Onion and pepper F: Pepper, vegetables (green)

M,S

F: Green, vegetable, onion F: Vegetables, sharp and green O: Vegetable soup with touch of barley, potato, green pepper and onion

M,S Ο

34, 35 52 35 35

0.0002 ppm M



MAILLARD REACTIONS

256

THIAZOLINES (DIHYDROTHIAZOLES) NAME

/

(SYNONYM)

R

±

2-Acetyl-2-thiazoline

CH^

CH^

CH

CH

COCH^

2,4,5-Trimethyl-3-thiazoline Downloaded by EMORY UNIV on June 19, 2014 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch012

R^

2

2,4-Dimethyl-3-thiazoline CH^

2-Propyl-3-thiazoline

2-(2-Methylpropyl)-4,5-dimethyl-3-thiazoline

R

3

3

D- 3 7 C

H

C H C H (CH,)

CH, *

CH,

2-(l-Methylpropyl)-4,5-dimethyl-CH(CH,)C H, -3-thiazoline *

CH, *

CH,

2-Propyl-2,4,5-trimethyl-3-thiazoline

CH,

CH,

?

>

7 1

n-C,H CH

7

?

y

3


12.

FORS

R

Sensory Properties:

Literature

257

Review

£—Ν

' -s


3

REM.

REF

DESCRIPTION

THRESHOLD VALUE

O: Cracker-like O: Freshly baked bread crust

Ο

1.3 ppb/water

F

3 ppb/water

F: Nutty, roasted, vegetable

F

0.02 ppm

F,M,S

92

F: Meaty, nutty, onion-like F at 0.2-1 ppm: Fresh chopped meat-like with light sour effect Τ at 2 ppm: Chemical

F

0.5 ppm

F,M,S

92

55 22 1

97

Ο at 0.2 ppm: Green, vegetable nutty and roasted Τ at 0.2 ppm: Sweet, green, vege table, roasted, cocoa powderlike

97

Ο at 2 ppm: Sweet, roasted meat like, roasted nut-like, dark chocolate-like, baked goods-like and vegetable green-like Τ at 2 ppm: Sweet, roasted meat-like, roasted nut-like, chocolate-like, vegetable green-like, hydrolyzed vegetable protein-like. Having a hydrolyzed vegetable protein aftertaste and astringent and choco late-like notes

97

Ο at 2 ppm: Sweet, herbaceous, spicy, chocolate-like, nutty, vegetable-like, hydrolyzed vegetable protein-like, roasted F at 2 ppm: Herbaceous, vegetable, green-like, nutty, roasted, chocolate-like, astringent

97

Ο at 1 ppm: Sweet, green bean-like, cucumber-like, geranium-like and spicy F at 1 ppm: Cucumber-like, green bean-like, spicy, watermelon-like, black pepper-like, astringent

97



MAILLARD REACTIONS

258

BENZOTHIAZOLES


NAME

/

(SYNONYM)

R^

Benzothiazole

H

2-(Methylthio)benzothiazole

SCH

R

R

2

3

1,3,5-DITHIAZINES

NAME

/

(SYNONYM)

ι

J

2,4,6-Trimethyldihydro-l,3,5-dithiazine C H 3 ^ N ^

H Ç

2-Ethyl-4,6-dimethyldihydro-l,3,5-dithiazine

2

I

C H

N

H

3

5

J

C H ' ^ N

C H

H

C H

ι

3

3

ό

4-Ethyl-2,6-dimethyldihydro-l,3,5-dithiazine C H


12.

FORS

Sensory Properties:

Literature

DESCRIPTION

Review

259

THRESHOLD VALUE

REM.

REF

F

7 34 82

F

6, 7

REM.

REF

O: Roasted beef-like Typical note of heated meat

F,M,S

88 6

O: Cooked beef-like

F,S

88

O: Onion-, cooked beef-like

F,S

88

O: Quinoline-like, rubbery Ο: Similar to pyridine O: Heated rubber-like, heavy and dirty


O: Imparts characteristic fatty and smoky odor to meat aroma

H

Ο

5 ppb/water

2

DESCRIPTION

THRESHOLD VALUE



MAILLARD REACTIONS

260

ALDEHYDES AND KETONES


NAME

/

(SYNONYM)

Ethanal (Acetaldehyde)

CH CHO

Butanal (Butyraldehyde)

n-C H CHO

3

3

7


12.

FORS

Sensory Properties:


DESCRIPTION

Literature

Review

261

THRESHOLD VALUE

O: Pungent ethereal-nauseating, in high dilution reminiscent of coffee or wine O: Characteristic pungent and penetrating Ο of GC eluates: Pungent O: Sour, greenhouse Ο 100°C Caramel, sweet 180°C: Burnt sugar O: Green, sweet Ο 0.21 ppm/air ι (recognition) > Ο 0.12 mg/m Zair Ο 0.041 mg/m /air Ο 0.005 mg/m /air

REM.

REF

F,M,S

17 23 19 98 18 50 99 55 100 23, 141, 142 101 102 20 25 103

3

F: Green leaves, fruity

Ο Ο Ο F F

15 ppb/water 109 ppb/water 120 ppb/water 25 ppb/beer 50 ppm/beer F,S

O: Very diffusive, penetrating pungent-irritating Only in extreme dilution truly fruity, banana-like, green-fresh odor O: Characteristic pungent Ο of GC eluates: Burnt, green, nasty

23 19

Ο Ο F

9 ppb/water 37.3 ppb/water 1.0 ppm/beer

104, 105 55 23, 141, 142 106 102 25

F

1.0 ppm/beer

103

Ο

bk-1983-0215.ch012

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