Chapter 40
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Process Meat Flavor Development and the Maillard Reaction G. A. M. van den Ouweland, E. P. Demole, and P. Enggist Firmenich SA, P.O. Box 239-CH-1211 Geneva, Switzerland
The flavor industry has introduced, over the years, methods of developing meat flavors by processing appropriate precursors under carefully controlled reaction conditions. As a result, meat flavors having a remarkably genuine meat character in the beef, chicken and pork tonalities are available for the food industry. It has repeatedly been stated that the Maillard reaction is particularly important for the formation of meat flavors. However, of the 600 volatile compounds isolated from natural beef aroma, only 12% of them find their origin in sugar/amino acid interactions and of these 70% are pyrazine derivatives. The precursors used for process meat flavors are reviewed and also discussed will be non-Maillard interactions of ribose-5-phosphate and lipid degradation products with sulfur giving a real meaty odor and meat specie specific odor compounds, respectively.
More than 50 years were needed before the flavor industry started to use Maillard's original work of heating together carbohydrates and amino acids for the development of flavoring materials. Processing hydrolysed vegetable protein with carbohydrates and cysteine giving a savoury meat-like flavor was one of the first examples of using the Maillard reaction on a commercial scale. Since then the development of process meat flavors has evolved in such a way that currently the food industry has a choice of chicken, beef, pork and ham flavors, which have authentic meat tonalities. The creation of these flavors is based on the processing of selected raw materials. For example in the cooking of meat complex flavor systems obtained are from a combination of fat oxidation products, thermal degradation products of sugars, amino acids, thiamine and nucleotides as well as Maillard reaction products. In the early 1980 s the flavor industry in Europe, through IOFI, produced guidelines for the composition and manufacture of process flavorings and the principal raw materials to be used. 1
0097-6156/89/0409-0433$06.00/0 o 1989 American Chemical Society Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
THERMAL GENERATION OF AROMAS
434
In the USA, the e x p e r t committee w i t h i n FEMA has produced s i m i l a r g u i d e l i n e s f o r the p r e p a r a t i o n o f such p r o d u c t s . In t h i s paper the r e l a t i v e importance o f the M a i l l a r d r e a c t i o n i s d i s c u s s e d as w e l l as the i n t e r a c t i o n o f t h i s w i t h r i b o s e - 5 - p h o s p h a t e and l i p i d d e g r a d a t i o n p r o d u c t s .
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MAILLARD REACTION and MEAT FLAVOURS I t has been r e p e a t e d l y s t a t e d t h a t the M a i l l a r d r e a c t i o n i s v e r y i m p o r t a n t f o r the f o r m a t i o n o f meat f l a v o r . The f i r s t s t a g e o f the M a i l l a r d r e a c t i o n i n v o l v e s the c o n d e n s a t i o n o f the amino-group o f the amino a c i d t o the c a r b o n y l - g r o u p o f the sugar f o l l o w e d by a rearrangement. These rearrangements o f g l u c o s e and f r u c t o s e are o f t e n r e f e r r e d t o as the Amadori and Heyns rearrangement p r o d u c t s ( R P ' s ) . I n our s t u d y i n v e s t i g a t i n g the occurence o f RP's i n p r o c e s s e d foods we l o o k e d a t r o a s t e d meat f o r such p r o d u c t s and c o u l d o n l y f i n d the RP d e r i v e d from g l u c o s e and g l y c i n e C5). I n o t h e r p r o c e s s e d foods the presence o f RP's i s more abundant as shown i n Table I .
Table I
RP's
i s o l a t e d from p r o c e s s e d foods
RP's derived from G L U C O S E and Glycine Alanine 4-a m inobutyricacid Valine Aspartic acid Asparagine Glutamic acid Proline Tyrosine Phenylalanine Theanine F R U C T O S E and Glycine 4-aminobutyric acid Aspartic acid
A= B= C= D= E= F= G= H=
Isolated from A A A
Β Β
C C C
A
Β
C
D E
F
G G G
E E
F F
G G
E E E
F
B
G G F
Apricots [ J J L i v e r [2] [3] Beet Molasses [4] Roasted meat [5] Flue Cured Tobacco [6] Liquorice [7] Tomato powder [5] Black Tea [5]
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
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40. VAN DEN OUWELAND ET AL.
Meat Flavor and the Maillard Reaction
435
When we f i r s t investigated processed foods f o r the occurence o f RP's there was no d i r e c t method f o r the determination o f t h e i r conformation. A n RP c a n exist i n the open keto-form or h e m i a c e t a l ring structures derived from i t (Figure 1) Generally the presence or absence of a C=0 absorption band i n the IR spectrum is used to assign the keto structure or the c y c l i c forms, respectively. As f a r as the c y c l i c forms were concerned, no further spectroscopic evidence was then available. The structures of RP's were c h a r a c t e r i z e d by c h e m i c a l methods, which often involved acid hydrolysis followed by i d e n t i f i c a t i o n of the amino acid, which was split o f f i n this decomposition r e a c t i o n . E x a m i n a t i o n o f the 220 MH2 P M R spectrum o f the RP isolated from the roasted meat i.e. derived from glucose and glycine (Figure 2) recorded i n D2O at pH3 shows that the product exists at least as a mixture of t w o components. The assignment o f the proton signals of the major pyranose component ( 85 %) is given and i t appears that the coupling constants are i d e n t i c a l with those ofr$(D)-fructose. The A Β doublet resonating at 3.33 and 3.38 ppm can be assigned to the methylene protons adjacent to the nitrogen atom. The complete exchangeability of these protons with Deuterium at pH 9.5 provides c o n f i r m a t o r y evidence of this assignment and indicates that i n D2O solution an equilibrium exists between the various possible structures, i.e. the pyranose form, furanose form and the open chain structure. The major component i n the mixture has the six-membered structure and exists exclusively i n the/3 ( D ) C5 c o n f o r m a t i o n and the minor component has the five membered r i n g . The presence of exclusively the RP from glucose and glycine i n roasted meat is remarkable, especially i n the light of the quantities of other free amino acids present i n beef diffusate. More than 600 components have been isolated [8] from n a t u r a l beef aroma · We have estimated that only 94 of these volatiles find t h e i r origin i n the Maillard r e a c t i o n and o f these 5 0 % are pyrazine derivatives which contribute more to a roasted aroma than to a meat aroma . 2
R E A C T I O N o f H Y D R O G E N S U L P H I D E with M E T H Y L F U R A N O L O N E One r e a c t i o n system delivering a meaty odour where the M a i l l a r d r e a c t i o n is not involved is the conversion o f ribonucleotides v i a ribose-5-phosphate and methyl-furanolone into meat f l a v o r [9]. Many of the i n d i v i d u a l r e a c t i o n products isolated from this r e a c t i o n have a c h a r a c t e r i s t i c meat odour, with thiofuran derivatives the most interesting · The amount of unsaturation and the position of the methyl group play predominant roles f o r the odour quality as ilustrated i n Figure 4. As shown f o r compounds 1-4, a f l a t 5-membered ring with at l e a s t one double bond and a methyl group adjacent to the t h i o l group gives the most c h a r a c t e r i s t i c meat flavor. Compounds 2 and 3 were also isolated as thiamine degradation products [10] and the occurence of 3 i n cooked meat was r e c e n t l y proven [11]. The importance of the position of the methyl group is also i l l u s t r a t e d f o r some thiophenols (Figure 4)· Only the methyl group on the ortho position gives meat-like flavor. C o m pounds 5,6,7 were isolated from a n a t u r a l meat aroma. Of the 600 or more substances isolated from n a t u r a l beef aroma, only a v e r y few possess a meat-like aroma. A 5 o r 6 membered more or less planar ring substituted with an enol-thiol and a methyl group adjacent to the t h i o l seems to be necessary f o r a meaty aroma.
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
HO-C
O-C HO^C
H
3
H3
(I)
a-anomer
OH
p-onomer
OH
OH
F i g u r e 1.
2
CH^0H
C=0
OH
OH
OH HS
/Hi
H,
/ R
-
cm)
a - anomer
'
p-anomer
OH
0H
4
D i f f e r e n t p o s s i b l e s t r u c t u r e s f o r an Amadori rearrangement product.
(I)
(^Η^0Η
H5-C-OH
I
H4-C-OH
6
X
| H,, R
N
U
(la)
e
HO—C-H3
5
H —C-OH
4
H —C-OH
I
HO-C-H3
I
C-OH
fc
H
- c- •N \ p 2
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OH
A''
•χ/ν
CP< Î 3
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VAN DEN OUWELAND ET AL.
F i g u r e 2.
220 MHz PMR glycine.
Meat Flavor and the Maillard Reaction
s p e c t r u m o f t h e RP f r o m g l u c o s e and
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
437
THERMAL GENERATION OF AROMAS
438
SH
SH
.CH,
ChL
1
Roast
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Green p e a - l i k e
SH
meat-like
SH
•CH, HC 3
Burnt r o a s t m e a t - l i k e
F i g u r e 3.
Green h e r b a c e o u s
O d o r d e s c r i p t i o n o f some m e r c a p t o f u r a n d e r i v a t i v e s i s o l a t e d from methylfuranolone reaction.
- H2S
7 meaty, p h e n o l i c
9 burnt, fatty
burnt
10
green,
burnt, phenolic
12
sulfury, fruity Buchu o i l
sulfury,rubbery
F i g u r e 4. O d o r d e s c r i p t i o n o f some c y c l i c m e r c a p t o derivatives.
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
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40. VAN DEN OUWELAND ET AL.
Meat Flavor and the Maillard Reaction
439
REACTION o f HYDROGENSULFIDE w i t h u n s a t u r a t e d ALDEHYDES The l i p i d f r a c t i o n o f meat i s an i m p o r t a n t group o f p r e c u r s o r s f o r meat f l a v o r and a s o u r c e o f f l a v o r d i f f e r e n c e s between t h e v a r i o u s s p e c i e s .During c o o k i n g , t h e r m a l and o x i d a t i v e d e g r a d a t i o n o f l i p i d s p r o c e e d s i m u l t a n e o u s l y and a range o f f l a v o r i n g compounds a r e formed. These d e g r a d a t i o n r e a c t i o n s o f l i p i d s a r e more pronounced f o r meat w i t h a r e l a t i v e l y h i g h c o n t e n t o f p o l y u n s a t u r a t e d f a t t y a c i d s , i . e . c h i c k e n [ Γ 3 ] , than i s t h e c a s e f o r b e e f [ 1 2 ] . These c a r b o n y l compounds a r e p o t e n t aroma c h e m i c a l s which n o t o n l y c o n t r i b u t e t o cooked meat f l a v o r , but a l s o a r e i n v o l v e d i n t h e f o r m a t i o n o f o t h e r s t r o n g l y odorous compounds. An example o f t h i s was g i v e n by P i p p e n and M e c c h i [L4] who o b s e r v e d t h a t when hydrogen s u l f i d e i s passed through m o l t e n c h i c k e n f a t , a c h i c k e n m e a t - l i k e aroma i s formed. In h e a t e d c h i c k e n f a t mono-, d i - , and t r i u n s a t u r a t e d a l d e h y d e s are p r e s e n t . I n o u r i n v e s t i g a t i o n o f t h e r e a c t i o n o f hydrogen s u l p h i d e w i t h t h e s e a l d e h y d e s we chose t h e C-10 a l d e h y d e s . The base c a t a l y z e d r e a c t i o n between 2-decenal and hydrogen s u l p h i d e i n aqueous s o l u t i o n a t pH ^ 7 f o l l o w s e s s e n t i a l l y t h e same r o u t e s as d e s c r i b e d e a r l i e r f o r 2 - b u t e n a l by B a d i n g s e t a l [L5] and o u t l i n e d i n F i g u r e 5. The s i m p l e a d d i t i o n p r o d u c t 3-mercaptodecanal 14 i s o b t a i n e d as the main p r o d u c t . On s t a n d i n g t h i s compound changed i n t o a v i s c o u s o d o r l e s s o i l o f s t r u c t u r e 15. As e x p e c t e d [16J compound 14 r e a c t s i n the p r e s e n c e o f NH3 and a c e t a l d e h y d e t o t h i a z i n e d e r i v a t i v e s 16 and 17 as i n d i c a t e d i n F i g u r e 6. In c o n t r a s t t o t h e r e a c t i o n o f 2 - d e c e n a l w i t h H2S a much more complex r e a c t i o n m i x t u r e i s o b t a i n e d from t h e r e a c t i o n o f 2,4d e c a d i e n a l w i t h H2S i n an aqueous medium a t pH 8 In view o f t h e e x p e c t e d i n s t a b i l i t y o f t h e mercapto a l d e h y d e s l i k e l y t o be formed , t h e r e a c t i o n m i x t u r e was e x t r a c t e d and t h e c o n c e n t r a t e d e x t r a c t t r e a t e d w i t h L1AIH4/ a c e t i c a n h y d r i d e / p y r i d i n e . The a c e t a t e s / t h i o a c e t a t e s i s o l a t e d from t h i s r e a c t i o n m i x t u r e were a n a l y z e d w i t h MS/NMR s p e c t r o s c o p y . From t h e r e s u l t s o f t h e s e a n a l y s e s , t h e r e a c t i o n r o u t e s as i n d i c a t e d i n F i g u r e 5 a r e f o l l o w e d . Compound 24 i s o b t a i n e d as t h e major r e a c t i o n p r o d u c t . The mercaptoaldehydes 19 and 20 o b t a i n e d v i a 1,6- and 1 , 4 - a d d i t i o n o f H2S t o the s t a r t i n g a l d e h y d e s c a n be c o n s i d e r e d as t h e p r e c u r s o r s f o r compounds 22, 24 and 25. The f o r m a t i o n o f t h e t h i o p h e n e d e r i v a t i v e 23 c a n be e x p l a i n e d t o p r o c e e d v i a mercaptoaldehyde 18, a l t h o u g h t h e l a t t e r c o u l d n o t be d e t e c t e d as i t s a c e t a t e / t h i o a c e t a t e i n the crude r e a c t i o n m i x t u r e . In view o f t h e ease w i t h which H2S r e a c t s w i t h p o l y u n s a t u r a t e d a l d e h y d e s i t i s tempting t o assume t h a t d u r i n g the c o o k i n g o f meat i n t e r a c t i o n o f these p r o t e i n and l i p i d d e g r a d a t i o n p r o d u c t s o c c u r s . The r e a c t i v e H2S-addition p r o d u c t s i n i t i a l l y formed c a n then e a s i l y r e a c t f u r t h e r w i t h aldehydes and NH3 t o g i v e a v a s t v a r i e t y o f odorous compounds which would have a major c o n t r i b u t i o n t o t h e f l a v o r o f cooked meat. The i d e n t i f i c a t i o n o f t h e s e types o f compounds i n meat f l a v o r remains a major c h a l l e n g e t o the f l a v o r c h e m i s t w i t h s o p h i s t i c a t e d modern a n a l y t i c a l t o o l s .
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
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440
THERMAL GENERATION OF AROMAS
CH CH0
15
3
NH
3
16
R=
C H ?
1
17
5
F i g u r e 5. R e a c t i o n o f 2 - d e c e n a l i n p r o c e s s
flavors.
SH
F i g u r e 6. R e a c t i o n o f 2 , 4 - d e c a d i e n a l
with
H2S.
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
40. VAN DEN OUWELAND ET AL.
Meat Flavor and the Maillard Reaction
441
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Literature Cited 1. Anet, E.F.L.J.; Reynolds, T.M. Austr. J. chem. 1975, 10, 182. 2. Heyns, K.; Paulsen, H. Ann. 1959, 622, 160. 3. Borsook, H.; Abrams, Α.; Lowy; P.H. J. Biol. Chem. 1955, 215, 111. 4. Carruthers, Α.; Dutton, J.V.; Oldfield, J.F.T. Intern. Sugar J. 1965, 65, 297. 5. van den Ouweland, G.A.M.; Peer, H.G.; Tjan, S.B., Flavor of Foods and Beverages: Chemistry and Technology, Charalambous, G.; Inglett, G.E. Eds. Academic Press, New York 1978, 131. 6. Yamamoto, K.; Noguchi, M. Agric. Biol. Chem. 1973, 37, 2185. 7. Nishi, H.; Morishita, I. Nippon Nogei Kagaku Kaishi 1971, 45, 507. 8. Macleod, G.; Seygedain-Ardebili, M. CRC Crit. Revs. Food Technol. 1981, 309. 9. van den Ouweland, G.A.M.; Peer, H.G. J. Agric. Food Chem. 1975, 23, 501. 10. Dwivedi, B.K.; Arnold, R.G. J. Agric. Food Chem 1973, 21, 54. 11. Gasser, U.; Grosch, W. Z. Lebensm. Unters. Forsch. 1988, 186, 489. 12. Watanabe, K.; Sato, Y. Agric. Biol. Chem. 1974, 35, 756. 13. Harkes, P.D.; Begeman, W.J. J. Am. Oil Chem. Soc. 1974, 51, 356. 14. Pippen, E.L.; Mecchi, E.P. J. Food Sci. 1969, 34 443. 15. Badings, H.T.; Maarse, H.; Kleipool, R.J.C.; Tas, A.C.; Neeter, R.; ten Noever de Brauw, M.C. Z. Lebensm. Unters. Forsch. 1976, 161, 53. 16. Asinger, F.; Fischer, M. J. Pract. Chem. 1967, 35, 81. RECEIVED May 2, 1989
Parliment et al.; Thermal Generation of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1989.