The Variety of Odors Produced in Maillard Model Systems and How

9

The

Variety

Model

of

Odors

Systems and

Produced How

They

in Are

Maillard Influenced

by Reaction Conditions Downloaded by UNIV OF NEW SOUTH WALES on April 20, 2016 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch009

1

2

M. J. LANE and H. E. NURSTEN The University, Procter Department of Food and Leather Science, Leeds, LS2 9JT, United Kingdom The odors of more than four hundred model systems drawn from twenty-one amino acids and eight sugars, treated under different conditions of temperature and humidity with the inclusion of selected third components, were evaluated by one assessor only. Organoleptic assessment of odors produced by a full range of common amino acids in "dry" 1:1 admixture with glucose was carried out by immersion of an ignition tube containing the reaction mixture into a heated Wood's metal bath. The investigator assessed variations in aroma produced by: (a) changes in heating temperature from 100 to 220°C at selected time intervals up to thirty minutes, (b) different levels of relative humidity of the reactants, (c) changes in the sugar used, and (d) adding third components, such as powdered cellulose and soluble starch and two nitrogen sources, asparagine and glutamine. The initial experiments, the heating of glucose-amino acid mixtures at selected temperatures, proved of greatest interest, many aromas being reported for the first time. However, as the experiments progressed from variations in time and temperature only to variations of water content, change of sugar and inclusion of third components, the aromas emerged as basically the same for each particular amino acid.

Current address: Quaker Oats Ltd., Bridge Rd., Southall, Middlesex

Current address: University of Reading, Department of Food Science, Whiteknights, Reading, Berkshire 1

2

0097-6156/83/0215-0141$06.00/0 © 1983 American Chemical Society Waller and Feather; The Maillard Reaction in Foods and Nutrition ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

Downloaded by UNIV OF NEW SOUTH WALES on April 20, 2016 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch009

142

MAILLARD REACTIONS

When o u r i n t e r e s t i n t h i s a r e a u a s a r o u s e d i n 1 9 6 9 , a s u r v e y o f p r e v i o u s work s h o u e d t h a t , a l t h o u g h many a q u e o u s m i x t u r e s had been s t u d i e d , a t t e n t i o n had been a c c o r d e d t o v e r y feu systems of very l o u water c o n t e n t . In f a c t , a t t h a t t i m e no " d r y " , t u o - c o m p o n e n t s y s t e m had been e x a m i n e d w i t h r e s p e c t to the v o l a t i l e s p r o d u c e d , a s u r p r i s i n g o m i s s i o n c o n s i d e r i n g t h e i m p o r t a n c e o f r o a s t i n g and g r i l l i n g . S i n c e t h e n , some i m p o r t a n t work a l o n g t h e s e l i n e s h a s been c a r r i e d o u t ( 2 . ) » c u l m i n a t i n g i n t h e r e c e n t p a p e r by de R i j k e , e t a l . ( 2 j , i n u h i c h a s u l f u r - c o n t a i n i n g amino a c i d , m e t h i o n i n e o r c y s t e i n e , u a s h e a t e d u n d e r " d r y " c o n d i t i o n s u i t h one o f s i x s u g a r s i n t u r n f o r 15 min a t 1 9 0 - 2 0 0 ° and 2 - 3 T o r r . , t h e v o l a t i l e s b e i n g c o l l e c t e d i n c o l d t r a p s and e x a m i n e d . Our a p p r o a c h u a s d i f f e r e n t , a m b i t i o u s , y e t s i m p l e . The o d o r s o f more t h a n 400 model s y s t e m s d r a u n f r o m 21 amino a c i d s and 8 s u g a r s , t r e a t e d u n d e r d i f f e r e n t c o n d i t i o n s o f t e m p e r a t u r e and h u m i d i t y u i t h t h e i n c l u s i o n o f s e l e c t e d t h i r d c o m p o n e n t s , u e r e e v a l u a t e d by one a s s e s s o r o n l y . Experimental Reagents. A n a l a r amino a c i d s and s u g a r s ( B . D . H . C h e m i c a l s Ltd) uere used. T h i n l a y e r c h r o m a t o g r a p h y r e v e a l e d no i m p u r i t i e s i n t h e r e a g e n t s a s d e l i v e r e d , and no f u r t h e r purification uas c a r r i e d o u t . The r e a g e n t s u e r e k e p t o v e r p h o s p h o r u s p e n t o x i d e i n a vacuum d e s i c c a t o r f o r a t l e a s t t h r e e d a y s b e f o r e use. Tuo-component systems (a) G l u c o s e - a m i n o a c i d systems F i n e l y g r o u n d , e q u i m o l a r m i x t u r e ( 0 . 3 g) u a s p l a c e d i n t o a s m a l l t e s t t u b e , a g l a s s s p a c e r a d d e d t o h o l d doun t h e s o l i d i n c a s e o f f r o t h i n g and a l s o t o i n c r e a s e t h e c o n t a c t o f t h e m i x t u r e u i t h t h e o u t s i d e u a l l ( s e e F i g u r e 1 ) , and t h e tube c l o s e d u i t h an aluminum c a p ( O x o i d L t d ) t o l e s s e n t h e e s c a p e o f v o l a t i l e s . The t e s t t u b e u a s p a r t i a l l y immersed i n a g l a s s d i s h o f m o l t e n w o o d ' s m e t a l , k e p t a t 180 ( Î 2 ) ° on a m a g n e t i c h o t - p l a t e stirrer. At r e g u l a r i n t e r v a l s t h e t e s t t u b e u a s u i t h d r a u n t o s m e l l t h e v o l a t i l e s produced. G l u c o s e uas heated u i t h the f o l l o u i n g amino a c i d s : a l a , a r g , a s n , a s p , c y s , c y s 2 , g l u , g i n , g l y , h i s , i l e , l e u , l y s , met, p h e , p r o , s e r , t h r , t r y , t y r , and v a l , h i s and l y s b e i n g i n t h e form o f t h e i r m o n o h y d r o c h l o r i d e s . The amino a c i d s and g l u c o s e u e r e a l s o h e a t e d a l o n e . The aromas u e r e n o r m a l l y a s s e s s e d a f t e r 1, 2 , 3 , and 4 m î n . The maximum y i e l d (0.5%) o f t h e i n t e r e s t i n g 2-(5hydroxymethyl-2-formyl-l-pyrrolyl) p r o p i o n i c l a c t o n e has been shoun t o o c c u r from a m i x t u r e o f g l u c o s e and a l a i n a b o u t 3 min under "dry c o n d i t i o n s a t 2 0 0 ° (.3). The f u l l r e s u l t s a r e a v a i l a b l e ( £ ) and a s e t o b t a i n e d a t 1 8 0 ± 2 ° i s g i v e n i n T a b l e I as an e x a m p l e . 1 1

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

9.

LANE AND NURSTEN

Odors Produced

in Maillard

143

Systems

ignition tube metal cap


glass spacer

53mm

sugar-amino acid mixture

13-5 mm

Figure 1.

Heating tube.

TABLE

I

EXAMPLE OF AROMA ASSESSMENT OF 1:1

GLUCOSE

; AMINO ACID MIXTURE AT 18Q

qlucose-cysteine 30, 60 s

strongly

2 min

crusty,

3 min

alone

very s l i g h t smell

burnt

1, 2 min

slightly

burnt bread, with underlying puffed wheat o r o v e r - r o a s t e d meat

3, 4 min

unpleasant r o u s , some wheat

meaty

at

wheat

cysteine 30 s

(cf.

puffed

C

H S 2

sulfurous sulfupuffed

150°) (5)


144

MAILLARD REACTIONS

(b) Temperature as a v a r i a b l e The e x p e r i m e n t s r e p e a t e d a t 1 0 0 , 1 4 0 , and 220 ( ± 2 ) ° f o r up t o 3 0 , 7 , respectively.

were and 1^

min,


(c) Humidity as a v a r i a b l e H e n c e f o r t h , to save t i m e , the number o f amino a c i d s i n v e s t i g a t e d u a s c u t f r o m 21 t o 6 : c y s , i l e , l y s , s e r , t h r , and t y r , g i v i n g a s e l e c t i o n o f interesting aromas, as u e l l as of s t r u c t u r e s . The g l u c o s e - a m i n o a c i d m i x t u r e s u e r e c o n d i t i o n e d i n d e s i c c a t o r s o v e r one o f 5 a p p r o p r i a t e s a t u r a t e d s o l u t i o n s o r s o l i d P 2 O 5 » n o m i n a l l y a t 98-Oji r . h . H e a t i n g u a s f o r up t o 5 min a t 1 4 0 ± 2 ° . (d) Sugar as a v a r i a b l e The s i x amino a c i d s u e r e h e a t e d i n d i v i d u a l l y u i t h each o f the s u g a r s , f r u c t o s e , g a l a c t o s e , m a l t o s e , r i b o s e , s u c r o s e , and x y l o s e ^ and u i t h a s c o r b i c a c i d . H e a t i n g u a s f o r up t o 5 min a t 1 4 0 ± 2 · Because o f the h i g h r e a c t i v i t y o f the tuo p e n t o s e s , t h e i r m i x t u r e s uere a l s o heated f o r up t o 30 min a t 1 0 0 ± 2 ° . Three-component systems (a) A n i t r o g e n s o u r c e , asn or P y r a z i n e s have been r e c o g n i z e d f o r some y e a r s a s i m p o r t a n t o d o r a n t s , and t h e a v a i l a b i l i t y o f a d d i t i o n a l n i t r o g e n u a s e x p e c t e d t o promote t h e i r f o r m a t i o n . B o t h a s n and g i n uhen h e a t e d a l o n e p r o d u c e ammonia, so 1:1:1 m o l . mixtures uere h e a t e d , each s e r v i n g as n i t r o g e n source i n t u r n .

gin

(b) A s p a r a g i n e u i t h c h a n g e o f s u g a r At t h i s s t a g e , the e f f e c t o f a s n on t h e l y s m i x t u r e s c o n s i d e r e d most i n t e r e s t i n g had a l r e a d y been i n v e s t i g a t e d . E i g h t other tuo-component s y s t e m s e x h i b i t d i s t i n c t and i n t e r e s t i n g aromas ( s e e T a b l e II), and t h e y u e r e nou h e a t e d i n p r e s e n c e o f an e q u i m o l a r amount o f asn. A number o f r e l a t e d s y s t e m s u a s a l s o h e a t e d . (c) C e l l u l o s e M i x t u r e s o f h a l f q u a n t i t i e s o f the s i x 1:1 g l u c o s e : a m i n o a c i d m i x t u r e s u i t h , i n t u r n , 0 , 1, 3 , and 10 50-mg p o r t i o n s o f c e l l u l o s e u e r e h e a t e d a t 1 4 0 Î 2 ° , a s u e r e a feu related systems. (d) S o l u b l e s t a r c h Four m i x t u r e s , p a r a l l e l l i n g c o n t a i n i n g c e l l u l o s e , uere heated at 1 4 0 ± 2 ° .

those

(e) P o l y m e r i z a t i o n - b l o c k i n g components The a l d o l c o n d e n s a t i o n i s an i m p o r t a n t r e a c t i o n i n t h e M a i l l a r d n e t u o r k (see Figure 2). Not a l l t h e r e a c t i o n s c a n o c c u r i n a l l c a s e s . E q u i l i b r i u m 1 c a n n o t o c c u r u h e r e t h e c a r b o n y l compound l a c k s - h y d r o g e n a t o m s , i . e . , i t b e l o n g s t o u h a t ue d e s i g n a t e Group 1 ( F i g u r e 3 ) . Vinylogues of - h y d r o g e n s may u e l l need t o be c o n s i d e r e d . In g e n e r a l , ^ - e l i m i n a t i o n n e x t l e a d s t o t h e t< , ^ - u n s a t u r a t e d a l d e h y d e by R e a c t i o n 3 . T h i s , the f i r s t " i r r e v e r s i b l e " s t e p , i s not p o s s i b l e uhere the a l d o l l a c k s 3


LANE AND NURSTEN

Odors Produced

in Maillard

Systems


TABLE I I T'jJQ-COMPQNENT SYSTEMS GIVING DISTINCT AND INTERESTING AROMAS

Amino a c i d

cys

Sugar

Temperature

ribose

100

Aroma

roast

beef

cys

ascorbic

acid

140

chicken

ile

ascorbic

acid

14C

celery

ile

glucose

100

celery

l y s HC1

glucose

140

bread

ser

glucose

100

thr

ascorbic

acid

140

chocolate beef

extrac

meaty tyr tyr

glucose ascorbic

acid

100

chocolate

140

chocolate


MAILLARD REACTIONS


146

? ft _CH=C-O 2

g*

R€HC=0

R CHJ-C=0

R

r

u

nucleophile Χ

4

v

θ

R,CH -C electrophile 2

Γ R H R R CH C-C-C=0 ι ι HO R, 2

2

o

2

aldol

β CL ? R,CH Ç=Ç-C=0

ι R,CH=C-CH-C=0

2

R

R R|

2

R,

2

unconjugated enal

conjugated enal Figure 2.

A Idol condensation.


9.

LANE AND NURSTEN

Odors Produced in Maillard Systems

147

s(-hydrogens. Such a l d o l s are formed from n u c l 8 o p h i l i c a l d e hydes having only one c< -hydrogen, uhich u/e designate Group 2 (Figure 4 ) . These a l d o l s may dehydrate by the l e s s favored Reaction 4, g i v i n g the Ρ , V - u n s a t u r a t e d aldehyde, provided the e l e c t r o p h i l i c aldehyde d i d not belong to Group 1· Thus, the a l d o l route w i l l be blocked, or p a r t i a l l y blocked, i f the only a v a i l a b l e aldehydes have fewer than two

The Variety of Odors Produced in Maillard Model Systems and How

Recommend Documents