Mechanism Responsible for Warmed-Over Flavor in Cooked Meat

13 Mechanism

Downloaded by EAST CAROLINA UNIV on December 20, 2016 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch013

Flavor

Responsible

in Cooked

for

Warmed-Over

Meat

A. M. PEARSON and J. I. GRAY Michigan State University, Department of Food Science and Human Nutritio East Lansing, MI 48824

Studies using a model meat system have demonstrated that phospholipids are the primary contributors to warmed-over flavor (WOF) in cooked meat. Although phosphatidylcholine has little effect upon WOF, phosphatidylethanolamine plays an important role which is related to the propensity of its constituent polyunsaturated fatty acids to autoxidation. Both nitrite and EDTA inhibit WOF as does removal of heme pigments, which suggests that myoglobin may catalyze WOF development. However, purified myoglobin in the model system does not cause autoxidation. It has been demonstrated that WOF is catalyzed by the non-heme iron released from meat pigments during cooking. Evidence has indicated that overheating of meat protects against WOF by producing Maillard reaction products possessing antioxidant activity.

The term "warmed-over flavor" (WOF) was coined by Tims and Watts (]_) to describe the rapid development of oxidized flavor in cooked meat upon subsequent holding. The rancid or stale flavor becomes readily apparent within 48 h in contrast to the more slowly developing rancidity that becomes evident only after freezer storage for a period of months. Although WOF was first recognized as occurring in cooked meat, hence the name WOF, it also develops in raw meat that is ground and exposed to air (2, 3). With increased consumption of precooked convenience meat entrees, such as quick-frozen meat dishes and TV dinners, preventing the development of WOF has become of great economic importance (4). The present review will cover evidence on the mechanism involved in WOF development, with description of a model system that has been utilized to clarify some of the pathways. The role of meat pigments and various lipid components will be reviewed. Finally some procedures for inhibiting WOF in cooked 0097-6156/83/0215-0287$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.

288

MAILLARD REACTIONS

meats w i l l be d i s c u s s e d . A l t h o u g h an e a r l i e r r e v i e w c o v e r s some o f t h e s e p o i n t s ( 5 ) , c o n s i d e r a b l e new i n f o r m a t i o n i s now a v a i l a b l e and w i l l be p r e s e n t e d h e r e i n .


D e s c r i p t i o n o f Model Meat System Love and P e a r s o n (6) have d e s c r i b e d a model meat s y s t e m i n which b o v i n e m u s c l e was ground and e x t r a c t e d w i t h d i s t i l l e d , d e i o n i z e d water a t 4°C u n t i l i t was d e v o i d o f c o l o r , i n d i c a t i n g t h e removal o f a l l meat p i g m e n t s , i . e . , m y o g l o b i n and h e m o g l o b i n . O t h e r w a t e r - s o l u b l e components would a l s o be p a r t i a l l y o r c o m p l e t e l y e x t r a c t e d by t h i s p r o c e d u r e . T h e r e m a i n i n g e x t r a c t e d m u s c l e was t h e n used as a model s y s t e m t o which p u r i f i e d m y o g l o b i n , f e r r o u s i r o n and f e r r i c i r o n were added back t o a s c e r t a i n t h e i r r o l e i n WOF. E s s e n t i a l l y t h e same s y s t e m has s i n c e been used i n our l a b o r a t o r y t o s t u d y t h e r o l e o f p h o s p h o l i p i d s and o f t r i g l y c e r i d e s i n development o f WOF u s i n g b e e f and c h i c k e n dark and w h i t e meat (_7). F i g u r e 1 shows n o t o n l y how t h e system was p r e p a r e d f o r s t u d y i n g t h e e f f e c t o f a d d i n g back m y o g l o b i n but a l s o how c h l o r o f o r m - m e t h a n o l was u t i l i z e d t o e x t r a c t t h e t o t a l l i p i d s (8) and t h e n how t r i g l y c e r i d e s and p h o s p h o l i p i d s c o u l d be s e p a r a t e e ! by s i l i c i c a c i d column c h r o m a t o g r a p h y w i t h e l u t i o n by c h l o r o f o r m and methanol ( 9 ) . Mechanism

o f WOF

Development

R o l e o f M y o g l o b i n and Non-Heme I r o n . The model meat s y s t e m c o n t a i n i n g t h e i n d i g e n o u s l i p i d s was used t o o b t a i n t h e d a t a p r e s e n t e d i n T a b l e I . O x i d a t i o n was f o l l o w e d by 2 - t h i o b a r b i t u r i c a c i d (TBA) numbers o b t a i n e d u s i n g t h e d i s t i l l a t i o n p r o c e d u r e o f T a r l a d g i s e t a l . ( J O ) . The d a t a show t h e e f f e c t s o f d i f f e r e n t c o n c e n t r a t i o n s o f metmyoglobin (MetMb) and f e r r o u s i r o n ( F e ^ ) upon TBA numbers i n t h e model b e e f m u s c l e s y s t e m ( 6 ) . MetMb c o n c e n t r a t i o n had no e f f e c t upon a u t o x i d a t i o n , whereas F e ^ i n c r e a s e d o x i d a t i o n o f t h e model s y s t e m w i t h t h e e x t e n t b e i n g d i r e c t l y r e l a t e d t o t h e c o n c e n t r a t i o n . Thus, i t was shown t h a t MetMb does n o t c a t a l y z e o x i d a t i o n o f t h e model s y s t e m , but F e 2 c a u s e s r a p i d a u t o x i d a t i o n o f t h e r e s i d u a l l i p i d s . These r e s u l t s a r e i n agreement w i t h an e a r l i e r r e p o r t ( 3 ) , i n which both F e ^ and a s c o r b a t e were shown t o c a t a l y z e development o f WOF. Thus, i t has been c l e a r l y shown t h a t m y o g l o b i n i s n o t d i r e c t l y r e s p o n s i b l e f o r development o f WOF, a l t h o u g h t h i s c o n c e p t has been w i d e l y a c c e p t e d ( 1 1 - 1 4 ) . A s u b s e q u e n t s t u d y (j_5) u s i n g t h e model meat s y s t e m showed t h a t removal o f t h e heme pigments o r a d d i t i o n o f 156 ppm o f n i t r i t e s i g n i f i c a n t l y i n h i b i t e d l i p i d o x i d a t i o n i n cooked meat, which s u p p o r t s t h e e a r l i e r c o n c e p t t h a t m y o g l o b i n (Mb) i s i n v o l v e d i n WOF. However, i t s h o u l d be borne i n mind t h a t removal o f heme pigments by l e a c h i n g w i l l a l s o remove a number +

+

+

+

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

PEARSON AND GRAY

Warmed-Over

Flavor

289

in Meat


Fresh Raw Meat (Beef, chicken dark or white meat) Grinding

(3/16 in. plate)

Ground Meat Extraction of lipids (CHCI :MeOH) 3

Total Lipids

Protein Matrix (residue)

Separation on silicic acid column

Vacuum dried Muscle fibers

Chloroform elution

I

Triglycerides Figure 1.

Methanol elution

—ι

Phospholipids

Preparation of model meat system. (Reproduced from Ref. 7. Copyright 1979, American Chemical Society.)


290

MAILLARD REACTIONS +

of o t h e r compounds i n c l u d i n g F e 2 . By u s i n g t h e scheme shown i n F i g u r e 2, Igene e t a l . (15) d e m o n s t r a t e d t h a t t h e l e v e l o f free F e g r e a t l y i n c r e a s e d " d " u r i n g c o o k i n g , and a c c e l e r a t e d 2 +

T a b l e I . E f f e c t s o f V a r i o u s C o n c e n t r a t i o n s of MetMb and F e on TBA Numbers o f Beef M u s c l e R e s i d u e

2 +

0

Fe2+

MetMb


Cone., mg/g

TBA n o .

Cone, ppm

b

TBA n o .

b

1.0 0 1.4 0 1.5 1.0 1.4 1.0 3.6 2.0 1.4 2.5 4.1 1.4 3.0 5.0 5.4 4.0 1.4 10.0 T h e r e a c t a n t s were m i x e d , h e a t e d , and s t o r e d f o r 48 h a t 4 b e f o r e m e a s u r i n g t h e TBA v a l u e s . T B A numbers = mg o f m a l o n a l d e h y d e p r o d u c e d p e r 1000 g o f meat. Taken f r o m Love and Pearson ( 6 ) . d

o C

b

l i p i d o x i d a t i o n i n cooked meat. T h i s i n d i c a t e s t h a t Mb s e r v e s as a s o u r c e o f F e , b e i n g r e a d i l y b r o k e n down d u r i n g t h e c o o k i n g p r o c e s s and c a t a l y z i n g a u t o x i d a t i o n . The d a t a showing t h e s e e f f e c t s a r e summarized i n T a b l e I I . 2 +

T a b l e I I . R o l e o f Heme and Non-heme I r o n on Development o f TBA Numbers i n Cooked B e e f . > a

Experimental

b

Mean TBA no.

treatment

5.00

r e s i d u e + t o t a l raw meat pigment r e s i d u e + t o t a l raw meat pigment ( c h e l a t e d ) r e s i d u e + t o t a l cooked f r e e meat pigment r e s i d u e + t o t a l cooked f r e e meat pigment ( c h e l a t e d ) residue + h^Oz-treated t o t a l meat pigment residue + h ^ - t r e a t e d pigment ( c h e l a t e d )

1.55 4.35 1.46 6.02 1.54

m e a t

a

E a c h e x p e r i m e n t a l t r e a t m e n t used 100 g o f b e e f r e s i d u e i n a d d i t i o n t o 50 mL o f t h e c o n c e n t r a t e d e x t r a c t . E D T A was used t o c h e l a t e t h e i n o r g a n i c o r f r e e i r o n a t a c o n c e n t r a t i o n o f 2%. Taken f r o m Igene e t al_. ( 1 5 ) . b



Extract Untreated

Extract Untreated

ι

Cooked Extract Treated with EDTA

1

Extract Untreated

Extract Treated with EDTA

Treated with 3 0 %

(concentrated by freeze-drying)

Extract

Extract

Figure 2. Preparation and design of experiment to compare the effect of heme and non-heme iron on the development of warmed-over flavor. (Reproduced with permission from Ref. 16.)

Extract Treated with EDTA

Uncooked extract

(through 3/8 and 3/16 inch plates)

Extracted with deionized H 2 O

2.0 kg Ground Beef ι


292

MAILLARD REACTIONS

I t i s i n t e r e s t i n g t o a l s o n o t e t h a t t r e a t m e n t w i t h H2O2 d e s t r o y s even more o f t h e heme pigments t h a n h e a t i n g , r e s u l t i n g i n s t i l l g r e a t e r o x i d a t i o n o f t h e meat s y s t e m ( T a b l e I I I ) . On the o t h e r hand, a d d i t i o n o f 2% EDTA m a r k e d l y r e d u c e d a u t o x i d a t i o n as shown by much lower TBA numbers. T a b l e I I I . C o n c e n t r a t i o n s o f T o t a l I r o n , Heme I r o n , and F r e e Non-heme Iron i n T r e a t e d and U n t r e a t e d Meat Pigment E x t r a c t Amount o f f r e e Fe , yg/g o f meat


2 +

Experimental

treatment

t o t a l i r o n i n f r e s h meat pigment e x t r a c t non-heme i r o n i n f r e s h meat pigment e x t r a c t heme i r o n i n f r e s h meat pigment e x t r a c t t o t a l i r o n i n cooked meat pigment f i l t r a t e f r e e non-heme i r o n i n cooked pigment f i l t r a t e t o t a l i r o n i n H202~"treated a t pigment extract f r e e i r o n i n H 2 0 2 ~ t r e a t e d meat pigment extract (chelated ) m e

20.64 1.80 18.84 5.51 4.18 13.59 12.33

8

Chelated

by a d d i n g 2% EDTA.

Taken f r o m Igene e t a l . (lj>).

R e s u l t s d e m o n s t r a t e t h a t Mb p e r se i s n o t t h e c a t a l y s t o f l i p i d o x i d a t i o n i n cooked meat. However, c o o k i n g d e s t r o y s p a r t o f t h e Mb, r e l e a s i n g F e which t h e n c a t a l y z e s t h e d e v e l o p m e n t o f WOF. A l t h o u g h t h e r o l e o f g r i n d i n g i n development o f WOF was not s t u d i e d , i t seems l i k e l y t h a t i t a l s o r e l e a s e s F e . I t has r e c e n t l y been shown t h a t s o l u b i l i z a t i o n o f i r o n f r o m g r i n d i n g equipment c a n i n c r e a s e t h e f r e e i r o n c o n t e n t o f f i s h m e a l , w h i c h c o u l d a l s o be a f a c t o r i n a u t o x i d a t i o n o f f r e s h ground meat (j_6). 2 +

2 +

R o l e o f P h o s p h o l i p i d s and T r i g l y c e r i d e s Circumstantial e v i d e n c e has s u g g e s t e d t h a t p h o s p h o l i p i d s a r e t h e m a j o r c o n t r i b u t o r s t o WOF, w i t h t h e c o r r e l a t i o n c o e f f i c i e n t s between TBA numbers and p h o s p h o l i p i d l e v e l s b e i n g h i g h e r than t h o s e f o r TBA numbers and t o t a l l i p i d s {]]_). 0 a d d i n g p h o s p h o l i p i d s , t r i g l y c e r i d e s , and t o t a l l i p i d s back t o a model meat s y s t e m , i t was v e r i f i e d t h a t p h o s p h o l i p i d s were t h e major c o n t r i b u t o r s t o WOF ( 7 ) . T h i s c o n c l u s i o n i s s u p p o r t e d by t h e d a t a g i v e n i n T a b l e IV, which d e m o n s t r a t e t h a t t h e same p r i n c i p l e s a r e i n v o l v e d i n d e v e l o p m e n t o f WOF i n b e e f and i n b o t h c h i c k e n d a r k and l i g h t meat. The d a t a i n t h e same t a b l e a l s o show a r e l a t i o n s h i p between s e n s o r y s c o r e s f o r WOF and TBA numbers. A l t h o u g h t h e a d d i t i o n o f t r i g l y c e r i d e s r e s u l t e d i n some i n c r e a s e i n TBA numbers, t h e e f f e c t was always c o n s i d e r a b l y lower t h a n n


13.

PEARSON AND GRAY

Warmed-Over

293

Flavor in Meat

T a b l e IV. TBA Numbers and S e n s o r y S c o r e s f o r Cooked B e e f , C h i c k e n Dark Meat and White Meat Model S y s t e m s > Downloaded by EAST CAROLINA UNIV on December 20, 2016 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch013

a

Composition o f treatments

Meat type beef

chicken dark meat

chicken white meat

a b

C

Mean s e n s o r y scores

Mean TBA no.

0

2.69 3.84 2.64 3.75

b

0.8% p h o s p h o l i p i d s 9.2% t r i g l y c e r i d e s 10% t o t a l l i p i d s control

5.76 1.88 6.81 1.16


8.48 6.30 >


b

a b a

11.74C

5.78

a

5.03 2.99 5.53 2.18

b a b a

b a b

a

b

a

a

b

2.97 3.65 > 3.25 3.88 > a

b

a

a

2.80 3.35 3.09 4.02

b

a a a b

T h e r e were f o u r r e p l i c a t e s f o r each t r e a t m e n t . T a s t e p a n e l s c o r e were f r o m 1-5, w i t h 1 v e r y p r o n o u n c e d WOF and 5 no WOF. A11 numbers i n same column w i t h i n a meat t y p e f o l l o w e d by t h e same s u p e r s c r i p t a r e n o t s i g n i f i c a n t a t t h e 5% l e v e l . Taken f r o m Igene and Pearson ( 7 ) .


MAILLARD REACTIONS


294

t h a t o f t h e p h o s p h o l i p i d s . The a d d i t i v e e f f e c t o f t r i g l y c e r i d e s was, however, g r e a t e r i n c h i c k e n dark meat than f o r c h i c k e n w h i t e meat o r b e e f . T h i s i s p r o b a b l y due t o t h e g r e a t e r d e g r e e o f u n s a t u r a t i o n i n t h e t r i g l y c e r i d e s from c h i c k e n dark meat. T a b l e V p r e s e n t s i n f o r m a t i o n on t h e r e l a t i v e e f f e c t s o f a d d i n g back p h o s p h a t i d y l c h o l i n e ( P C ) , phosphatidylethanolamine ( P E ) , and t o t a l b l o o d serum p h o s p h o l i p i d s (TP) t o t h e model meat s y s t e m . N i t r i t e was a l s o added but w i l l be d i s c u s s e d l a t e r h e r e i n . The a d d i t i o n o f both PE and TP i n c r e a s e d TBA numbers, w i t h t h e e f f e c t o f PE b e i n g t h e g r e a t e s t . S e n s o r y s c o r e s a l s o i n d i c a t e d t h a t o x i d a t i o n o f PE, TP, and PC c o n t r i b u t e d t o WOF, w i t h PE a g a i n h a v i n g t h e g r e a t e s t e f f e c t . T a b l e V. TBA Numbers and S e n s o r y S c o r e s f o r Cooked Meat Model Systems C o n t a i n i n g Added PC, PE, Serum P h o s p h o l i p i d s , o r Nitrite > a

b

Experimental

treatment

model model model model model moael model model

only + nitrite + PC + PC + n i t r i t e + PE + PE + n i t r i t e + TP + TP + n i t r i t e

d b

system system system system system system system system

Mean TBA no. 0.36 0.26 0.34 0.29 0.81 0.36 0.62 0.34

+ + + + + + + +

Mean s e n s o r y score

b

0.07 0.06 0.03 > 0.07 0.13 0.07 0.12 0.05 > a

a

b

a

d

b

c

a

b

3.33 4.11 3.36 4.52 2.64 3.61 3.29 4.04

+ + + + + + + +

0.42 0.44 0.51 0.27 0.58 0.23 0.49 0.43

a b a

> » >

b c b

c a

b d b

> >

b c

E a c h t r e a t m e n t was r e p l i c a t e d f o u r t i m e s . A s i g n i f i c a n t P1,000 ppm), however, a s c o r b i c a c i d r e t a r d s o x i d a t i o n ( 3 ) . A l t h o u g h t h e mechanism o f r e t a r d a t i o n i s not known, i t F a s been s u g g e s t e d t h a t h i g h l e v e l s o f a s c o r b a t e s may u p s e t the b a l a n c e between


296

MAILLARD REACTIONS 3 +

Fe2+ and F e o r e l s e c o u l d have i t s e f f e c t by a c t i n g as an oxygen s c a v e n g e r ( 5 ) . Tims and Watts (]_) showed t h a t a c o m b i n a t i o n o f a s c o r b a t e s and p h o s p h a t e s a c t e d s y n e r g i s t i c a l l y t o r e t a r d d e v e l o p m e n t o f r a n c i d i t y . S a t o and H e g a r t y (3) v e r i f i e d the a n t i o x i d a n t a c t i v i t y o f t h e c o m b i n a t i o n and s u g g e s t e d t h a t a s c o r b i c a c i d a c t s by k e e p i n g p a r t o f t h e i r o n i n t h e F e s t a t e . I t has been shown t h a t a s c o r b i c a c i d and p h o s p h a t e s a c t s y n e r g i s t i c a l l y i n p r e v e n t i n g o x i d a t i o n o f c u r e d meat ( 2 3 ) , and p r o b a b l y h e l p i n e x p l a i n i n g the v i r t u a l a b s e n c e o f WOF i n c u r e d m e a t s . Downloaded by EAST CAROLINA UNIV on December 20, 2016 | http://pubs.acs.org Publication Date: April 29, 1983 | doi: 10.1021/bk-1983-0215.ch013

2 +

R o l e o f NaCI The a c t i v i t y o f NaCl i n i n i t i a t i n g c o l o r and f l a v o r changes i n meat i s w e l l known but p o o r l y u n d e r s t o o d . T h e e f f e c t i s f u r t h e r c o m p l i c a t e d by t h e f a c t t h a t NaCl i s both a p r o o x i d a n t and an a n t i o x i d a n t , d e p e n d i n g upon the c o n c e n t r a t i o n d i s s o l v e d ( 2 4 ) . Lea (25) has d i s c u s s e d t h e f a c t t h a t s a l t may be a p r o o x i d a n t i n some c a s e s and e i t h e r have no e f f e c t or be an a n t i o x i d a n t i n o t h e r f o o d s . Watts (26) c o n c l u d e d t h a t s a l t may have a n t i o x i d a n t a c t i v i t y i n d i l u t e s o l u t i o n s but on c r y s t a l l i z a t i o n has a p r o o x i d a n t e f f e c t . On t h e o t h e r hand, Mabrouk and Dugan (24) found t h a t s a l t i n h i b i t e d a u t o x i d a t i o n i n aqueous e m u l s i o n s o T H n e t h y l l i n o l e a t e , i t s e f f e c t i v e n e s s as an antioxidant being d i r e c t l y associated with i n c r e a s i n g c o n c e n t r a t i o n s . They s u g g e s t e d t h a t d i s s o l v e d oxygen may be e l i m i n a t e d f r o m t h e s y s t e m as the NaCl c o n c e n t r a t i o n i s increased. Some o f t h e s t u d i e s on s a l t a r e , no d o u b t , c o m p l i c a t e d by the f a c t t h a t s a l t may c o n t a i n m e t a l c o n t a m i n a n t s , which c o u l d s e r v e as c a t a l y s t s o f l i p i d o x i d a t i o n . N e v e r t h e l e s s , r a n c i d i t y may s t i l l d e v e l o p i n the f a t o f d r y c u r e d hams, even though s a l t w i t h a low m e t a l c o n t e n t i s used ( 2 7 ) . The use o f an a n t i o x i d a n t i n c o m b i n a t i o n w i t h such s a l t , however, d i d i n h i b i t r a n c i d i t y and improve f l a v o r s c o r e s . F u r t h e r work t o c l a r i f y the r o l e o f s a l t i n l i p i d o x i d a t i o n i s needed b e f o r e i t s mechanism i s f u l l y u n d e r s t o o d . Role of N i t r i t e S a t o and H e g a r t y (3) r e p o r t e d t h a t 2000 ppm o f n i t r i t e c o m p l e t e l y e l i m i n a t e d WOF, w h i l e as l i t t l e as 50 ppm g r e a t l y i n h i b i t e d i t s d e v e l o p m e n t . B a i l e y and Swain (28) f u r t h e r c o n f i r m e d the e f f e c t i v e n e s s o f n i t r i t e i n p r e v e n t i n g o x i d a t i o n o f f r e s h meat s t o r e d under r e f r i g e r a t i o n and v e r i f i e d i t s r o l e i n p r e v e n t i n g WOF. A c o n c e n t r a t i o n o f 156 ppm o f n i t r i t e has been shown t o i n h i b i t WOF d e v e l o p m e n t i n cooked meat, w i t h a t w o f o l d r e d u c t i o n o f TBA v a l u e s f o r beef and c h i c k e n and a f i v e f o l d r e d u c t i o n f o r pork ( 2 9 ) . T a b l e V a l s o d e m o n s t r a t e s t h a t n i t r i t e i n h i b i t s WOF d e v e l o p m e n t . U n d o u b t e d l y t h e s e r e s u l t s e x p l a i n t h e h i g h e r f l a v o r s c o r e s f o r n i t r i t e as compared t o N a C l - c o n t a i n i n g c u r e d pork ( 3 0 ) . The mechanism by which n i t r i t e p r e v e n t s o r i n h i b i t s WOF has been s u g g e s t e d t o be r e l a t e d t o s t a b i l i z a t i o n o f the l i p i d s i n


13.

PEARSON AND GRAY

Warmed-Over

Flavor in Meat

297

the membrane (3, 5 ) , which are n o r m a l l y d i s r u p t e d and exposed t o oxygen by c o o k i n g o r g r i n d i n g . Z i p s e r e t a i . (32) p r o p o s e d t h a t n i t r i t e forms a s t a b l e complex w i t h t h e i r o n p o r p h y r i n s o f h e a t d e n a t u r e d meat, thus i n h i b i t i n g WOF. Kanner (32) has d e m o n s t r a t e d t h a t S - n i t r o s o c y s t e i n e i s a p o t e n t a n t i o x i d a n t and has s u g g e s t e d t h a t i t may be g e n e r a t e d i n the n i t r i t e c u r i n g o f meat. Thus, S - n i t r o s o c y s t e i n e c o u l d a l s o s e r v e as an i n h i b i t o r o f WOF i n c u r e d meat. S i n c e non-heme i r o n has been shown t o be the m a j o r l i p i d p r o o x i d a n t i n u n c u r e d , heated meat systems ( 3 , 6, 2 § ) > i t seems more p r o b a b l e t h a t n i t r i t e s t a b i l i z e s the heme p i g m e n t s s o t h a t t h e y do not r e l e a s e F e and thus c a t a l y z e d e v e l o p m e n t o f WOF. The i n h i b i t i o n o f WOF b y EDTA l e n d s f u r t h e r c r e d e n c e t o t h i s t h e o r y , which as y e t i s u n p r o v e n .


2 +

Role of M a i l l a r d Reaction Products C e r t a i n products o f the M a i l l a r d r e a c t i o n a r e known t o have a n t i o x i d a n t p r o p e r t i e s and a r e p r o d u c e d d u r i n g r e t o r t i n g o f meat. Z i p s e r and Watts (33) f i r s t d e s c r i b e d the development of"an a n t i o x i d a t i v e e f f e c t i n o v e r c o o k e d meat and s u g g e s t e d t h a t d i l u t e d s l u r r i e s c o u l d be used t o p r o t e c t n o r m a l l y cooked meats f r o m o x i d a t i o n . S a t o e t a l . (34) d e m o n s t r a t e d t h a t r e t o r t e d meat, i n d e e d , p o s s e s s e d s t r o n g a n t i o x i d a n t a c t i v i t y a g a i n s t d e v e l o p m e n t o f WOF. They then d e m o n s t r a t e d t h a t t h e m a t e r i a l r e t a i n e d b y d i a l y s i s o f e x t r a c t s o f the r e t o r t e d meat had no a n t i o x i d a n t a c t i v i t y but t h a t the d i f f u s a t e p o s s e s s e d s t r o n g i n h i b i t o r y a c t i v i t y a g a i n s t WOfL. This" s u g g e s t e d t h a t the s u b s t a n c e s r e s p o n s i b l e f o r inhibiti«*g WOF i n r e t o r t e d meat are w a t e r s o l u b l e and o f low m o l e c u l a r w e i g h t . Huang and Greene (.35) c o n f i r m e d t h e s e f i n d i n g s and s u g g e s t e d t h a t a t e m p e r a t u r e o f about 90°C i s r e q u i r e d t o p r o d u c e the browning compounds r e s p o n s i b l e f o r t h e a n t i o x i d a n t a c t i v i t y iri cooked meat. They f u r t h e r showed t h a t t h e r e was a r e l a t i o n s h i p between a n t i o x i d a n t a c t i v i t y and d e v e l o p m e n t o f t h e brown c o l o r , which was accompanied b y an increase in fluorescence. P o r t e r (3j5) has reviewed the r o l e o f M a i l l a r d r e a c t i o n p r o d u c t s as a n t i o x i d a n t s i n f o o d s y s t e m s , p o i n t i n g out t h e importance o f high temperatures (~100°C) to t h e i r development i n c o n t r a s t t o lower t e m p e r a t u r e s (~70°C), which a c c e l e r a t e d e v e l o p m e n t o f WOF. E i c h n e r (37) has shown t h a t browning i n t e r m e d i a t e s -- p r i m a r i l y Amaïïôri r e a r r a n g e m e n t p r o d u c t s — have s t r o n g a n t i o x i d a n t a c t i v i t y even though t h e y a r e c o l o r l e s s . The mechanism by which t h e s e r e d u c t o n e and r e d u c t o n e - 1 i k e compounds i n h i b i t a u t o x i d a t i o n seems t o b y decomposing h y d r o p e r o x i d e s and i n a c t i v a t i o n o f f r e e r a d i c a l s (.37). S a t o and H e r r i n g (38) have r e p o r t e d t h a t r e d u c t i c a c i d and m a l t o l , which are browning p r o d u c t s , p o s s e s s s t r o n g a n t i o x i d a n t a c t i v i t y a g a i n s t WOF. Ascorbic acid, a related r e d u c t o n e , has been r e p o r t e d t o a c c e l e r a t e WOF a t c o n c e n t r a t i o n s o f 100 ppm o r l e s s but t o i n h i b i t the r e a c t i o n a t l e v e l s o f 1,000 ppm o r o v e r ( 3 ) . L i n g n e r t and E r i k s s o n (39) have


298

MAILLARD REACTIONS


demonstrated that M a i l l a r d r e a c t i o n products i n h i b i t o x i d a t i o n in emulsion-type sausages. The s t u d i e s r e v i e w e d d e m o n s t r a t e t h a t browning p r o d u c t s p r o d u c e d on r e t o r t i n g o f meat i n h i b i t d e v e l o p m e n t o f WOF, s o t h a t canned meat p r o d u c t s a r e not s u b j e c t t o t h i s f l a v o r d e f e c t . The f l a v o r o f canned meat i s l e s s d e s i r a b l e , however, than t h a t o f f r e s h l y cooked meat. N e v e r t h e l e s s , t h e s t r o n g i n h i b i t o r y a c t i o n o f the 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 g a i n s t WOF s u g g e s t s t h a t t h e y c o u l d be u s e f u l i n p r e v e n t i n g d e v e l o p m e n t o f WOF, so f u r t h e r r e s e a r c h i n t h i s a r e a c o u l d be f r u i t f u l . Role of Other A n t i o x i d a n t s A g r e a t d e a l has been w r i t t e n about the p r i m a r y a n t i o x i d a n t s , which may be used t o i n h i b i t d e v e l o p m e n t o f WOF. P o r t e r (36) has r e v i e w e d t h e s e compounds, t h e i r s t r u c t u r e s , and p r o b a b l e modes o f a c t i o n so t h e y w i l l not be d i s c u s s e d . The d i s c u s s i o n w i l l f o c u s on the o t h e r n a t u r a l a n t i o x i d a n t s t h a t may be u s e f u l i n c o n t r o l l i n g WOF d e v e l o p m e n t . S a t o e t a i . (34) d e m o n s t r a t e d t h a t a v a r i e t y o f common meat a d d i t i v e s , i n c l u d i n g cottonseed f l o u r , nonfat dry milk, sprayd r i e d whey, wheat germ, and t e x t u r e d soy f l o u r , i n h i b i t e d WOF i n the meat s y s t e m . These p r o d u c t s may have e x e r t e d t h e i r i n h i b i t o r y e f f e c t on WOF t h r o u g h t h e M a i l l a r d r e a c t i o n , s i n c e most o f them c o n t a i n some r e d u c i n g s u g a r s . P r a t t (40) r e p o r t e d s o y b e a n s and soy p r o t e i n c o n c e n t r a t e had an i n h i b i t o r y e f f e c t upon d e v e l o p m e n t o f WOF and was a b l e t o d e m o n s t r a t e t h a t t h e a c t i v e components a r e w a t e r s o l u b l e . F r a c t i o n a t i o n and a n a l y s i s o f the w a t e r - s o l u b l e f r a c t i o n showed the a n t i o x i d a n t a c t i v i t y was due t o t h e p r e s e n c e o f i s o f l a v o n e s and h y d r o x y l a t e d c i n n a m i c a c i d s ( 4 0 ) . T h i s c o n f i r m s e a r l i e r work showing t h a t the flavonoTcfs present i n p l a n t e x t r a c t s i n h i b i t o x i d a t i o n i n s l i c e d r o a s t b e e f (42). The a d d i t i o n o f smoke t o meat a l s o i m p a r t s a n t i o x i d a n t p r o p e r t i e s ( 4 2 ) . T h i s has a l s o been shown on a p p l i c a t i o n o f smoke t o f a t t y f i s h e s ( 4 3 ) . P o r t e r (36) has r e v i e w e d the a n t i o x i d a n t p r o p e r t i e s o f smoke and c o n c l u d e d t h a t a number o f p h e n o l i c compounds a r e r e s p o n s i b l e . S e v e r a l o f t h e s e p h e n o l i c components, i n c l u d i n g p h e n o l , g u a i a c o l and c a t e c h o l , are not o n l y p o t e n t a n t i o x i d a n t s but a l s o have a n t i b i o t i c a c t i v i t y . These components would a l s o s e r v e as i n h i b i t o r s o f WOF, but some o f t h e components o f wood smoke are known c a r c i n o g e n s (36, 4 2 ) . Summary The use o f model meat systems has been shown t o be h e l p f u l i n e l u c i d a t i n g the r o l e o f d i f f e r e n t compounds i n d e v e l o p m e n t o f WOF. R e s u l t s o f t h e s e s t u d i e s have shown t h a t t h e m a j o r c a t a l y s t o f WOF i s Fe2+, which i s r e l e a s e d f r o m t h e heme p i g m e n t s by h e a t i n g , and p r e s u m a b l y by g r i n d i n g . T h e p h o s p h o l i p i d s are the major l i p i d s i n v o l v e d i n development of WOF, i n c o n t r a s t t o o x i d a t i o n d u r i n g f r o z e n s t o r a g e , where the


13.

Pearson and gray

Warmed-Over Flavor in Meat

299


triglycerides are mainly involved. The role of phosphates, nitrite, salt, ascorbate, other additives, and of Maillard reaction products are discussed in light of their role as possible inhibitors of WOF. These active inhibitors of WOF could play an important role in protecting pre-cooked meat entrees against WOF. Literature Cited 1. Tims, M.J.; Watts, B.M. Food Technol. 1958, 12, 240-243. 2. Greene, B.E. J. Food Sci. 1969, 34, 110-113. 3. Sato, K.; Hegarty, G.R. J. Food Sci. 1971, 36, 1098-1102. 4. Love, J.D.; Pearson, A.M. J . Am. Oil Chem. Soc. 1971, 48, 547-549. 5. Pearson, A.M.; Love, J.D.; Shorland, F.B. Adv. Food Res. 1977, 34, 1-74. 6. Love, J.D.; Pearson, A.M. J . Food Sci. 1974, 22, 1032-1034. 7. Igene, J.O.; Pearson, A.M. J. Food Sci. 1979, 44, 1285-1290. 8. Folch, J.; Lees, M.; Stanley, G.H.S. J . Biol. Chem. 1957, 226, 497-509. 9. Choudhury, R.B.R.; Arnold, L.K. J. Am. Oil Chem. Soc. 1960, 37, 87-88. 10. Tarladgis, B.G.; Watts, B.M.; Younathan, M.T.; Dugan, L.R. J. Am. Oil Chem. Soc. 1960, 37, 44-48. 11. Tappel, A.L. "Symposium on Foods: Lipids and Their Oxidation," Schultz, H.W.; Day, E.A.; Sinnhuber, R.O., Eds.; Academic Press; New York, 1962; pp. 122-138. 12. Watts, B.M. "Symposium on Foods: Lipids and Their Oxidation," Schultz, H.W.; Day, E.A.; Sinnhuber, R.O., Eds.; Academic Press; New York, 1962; pp. 202-214. 13. Wills, E.D. Biochem. J. 1966, 99, 667-676. 14. Liu, H.P.; Watts, B.M. J. Food Sci. 1970, 35, 596-598. 15. Igene, J.O.; King, J.A.; Pearson, A.M.; Gray, J . I . J . Agric. Food Chem. 1979, 27, 838-842. 16. Soevik, T.; Opstvedt, J.; Braekan, O.R. J. Sci. Food Agric. 1981, 32, 1063-1068. 17. Wilson, B.R.; Pearson, A.M.; Shorland, F.B. J . Agric. Food Chem. 1976, 24, 7-11. 18. Shorland, F.B.; Igene, J.O.; Pearson, A.M.; Thomas, J.W.; McGuffey, R.K.; Aldridge, A.E. J . Agric. Food Chem. 1981, 28, 863-871. 19. Igene, J.O.; Pearson, A.M.; Merkel, R.A.; Coleman, T.H. Anim. Sci. 1979, 49, 701-707. 20. Igene, J.O.; Pearson, A.M.; Dugan, L.R. J r . ; Price, J.F. Food Chem. 1980, 5, 263-276. 21. Igene, J.O.; Pearson, A.M.; Gray, J . I . Food Chem. 1981, 7, 289-303. 22. Watts, B.M. J. Am. Oil Chem. Soc. 1950, 27, 48-51. 23. Chang, I.; Watts, B.M. Food Technol. 1943, 3, 332-336. 24. Mabrouk, A.F.; Dugan, L.R., Jr. J . Am. Oil Chem. Soc. 1960, 37, 486-490.


300 25. 26. 27. 28. 29.


30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43.

maillard reactions Lea, C.H. "Rancidity in Edible Fats;" Chemical Publishing Co.: New York, 1939. Watts, B.M. Adv. Food Res. 1954, 5, 1-52. Olson, D.G.; Rust, R.E. J . Food Sci. 1973, 38, 251-253. Bailey, M.E.; Swain, J.W. Proc. Meat Ind. Res. Conf. 1973, pp. 29-46. Fooladi, M.H.; Pearson, A.M.; Coleman, T.H.; Merkel, R.A. Food Chem. 1979, 3, 283-292. Cho, I.C.; Bratzler, L . J . J . Food Sci. 1970, 35, 668-670. Zipser, M.W.; Kwon, T.W.; Watts, B.M. J . Agric. Food Chem. 1964, 12, 105-109. Kanner, J . J . Am. Oil Chem. Soc. 1979, 56, 74-76. Zipser, M.W.; Watts, B.M. J. Food Sci. 1961, 15, 445-447. Sato, K.; Hegarty, G.R.; Herring, H.K. J. Food Sci. 1973, 38, 398-403. Huang, W.H.; Greene, B.E. J. Food Sci. 1978, 43, 1201-1203. Porter, W.L. "Autoxidation in Food and Biological Systems," Simic, M.G.; Karel, M., Eds.; Plenum Press: New York, 1980, pp. 295-365. Eichner, K. "Autoxidation in Food and Biological Systems," Simic, M.G.; Karel, M., Eds.; Plenum Press: New York, 1980, pp. 367-385. Sato, K.; Herring, H.K. Proc. Recip. Meat Conf. 1973, 26, 64-75. Lingnert, H.; Eriksson, C.E. "Maillard Reactions in Food," Ericksson, C., Ed.; Pergamon Press: Oxford, 1981, pp. 453-466. Pratt, D.E. J . Food Sci. 1972, 37, 322-323. Pratt, D.E.; Watts, B.M. J. Food Sci. 1964, 29, 27-33. Kramlich, W.E.; Pearson, A.M.; Tauber, F.W. "Processed Meats," Avi: Westport, CT; 1972; Chapt. 4. Erdman, A.M.; Watts, B.M.; Ellias, L . C . Food Technol. 1954, 8, 320-323.

Received October 13, 1982


Mechanism Responsible for Warmed-Over Flavor in Cooked Meat

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