Imre Blank

Nestec Ltd., Nestlé Research Centre, P.O. Box 44,Vers-chez-les-Blanc, 1000-Lausanne 26, Switzerland

31st FNK Europe Conference on Potato Processing- Recent Developments in the Maillard Reaction -

• Conceptual representation of the Maillard reaction

• Reactive intermediates

• Formation of flavour

• Formation of colour

• Analytical aspects

Recent developments in the Maillard reaction- Structure of the presentation -

• Conceptual representation of the Maillard reaction

• Reactive intermediates

• Formation of flavour

• Formation of colour

• Analytical aspects

A conceptual approach in the classificationof the Maillard reaction

Pathways of the Maillard reaction

AMADORI PRODUCT

Aldose sugar +Amino compound

Fission productsFurfural or HMF Reductones

Dehydroreductones

CO2

Aldols, N-free polymers

+ Amino acid

Strecker degradation

Aldimines, ketimines

MELANOIDINSWith or withoutamino compound

+ Aminocompound

ALDEHYDES

+ Aminocompound

- 2H + 2H

pH < 7- Amino compound- water

pH > 7

- Water

+ Aminocompound

N-substitutedglycosylamine

+

+ Aminocompound

EARLY

ADVANCED

Initial phase of the Maillard reaction

(Hodge, 1953;Isbell & Frush, 1958;Mauron, 1981)

Aldohexose Amino acid

Schiff base

Amadori compound(Aminoketose)

Aldosylamine

Advanced phase of the Maillard reaction- Degradation of Amadori compounds -

(Hodge, 1953; Anet, 1958; Mauron, 1981)

Amadori compound(Aminoketose)

3-Deoxy-2-hexosulose

1,2-Enolisation2,3-Enolisation

Aldohexose

Furans (HMF) Furanones (Furaneol) Melanoidins

1-Deoxy-2,3-hexodiulose Aminodiketose

Initial phase of the Maillard reaction

(Hodge, 1953; Mauron, 1981)

Generation of ‘primary fragmentation pools’from the components of the ‘parent pool’

(V. Yaylayan, Trends Food Sci. Technol., 8, 13, 1997)

Amadori and Heyn’s products

Amino acids Reducing sugars

{D}

{S}{A}

Primary fragmentation pools

Principal precursors

Composition of ‘primary fragmentation pools’

Amino acid fragmentation pool {A}:Amino acids, amines, carboxylic acids, amino acid-specific side-chain fragments (methylsulfide from methionine, styrene from phenylalanine)

Sugar fragmentation pool {S}:C1 fragments (formaldehyde, formic acid)C2 fragments (glyoxal, glycolaldehyde, acetic acid)C3 fragments (glyceraldehyde, pyruvaldehyde, hydroxyacetone, …)C4 fragments (tetroses, diacetyl, hydroxybutanone, …)C5 fragments (pentoses, pentuloses, deoxy derivatives, furanones, furans, ...)C6 fragments (pyranones, furans, glucosones, deoxyglucosones, …)

Amadori and Heyn’s fragmentation pool {D}:C3-C6 ARP/HRP derivatives

Genealogy of ‘self-interaction pools’ and‘secondary interaction pools’ from ‘primary

interaction pools’

(V. Yaylayan, Trends Food Sci. Technol., 8, 13, 1997)

Some examples for compounds formed in the‘interaction pools’

• Self-interaction pools: {S x S}, {A x A}, {D x D} e.g. early polymers, dimers, aldol condensation products

• Secondary interaction pools: {A x S}, {S x D}, {A x D} e.g. Strecker aldehydes, α-amino carbonyls {A x S}, e.g. di-sugar ARP/HRP {S x D}, e.g. maltoxazine and quinoxalinones {A x D},

• Multiple-interaction pools: e.g. late polymers

Some elementary processes occurring in the‘interaction pools’

• Aldol condensation: chain elongation simple carbonyls, α-hydroxy carbonyls

• Retro aldol reaction: chain-cleavage processes

• Reduction by formic acid: imine → amine, aldehyde → alcohol

• Redox reactions: disproportionation, cyclisation/decomposition

• Carbonyl group migration

• Other processes: β-elimination, cyclisation, dimerisation, polymerisation, ...

Conceptual representation of the Maillard reaction- The formation and interaction of ‘chemical pools’

-Polymers

Heterocycles Dimers

Other

(V. Yaylayan, Trends Food Sci. Technol., 8, 13, 1997)

Role of the Maillard reaction in food

Sensory propertiesDevelopment of appealing flavour and colourOff-flavour formation, undesired browning

Quality and safetyFood preservationLoss of nutritional value

Formation mechanism of the Amadori compoundDFG from glucose and glycine

(H+)

OH

OH

OHOH

O

OHO

OH

OH

HOHO O

OH

OH

HOHO NH

H2N COOHCOOH

NH COOH (H+)OH

OH

OH

HOHO NH COOH

(H+)

(Hodge, 1955; Isbell & Frush, 1958; Paulsen & Pflughaupt, 1980; Westphal & Kroh, 1985)

4C1-β-D-Glucose N-Glucosylglycine

2C5-β-DFG Eneaminol

Mechanism of the decompositionof Amadori compounds

(Hodge, 1953; Anet, 1964; Simon & Heubach, 1965)

H2C-NHR

C = O

HO-C-H

H-C-OH

H-C-OH

CH2OH

HC-NHR

C-OH

HO-C-H

H-C-OH

H2C-NHR

C-OH

C-OH

H-C-OH

HC=NHR

C-OH

C-H

H-C-OH

+

CH2C-OH

C = O

H-C-OH

HC = O

C = O

CH2H-C-OH

CH3C = O

C = O

H-C-OH

H2O- OH-

- H2NR

O

OHO

OOH

CHO

1,2-Eneaminol 3-Deoxy-2-hexosulose HMF

2,3-Enediol 1-Deoxy-2,3-hexodiulose Furaneol

DFG

Study on the Formation and Decompositionof Amadori Compounds in Maillard Model Systems

• Conceptual representation of the Maillard reaction

• Reactive intermediates

• Formation of flavour

• Formation of colour

• Analytical aspects

Pathways of the Maillard reaction(Hodge, 1953)

AMADORI PRODUCT

Aldose sugar +Amino compound

Fission productsFurfural or HMF Reductones

Dehydroreductones

CO2

Aldols, N-free polymers

+ Amino acid

Strecker degradation

Aldimines, ketimines

MELANOIDINSWith or withoutamino compound

+ Aminocompound

ALDEHYDES

+ Aminocompound

- 2H + 2H

pH < 7- Amino compound- water

pH > 7

- Water

+ Aminocompound

N-substitutedglycosylamine

+

+ Aminocompound

EARLY

ADVANCED

Role of N-(1-deoxy-D-fructos-1-yl)-glycine (DFG)in the nonenzymatic browning reaction

• Formation of DFG from glucose and glycine• Thermal-induced decomposition of DFG• Formation of flavour (Furaneol)

OH

OH

OH

OH

Hexose

N

OH

OH

OH

O

OH

OH

Amadori compound

GlycineOHOH

O

O

O OH

3(2H)-FuranoneGluose N-(1-Deoxy-D-fructos-1-yl)-glycine

(DFG)Furaneol

Occurrence:

Liver (hog) Borsook et al., 1955Apricot, peach (freeze-dried) Anet & Reynolds, 1957Molasses (sugar beet) Carruthers et al., 1963Soy sauce Hashiba, 1978Meat (roasted), tomato powder van den Ouweland, 1978Malt, beer Wittmann & Eichner, 1989Cocoa (roasted) Heinzler & Eichner, 1991

Concentration:

10-70 mg/kg (malt) Wittmann & Eichner, 198930-60 mg/kg (cocoa) Heinzler & Eichner, 1991

DFG is a stable intermediate formed during theMaillard reaction of glycine and glucose or mannose

Formation of the Amadori compound DFG1 M aqueous solution of glucose and glycine, pH= const., T= 90 °C

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 20 40 60 80 100 120Time ( min )

DFG

( m

ol )

pH 6pH 7

Initial phase of the Maillard reaction

Hodge, 1953;Isbell & Frush, 1958;Mauron, 1981

Aldohexose Amino acid

Schiff base

Amadori compound(Aminoketose)

Aldosylamine

Decomposition of the Amadori compound DFG1 M aqueous solution, no buffer, pH= const., T= 90 °C

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120Time ( min )

DFG

( m

ol )

pH 6pH 7

Advanced phase of the Maillard reaction- via the Amadori compound -

Hodge, 1953; Anet, 1958; Mauron, 1981

1-Deoxy-2,3-hexodiulose

Amadori compound(Aminoketose)

3-Deoxy-2-hexosulose

Aminodiketose

1,2-Enolisation2,3-Enolisation

Aldohexose

Furans (HMF) Furanones (Furaneol) Melanoidins

O

OHO

FuraneolConcentration: 1-10 mg/kgFlavour note: Caramel-like, sweetThreshold: 0.1 mg/L water ; 1 ng/L air

Furaneol contributes to the overall flavourof many thermally processed foods

Occurrence: Beef (boiled) Tonsbeek et al., 1968Coffee (roasted) Tressl et al., 1978Cocoa (roasted) Ziegleder, 1991Bread crust (wheat, rye) Schieberle, 1992Beef (roasted) Cerny & Grosch, 1992Sesame seeds (roasted) Schieberle, 1993Meat flavours (commercial) Blank et al., 1994French fries Wagner & Grosch, 1997

Formation of furaneol from the Amadori compound DFG1 M aqueous solutions, no buffer, pH= const., T= 90 °C

0

20

40

60

80

100

120

140

160

180

200

15 30 60 120Time ( min )

Fura

neol

( m

g / m

ol )

pH 6.0pH 7.0

Formation of furaneol from glucose and glycine1 M aqueous solutions, no buffer, pH= const., T= 90 °C

0

5

10

15

20

25

30

15 30 60 120Time ( min )

Fur

aneo

l ( m

g / m

ol )

pH 6.0pH 7.0

O

O OH

O

OH O

OHc

b

1-Deoxy2,3-hexodiulose

Acetylformoine

N

OH

OH

OH

O

OH

OOH

R

H

N-(1-Deoxy-D-fructose-1-yl)-glycine (DFG)

a

O

OH OH

OH

- Amino acid

H

O

O

OH

OH

OH O

OH

OH

O- H2O

- H2O

OHOOO

(Blank et al., 6th Maillard Symp. London, 1997)

Schematic formation of furaneol from the Amadoricompound DFG via acetylformoine

Summary

favoured at pH 7compared to pH 6

Maillard model systems:

• Composed of the Amadori compound DFG or its precursors glucose and glycine

• Heated in unbuffered aqueous solutions at 90 °C over 2 hours under pH control

Results:

• Formation of the Amadori compound DFG• Decomposition of DFG• Generation of Furaneol from DFG

(J. E. Hodge & B. E. Fisher,Meth. Carbohydr. Chem. 2, 99, 1963)

Glycine

OH

OH

OHOH

ONH

OHO

OH

OH

HOHO

Na2S2O5

Amberlite / H+

OH

OH

OHOH

ONH

COOH

COOH

H2N-CH2-COOHNa2S2O5 / H2O

Amberlite / H+�

�

4C1-β-D-Glucose DFG (β-pyranose, 2C5)

13C-DFG

Synthesis of N-(1-deoxy-D-fructos-1-yl)-glycine (DFG)and 13C-DFG used as labelled internal standard

Synthesis of 13C-labelled furaneol: internal standard forquantification by isotope dilution assay (IDA)

OBocBocO

OBocBocO

O

O

O

H

O

OHO

O

OOH

�

�

�

�

��

�

�

O O

1. LIDA2. 13CH3

13CHO

3. (t-BuOCO)2O, THF

KMnO4acetone/H2O/HOAc

Oxalic acid/H2O

(I. Blank et al., J. Agric. Food Chem. 45, 2642, 1997)

Quantification of furaneol by isotope dilution assayusing 13C2-furaneol as internal standard in GC-MS

100000

150000

10000

20000

30000

50000

8.00 10.00 11.00

Furaneol

13 C -2 FuraneolO

OHO

O

OOH

��

�

�

9.00

O

OHO

O

OOHm/z 128

m/z 130

Time (min)

(I. Blank et al., J. Agric. Food Chem. 45, 2642, 1997)