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BROWNING IN THERMALLY PROCESSED FOODS: THE MAILLARD REACTION. Food modifications during thermal treatment (1). Protein denaturation Physical changes (starch gelatinization, structural alterations of cell wall, depolymerization of dietary fibre ) Lipid oxidation - PowerPoint PPT Presentation
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BROWNING IN THERMALLY PROCESSED FOODS: THE MAILLARD
REACTION
Food modifications during thermal treatment (1)
• Protein denaturation• Physical changes (starch
gelatinization, structural alterations of cell wall, depolymerization of dietary fibre)
• Lipid oxidation• Degradation of some bioactive
components
Food modifications during thermal treatment (2)
• Reaction between different components generate new compounds.
• Proteins-sugar: Maillard reaction formation of Advanced Glycosilation End-products (AGEs)
• Lipid-protein: Advanced lipoxidation end products (ALEs)
The same chemistryThe reaction is in both cases (sugars or oxidised lipids) between a carbonyl moiety and an amino group
The same products
The final product of both reaction patways (AGEs and ALEs) are polymeric brown macromolecules
The Maillard Reaction in Foods
Produces aromas in heated foods
Responsible for colour formation (non-enzymatic browning)
Maillard products have antioxidant properties
•Can cause loss of nutrients
•Some products may be toxic
LATTE UHT
LATTE STERILIZZATO
BIRRA CHIARA
PASTA
PRODOTTI DA FORNO
BIRRA SCURACACAO
CARNE ARROSTITA
CAFFE’
Stadi iniziali
Stadi intermedi
Stadi avanzati
Tem
pera
tura
e te
mpo
di t
ratt
amen
to te
rmic
oD
iminuzione dell’attività dell’acqua
Louis-Camille Maillard(1878 - 1936)
Photographed in his laboratory
ca 19151912 – 1916: He published 8 papers on his
observations of colour changes on mixing amino acids
and sugars.
No one else took much interest in the reaction until 1950s
Maillard-Hodge Reaction?
John Hodge: 1914 -1996 • Chemist at USDA in Illinois (1941 – 1980)
• His proposed mechanism for the chemistry of non-enzymic browning is largely unchanged after 60 years.
Citations since 1970
Paper Citations
Hodge, J. E.Chemistry of browning reactions in model systems.J. Agric. Food Chem. 1953, 1: 928-943.
890
Maillard, L. C.Action des acides amines sur les sucres: formation des melanoidines par voie methodique.Compt. Rend. 1912, 154: 66-68.
634
Hodge Scheme
Hodge J E. Dehydrated foods: chemistry of browning reactions in model systems. J. Agric. Food Chem. 1:928-43, 1953.
First step: formation of Amadori product
RNH
HC
(HCOH)n
HC
CH2OH
O
GlicosilamminaN-sostituita
+H+
RNH
CH
(HCOH)n
HCOH
CH2OH
+
Catione dellabase di Schiff
-H+
RNH
CH
COH
(HCOH)n
CH2OH
Forma enolicadel PA
RNH
CH2
CO
(HCOH)n
CH2OH
1-ammino-1-deossi-2-chetoso (PRA)
PRODOTTO DIAMADORI
slow
fast
Formation of Carbonyl through Maillard Reaction
OH
OH
OH
OH
NH
R2,3-enolisation
OH
OH
OH
O
NH
R
OH
OH
OH
OH
NH
R
1,2-enolisation
Amadori compound
O
O
OH
OH
O
O
O
OHO
O
O
O
O
1-deoxyosone
RNH2 H2O
- H2O
H2O
OH
OHO
O
O CHO
3-deoxyosone
OH
OHOH
NH
R +
H2O
RNH2
H +
slow
fast
Strecker Degradation
Free amino acids with dicarbonyl compounds
R-CHO
Aldeide di Strecker
Flavour and Colour in the Maillard Reaction
H2O
rearrangement
NHROH
OOH
H
OH
OH
Amadori intermediate
carbonyl compounds
H2O RNH2
O
O
H
O
O
O CHOHO
O
OOH
O OH
OO CHO
O OH
O
amino acids
FLAVOUR COMPOUNDS
MELANOIDIN PIGMENTS
H
O
OH OH
OHOH
OH
R NH2+
reducing sugar aminocompound
Amino acid or
proteins
General scheme of MR browning
Amine AmmoniaPhospholipidsAmino acidsProteins
CarbonylAldehydesKetonesReducing sugarsPolysaccharidesOxidised lipids
Amino CarbonylInteraction
(Amadori product)HEAT
MelanoidinsBrown colour
AmidesAcrylamide
Furans, Pyrroles,Thiopenes, Thiazoles,Oxazoles, Imidazoles,Pyridines, Pyrazines
N
R
CHO
R
O
RN
HOO
O OH
CH3N
HO
OH
CH3
O
R
N
N+
H2N
N
NN
O
R
H
R
NN
NN
NN
O
O
O
O
O
O
O R'
R' R'
R'
R'
R
NN
NN
N
O
O
O
O
O R' R'
R'
R'
Protein A
Protein B
LysineN
NN
NN
NN
NN
N
O
O
O
O
O
O
O
O
O
O R'
R'
R'
R'
R' R'
H
H
H
H
H
H
H
H
H
H
Food “melanoproteins”
Pronyl-lysine
This compound is formed on the lateral
chain of Lysine residues
Pronyl-lysine has a high antioxidant activity
Possible toxicants
• Acrylamide
• Furan
• Heterocyclic amines
• 3-MPCD (Mono Chloro Propan Diol)
• 3-Methyl Imidazolone
Development of mitigation strategies to reduce their concentration
A network of many reactions giving thousands of products
Products formed depends on:
•Chemical nature of the reactants
•Time and temperature of heating
•Technological conditions
•Water activity, pH
Practice
Effects of reactants:
Sodium Carbonate (pH effects)
Protein and carbohydrates
Water activity (fibre addition)
Butter clarification
Control
Added with sodium bicarbonate
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