2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 1 Maillard-type reactions in food - Perspectives and constraints - 9 th International Symposium on the Maillard Reaction, Munich, September 1–5, 2007 Imre Blank Nestlé Product Technology Centre, Orbe, Switzerland
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2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 1
Maillard-type reactions in food
- Perspectives and constraints -
9th International Symposium on the Maillard Reaction,
Munich, September 1–5, 2007
Imre Blank
Nestlé Product Technology Centre, Orbe, Switzerland
2
Definition of the “Maillard reaction”
The “Maillard reaction” is a special case of the amino-carbonyl reactions of reducing sugars and amino acids or derivatives thereof
→ Amine assisted carbohydrate degradation
Goal: Better control of the Maillard reaction cascade
☺ Aroma
☺ Taste
☺ Colour
☺ Antioxidants
☺ Health benefits
☺ Texture
� Nutritional value loss
� Shelf-life issues
� Toxic compounds
∆T
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 3
(Hodge, 1953)
The Maillardreaction cascade
�Amino-carbonyl reaction
�Dehydration
�Enolisation
�Decarboxylation
�Cyclisation
�Hydrolysis
�Oxidation
�Reduction
�Retro-aldol reaction
�Radical reaction
�Disproportionation
�Canizzaro reaction
�Retro-Claisen reaction
�Acyloin reaction
�Baeyer-Villiger rearrangement
�Benzilic acid rearrangement
�and others …
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 4
OH
OH
NH
O
COOHOH
OH
O
NH
O
COOHOH
OH2
OH
O
OH OH
CH2OH
OH
O
OH O
CH3OH
O
O
OH OH
CH3
NH2
COOHOH
2
OH
OH
OH
N
OH
OHCOOH
OH
OH
OH
NH
OH
OHCOOH
OH
OH
OH
NH
O
OHCOOH
O
OH
OH
NH
OH
OHCOOH
OH2OH
2
O
OH
OH
OH
OH
OHNH
2COOH
I
OH
OH
OH
NOH CH
2
CO2
OH
OH
OH
NH2
OH
OH2
CH2
O
OH2
OH
O
OH
OH
OH
NH
COOH
CH2
N
N
COOH
CH2
COOH
e-
OH2
CH2
N
N
COOH
CH2
COOH
+.
OH
OH
NH
+
OH
COOHOH
OH
OH
O
O
OH
O CHOOH
H+
H+
OH2
OH2
NH2
COOH
OH2
NH2
COOH
OH
OH
N
O
OH
OHCOOHO
OH OH
OH
COOHNOH
O
OH OH
OH
CH2
N
O
OH OH
OH
NH2
OH
OH
O
O
OH
OH
IX
X
XI
O2/Me2+
OH2
CO2 OH
2,
OH2
CH2
O
(Davidek et al., 2002)
Means of control
• Composition
• Concentration
• pH
• Catalyst
• Heat load (t, T)
• Redox state
• React. medium
• Physical state
• Structure
• Molecular
organisation
• Moisture
• Water activity
• …(pH > 6)
(pH < 6)
Oxidation
Decarboxylation
Dehydration 2,3-Enolisation
1,2-Enolisation
Retro-aldol
OH
OH
OH
NH
OH
COOHOH
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 5
12 Symptoms of the Maillard reactionA highly complex system
• Lowering of pH
• Increasing reducing power
• Decreasing solubility
• Chelation of metals
• Production of fluorescence
• Production of colour and discoloration
• Production of flavour and off-flavour
• Production of water
• Production of carbon dioxide
(H.E. Nursten)
• Loss of vitamin C activity
• Loss of biological value of protein
• Production of toxicity
Chemistry
Physico-chemistry
Biochemistry
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 6
Structural and functional characterization of Pronyl-lysine, a novel protein modification in bread crust melanoidins showing in vitro antioxidative and
phase I/II enzyme modulating activity.
Journal of Agricultural and Food Chemistry (2002), 50, 6997-7006.
mol%) from polyphenols under oxidative conditions.
(Rizzi, 2006)
Y = amino acid residue, R = alkyl group; [O] = molecular oxygen
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 37
Trapping of reactive Maillard intermediates by polyphenols
(Totlani & Peterson, 2006; Noda & Peterson, 2007)
Glc/Gly
1,2,3-THB
Me-Gallate
EGCG, ECG, 1,3,5-THB
Epicatechin
O
O
O
OH
OOH
OH
OH
OH
OH
OH
O
OOH
OH
OH
OH
OH
Epicatechin
O
O
(Electrophilic aromaticsubstitution reaction,
hydroxyalkylation)
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 38
Polyphenols interfere in the Maillard reaction
• Epicatechin: Quenching of sugar fragmentation products (pressure cooking)
Trapping agent of 3-deoxy-2-hexosulose (roast conditions)
• Phenolic chemistry alters the mechanisms of the Maillard reaction
→ Need for a better understanding of Maillard chemistry in processed food
Co
nc
en
tra
tio
n (
µµ µµg
/mm
ol
glu
co
se
)
16
12
4
8
0
N
N
OH
O
OO
���� Glc/Gly
���� Glc/Gly/EC
N
N
O
O
N
N
O
O
O
O
O
OH
NH
O
(Totlani & Peterson, 2005; 2007)
Maillard precursors
Modified composition
OOH
OH
OH
OH
OH
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 39
Trapping of key odorants (thiols) by polyphenols via oxidative coupling
(Müller & Hofmann, 2007)
The loss of 2-furfurylthiol during coffee storage is mainly due to the oxidative coupling
of the odorant to hydroxyhydroquinone (2), giving rise to the conjugates 9 and 10.
40
Loss of Nutritional Value: Lysine Blockage Loss of Nutritional Value: Lysine Blockage Loss of Nutritional Value: Lysine Blockage Loss of Nutritional Value: Lysine Blockage
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 41
Loss of lysine during storage of skim milk powder
Uptake of moisture
Threonine
Leucine
Valine
Isoleucine
Phenylalanine
Lysine
Methionine
Histidine
Arginine
Tryptophan
Am
ino
acid
s (
%)
Cystine
Storage (d)
(Henry & Kon, 1948)
Changes in content of essential amino
acids during storage
0
1
2
3
4
5
6
0 0.1 0.2 0.3 0.4 0.5 0.6
Water activity (aw)
Re
ac
tiv
e l
ys
ine
(g
/16
gN
)
0
5
10
15
20
25
30
35
40
Ly
sin
e b
loc
ka
ge
(%
)
Reactive Lys
Blocked Lys
0 %
0 %
0 – 2 %
0 – 2 %
5 – 10 %
5 – 10 %
20 – 50 %
Freeze-drying
Pasteurization
UHT sterilization
Spray-drying
Spray-dried formula
HTST sterilization
Roller-drying
Blocked lysineHeat process
(Finot & Hurrell, 1983)
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 42
-60
-40
-20
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90 100
Total solids [%]
Te
mp
era
ture
[°C
]
Milkpowder
Fresh milk
concentration
pasteurisation
drying
atomisation
homogenisation
after-drying
after-cooling
Manufacturing of milk powder
Tf
Ts
Solution (emulsion)
Lactose crystals and solution
Ice and solution
Glassy
state
Tg
(Vuataz, 2002)
43
ShelfShelfShelfShelf----life Issues: Browning of Milk Powderlife Issues: Browning of Milk Powderlife Issues: Browning of Milk Powderlife Issues: Browning of Milk Powder
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 44
Shelf-life issues:Browning of milk powder
Issue:
Browning of milk powder was extensively detected under hot climatic conditions
Spontaneous nucleation and crystal formation is possible above the Tg
in a certain range which depends on (T – Tg)
glassyVisco-
elasticTg
Heat orWater addition
Glass transition(reversible)
crystalline
Crystallisation(irreversible)
Mechanism: Recrystallisation of an amorphous powder
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 45
-60
-40
-20
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90 100
Total solids [%]
Te
mp
era
ture
[°C
]
Solution
(emulsion)
Ice and solution
Glassy
state
Ts
Tf
Tg
10 min.
1 h.
1 d.
Rubbery stateLactose crystals
and solution
Risk of lactose crystallisation during storage (water uptake)
(Vuataz, 2002)
visco-elastic region
T > Tg : spontaneous
nucleation (β-from)
glassy solid region
T < Tg : no risk
of crystallisation
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 46
Risk of heat
shocks in hot
countries
1 hour WM
20
30
40
50
60
70
80
90 91 92 93 94 95 96 97 98 99 100
Total Solids [%]
Te
mp
era
ture
[°C
]
10 min. 1 day Tg5 min.
1 w
eek 1
mon
th
Risk of lactose crystallisation during storage (heat shock)
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 47
Means of control: Adjust water content and/or limit heat shock
The temperature increases up to 65°C
for a short time (less than one day), due
to transport conditions or sun exposure
during unloading of containers.
Temperature 65°C
30°C
12 h
Strategy:- Adapt the norm of water content to the risk of heat shock (T and duration)
- Better control the final water content of the processed powder
state of lactose
amorphous
crystallineAfter a certain delay (some hours), the
lactose crystallization is initiated and
rapidly achieved (in the beta anhydrous
or the alpha monohydrate form).
water activity
0.20
0.55
The water previously adsorbed on the
amorphous lactose is released, inducing
a large water activity increase (closed
can situation).
Time
browning
white
brownThe resulting high Aw is responsible for
the high rate of Maillard reaction, even
if the temperature is reduced to the
previous value.
48
Process ContaminantsProcess ContaminantsProcess ContaminantsProcess Contaminants
Mitigation Concepts for AcrylamideMitigation Concepts for AcrylamideMitigation Concepts for AcrylamideMitigation Concepts for Acrylamide
2007-09-04 Nestle PTC Orbe / I. Blank / 9th Maillard Munich 49
Agronomic
- Sugars
- Asparagine
- Sugars
- Asparagine
Agronomic Recipe
recipe…….……..
- NH4HCO3
- pH
- Minor ingredients
- Dilution
- Rework
recipe…….……..
recipe…….……..
recipe…….……..
- NH4HCO3
- pH
- Minor ingredients
- Dilution
- Rework
Recipe Process
Fermentation
Thermal input
Pre-treatment
Fermentation
Thermal input-
-
-
-
- Pre-treatment
Final Preparation
- Color endpoint
- Texture/flavour
- Product
storage/shelf life/consumer prep.
- Color endpoint
- Texture/flavour
- Product
storage/shelf life/consumer prep.
Final Preparation
� Guidance to assist in reducing AA levels in food
� Not meant as a formal prescriptive manual
� « Live » document
Means of control: Options to achieve acrylamide mitigation