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Understanding Maillard-type
reactions in food processing
Case study: Extrusion
Imre Blank
Nestlé PTC Orbe, Switzerland
Nancy, September 17, 2012
Goal: Better control of the Maillard reaction cascade
under food processing conditions
Food processing: Extrusion
Holistic approach
Food chemistry: Flavour formation
Targeted approach
11th International Congress on the Maillard reaction 2
O
OHO
CH3
CH3
Extrusion with direct expansion A multi unit operation process
Flour Mix (~10% H2O)
Water, Oil, ...
Steam
Expansion 10%
~15–20%
~5-10%
Moisture:
110–180°C
80–170 bars
Average residence time: 20–30 seconds
3 11th International Congress on the Maillard reaction
Extrusion is an integrated process in
which raw materials rich in starch and
protein are plastified and structure-
modified in a cylinder under pressure
and shear at elevated temperatures
followed by expansion of the die at
the end of the extruder.
Parameters affecting product quality
Extrusion
Heat load (T, t)
Screw speed, SME
Moisture
Number of barrels
Slurry vs. dry addition
…
Recipe
Ingredients
Specific precursors
Concentration, ratio
Catalyst
pH
…
4
Study the effect of extrusion parameters and recipe composition
on furaneol formation from rhamnose and lysine
Identify recipe and processing conditions during extrusion of rice
flour favouring the formation of caramel flavour while considering
physico-chemical properties of the final product
NH2 OH
O
NH2 O
OHO
CH3
CH3
+ Recipe & Process
parameters
11th International Congress on the Maillard reaction
Experimental design: Key product attributes are
affected by both recipe and extrusion parameters
Recipe parameters • pH
• Ratio Rha/Lys
• Phosphate
Extrusion parameters • Moisture levels
• Screw speed
• Temperature
• Residence time
• Slurry vs. dry
Mixing
Extrusion
Drying
Milling
Final product
Product characterisation
• Texture
• Crispness
• Colour
• Flavour
• Acrylamide
• Starch degradation
• Granulometry
• Viscosity
• Sensory
Fractional factorial design:
- 32 instead of 576 trials
- Determining all main effects and
two-factor interactions of 3 recipe
and 5 process parameters
Holistic product characterisation:
- Chemical, physical, sensorial
- Using 16 methods
500 400 300 Screw speed (rpm)
150 135 120 Temp. (°C)
0.134 0.035 PO4 (mol/kg)
23 20 17 Moisture (%)
Slurry Dry Addition
7 5 Barrel length
3:1 3:0 Rha:Lys
7.7 6.4 pH
SME
5
• Trained panel (14 panelists)
• Product – Extruded powder (85%)
– Sugar (15%)
• Reconstitution – 12.4g product
– 100mL milk at 70°C
• 32 Products evaluated vs. reference
• Identification of statistically relevant
trends
Parameters units Low Medium High
pH 6.4 7.7
Rha:Lys 3:0 3:1
Phosphate mol/kg 0.035 0.134
Moisture % 17 20 23
Screw speed rpm 300 400 500
T °C 120 135 150
length barrel short long
Addition dry slurry
Sensory assessment Reconstituted products from experimental design
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
tEasySwallow
aLump
tSmooth
Burnt
Nutty
aDark
Caramel
Toasted
Processy
Off
Overall
acid
WholeGrain
Mushroom
astringent
bitter
aftertaste
t1Thick
tThick
tFluffy
t1Wettability
tSemolina
Cooked
Milky
Rice
Vanilla
sweet
Range covered by A01-A32 (vs. REF)
Fla
vor
Textu
re &
Appeara
nce
Range of sensory attributes
Wide diversity of sensory perception
6 11th International Congress on the Maillard reaction
Colour generation
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
tEasySwallow aLump
tSmooth
Burnt Nutty
aDark
Caramel Toasted
Processy
Off Overall
acid WholeGrain Mushroom
astringent bitter
aftertaste
t1Thick tThick tFluffy
t1Wettability tSemolina
Cooked Milky Rice
Vanilla sweet
Range covered by A01-A32 (vs. REF)
Sensory
im
pact
Colour development Modulation of colour in product through recipe
Browning reactions
-6 -4 -2 0 2 4 6
pH 6 pH 7
Rha:Lys 3:0 Rha:Lys 3:1
Phosphate low Phosphate high
17% H2O 20% H2O 23% H2O
300rpm 400rpm 500rpm
120°C-Long 120°C 135°C 150°C
Dry Slurry
Colour (C)
** Lysine
* High pH
Key p
ara
mete
rs
Light Dark
pH 6
Rha/Lys 3:0
pH 7
Rha/Lys 3:1
7 11th International Congress on the Maillard reaction
Furaneol formation Free amino acids, moisture, T and phosphate are most critical
-6 -4 -2 0 2 4 6
pH 6.4pH 7.7
Rha:Lys 3:0Rha:Lys 3:1
Phosphate 0.035 mol/kgPhosphate 0.134 mol/kg
17% H2O20% H2O23% H2O
300 1/min400 1/min500 1/min
120 °C-Long120 °C135 °C150 °C
DrySlurry
Furaneol ext / mol% Furaneol dry / mol%
Conversion of rhamnose to furaneol
can be modulated through
1. changes of extrusion and/or
2. recipe parameters
8 11th International Congress on the Maillard reaction
O
O OH
Acrylamide Temperature is most critical
-75 -50 -25 0 25 50 75
pH 6.4
pH 7.7
Rha:Lys 3:0
Rha:Lys 3:1
Phosphate 0.035 mol/kg
Phosphate 0.134 mol/kg
17% H2O
20% H2O
23% H2O
300 1/min
400 1/min
500 1/min
120 °C-Long
120 °C
135 °C
150 °C
Dry
Slurry
Acrylamide
9 11th International Congress on the Maillard reaction
-6 -4 -2 0 2 4 6
pH 6.4pH 7.7
Rha:Lys 3:0Rha:Lys 3:1
Phosphate 0.035 mol/kgPhosphate 0.134 mol/kg
17% H2O20% H2O23% H2O
300 1/min400 1/min500 1/min
120 °C-Long120 °C135 °C150 °C
DrySlurry
Furaneol ext / mol% Furaneol dry / mol%
O
O OH
NH2
O
Mitigation
options
Structure and Texture Moisture and temperature are most critical
-1500 -1000 -500 0 500 1000 1500
pH 6.4pH 7.7
Rha:Lys 3:0Rha:Lys 3:1
Phosphate 0.035 mol/kgPhosphate 0.134 mol/kg
17% H2O20% H2O23% H2O
300 1/min400 1/min500 1/min
120 °C-Long120 °C135 °C150 °C
DrySlurry
Visco5min / mPas ViscoMax / mPas
10 11th International Congress on the Maillard reaction
Structure = f (SME)
Texture = f (SME)
-15 -10 -5 0 5 10 15
Cell walls / µm
Semolina Crispy Low High
Long Chain
DP~50
Short Chain
DP~25
0
20
40
60
80
100
0 50 100
SME
Sta
rch
(%
)
Amylopectin
High MW
intermediate
Low MW
intermediate
Starch degradation MW = f (SME)
11
Rice Flour
Moisture % 8-13
Starch %d.b. 88-92
Total fibers %d.b. 0.3-1
Proteins %d.b. 6-9
Fat %d.b. 0.5-1
Ash %d.b. 0.3-1
0
1000
2000
3000
4000
5000
6000
0 2 4 6 8 10 12
Vis
co
sit
y (
mP
a.s
)
Time (min)
SM
E 9
2
SM
E 3
5
Viscosity = f (MW) High H2O
High T
Low H2O
Low T
SME 92 SME 35
Effect of recipe/extrusion parameters Options for flavour optimization
pH 6pH 7
Rha:Lys 3:0
Rha:Lys 3:1
Phosphate low
Phosphate high
17% H2O
20% H2O
23% H2O
300rpm
400rpm
500rpm
120°C-Long
120°C135°C
150°C
Dry
Slurry
-4
-3
-2
-1
0
1
2
3
4
-20 -15 -10 -5 0 5 10 15 20
SME-measured
%F
ura
ne
ol-
dry
Temperature affects both
furaneol and SME
150°C → more viscous
Free amino acid and
phosphate affect
furaneol, but not SME
Moisture affects both
furaneol and SME
17% → less viscous
12 11th International Congress on the Maillard reaction
Next step:
Full factorial design in a
smaller space for final
product optimisation
Goal: Better control of the Maillard reaction cascade
under food process conditions
Food processing: Extrusion
Holistic approach
Food chemistry: Flavour formation
Targeted approach - CAMOLA
11th International Congress on the Maillard reaction 13
0.15 mmol [12C6]-glucose
0.15 mmol [13C6]-glucose
0.1 mmol glycine or proline
1 mL 0.5 M phosphate buffer pH 5, 7 or 9
Heating:
135°C/20min
O
OHO
CH3
CH3
Glucose + Proline Furaneol
Major pathways
• Aqueous systems: Intact skeleton at pH 5; recombination of C3+C3 at pH 7 and 9
100%
26%
14%
0%
52% 56%
0%
12%
18%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Aqueous system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
11th International Congress on the Maillard reaction
100% 96%
84%
0% 0% 4%
0% 4%
12%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Dry system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
Major pathways
• Aqueous systems: Intact skeleton at pH 5; recombination of C3+C3 at pH 7 and 9
• Dry systems: Intact skeleton (>84%)
Major pathways
• Aqueous systems: Intact skeleton at pH 5; recombination of C3+C3 at pH 7 and 9
• Dry systems: Intact skeleton (>84%)
• Rice: Intact skeleton (>80%), some recombination of sugar fragments at pH 7 and 9
98%
85% 80%
0%
6% 10%
0%
8% 10%
0% 0% 0% 2% 1% 0% 0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Rice Model
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly Inherent prec. Rice
Glucose + Glycine Furaneol
100%
70%
60%
0%
18%
26%
0%
8% 8%
0% 0% 4%
0% 4% 2%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Aqueous system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
100% 98% 96%
0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 2% 4%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Dry system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
Major pathways
• Aqueous systems: Intact skeleton at pH 5; less relevant with increasing pH
• Dry systems: Intact skeleton independent of pH
• Rice models: Intact skeleton independent of pH, only little by sugar fragmentation
94% 94% 92%
0% 0% 2% 0% 0% 4%
0% 0% 0% 0% 4% 2%
6% 2% 0%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Rice Model
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly Inherent prec. Rice
11th International Congress on the Maillard reaction
Glucose + Glycine Furaneol (pH 7)
• Aqueous system: Intact skeleton (major) and C3+C3 recombination (minor)
• Dry system: Intact skeleton (almost exclusive)
• Rice model: Intact skeleton (almost exclusive)
• Extrusion: Intact skeleton (almost exclusive), about 8% from inherent precursors
100%
70%
60%
0%
18%
26%
0%
8% 8%
0% 0% 4%
0% 4% 2%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Aqueous system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
100% 98% 96%
0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 2% 4%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Dry system
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly
94% 94% 92%
0% 0% 2% 0% 0% 4%
0% 0% 0% 0% 4% 2%
6% 2% 0%
0%
25%
50%
75%
100%
pH 5 pH 7 pH 9
Rice Model
Intact skeleton C3+C3
C2+C4 C5 +C1Glc
C5 +C1Gly Inherent prec. Rice
92%
0% 0% 0% 0%
8%
0%
25%
50%
75%
100%
pH 7
Extruded system
Intact skeleton
Inherent prec. Rice
11th International Congress on the Maillard reaction
CH2OH
OH
OH
OH
OH,OH
OH
OH
OH
O
O
CH3
CH3
O
OH
OH
O
CH3
CH3
O
CH3
OH
O
N COOH
H
O
CH3
OH
OH
CH3
O
- H2O
N, H2O, CO2
HDMF
O
O
CH3
OH
O
OH
OH
O
OH
OH
O
CH3
CH3
O
OH
OH
O
CH3
O
CH3
OH
OH
CH3
O
- H2O
CH3
O
CH3
OH
O
N COOH
H
N, H2O, CO2
HDMF
Roasting: 0%
Solution: 60%
Acetylformoin
(Schieberle et al., 2003; Schieberle, 2005)
Roasting: 100%
Solution: 40%
Formation of Furaneol
Model systems:
• Furaneol is mainly formed from intact glucose skeleton
• Except in aqueous systems at weak basic pH where fragmentation is dominating
Food system & extrusion:
• Furaneol is almost exclusively formed from the intact glucose skeleton
Conclusions & Outlook
• Flavour generation can be modulated and optimised with respect to other food
product attributes (colour, texture, …)
• The holistic approach based on experimental design and a global product
characterisation allows rapid optimisation of recipe and extrusion parameters
• This requires an integrated approach of various scientific and engineering
disciplines
18 11th International Congress on the Maillard reaction
• Better understanding of chemical reactions taking place and their interactions
during food processing (targeted experiments, CAMOLA, …)
• Better understanding of material properties and transformation in Maillard
systems
• Better integration of food physics & engineering (e.g. physical state, Tg, heat
load) in our Maillard world to achieve better control
Ensuring product quality by extrusion
Future focus
Hélène Chanvrier PTC Orbe Structure, texture
Tomas Davidek PTC Orbe Flavour, acrylamide
Daniel Festring PTC Orbe Flavour, processing
Valérie Leloup PTC Orbe Macromolecular chemistry
Werner Pfaller PTC Orbe Extrusion
Andreas Rytz NRC Lausanne Experimental design
Silke Illmann Univ. Karlsruhe Diploma work (Prof. H. Schuchmann)
Rosa Delgado Sanchez Univ. Sevilla PhD thesis (Prof. F. Hidalgo)
Lara S. Kirsch TU Munich Master thesis (Prof. T. Hofmann)
Thanks to…
… and to you for your kind attention ! 19 11th International Congress on the Maillard reaction