m. migliori – 13 marzo 2008 rheological modelling of food production: cereal goods massimo...
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M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Rheological modellingRheological modellingof food production:of food production:
Cereal goodsCereal goods
Massimo MiglioriMassimo MiglioriLaboratory of Rheology and Food EngineeringLaboratory of Rheology and Food Engineering
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Food Process: Technological viewFood Process: Technological view
Raw MaterialsRaw Materials•Technological specificationsTechnological specifications•Chemical compositionChemical composition•Mechanical characteristicsMechanical characteristics
Unit operationsUnit operations•MixingMixing•Concentration - DryingConcentration - Drying•BakingBaking•PackagingPackaging
Operating conditionsOperating conditions•PressurePressure•TemperaturesTemperatures•HumidityHumidity•Flow ratesFlow rates
ProductProduct•Quality controlQuality control•TextureTexture
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling viewModelling view
Raw MaterialsRaw Materials•Technological specificationsTechnological specifications•Chemical compositionChemical composition•Mechanical characteristicsMechanical characteristics
Unit operationsUnit operations•MixingMixing•Concentration - DryingConcentration - Drying•BakingBaking•PackagingPackaging
Operating conditionsOperating conditions•PressurePressure•TemperaturesTemperatures•HumidityHumidity•Flow ratesFlow rates
ProductProduct•Quality controlQuality control•TextureTexture
Transport phenomenaTransport phenomena•Momentum balanceMomentum balance•Energy BalanceEnergy Balance•Mass balanceMass balance
ThermodynamicThermodynamic•EquilibriaEquilibria
Boundary conditionsBoundary conditions•Mechanical powerMechanical power•Heat fluxesHeat fluxes•Air flow characteristicsAir flow characteristics•Residence timeResidence time Constitutive EquationsConstitutive Equations
•Rheological propertiesRheological properties•Kinetic equationKinetic equation
ResultsResults•Process – product interactionProcess – product interaction•Product development - designProduct development - design
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Rheology in food processRheology in food process
Different mechanical behaviour Different mechanical behaviour
Food system characteristicsFood system characteristicsMultiphase complex systems: emulsion, suspensionsMultiphase complex systems: emulsion, suspensions
Often aerated:Often aerated:
““Weakly” StructuredWeakly” Structured““Strongly “ StructuredStrongly “ Structured
ExtrusionExtrusion
PouringPouring
SheetingSheeting
LeaveningLeavening
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Dough characterisationDough characterisation
Equilibrium spectrumOscillatory regime
Linear visco-elastic region
Dough Structure
Large deformation1
Transient regime
Non linear visco-elastic region
Process properties Forming
Bubble expansion
Gas retention
11 Uthayakumaran et al., Rheol. Acta (2002), 41, 162-172 Uthayakumaran et al., Rheol. Acta (2002), 41, 162-172
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
Final remarksFinal remarks
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
RHEOLOGY IN BISCUIT MANUFACTURINGRHEOLOGY IN BISCUIT MANUFACTURING
Rheology development...Rheology development...
• Theoretical modelTheoretical model
• Oscillatory measurementsOscillatory measurements
• Creep / Step shear rate testCreep / Step shear rate test
• Strain / Stress relaxationStrain / Stress relaxation……Industrial application…Industrial application…
• Empirical testEmpirical test
• Uncontrolled flow fieldUncontrolled flow field
• Viscosity measurementViscosity measurement
……Why ?Why ?
• Lack of theoretical knowledge (Modelling)Lack of theoretical knowledge (Modelling)
• Time saving analysis needTime saving analysis need
• Materials / process conditions variabilityMaterials / process conditions variability
R&D Laboratories
Process / Product design
Process control
Optimisation
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
RICH TEA PRODUCTION PROCESSRICH TEA PRODUCTION PROCESS
Process operationsProcess operations
• MixingMixing
• SheetingSheeting
• BakingBaking
• PackagingPackaging
Dough characteristicsDough characteristics
• Developed doughDeveloped dough
• Mixing time Mixing time ~~ 10 min 10 min
• Final temperature 38 Final temperature 38 ~ 41 ~ 41 °C°C
Changes in dough may lead Changes in dough may lead to:to:
• Machine-ability issues Machine-ability issues
• Biscuit roundness variabilityBiscuit roundness variability
• Biscuit height variabilityBiscuit height variability
• Moisture issuesMoisture issues
• Colour out of controlColour out of control
Ingredient Range
% [w/ w]
Flour 59.9% - 60.8%
Water 9.7% - 8.3%
Sugar 16.7% - 17.0%
Fat 13.0% - 13.2%
Salt 0.6%
RecipeRecipe
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
ON LINE PRODUCTION MONITORINGON LINE PRODUCTION MONITORING
Dough Dough FeedFeed
To the To the ovenoven
CutterCutter
RollersRollersSampling Sampling pointpoint
Rheological testRheological test
• Stress relaxation out of linear Stress relaxation out of linear rangerange
• Sampling end of sheetingSampling end of sheeting
• Low total testing time (Low total testing time (~ 5 min)~ 5 min)
AdvantagesAdvantages
• Continuous production monitoring over Continuous production monitoring over 8 hr8 hr
• Fundamental measurementFundamental measurement
• Dough visco-elastic properties analysisDough visco-elastic properties analysis
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
STRESS RELAXATION TEST – SET UP AND ANALYSISSTRESS RELAXATION TEST – SET UP AND ANALYSIS
0,1
1
10
100
0,01 0,1 1 10 100
Time [s]
Ela
stic
Modulu
s G
[kPa]
0
0,05
0,1
0,15
0,2
Str
ain
[%
]
• Temperature 32°CTemperature 32°C
• Strain 15%Strain 15%
• Weak Gel data Weak Gel data treatmenttreatment22
• Time range 1 to 10 sTime range 1 to 10 s
ntStG
11 Gabriele et al., Rheol. Acta (2001), Gabriele et al., Rheol. Acta (2001), 40-240-2, , 120-127120-127
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
PRODUCTION AUDIT RESULTSPRODUCTION AUDIT RESULTS
4000
4200
4400
4600
4800
5000
10.30 12.30 14.30 16.30
Time [hh:mm]
S [
Pa s
-n]
0,340
0,345
0,350
0,355
0,360
0,365
0,370
n [
-]
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
LenghLenghtt
MODEL PARAMETERS INTERPRETATIONMODEL PARAMETERS INTERPRETATION
S S Network strenghtNetwork strenght
Mainly responsible for dough recovery after cutting Mainly responsible for dough recovery after cutting
Biscuit Biscuit roundnessroundness
NN Network extensionNetwork extension
Related to dough behaviour during bakingRelated to dough behaviour during baking
(gas retention ability)(gas retention ability)Biscuit heightBiscuit height
• Moisture contentMoisture content
• TextureTexture
ntStG
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
DOUGH NETWORK STRENGHT – BISCUIT LENGTHDOUGH NETWORK STRENGHT – BISCUIT LENGTH
• S S
• Biscuit Biscuit length length 4000
4200
4400
4600
4800
5000
10.00 12.00 14.00 16.00Time [hh:mm]
S [
Pa s
-n]
62
62,2
62,4
62,6
62,8
63
Bis
cuit
Length
[m
m]
Low S (Weak Dough)Low S (Weak Dough)
+ Good recovery + Good recovery capabilitycapability
- Machine-ability - Machine-ability IssuesIssues
High S (Tough High S (Tough Dough)Dough)
+ Good machine-+ Good machine-abilityability
- Roundness control- Roundness control
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
DOUGH NETWORK EXTENSION – BISCUIT HEIGHTDOUGH NETWORK EXTENSION – BISCUIT HEIGHT
0,335
0,340
0,345
0,350
0,355
0,360
10.00 12.00 14.00 16.00Time [hh:mm]
n [
-]
5,8
6
6,2
6,4
6,6
6,8
Bis
cuit
Heig
ht
[mm
]
• n n
• Biscuit Biscuit height height
High value:High value: Good gas retention ability Good gas retention ability (bulky biscuits risk)(bulky biscuits risk)
Low value:Low value: Poor rise during baking Poor rise during baking (flat biscuits risk)(flat biscuits risk)
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
S VARIABILITY DURING NORMAL PRODUCTIONS VARIABILITY DURING NORMAL PRODUCTION
p≥95%
Average Lower limit Upper limit
S [Pa s-n] 4585 4304 4866
3600
4100
4600
5100
5600
6/11 20/11 4/12 18/12 1/1 15/1 29/1 12/2 26/2 12/3 26/3 9/4 23/4
Date [dd/ mm]
S [
Pa s
-n]
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
0,320
0,330
0,340
0,350
0,360
0,370
0,380
6/11 20/11 4/12 18/12 1/1 15/1 29/1 12/2 26/2 12/3 26/3 9/4 23/4
Date [dd/ mm]
n [
-]
n VARIABILITY DURING NORMAL PRODUCTIONn VARIABILITY DURING NORMAL PRODUCTION
p≥95%
Average Lower limit Upper limit
n [-] 0.348 0.333 0.363
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
3500
4000
4500
5000
5500
6000
0.00 2.00 4.00
Time [hh:mm]
S [
Pa s
-n]
0,320
0,330
0,340
0,350
0,360
0,370
0,380
n [
-]
DOUGH RHEOLOGY DURING UNOPTIMISED DOUGH RHEOLOGY DURING UNOPTIMISED START-UPSTART-UP
Cold plant increases dough Cold plant increases dough toughness (low mixing toughness (low mixing temperatures)temperatures)
Machinability issuesMachinability issues
High waste levelHigh waste level
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
START-UP ANALYSIS AND ACTIONSSTART-UP ANALYSIS AND ACTIONS
Corrections may be Corrections may be introduced in introduced in
• Recipe Recipe
• Process conditionsProcess conditionsActionsActions
• Addition of SodiumMetaBisulphite (SMS) Addition of SodiumMetaBisulphite (SMS)
It Acts as dough conditioner breaking sulphuric It Acts as dough conditioner breaking sulphuric bridges bridges (Dough weaking)(Dough weaking)
• Mixing timeMixing time
Both to improve dough development and increase final Both to improve dough development and increase final dough temperature.dough temperature.
Plant warm-up is speeded upPlant warm-up is speeded up Modifications in start-Modifications in start-upup
Start-up SMS in water solution Mixing time
A +20% Standard
B +10% +50%
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
3600
4000
4400
4800
0.00 1.00 2.00
Time [hh:mm]
S [
Pa s
-n]
0,320
0,340
0,360
0,380
0,400
n [
-]
START-UP ASTART-UP AStart-up SMS in water solution Mixing time
A +20% Standard
B +10% +50%
Increase in SMSIncrease in SMS
Improves dough toughness control (S on target straight away)Improves dough toughness control (S on target straight away)
Decrease in network extension (n above the target)Decrease in network extension (n above the target)
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
3600
3800
4000
4200
4400
4600
4800
5000
0.00 1.00 2.00
Time [hh:mm]
S [
Pa s
-n]
0,320
0,340
0,360
0,380
0,400
n [
-]
START-UP BSTART-UP BStart-up SMS in water solution Mixing time
A +20% Standard
B +10% +50%
Increase in mixing time Increase in mixing time
Recover of network extension (n on target after 20 min)Recover of network extension (n on target after 20 min)
also as result of decreasing extra SMSalso as result of decreasing extra SMS
Overdeveloped dough (S below the target)Overdeveloped dough (S below the target)
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
4200
4400
4600
4800
5000
0.00 1.00 2.00 3.00 4.00
Time [hh:mm]
S [
Pa s
-n]
0,320
0,330
0,340
0,350
0,360
0,370
0,380
n [
-]
Start-up SMS in water solution Mixing time
A +20% Standard
B +10% +50% C +10% +25%
OPTIMISED START-UP CONDITIONSOPTIMISED START-UP CONDITIONS
Both parameters on target straight Both parameters on target straight away!away!
Start-up SMS in water solution Mixing time
A +20% Standard
B +10% +50% C +10% +25%
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
FINAL REMARKSFINAL REMARKS
• Application of stress relaxation test as “on site measurement”Application of stress relaxation test as “on site measurement”
• Data interpretation using theoretical modelData interpretation using theoretical model
• Physical meaning of parametersPhysical meaning of parameters
• Continuous process monitoring allows determination of optimal Continuous process monitoring allows determination of optimal rangerange
• Start-up optimisation based on structure/process relationship Start-up optimisation based on structure/process relationship knowledgeknowledge
IMPACT ON INDUSTRIAL BUSINESSIMPACT ON INDUSTRIAL BUSINESS
• Reduction of waste at the start-upReduction of waste at the start-up
• Rheological tool to control process conditionsRheological tool to control process conditions
• Support to process optimisationSupport to process optimisation
• Help in tackling usual raw material variability Help in tackling usual raw material variability
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
Strong networkStrong network
Weakly structured materialWeakly structured material
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
MACROSYSTEMMACROSYSTEM
Modelling approachModelling approach
MicrosystemMicrosystem (Heterogeneous) (Heterogeneous)Thermodynamic status (T, P, concentrations) from macrosystem balancesThermodynamic status (T, P, concentrations) from macrosystem balances
Multi phase – Generally one is gasMulti phase – Generally one is gas
Mass exchange among phasesMass exchange among phases
Thermodynamic equilibrium at interfacesThermodynamic equilibrium at interfaces
Momentum balance accounting visco-elasticityMomentum balance accounting visco-elasticity
Macrosystem (Homogeneus)Macrosystem (Homogeneus)Continuous mediumContinuous medium
Material properties accounting of multiphase system Material properties accounting of multiphase system
Effect of external boundary conditionsEffect of external boundary conditions
Mass and heat exchange in microsystem as sinkMass and heat exchange in microsystem as sink
Transport Phenomena hold in a pseudo-homogeneous system.Transport Phenomena hold in a pseudo-homogeneous system.
Heterogeneity is accounted in a MicrosystemHeterogeneity is accounted in a Microsystem
MICROSYSTEMMICROSYSTEM
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Heterogeneous system
Gas + Paste
SPONGYCLOSED Gas Cells
SPONGYCLOSED Gas Cells
CRUNCHYOPEN Gas CellsCRUNCHYOPEN Gas Cells
STABILISATIONSTABILISATION
COALESCENCECOALESCENCE
Rheological behaviour controls the gas cells evolutionRheological behaviour controls the gas cells evolution
BAKINGBAKINGBAKINGBAKING
Cereal product texture is controlled by void fraction and bubbles morphology Cereal product texture is controlled by void fraction and bubbles morphology
Texture of Cereal GoodsTexture of Cereal Goods
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
BAKING PROCESS - 1BAKING PROCESS - 1
Formulation Process
“wrong” profile
time
Product height “optimal
” profile
Structure development
Organoleptic properties
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
Strong networkStrong network
Weakly structured materialWeakly structured material
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
ObjectiveObjective
2
3
4
5
6
7
8
0 50 100 150 200 250 300
Bisc
uit h
eigh
t, m
m
Baking Time, s
Predict biscuit behaviourPredict biscuit behaviourRaiseRaise
Peak height - timePeak height - time
Collapse mechanismCollapse mechanism
Final biscuit heightFinal biscuit height
Moisture contentMoisture content
Main Modelling issues Main Modelling issues Predict changes in rheologyPredict changes in rheology
Account for process parameters:Account for process parameters:
Oven baking profilesOven baking profiles
Raising agent amountRaising agent amount
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Macrosystem - EquationsMacrosystem - EquationsHypothesisHypothesis
Cylindrycal systemCylindrycal system
Axial and radial symmetryAxial and radial symmetry
Every internal nods includes a microsystem of expanding bubblesEvery internal nods includes a microsystem of expanding bubbles
Biscuit growthBiscuit growth
Raising agents
Water evaporation
Internal diffusive mechanism for energy and mass transfer Internal diffusive mechanism for energy and mass transfer
ie
iiBPB S
zT
Kz
Tct B
PWbww
effw nRFzc
Dz
ct
141 2*
*
From microsystemFrom microsystem
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Thermodynamic equilibrium of two
phase multi-component system
Thermodynamic equilibrium of two
phase multi-component system
Mechanical equilibrium in biaxial extension of
an aerated system
Mechanical equilibrium in biaxial extension of
an aerated system
Growth stops as effect of coalescence modelGrowth stops as effect of coalescence model
Single bubble Single bubble modelmodel
RPG
rPR
Pinf
Closed MicrosystemClosed Microsystem2
3
4
5
6
7
8
0 50 100 150 200 250 300
Bisc
uit h
eigh
t, m
m
Baking Time, s
Gas - Liquid Gas - Liquid equilibrium equilibrium constitutive constitutive
equationequation(Water, R.A., Air, Dry
matter) iii xky
Paste Weak Gel Paste Weak Gel constitutive constitutive
equationequation
wxTtnww
R
t
wrr
xTtsxTtG
dtRtR
RtRtR
tRxTtGdrr
,,'
3
2
0
,,',,'
''
ln'
'',,'3
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Expansion: rheological dataExpansion: rheological data2
3
4
5
6
7
8
0 50 100 150 200 250 300
Bisc
uit h
eigh
t, m
m
Baking Time, s
0
0.1
0.2
0.3
0.4
0.5
1000
10000
100000
1000000
20 40 60 80 100
Tan
del
ta [
-]
G',
G"
[Pa]
Temperature [°C ]
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Coalescence implies the opening of the interacting bubbles.
This phenomenon may occur in different ways:
Coalescence implies the opening of the interacting bubbles.
This phenomenon may occur in different ways:
Thickness reaches locally a minimum value ...Thickness reaches locally a minimum value ...
DEFORMATION WORK REACHES A CRITICAL VALUEDEFORMATION WORK REACHES A CRITICAL VALUE
(RUPTURE POINT)(RUPTURE POINT)
DEFORMATION WORK REACHES A CRITICAL VALUEDEFORMATION WORK REACHES A CRITICAL VALUE
(RUPTURE POINT)(RUPTURE POINT)
…local stress reaches a critical value……local stress reaches a critical value…
In both casesIn both cases
Coalescence modelCoalescence model2
3
4
5
6
7
8
0 50 100 150 200 250 300
Bisc
uit h
eigh
t, m
m
Baking Time, s
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Rupture workRupture work
22 Charalambides et al, Rheol. acta (2002), 41, 532-540 Charalambides et al, Rheol. acta (2002), 41, 532-540
Under the hypothesis of affine deformation2
max
2 R0
h(t)
R(t)
h
R
Kinematic parameter: peak deformation
2cos
1
max20 R
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
ModelModel
Instantaneous strain power4
IIIIIIIIIIIIIIIIIIIIIIIIW
"""''
0dttCttIp
t
1 ntnSdt
tdGt
55Constitutive equation: “Weak Gel model”Constitutive equation: “Weak Gel model”
Elastic energyElastic energy(up to rupture point)
ln
1CIII
t
olndWdt
r
44 Williams JG, Stress Analysis of Polymers (1980), E. Horwood, Chichester Williams JG, Stress Analysis of Polymers (1980), E. Horwood, Chichester
55 Gabriele et al., Rheol. Acta (2001), 40-2, 120-127 Gabriele et al., Rheol. Acta (2001), 40-2, 120-127
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Device set-upDevice set-up
Laser beamSample
Air In
Heating systemHeating system**
• Integrated as sample holder Integrated as sample holder
• Surface termo-coupleSurface termo-couple
• PID ControllerPID Controller
**www. minco.comwww. minco.com
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Deformation workDeformation work
0
20
40
60
80
0 10 20 30 40Time [s]
Bubble
heig
ht
[mm
]
T= 30°CT= 40°CT= 50°C
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Open microsystemOpen microsystem
Coalesced bubbles act as a necklaceCoalesced bubbles act as a necklace
2
3
4
5
6
7
8
0 50 100 150 200 250 300
Bisc
uit h
eigh
t, m
m
Baking Time, s
Mass exchange in an “equivalent” channel open toward the ambientMass exchange in an “equivalent” channel open toward the ambient
A different mechanical equilibrium holds, based on A different mechanical equilibrium holds, based on elastic recoveryelastic recovery
Hencky Hencky StrainStrain
Hencky Hencky StrainStrain *2
1
c
c
RR
LN Kelvin Voigt Kelvin Voigt mechanical modelmechanical model
Kelvin Voigt Kelvin Voigt mechanical modelmechanical model
i
t
iieww
00
ie
iiBPB S
zT
Kz
Tct B
PWbww
effw nRFzc
Dz
ct
141 2*
*
From microsystemFrom microsystem
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Validation – Different Baking profilesValidation – Different Baking profilesHeight evolutionHeight evolution
2
4
6
8
10
0 50 100 150 200 250 300
Bisc
uit H
eigh
t [m
m]
Baking time [s]
Fast ProfileFast Profile
Normal ProfileNormal Profile
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Validation – Different Baking profilesValidation – Different Baking profilesWeight lossWeight loss
8
8.5
9
9.5
10
10.5
0 50 100 150 200 250 300
Bisc
uit W
heig
ht [g
]
Baking time [s]
Fast ProfileFast Profile
Normal ProfileNormal Profile
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Validation – Different RheologyValidation – Different RheologyChange in flour Change in flour
2
4
6
8
10
0 50 100 150 200 250 300
Bisc
uit H
eigh
t [m
m]
Baking time [s]
Fast ProfileFast Profile
Normal ProfileNormal Profile
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Sensitivity – Void fractionSensitivity – Void fraction
2
4
6
8
0 50 100 150 200 250
Bisc
uit H
eigh
t [m
m]
Baking time [s]
0.050.05
0.040.04
0.030.03
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
Modelling View of Food ProcessesModelling View of Food Processes
Start up optimisationStart up optimisation
Biscuit BakingBiscuit Baking
Strong networkStrong network
Weakly structured materialWeakly structured material
SummarySummary
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
BAKING PROCESS - 2BAKING PROCESS - 2
PSEUDO HOMOGENEOUS APPROACH
1. Bubble expansion (micro)
2. Bubble interaction (stabilisation)
3. Dough spreading
4. Macroscopic transport phenomena
t
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
2. BUBBLE STABILISATION - 12. BUBBLE STABILISATION - 1
Bubble Bubble ExpansionExpansion
Stabilisation by Stabilisation by Strain HardeningStrain Hardening
limφφ
limhhoror
h(t)h(t) void void fractionfraction
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
2. BUBBLE STABILISATION - 22. BUBBLE STABILISATION - 2
Cellular materialsCellular materials11
φE
ν21Pφ1
E
E eff2
eff
1Schjodt-Thomsen et al., Pol. Eng.Sci., 41 (2001)
considering a dough, E<<P, considering a dough, E<<P, effeff1/3, limit 1/3, limit conditionsconditions
eff
lim
E3
Pφ
Limit conditionsLimit conditions
DoughDough Cellular structureCellular structure
Poisson modulusPoisson modulus
E Young modulusE Young modulus
P cell pressureP cell pressureeffeff related to the related to the cellular systemcellular system
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
3. DOUGH SPREADING - 13. DOUGH SPREADING - 1
N dough layersN dough layers
F=Above layers weight
i-th layer: internal i-th layer: internal frictionfrictionUNLUBRICATED SQUEEZE UNLUBRICATED SQUEEZE
FLOWFLOW
F= Biscuit weight
1-st layer: no friction 1-st layer: no friction on bandon bandLUBRICATED SQUEEZE FLOWLUBRICATED SQUEEZE FLOW
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
3. DOUGH SPREADING - 23. DOUGH SPREADING - 2
UNLUBRICATED SQUEEZE UNLUBRICATED SQUEEZE FLOWFLOW
Power law fluidPower law fluid
LUBRICATED SQUEEZE LUBRICATED SQUEEZE FLOWFLOW
Power law fluidPower law fluid
3n
kRπ
n2
1n2
h
hF
3nn
1n2
n
F
h
εRπ
Fγη6
2
dt
dh
h2
1ε γη6εη
Biscuit diameter
i
ihHH
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
4. MACROSCOPIC TRANSPORT PHENOMENA4. MACROSCOPIC TRANSPORT PHENOMENA
iPiiziri Sρφ1RN
zrN
rr
1
t
φ1c
MASS BALANCE EQUATION (water, R.A., R.A. MASS BALANCE EQUATION (water, R.A., R.A. products)products)
rzc
DN wD,wrwz
rwziiww,iriz Nxxφ1crz
DN
ENERGY BALANCE ENERGY BALANCE EQUATIONEQUATION
iiizrp Sλq
zq
r
1
t
Tcρ
CONSTITUTIVE CONSTITUTIVE EQUATIONSEQUATIONS
Fick lawFick law
Fourier Fourier lawlaw
Tkq
SSii: net flow : net flow bubble-pastebubble-paste
ii: water latent : water latent heatheat
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
MATERIAL CHARACTERISATIONMATERIAL CHARACTERISATION
Bubble Bubble expansionexpansion
Paste Linear Viscoelastic properties
Frequency sweep test, 0.1-20 Hz; Time cure 0.1 Hz, 30°C – 110
°CBiscuit Biscuit spreadingspreading
Dough Steady Shear propertiesFlow curve 0.1 – 20 s-1
Bubble Bubble stabilisationstabilisation
Elongational propertiesBack extrusion test
Dough formulationFlour, sugars, glucose syrup, liquid egg, fats, water, raising agents
D1 RA
D2 RA
D3 vacuum
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
LINEAR VISCOELASTIC PROPERTIES - 1LINEAR VISCOELASTIC PROPERTIES - 1
10
100
1000
30 50 70 90 110T [°C]
G',G
'' [P
a]
0
0.2
0.4
0.6
0.8
1
1.2
tg
[-]
G' G" tg delta [-]
Sample D3, Time cure, 1°C/min
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
LINEAR VISCOELASTIC PROPERTIES - 2LINEAR VISCOELASTIC PROPERTIES - 2
Sample D3, Frequency sweep
10
100
1000
10000
0.1 1 10 100
Frequency [Hz]
G* [
Pa]
30°C 50°C
70°C 90°C
10
100
1000
10000
0.1 1 10 100
Frequency [Hz]
G* [
Pa]
30°C 50°C
70°C 90°C
0
0.4
0.8
1.2
1.6
2
0.1 1 10 100
Frequency [Hz]
tg d
elt
a [
-]30°C 50°C
70°C 90°C
z
1* ωAG Weak gel
model
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
STEADY SHEAR PROPERTIESSTEADY SHEAR PROPERTIES
Sample D2, Flow curve nγkτ
1
10
100
1000
0.1 1 10 100
Shear Rate [1/ s]
Vis
cosi
ty [
Pa.s
]
30°C 50°C
70°C
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
BACK EXTRUSION TESTSBACK EXTRUSION TESTS
Head
2
P
eff
eff Rπ
Fσ
h
hln
2
1ε 0
ε
σE eff
eff
FFeff = F - Fdrag
Instron machine
Rp
h
z
Re
Dough
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
BACK EXTRUSION TESTSBACK EXTRUSION TESTS
Sample D1-D2
ε
σE eff
eff
0
2000
4000
6000
8000
0 0.1 0.2 0.3 0.4 0.5
P
a
D1 D2
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
MODEL SENSITIVITY - 1MODEL SENSITIVITY - 1
Standard oven conditions: typical surface temperature profile
0 100 200 300 400Time [s]
T [
°C]
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
MODEL SENSITIVITY - 2MODEL SENSITIVITY - 2
Raising Agent Effects
3
4
5
6
7
8
9
0 100 200 300 400
Time [s]
Bis
cuit
Heig
ht
[mm
] D1 D2
lim
D1 0.55
D2 0.73
M. Migliori – 13 Marzo 2008M. Migliori – 13 Marzo 2008
MODEL SENSITIVITY - 3MODEL SENSITIVITY - 3
Oven conditions Effects
3
4
5
6
7
8
9
0 100 200 300 400
Time [s]
Bis
cuit
Heig
ht
[mm
] Std +5%
Std: standard heat fluxes+5% : 5% increased fluxes