Analysis of the expansion phenomenon during the extrusion process: Experiments and model

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1 Analysis of the expansion phenomenon during the extrusion process: Experiments and model Magdalena KRISTIAWAN & Guy DELLA VALLE LudovicClub, March 26, Lyon 1

2 Objective of this work Test the validity of Ludovic simulation for starch extrusion Show how to integrate the phenomenological model of expansion with Ludovic s interface Aims: Extend the Ludovic s capability to predict macro & microstructure of starchy foam 2

3 Concept map: Structure of Ludovic Input variables of models = Extrusion s output variables at die exit (calculated by Ludovic ) 3

4 EXPERIMENTS 4

5 1) Raw material - Maize starches Starch Product Amylose / Amylopectine A Amylomaize 70/ 30 B Blend of A : D = 2 : 1 47/ 53 C Blendof A : D = 1 : / 76.5 D Waxy maize 0/ 99 2) Extrusion Plasticizer : water Control Water content Product temperature SME variables MC Tp C kwh/t Min Max Experimental sets: Low MC with Med & High Tp High MC with Low & Med Tp Q =12 35 kg/h N = rpm 5

Extruder configurations: Clextral BC45 & Slit die Profil 1: Low / Medium %water (MC), L total barrel = 1000 mm Feed -15 15 25 35 25 15 25 35 50 pitch 50 50 100 100 50 150 100

6 Extruder configurations: Clextral BC45 & Slit die Profil 1: Low / Medium %water (MC), L total barrel = 1000 mm Feed pitch length(mm) Profil 2: High %water (MC) Low Tp C, L total barrel = 1250 mm Feed pitch length(mm) 6

7 3) Determination of melt viscosity using Rheopac Top view L=300 mm P & T sensors An in-line rheometer A slit die with twin rectangular channels attached to the die head of the extruder Principle Channel 1 for the measurement Channel 2 for bypass a part of the total flow rate Q by adjusting the piston valves - Vary the local shear rate in the Channel 1 - Keep constant the Q, SME and die head P in extruder - Measurement of ΔP/ ΔLand Q1in the Channel 1 to obtain shear viscosity Using Rabinowitsch correction 7

8 General rheological model for the plasticized starch Power law fluid with Non-newtonian and Shear thinning behavior Case 1) Dependency ofkand nonlyon temperature (T)and moisture content (MC) 1 1 Case 2) Dependency of K and n on thermomechanical history through a specifc mechanical energy (SME)term 1 1 8

9 RESULTS & DISCUSSIONS 9

10 Shear viscosity of molten starch: SME (+) then viscosity(-) Effect of Specific Mechanical Energy: Complex dependency with amylose, water content & temperature η (Pa.s) Amylose 0.245, T = C η (Pa.s) 6.E+02 T = 160 C Amylose 0.70 MC 0.205, 209 & 406 kwh/t 7.E+02 MC 0.205, 194 & 429 kwh/t 147 kwh/t MC kwh/t Amylose 0.0 MC MC 0.275, 99 &121 kwh/t 7.E+01 1.E+01 1.E+02 1.E+03 ( 6.E+01 1.E+01 1.E+02 1.E+03 ( 10

11 Determination of shear viscosity parameters for Ludovic input Starch A B C D Amylose content Rheopac data: ; K, n = f(mc, Tp, SME) K' o (Pa.s) 1.13E E E E+06 E/R (K) 11,298 5,638 9,869 9,350 α β (kj/kg) E E E-03 n o a 1 ( C) E E E E-04 a E E-01 0 a 3 (kj/kg) E E-04 a 4 ( C kj/kg)^ E E E-02 a ( C)^ a (kj/kg)^ E E Compute new parameters K,n=f(MC, Tp) Create Set of data points,-,γ,, η) 11

12 How to activatesme couplingin viscositylawfor Ludovic material input? 1) Create Set of Points 2) Active coupling 12

13 Ludovic simulation: Experimental set (Amylose 0.0, Water 0.25, Tp 158 C, SME 131 kwh/t) Sensibility to thermomechanical history(sme, Tp, MC) T ( C) Δ=4 C No coupling Total SME (kj/kg) 140 Melt viscosity η 12 K, n = f(water, Tp) K, n = f(sme, Water, Tp) 152 SME coupling 112 Δ=68 kj/kg No coupling Die exit 28 SME coupling Die exit 0 Significant effect of SME!!! 13

14 Ludovic simulation: Experimental set (Amylose 0.70, MC 0.21, Tp 166 C, SME 750 kj/kg Sensibilityto thermal conductivityk k starch of solid& melt= f(mc, Tp) k (W/m.K) : 3 ;<=> Temperature C MC (Colonna & Della Valle,1994) Computed Tp ( C) k estimed Tayeb 1989 ΔP = 20 bar ΔT = 10 C k at Tmelting k of solid phase (W/m.K) Computed P max (bar) Significant effect of k!!! 14

15 Ludovic simulation Sensibilityto meltingtemperaturet m T m starch= f(mc) DSC thermogram Normal maize starch(rezzoug et al., 2008) T onset T offset DSC T onset T peak T peak T m ( C) ΔT=30+3 C The higheramylose content, the broader melting endotherme (Mateev 2001) Water content MC LUDOVIC : T m = T peak 15

16 Ludovic simulation: Experimental set (Amylose 0.70, MC 0.21, Tp 166 C, SME 750 kj/kg Tp ( C) Sensibilityto meltingtemperaturet m T m 185 C 175 C Without SME - viscosity coupling ( ) 165 C 155 C 145 C Total SME (kj/kg) ( ) Die exit 135 C 125 C 125 C Tm 185 C Die exit Negligible effect of T m!!! 16

17 Ludovic s validations Experiments vs Simulations Amylose 0.7 Amylose 0.47 Amylose 0.0 SME coupling Without coupling Amylose 0.7 Amylose 0.47 Without coupling Amylose 0 SME coupling SMEexp (kj/kg) 1000 Tp ( C) Computed SME (kj/kg) Computed Tp ( C) Computed SME is underestimated. LUDOVIC doesn t take account dissipated energy before melting section 17

18 Ludovic s validations Experiments vs Simulations 160 P exp (bar) Amylose 0.7 Amylose 0.47 Amylose Computed Pmax (bar) Without coupling SME coupling May be the problem on: - Die geometry???? - Rheological model???? 18

19 Computing of starch destructurization using Ludovic FBCFFE KFEIFBL FFBFHM FBCFFE KFEIFBL 70 Native maize starch % destructurization Amylose 0.0 Amylose 0.47 Amylose 0.70 SME coupling Without coupling Computed SME (kj/kg) Amylose / Amylopectine Intrinsic viscosity (ml/g) 0 / / / / Amylopectine(higherMW)ismore sensitive to thermomechanical treatment than amylose (lower MW) 19

20 CONCLUSIONS The determination of material properties is primordial -The rheologicalbehaviorof moltenpolymer, f(thermomechanicalhistory) -The thermal physicalpropertiesof material, f(t, water content) The computed dissipated mechanical energy is underestimated -WellcorrelationbetweenSME computed and the SME experimental -Wellcorrelationbetween% starchdestructurizationand SME computed 20

Indices Expansion Volumique (VEI) - Indices Expansion Radial & Longitudinal - Anisotropie factor 2)

21 PERSPECTIVES Integration of Ludovic with phenomenological model of expansion 1) Coupling the model with Ludovic 2) Simulation and validation (experiments) New Ludovic outputs: 1) Macrostructure: - Indices Expansion Volumique (VEI) - Indices Expansion Radial & Longitudinal - Anisotropie factor 2) Microstructure: - Mean cell size (MCS) - Mean cell wall thickness (MCWT) - Finesse MCS (mm) Frequency 21

22 Concept map: Structure of Ludovic Input variables of models = Extrusion s output variables at die exit (calculated by Ludovic ) 22

Context: Starchy material processing using extrusion-cooking Expansionby extrusion cooking: Relation with Glass transition temperature Tg Die exit Bubble growth stop Add the Sugar

23 Context: Starchy material processing using extrusion-cooking Expansionby extrusion cooking: Relation with Glass transition temperature Tg Die exit Bubble growth stop Add the Sugar Extruder die outlet Acquisition of texture... Nucleation & Bubble growth Coalescence cell rupture solidification and/or shrinkage The bubble growth stops (solidification) at Tp> Tg+ 30 C 23

24 Concept map: Phenomenological model of expansion ρ* z [η(γ)] x [MC] [Tp] [E (Tα)] y wherez, x, y= f(mc, Tp, ) 24

25 Volumetric expansion indices VEI VEI= H Water = 0.245, 185 C, 150 kwh/t, h die = 3 mm OP Q R 1 R S 1 U. U X V, U MC. U ).ln(e ( V )) Amylose 70%, 165 C, 200 kwh/t, h die = 3 mm VEI HigherAmylose% highere (T α ) higherη(ε) 10 Amylose VEI Water MC Shear viscosity (Pa.s) Shear viscosity (Pa.s) 25

26 , March 26, Lyon 26

Rheological Characteristics of Intermediate Moisture Blends of Pregelatinized and Raw Wheat Starch

6740 J. Agric. Food Chem. 2002, 50, 6740 6745 Rheological Characteristics of Intermediate Moisture Blends of Pregelatinized and Raw Wheat Starch SAJID H. ALAVI,* KWAN-HAN CHEN, AND SYED S. H. RIZVI Institute