Extrusion Technology for the production of food and non-food materials
Osvaldo H. Campanella PRESENTATION OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Product • Some Extrusion Processes PRESENTATION OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Product • Some Extrusion Processes Whistler Center Activities in Extrusion
• Mission to Mars • 6-8 months outbound • 600 day surface stay • 6-8 months return
Lift cost to Mars: ~$200,000/kg Whistler Center Activities in Extrusion
Design a multipurpose small extruder
First Extrusion soybeans soy flour Extrusion Pressing Drying Grinding meal
oil
Second Extrusion
soy flour Texturized soy protein Extrusion Drying Whistler Center Activities in Extrusion
LARGE SCALE “MODEL” EXTRUDER
Triple F - Model RC 2000 Whistler Center Activities in Extrusion Cutaway views of extruder
Steam locks Die
Cut-away view Of steam locks 4.125” 5.375” 5.625”
0.562” 0.313” Actual geometry with mesh 1.625” Whistler Center Activities in Extrusion Design a multipurpose small extruder Modeling an ExtrusionBalance Process of mass u=0 Momentum Transfer (forces and velocities ) p 0
Rheology Energy Transfer (temperatures)
Pressure External heating Friction Length dT Cuu (): k T p dt Rheology Whistler Center Activities in Extrusion
Rheological Model For Soy Flour
3.5 Temperatures = 50oC - 90oC Moistures = 30% - 42% 3.0 Oil = 0% - 12.2%
2.5
2.0
1.5
log (Viscosity) 1.0
0.5
0.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 log (a x a x a x Shear Rate) M T o 0... 852 1 373 0 373 log0 . 70 log ( aM a T a o ) 5 . 7
log aM 12.55(M b)- 2.13 b -0.00034 T 0.0223
log aT 0.020 T - 1.23
log ao 9.3 (Oil Content A) - 0.088 A - 0.001347 T 0.06866 Whistler Center Activities in Extrusion Pressure measurements during soy dough extrusion 450 Port 4 400 Port 5 350 Port 6 Port 7 300 250 200
Pressure (Psi) Pressure 150 100 50 0 0 10 20 30 40 50 60 350
Time (min) 300
250
200
150
Pressure (Psi) 100
50
0 3 4 5 6 7 8 Port number Whistler Center Activities in Extrusion Whistler Center Activities in Extrusion Design of the Small (60 lb/h) extruder Whistler Center Activities in Extrusion
Small-scale extruder was developed at Purdue University, and installed and tested at the Institut de Technologie Alimentaire (ITA) in Senegal to produce high quality, nutritious cereal-based products. The same type of extruder has now been installed at food processing incubation centers in Niger, Senegal and Kenya, allowing local production of grain-based instant foods such as thick and thin porridges and weaning foods.
https://www.purdue.edu/postharvest/we-collaborate-we-partner-with-public-or-private-groups-to-get-the-job-done Whistler Center Activities in Extrusion Interrelationship between activities associated with extrusion modeling Experimental trials Production scale
Planned process Extrusion Process results Raw materials Modeling Finished product
Whistler Center Scale up concepts Activities
Model validation Experimental trials Pilot scale Modeling Thermo-Mechanical Processing • How rigorous do we need to find useful models? • Could we use simple models to describe extrusion processes? • Could we have models that have a perfect description of the process? Dimension “0” models
Pshaft q barrel U Q p q loss H vap H melting
Pshaft : is the power in the extruder motor U : the rate of internal energy change in the product (i.e. temperature) p : is the pressure
Hvap : the rate of enthalpy (heat) change involved in the vaporization of the plasticizer/solvent : the rate of enthalpy necessary for the transformation of the Hmelting feed from a powdery solid to a melt qbarrel : rate of heat transferred through the extruder barrels qloss : heat loss Q : Volumetric flowrate The value of process modeling
Pshaft q barrel U Q p q loss H vap H melting Let’s assume simple “autogenous” extruder and ignore heat of vaporization and melting, and not heat loss
U Pshaft Q p
Heating the material U m c() Tout T in Pm/ p e p TT shaft out in m cc c c Q Important to analyze the sign of p , it is not so important in single screw extruders because is always positive. However in twin screw extruders the pressure difference can be negative or positive The value of process modeling 2D-3D Models – Importance of the extruded material The value of process Flow field (velocity, pressure) modeling Primary Temperature field fields Concentration field (reactive extrusion) Viscosity field Secondary Shear stress field Process fields Diffusion flux fields variables (reactive extrusion) Power Scalar Axial pressure shaft variables Temperature
Temperature field Product Time Reaction kinetics transformation Concentration field
Other process Mixing efficiency variables Residence time distribution
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Product • Some Extrusion Processes EXTRUSION INTRODUCTION
Extrude “To push or force out a material through an opening (Die)”
Die Material
• The extrusion process was first used in the plastic industry. In the food industry the process was first applied for the continuous extrusion of pasta in 1935 • It is a process of increasing importance in the food industry FOOD EXTRUSION COOKING VERSATILITY Flat Bread Pellet-to- flakes cereals
Directly expanded cereals Snack pellets
Co-filled cereals Porous Powders Other Applications Proteins • Textured Vegetable Proteins • Protein “Fibration” • Caseinates Other ……. • Functional Ingredients • Flavor Encapsulation • Pre-cooked flours • Pre-gelatinized starches • Oil seed Extraction • Confectionary Proteins • Textured Vegetable Proteins • Protein “Fibrilation” Footprint of different proteins
Courtesy Clextral 25 Protein “Fibration
Fibration texturizes proteins under high moisture 50-70% At temperature close or above 140oC in a twin screw extruder
Courtesy Clextral 26 Protein “Fibration
Extruder Texturizing Die
Courtesy Clextral 27 FIBRATION MECHANISMS
Courtesy Clextral 28 Other Applications Animal Feed Dry Pet Feed (cat & dog)
Aquafeed pellets OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Products • Some Extrusion Processes • Extrusion Technology SSE and TSE
What is it ? How does it work ? Single Screw Extruder Design (SSE) What can I do with it ?
Twin Screw Extruder Design (TSE) Extrusion Technology SSE Extruder Barrel Assembly The Monoblock System (two options) • Screw design – a single piece (constant pitch, decreasing channel depth) • A splined shaft holding screw sections of varying pitch
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell BASICS OF SSE TECHNOLOGY FLOW CHARACTERISTICS IN THE SCREW CHANNEL • The forward pitch of the screw flight conveys the materials down the channel by developing a DRAG FLOW, the velocity of that flow is directly proportional to the screw speed N. • Because of the die restriction at the extruder’s discharge, there is a PRESSURE FLOW, which is opposite in direction to the drag flow. Thus, SSE Flow rate = Drag flow rate – Pressure flow rate Pressure Flow K dP QN dZ Melt Viscosity Drag Flow a
Operational flow rate is dictated by screw geometry, N, die pressure, and melt rheological properties: the coupling of these variables limits the operating range and flexibility of SSE technology BASICS OF SSE TECHNOLOGY
FLOW CHARACTERISTICS IN THE SCREW CHANNEL
Drag flow Velocity profiles in the screw channel BARREL
K dP QN a dZ N
SCREW
Pressure flow
FEED DIE Down channel direction, Z
Courtesy Professor Bouvier BASICS OF SSE TECHNOLOGY FLUID DYNAMICS IN THE SCREW CHANNEL – Mixing and Residence time
Screw channel (unwound)
Down channel direction
Mixing: fluid particles have different Screw channel velocities and do not mix. It leads to a (cross section) distribution of residence times and poor mixing. Heat transfer and mechanical energy input in the cooking section are limited. Shear is not uniform leading to product Flow pattern in the screw channel with heterogeneous properties. SSE TECHNOLOGY
EFFECT OF MELT SLIP AT THE BARREL WALL • In SSE, perfect melt adherence to the barrel wall is required to obtain maximum throughput of the extruder. Any change in the melt composition which generates MELT SLIP at the barrel wall would lead to dramatic decrease of the extruder throughput. For example, in feed extrusion processing, « SLIP INDUCERS » are : moisture, meat slurries, protein hydrolysates, fat. • Melt slip at the barrel wall decreases importantly the extent of mixing as well as the heat transfer and shear rate (mechanical energy input).
Velocity profiles in the screw channel BARREL
Melt Slip Perfect melt adherence
SCREW Extrusion Technology TSE
The “modular” screw-barrel assembly – Twin-Screw Extruders (TSE)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Extrusion Technology TSE Classification
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Extrusion Technology TSE Co-Rotating Screws Mixing Disks Compression disks BASICS OF COROTATING TSE
DESIGN AND PROCESS CHARACTERISTICS Feed • Splined shafts that hold screw sections of varying configuration (forward pitch, reverse screw, kneading disks…..) Venting PRECONDITIONER
Compression Disks Transport Melting Degassing Compression Shearing Shaping P Mixing or Kneading Disks
Axial distance, z BASICS OF COROTATING TSE
FLOW DYNAMICS IN THE SCREW CHANNEL
Intermeshing zone
In co-rotating TSE, VERY INTENSE MIXING is observed in the intermeshing zone of the screws (macromixing, micromixing). Consequently, heat transfer coefficient in the fully filled sections is high. Homogeneous products can be obtained. Die expansion develops consistently, which leads to give consistent product density, texture and shaping as well as uniform final product color. Comparing SSE and TSE Technologies
• SSE - ONE SINGLE PROCESSING SECTION • SSE - Dependency of THROUGHPUT and SCREW SPEED • SSE - VERY POOR MIXING, limiting heat transfer, mechanical energy input, and generates heterogeneities of extrudates properties (conversion extent, composition, temperature, strain…) • SSE - as screw wear increases, EXTRUDER THROUGHPUT DECREASES. A decrease of 10-20% may be observed over the lifetime of the screw • SSE “slip inducers” in the extrudate composition generate SLIP, which decreases the EXTRUDER THROUGHPUT, as well as the extent of MIXING and MECHANICAL ENERGY INPUT • Co-rotating TSE is a POSITIVE DISPLACEMENT PUMP, due to the interpenetration of the screws. It allows to handle viscous, oily, sticky or very wet materials, with the same level of pumping efficiency. • Throughput of co-rotating TSE is, within the limits of reasonable operation, INDEPENDENT OF DIE PRESSURE PRESENTATION OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Products • Some Extrusion Processes Transformation of Raw Materials
Raw Materials - Native Flours - Pregelatinized flours - Semolina (pasta production) - Cereal grains (coarse milled) - Starches - Proteins - Fibers. Bran - Water/Steam - Oil/Fat/Meat - Salt, Sugar, Spices - Flavors, Vitamins, Emulsifiers, Colors (under moderate extrusion conditions) Transformation of Raw Materials How different are technologies applied to plastics and foods? Transformation of Raw Materials
Glass Transition Concept Transformation of Raw Materials
GLASS TRANSITION CONCEPT
C o RUBBERY STATE Increasing temperature
Increasing moisture
GLASSY STATE Glass transition temperature transition Glass Moisture Content (%) Transformation of Raw Materials GLASS TRANSITION CONCEPT
LIQUID (AMORPHOUS)
Heating Glass Transition Expansion
Temperature TEMPERATURE GLASS
Dry Material Wetting and Mixing
MOISTURE Transformation of Raw Materials THERMOMECHANICAL COOKING OF STARCH
DSC ENDOTHERMS (Potato starch; Donovan, 1979) Volume fraction of water
DSC gelatinization endothermTC60 70o
DSC melting endotherm (T > 60oC)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Transformation of Raw Materials Effects on starch molecules - Chromatography Starch Granules Under polarized Light
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Transformation of Raw Materials
THERMOMECHANICAL PROCESSING AND STARCH CONVERSION
Native starch Gelatinized/Melted starch Dextrinized starch
ENERGY INPUT
H2O (16-30%) - SME (> 380-400 kJ/kg) - T 110°C
Courtesy Professor Bouvier PRESENTATION OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Product • Some Extrusion Processes Quality of Final Product Product Expansion and Quality Bubble
Steam Air Moisture Heat
Set
Die Puff Collapse Harden P, T
Boiling Pt. Newtonian Elastic 0 0 TIME Quality of Final Product
Schematic representation of steam-induced expansion of biopolymeric melt at the die exit
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product
Visualization of steam-induced melt expansion at the exit of die insert Quality of Final Product PRODUCT EXPANSION AND QUALITY
• Shear viscosity resists expansion • Extensional viscosity and elasticity of the bubble membrane affect expansion and recovery Quality of Final Product Quality of Final Product Quality of Final Product
A
A. Control Starch
From Hoseney, C., et al (1992). Factors Affecting the Viscosity and Structure of Extrusion-Cooked Wheat Starch. In “Food Extrusion and Science and Technology” Kokini, J.L., Ho, C.T and Karwe, M.V. QUALITY OF FINAL PRODUCT PRODUCT EXPANSION AND QUALITY
Tg Tg Moisture
Tg
Temperature Shrinkage Region Temperature New Region
Time Moisture Quality of Final Product Dimensionless expansion indices of directly expanded extrudates
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product
Expansion chart of directly expanded extrudates
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product Effect of insert diameter on melt expansion
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product Effect of insert land length on melt expansion
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product
Rapid Visco Analyzer (RVA)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Quality of Final Product
RVA Sample Preparation
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Typical RVA Results
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Typical RVA responses of extrusion-cooked cereal starch-based materials
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell RVA responses of low-SME extrusion-processed corn-based material
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell RVA responses of high-SME extrusion-processed corn- based material
Bouvier and Campanella (2013). Extrusion Processing Technology. J. Wiley (In press) RVA responses of extrusion-processed corn-based material under intermediate range of process SME (200 kJ/kg < SME < 400 kJ/kg)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Effect of screw design on the RVA response; closed symbols: 250 rpm/17% (: profile 1; : profile 2; : profile 3); open symbols: 400 rpm/17% (: profile 1; : profile 2; : profile 3 RVA viscosity at the gelatinization peak versus process SME (corn-based material)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Properties of the Final Product
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Experimental Apparatus to use in Image Analysis
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Effect of Die Melt Temperature on Cell Density () and Average Cell Size () of Directly Expanded Extrudates
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell LEI () and SEI () versus average cell size (process SME range of 430-570 kJ/kg)
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell PRESENTATION OUTLINE
• The Whistler Center and its Activities in Extrusion • Extrusion Introduction – Applications • Extrusion Technology – Single Screw Extrusion (SSE) versus Twin Screw Extrusion (TSE) • Transformation of Raw Materials • Quality of Final Product • Some Extrusion Processes Some Extrusion Processes Production of Directly Expanded Breakfast Cereals
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Traditional Extrusion Corn Flake Corn Flake
Pressure Extrusion cooking cooking
Tempering Tempering
Flaking Flaking
Conceptual diagram of an AFM (Asylum, Santa Barbara, CA) Traditional Corn Flake Extrusion Based Corn Flake Typical processing conditions for the generic Direct Expanded (DX) extrusion-textured breakfast cereals
PRODUCT THERMOMECHANICAL COOKING DIE TEXTURIZATION Screw speed Barrel temperature SME Insert mass flux Bulk density (rpm) (°C) (kJ/kg) (kg/h.mm2) (g/l)
Ball (corn-based) 300-450 130-150 400-450 4-5 40-60 Crisp rice (rice-based) 300-400 160-180 380-450 3-4 110-120 Loop (oat-based) 200-300 140-160 320-400 5-6 180-220 Cup (wheat-based) 250-350 110-130 620-700 3-4 120-140 Bran stick 200-300 115-135 550-620 2-3 180-200
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell EXTRUSION-POROSIFICATION TECHNOLOGY
Aimed to: • Create porous powders with better rehydration time • Reduce conversion costs (energy, capital) • Overcome some limitations of spray drying & drum drying technologies • Process complete formulations without further mixing • Leverage in-built extrusion flexibility Typical Skim Milk Powder Process
Spray Drying
Milk Multiple Storage Heating Effect Fluidized Bed Separation Evaporation Drying
cream
% Solids 12 50 93 96 Effect of solid content in the feed on the energy consumption for the evaporation of water in the spray drying process
Solids in the feed Energy consumption (%) (kJ/kg powder) 10 24,000 20 10,500 30 6,200 40 4,000 50 2,700
Energy Saving EXTRUSION-POROSIFICATION TECHNOLOGY
VISCOSITY OF PROTEINS AND OTHER MACROMOLECULES Limitations of spray drying Maximum concentration permissible for spray drying Time-independent non-Newtonian Whey Protein 100 behavior Skim milk Whey Protein Concentrate
C
o 80 Time-dependent “thixotropic” non-Newtonian 60 behavior
Newtonian Viscosity 40Behavior
20
Brookfield Viscosity at 25 at Viscosity Brookfield 10 20 30 40 50
0 Solids Concentration (%) 0 10 20 30 40 50 60 Solids Concentration (%) Simplified flowsheet for the extrusion-porosified milk powder manufacturing process
Process Modification
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Characteristics of the Product Extrusion-textured foam obtained from Typical SEM picture of an extrusion-porosified 38% dry solids milk protein concentrate milk powder particle
Energy Analysis 0.5
Spray Drying Process 0.4
Extrusion-Porosification 0.3 Process
0.2
Energy Consumption Energy 0.1
kg steam/kg of incoming milk incoming of kg steam/kg
0.0 0 20 40 60 80 100 Percent Solids (%) Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell Characteristics of extrusion-porosified whole milk powder
Characteristics Extrusion-porosified Standard values powder Moisture (%) 2.5 – 3.9 < 4 Fat (%) 27 – 28 27 – 29 Insolubility Index (mL) 0.1 – 0.2 < 0.5 Titratable acidity (%) 0.1 < 0.15 Flavor & Odor Good Good Appearance & Color Normal Normal pH (10% solution) 6.73 – 6.77 > 6.6 Free fat (%) 3.2 – 6.7 < 5
Peroxide value (meq. O2/kg fat) 0.3 < 1 Water activity 0.22 – 0.27 < 0.5 Density (kg/L) 0.41 – 0.44 > 0.4
Bouvier and Campanella (2014). Extrusion Processing Technology. Wiley-Blackwell
Reactive Extrusion Single screw extruder as a bioreactor for sago starch hydrolysis Starch + enzyme 60-120oC amylase Termamyl 120L
Conditions Results • Feed Moisture Extrusion • Water Solubility Index (WSI) • Enzyme concentration • Water Absorption Index (WAI) • Mass Temperature • Degree of Gelatinization (DGR) • Dextrose Equivalent (DE)
Bouvier and Campanella, 2014 Reactive Extrusion Reactive Extrusion
High moisture twin screw extrusion of sago starch. Saccharification, influenced by thermomechanical history
Amyloglucosidase
Starch Twin Screw Extruder Batch Product Reactor • DE • % Saccharification Rx times amylase Termamyl 120L 8hrs
Bouvier and Campanella, 2014 Reactive Extrusion - High moisture twin screw extrusion of sago starch and subsequent saccharification Amyloglucosidase Starch Twin Screw Extruder
amylase Termamyl 120L THANK YOU
QUESTIONS ?
Osvaldo Campanella [email protected] (daily checked) [email protected] (not frequently checked)