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DRY COATING : Techniques & Potentials
Water in Food Workshop
E. TEUNOU - E. IVANOVA - D. PONCELET
Département du Génie des Procédés Alimentaire
Lausanne 2004
Nantes
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Content
• Who are we ?
• Importance and Functionality of powders
• Definitions of coating and principles
• Potentials of dry coating
• Case study
• Perspectives
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Who are we ?
• Micro encapsulation- Encapsulation- Development- Implementation- Application to food area- …
Department of food Process Engineering
Nantes
• Granular Materials- Characterisation- Flowability- Spray drying- Coating- …
Micro encapsulation and Granular MaterialTeam (Poncelet)
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1990 - 900 groups - 60 countries - 25 % of industrials.
• promoting the development of bioencapsulation• encouraging multidisciplinary research• developing and transferring the technology• supporting and organizing training and workshop
Virtual Institute on Bio&MicroEncapsulationSciences and Technologies
• promote and support collaboration between RTD • develop professional communication tools• provide integrated problem solutions and technology transfer • offer a contact platform for the industry
VI-BEST
Bioencapsulation Research Group
2003 - 15 partners - 9 countries.
http://www.bioencapsulation.net
http://www.ncapsolution.net
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Tons of powders today• Stable form• Easy to handle (flowability)• Reconstitution (Dissolution - Dispersion)• Used in various industries
(Multiple functional properties)
Importance & functionality of powders
Powder cost = f (functionality)F
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• Protection• Composition• Stability• Reconstitution• Dissolution• Dispersion)• Dust free• Free flowing• Nutritive• Etc…
Trends in powders functionalization
F• Mixing
• Spray drying
• Agglomeration
• Granulation
• Coating
Enrichment & Use of additives
For By
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What is coating ?
Water vapor
Gastric juices
Core
Shell
UV, T°
Gas: O2, CO2, N2
Fats
Solutions
Mechanical constraintsMicroorganisms
Confining for
• Immobilization• Protection• Releasing• functionalization
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Types of capsules ?
Beads Multi-core Multi-cores
Reservoir system
Multi-layers
Physical states
Morphology
• Solid - dry or liquid core• Wet or dry shell material• Soft, elastic or rigid capsules
Matrix system
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Fluid bed coating (aqueous)
Coating material dissolvedin water
Pump
Fluidizedparticles
Filter
Outlet Air
InletAir
Nozzle
Sprayedliquid
Heating
Fan
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Fluid bed coating (aqueous)
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Mechanism of aqueous coating
• Similar mechanism is expected when:- The coating material is dispersed in any solution- The coating material is in liquid form
Droplets
Core Particle
Spraying Spreading Solidification
Many
cycles
OnionStructure
Evaporation
Notes• The core particle is wetted
Wetting
Layering
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Variation of humidity in the fluid bed
è Water uptake is quite impressive
0
20
40
60
80
Coating time (minutes)
0
5
10
15
HR (%)X (%)
Spray End Spray
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For Water sensitive products(Powders & active materials)
Dry coating is imperative
• Pharmaceuticals• Nutraceuticals• Probiotics
• Bacterial growth• Toxin production• Activation
• Vitamins• Oils and fats• etc…
• Browning• Oxidation• Unwanted flavors• etc…
Why ?
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Definitions of Dry Coating
• Dry coating = Coating without wetting particles with:
1
2
3
4
• Water
• Solvent
• Oil or wax
• Nothing at all
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Principles of dry coating:
solvent
orhot-melt
Particle
Film layer
a/ Solvent and
hot-melt
c/ Dry powder coating
a/ Plasticizer
Fines
Mechanicalforces
Fines
Plasticizer
Porous layer
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Principle of dry powder coating:
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Dry coating process• Use of solvents
Polymer in
solvent
pump Fluid bed
Heating
Fan
Cooling
filter
Solventrecovered
Vacuum pump
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• Use of plasticizers
a) Pan coater
Air outlet
Balance
Air inlet
Finepowder
b) Fluid bed
Plasticizer
plasticizer
Dry coating process
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• Dry particles coating
Hybridizer
Dry coating process
Powder inlet
Powder outlet
RotorJacket
Stator
Cycletube
Blade
Particle trajectory
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Stationaryhammer
Rotatingvessel
ScraperAir inlet
Air outlet
Fluidisedparticles
Cage
Rotating air
distributor
Mechano - fusion
Rotating fluid bed
• Dry particles coating
Dry coating process
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Rotor
Rotatingvessel
Minimum clearence
region
Particles
Guest partcle
AC power supply
Collar coil
Chamber
N-S S-N
Magnetic partcleHost particle
Magnetic Impact
High speed ellipticalRotor mixer
• Dry particles coating
Dry coating process
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Advantages
• Coated particles are not wetted
• Can be processed in existing devices
• High productivity
• Energy saved
• Low pollution (dust free)
• Time saved
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Productivity
70-80Solvent (2 to 30% DM)
90-98Dry particles (100% DM)
~ 90Plasticizer (100 % DM)
85-99Hot melt (100 % DM)
70-80Aqueous (2 to 8% DM)
Yield (%)Types of process
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Productivity
0
5
10
15
20
25
30
0 10 20 30
Qm (g/min)
QD
M (
g/m
in)
Dry ParticlePlasticizerSolventAqueous
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Time saved
Without time for:- solution preparation- finishing heating
5-10Dry particle coating80Plasticizer60Hot melt
200Aqueous or solventTime (min)Types of process
Process time for: - 20% of coating material- 10 kg load
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Energy saved
Air heatingVaporization heat
Solvent
Mechanical energyDry coating particles
Ambient temperaturePlasticizer
Heating of the melting solutionCooling the chamber
Hot melt
Air heatingVaporization heat
Aqueous
EnergyTypes of process
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Multiple potentials
• Integration of functionalization
• Coating of water sensitive materials
• Quick dispersion
Ex: Free flowing additives
Ex: Reconstitution of liquids
Ex: Coating of probiotics
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Case study: Dry Coating of Probiotics
• Core material
• Coating materialAQOAT (10 µm) (Synthafarm)
Triethyl citrate & acetylated monoglyceride
Beads photo
• Plasticizer
• White polymer beads• 835 µm, 828 kg/m3• Dried for 48 hours, 100 °C
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The coating system
A Wurster (Uniglatt) for dry coating
Air outlet
Balance
Finepowder
plasticizer
Air inlet
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Example: Coating of probiotics
X% of capsules at different steps
6%6%8%Storage (196h-50% HR)
6%6%6%Storage (48h-50% HR)
2%4%4%Process
0%Initial
CapsulesPlasticizer
CapsulesAqueous
BeadsSteps
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Variation of humidity in the fluid bed
è Water uptake is quite impressive
0
20
40
60
80
Coating time (minutes)
0
5
10
15
HR (%)X (%)
Spray End Spray
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Coating system with Air de-hidration
De- hydration Unit
Air outlet
Balance
Finepowder
plasticizer
Dry Air InletAir Inlet
Target: HR = 5% in the fluid bed chamber
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De-humidification of the inlet air
• High drying rate• Coating at room temperature• In clean conditions
• Size• Cost
• No wetting
Advantage
Inconveniences
Others advantages
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26 C
70%20.1 C
14.8g
27.8 C 23.8g
50C, 20%
Drying rate = 23.8-14.8= 9.0g/kg
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Case 1: 9 g/kg dry air
Case 2
Case 1
Case 2: 10.5 g/kg dry air
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• Advantages• Potentials Real needs
Conclusion
Dry coating :F
F• Methodic study
Perspectives
ü Comparison of different methodsü Evaluation of potentialsü Applications
• Test the new air drying system
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Thanks for your...
And ...
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