DRY COATING : Techniques & Potentials
Water in Food Workshop
E. TEUNOU - E. IVANOVA - D. PONCELET
Département du Génie des Procédés Alimentaire
Lausanne 2004
Nantes
Content
• Who are we ?
• Importance and Functionality of powders
• Definitions of coating and principles
• Potentials of dry coating
• Case study
• Perspectives
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)
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
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
• 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
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
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
Fluid bed coating (aqueous)
Coating material dissolvedin water
Pump
Fluidizedparticles
Filter
Outlet Air
InletAir
Nozzle
Sprayedliquid
Heating
Fan
Fluid bed coating (aqueous)
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
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
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 ?
Definitions of Dry Coating
• Dry coating = Coating without wetting particles with:
1
2
3
4
• Water
• Solvent
• Oil or wax
• Nothing at all
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
Principle of dry powder coating:
Dry coating process• Use of solvents
Polymer in
solvent
pump Fluid bed
Heating
Fan
Cooling
filter
Solventrecovered
Vacuum pump
• Use of plasticizers
a) Pan coater
Air outlet
Balance
Air inlet
Finepowder
b) Fluid bed
Plasticizer
plasticizer
Dry coating process
• Dry particles coating
Hybridizer
Dry coating process
Powder inlet
Powder outlet
RotorJacket
Stator
Cycletube
Blade
Particle trajectory
Stationaryhammer
Rotatingvessel
ScraperAir inlet
Air outlet
Fluidisedparticles
Cage
Rotating air
distributor
Mechano - fusion
Rotating fluid bed
• Dry particles coating
Dry coating process
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
Advantages
• Coated particles are not wetted
• Can be processed in existing devices
• High productivity
• Energy saved
• Low pollution (dust free)
• Time saved
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
Productivity
0
5
10
15
20
25
30
0 10 20 30
Qm (g/min)
QD
M (
g/m
in)
Dry ParticlePlasticizerSolventAqueous
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
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
Multiple potentials
• Integration of functionalization
• Coating of water sensitive materials
• Quick dispersion
Ex: Free flowing additives
Ex: Reconstitution of liquids
Ex: Coating of probiotics
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
The coating system
A Wurster (Uniglatt) for dry coating
Air outlet
Balance
Finepowder
plasticizer
Air inlet
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
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
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
De-humidification of the inlet air
• High drying rate• Coating at room temperature• In clean conditions
• Size• Cost
• No wetting
Advantage
Inconveniences
Others advantages
26 C
70%20.1 C
14.8g
27.8 C 23.8g
50C, 20%
Drying rate = 23.8-14.8= 9.0g/kg
Case 1: 9 g/kg dry air
Case 2
Case 1
Case 2: 10.5 g/kg dry air
• 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
Thanks for your...
And ...