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 ...