1. Cocoa Butter Crystallisation
Kevin W. Smith
&
Kees van Malssen
Unilever R&D Colworth

2. Outline Introduction Cocoa Butter Crystallisation Conclusion
Cocoa Butter and Chocolate
Cocoa Butter Crystallisation
Phase Transformations
Phase Behaviour and Crystallites
Conclusion
October 2002

3. Cocoa Butter & Chocolate
Crucial role in chocolate characteristics
Gloss
Snap
Texture
Cool melting in mouth
Shelf-life
Important to crystallise cocoa butter correctly
10mm
October 2002

4. Fat Polymorphism Crystal Structure few triacylglycerols known
main components of cocoa butter not known
POP, POSt and StOSt
many proposed structures
natural fats are complex mixtures
observed crystal structure is an average
new polymorphs may occur
October 2002

5. Cocoa Butter Polymorphism
Wille and Lutton (JAOCS, 1966)
October 2002

6. Cocoa Butter Polymorphism
Current understanding
October 2002

7. Static Isothermal Crystallisationb b 
g/sub-
liquid
-20
-10 10 20 30 40
Tc (°C)
10s
20s
30s 2m 3m 4m
10m
20m
30m 2h 3h 6h
12h
18h 2d 3d 4d 2w 3w
1 min
1 hour
1 day
1 week
Time (logarithmic)
October 2002

8. ' Phase Range Diffraction
b'25.0
b'22.5
b'20.0
b'17.5
b'15.0
b'12.5
b'10.0
b'5.0
6.0
5.0
4.5
4.0
3.5
d(Å)
October 2002

9. ' Melting Dependent on Crystallisation Temperature
October 2002

10. Cocoa Butter Phase Scheme
Melt
VI V 
or g
sub- '
Solvent
October 2002

11. Assignment of Polymorphs
October 2002

12. Phase Behaviour and Crystallites
Temperature
100 1
Liquid
L+S 2 3 6 5
Solid 20 40 60 80 4
October 2002

13. Crystallites Composition
October 2002

14. Crystallites - Small Crystals
October 2002

15. Crystallites - Different Sizes
October 2002

16. Crystallites - Different Composition
October 2002

17. Complex Phase Behaviour
Temperature L
L+SB
L+SA SB SA
SA + SB
100 20 40 60 80
October 2002

18. Cocoa Butter Crystallisation
Composition dependent
Solidification in two stages
high melting fraction first
molten cocoa butter cooled to 30°C will develop a cloudiness but will not crystallise over 12 weeks
bulk second
Increasing first stage may not accelerate second stage
trisaturated triacylglycerols are not good accelerators
October 2002

19. Memory Effect & Crystallisation
Memory of  crystal form remains in liquid cocoa butter
up to 7°C above melting point
Subsequent crystallisation occurs into stable  form
a type of seeding
can be used to 'temper' chocolate
Temperature for loss of memory effect is independent of cocoa butter composition
October 2002

20. Summary Assignment of polymorphs to melting points has been mistaken
Solidification temperature determines phase, more than cooling rate
Phases develop faster through phase transitions than through nucleation
 phases do not crystallise from the melt (excluding seeding effects)
October 2002

21. Acknowledgements Unilever R&D Colworth: Dr. Kees van Malssen
Loders Croklaan
University of Amsterdam: A van Langevelde, R Peschar, H Schenk
Netherlands Foundation for Chemical Research (NWO/CW) and Dutch Technology foundation (STW)
October 2002

22. October 2002

23. Additional Wille and Lutton Van Malssen I sub  mp 17 II  mp 23
III ' mp 25
IV ' mp 28
V  mp 33
VI  mp 36
Van Malssen
 / sub  mp 0
 mp 17
' x mp 23*
' y mp 25*
' z mp 28*
 mp 31
 mp 33
* and many more possible!
October 2002