Cocoa Butter Crystallisation
Kevin W. Smith
&
Kees van Malssen
Unilever R&D Colworth
u
on behalf of
Outline
 Introduction

Cocoa Butter and Chocolate
 Cocoa Butter Crystallisation
Phase Transformations
 Phase Behaviour and Crystallites

 Conclusion
October 2002
2
Cocoa Butter & Chocolate
 Crucial role in chocolate characteristics
Gloss
 Snap
 Texture
 Cool melting in mouth
 Shelf-life

10mm
 Important to crystallise cocoa butter correctly
October 2002
3
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
4
Cocoa Butter Polymorphism
 Wille and Lutton (JAOCS, 1966)
Stability
I
II
III
IV
V
VI
October 2002
least stable
meta-stable
meta-stable
meta-stable
stable
most stable
Melting
Basic
Point (°C) Polymorph
17
 /sub-
23

25
'2
28
'1
33
2
36
1
5
Cocoa Butter Polymorphism
 Current understanding
Melting
Basic
Stability
Point (°C) Polymorph
unstable
0
 /sub-
unstable
17

meta-stable
21-28
'
stable
31.5
V
most stable
33.5
VI
October 2002
6
30
2w
3w
liquid

20
Tc (°C)
2d
3d
4d
12h
18h
6h
2h
3h
20m
30m
10m
2m
3m
4m
20s
30s
40
10s
Static Isothermal Crystallisation


10
0
-10
-20
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/sub-
1 min
1 hour
Time (logarithmic)
1 day
1 week
7
' Phase Range Diffraction
Intensity
'25.0
'22.5
'20.0
'17.5
'15.0
'12.5
'10.0
'5.0
14
16
18
20
22
24
26
28
2q(°)
October 2002
6.0
5.0
4.5
d(Å)
4.0
3.5
8
Peak Intensity (% of max)
' Melting Dependent on
Crystallisation Temperature
100
80
20°C
15°C
10°C
5°C
60
40
20
0
20
22
24
26
28
30
Temperature (°C)
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9
Cocoa Butter Phase Scheme
V
or 
sub-
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
'
VI
10
Assignment of Polymorphs
Approx. Wille &
Traditional
MPt. (°C) Lutton
0
Current
Data
 / sub-
17
I
sub-

23
II

'*
25
III
'
'*
28
IV
'
'*
33
V


36
VI


* and many more
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11
Phase Behaviour and Crystallites
A
B
1
Temperature
Liquid
L+S
2
6
3
5
Solid
0
October 2002
20
40
60
B (%)
80 4
100
12
Crystallites Composition
October 2002
13
Crystallites - Small Crystals
October 2002
14
Crystallites - Different Sizes
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15
Crystallites - Different Composition
October 2002
16
Complex Phase Behaviour
A
B
L
Temperature
L+SA
L+SB
SA
SB
SA + S B
0
October 2002
20
40
60
B (%)
80
100
17
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
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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
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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
20
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
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October 2002
22
Additional
 Wille and Lutton
 Van Malssen







I
II
III
IV
V
VI
sub 

'
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
mp 17
mp 23
mp 25
mp 28
mp 33
mp 36

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



 / sub 

' x
' y
' z

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mp 0
mp 17
mp 23*
mp 25*
mp 28*
mp 31
mp 33
• * and many more possible!
October 2002
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