on behalf of

u

Cocoa Butter CrystallisationCocoa Butter CrystallisationKevin W. Smith

&

Kees van Malssen

Unilever R&D Colworth

October 2002 2

OutlineOutline

Introduction Cocoa Butter and Chocolate

Cocoa Butter Crystallisation Phase Transformations Phase Behaviour and Crystallites

Conclusion

October 2002 3

Cocoa Butter & ChocolateCocoa Butter & Chocolate

Crucial role in chocolate characteristics Gloss Snap Texture Cool melting in mouth Shelf-life

Important to crystallise cocoa butter correctly

1010mm

October 2002 4

Fat PolymorphismFat 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 PolymorphismCocoa Butter Polymorphism

Wille and Lutton (JAOCS, 1966)

StabilityMelting

Point (°C)Basic

PolymorphI least stable 17 /sub-

II meta-stable 23

III meta-stable 25 '2IV meta-stable 28 '1V stable 33

2

VI most stable 36 1

October 2002 6

Cocoa Butter PolymorphismCocoa Butter Polymorphism

Current understanding

StabilityMelting

Point (°C)Basic

Polymorphunstable 0 /sub-

unstable 17

meta-stable 21-28 '

stable 31.5 V

most stable 33.5 VI

October 2002 7

Static Isothermal CrystallisationStatic Isothermal Crystallisation

/sub-

liquid

-20

-10

0

10

20

30

40

Tc

(°C

)

1 0s 2 0s3 0s 2 m 3 m4 m 10 m 20 m30 m 2 h3 h 6 h 12 h 18 h 2 d3 d4 d 2 w3 w

1 min 1 hour 1 day 1 week

Time (logarithmic)

October 2002 8

' Phase Range Diffraction' Phase Range Diffraction

'25.0

'22.5

'20.0

'17.5

'15.0

'12.5

'10.0

'5.0

6.0 5.0 4.5 4.0 3.5d(Å)

14 16 18 20 22 24 26 282q(° )

Intensity

October 2002 9

' Melting Dependent on ' Melting Dependent on Crystallisation TemperatureCrystallisation Temperature

0

20

40

60

80

100

20 22 24 26 28 30

Temperature (°C)

Pea

k I

nte

nsi

ty (

% o

f m

ax)

20°C15°C10°C5°C

October 2002 10

Cocoa Butter Phase SchemeCocoa Butter Phase Scheme

Melt

VI

V

or sub-

'

Solvent

October 2002 11

Assignment of PolymorphsAssignment of PolymorphsApprox.

MPt. (°C)Wille &Lutton

TraditionalCurrent

Data0 / sub-

17 I sub-

23 II '*

25 III ' '*

28 IV ' '*

33 V

36 VI

* and many more

October 2002 12

Phase Behaviour and CrystallitesPhase Behaviour and Crystallites

B (%)

A BT

empe

ratu

re

100

LiquidL+S

Solid

0 20 40 60 80

23

4

6 5

1

October 2002 13

Crystallites CompositionCrystallites Composition

October 2002 14

Crystallites - Small CrystalsCrystallites - Small Crystals

October 2002 15

Crystallites - Different SizesCrystallites - Different Sizes

October 2002 16

Crystallites - Different CompositionCrystallites - Different Composition

October 2002 17

Complex Phase BehaviourComplex Phase Behaviour

B (%)

A BT

empe

ratu

re L

L+SB

L+SA

SBSA

SA + SB

1000 20 40 60 80

October 2002 18

Cocoa Butter CrystallisationCocoa 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 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

SummarySummary

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

AcknowledgementsAcknowledgements

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

AdditionalAdditional

Wille and Lutton

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!