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

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

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

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

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

Cocoa Butter Polymorphism Current understanding October 2002

Static Isothermal Crystallisation b 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

' 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

' Melting Dependent on Crystallisation Temperature October 2002

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

Assignment of Polymorphs October 2002

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

Crystallites Composition October 2002

Crystallites - Small Crystals October 2002

Crystallites - Different Sizes October 2002

Crystallites - Different Composition October 2002

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

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

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

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

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

October 2002

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