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Cocoa Butter Crystallisation

Cocoa Butter Crystallisation. Kevin W. Smith & Kees van Malssen Unilever R&D Colworth. Outline. Introduction Cocoa Butter and Chocolate Cocoa Butter Crystallisation Phase Transformations Phase Behaviour and Crystallites Conclusion. Cocoa Butter & Chocolate.

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Cocoa Butter Crystallisation

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

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

  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

  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

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

  6. Cocoa Butter Polymorphism • Current understanding

  7. 10m 20m 30m 12h 18h 10s 20s 30s 2m 3m 4m 2w 3w 2h 3h 6h 2d 3d 4d 40 liquid 30 b 20 b Tc (°C)  10 0 -10 g/sub- -20 1 min 1 hour 1 day 1 week Time (logarithmic) Static Isothermal Crystallisation

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

  9. ' Melting Dependent on Crystallisation Temperature

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

  11. Assignment of Polymorphs

  12. A B Temperature 100 B (%) Phase Behaviour and Crystallites 1 Liquid L+S 2 3 6 5 Solid 0 20 40 60 80 4

  13. Crystallites Composition

  14. Crystallites - Small Crystals

  15. Crystallites - Different Sizes

  16. Crystallites - Different Composition

  17. A B L L+SA Temperature L+SB SA SB SA + SB 0 20 40 60 80 100 B (%) Complex Phase Behaviour

  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

  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

  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)

  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)

  22. 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! Additional

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