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Cocoa Butter Crystallisation

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Cocoa Butter and Chocolate. Cocoa Butter Crystallisation. Phase Transformations ... Assignment of polymorphs to melting points has been mistaken ... – PowerPoint PPT presentation

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Title: Cocoa Butter Crystallisation


1
Cocoa Butter Crystallisation
  • Kevin W. Smith
  • Kees van Malssen
  • Unilever RD 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
Static Isothermal Crystallisation
8
?' Phase Range Diffraction
9
?' Melting Dependent on Crystallisation
Temperature
10
Cocoa Butter Phase Scheme
11
Assignment of Polymorphs
12
Phase Behaviour and Crystallites
1
Liquid
LS
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
Complex Phase Behaviour
18
Cocoa Butter Crystallisation
  • Composition dependent
  • Solidification in two stages
  • high melting fraction first
  • molten cocoa butter cooled to 30C 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 7C 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 RD 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
(No Transcript)
23
Additional
  • 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!
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