1. Cocoa Butter crystallization, tempering, bloom

2. Plan Lipid structure, crystallization & polymorphism Tempering theory & practice Bloom

3. Fatty Acids Stearic acid 18 carbon carboxylic acid linear molecule Oleic Acid 16 carbon carboxylic acid single double bond puts a “kink” C O HO

4. Fatty Acids in Cocoa Butter …plus about 5 others

5. Triglycerides take on a tuning fork configuration

6. True meltCrystal embryos Crystal lattice T>T melt T=T melt T<<T melt supercooling Homogeneous Nucleation

7. True meltNucleation Crystal lattice T>T melt T=T melt T<T melt less supercooling Heterogeneous Nucleation

8. Temperature cold hot 100% liquid 100% solid Solid Fat Content cooling heating SFC is a function of temperature SFC is a function of temperature history SFC is a function of time SFC is a function of composition

9. Molecular packing can vary by angle of tilt... Polymorphism

10. …and by chain packing

11. Consequently there are several types of triglyceride crystal Higher MP More dense More desirable

12. Key Facts Desirable forms have a high melting point The higher melting point, the more stable More stable fats are more dense More stable forms are slow to form Like crystals will grow from like Cocoa butter can convert from a less to more stable form

13. As the oil cools the fat molecules slow down Eventually try to “stop” in contact with another molecule (crystal lattice) It takes time to get into optimal position (most dense) Pre-existing nuclei can help form a template

14. Rapid cooling leads to a less well ordered structure!

15. Cocoa butter Cocoa butter is largely triglycerides There has several stable crystal polymorphs Good chocolate can only be made from the stable crystals

16. Tempering Tempering is a time-temperature process ensure the formation of chocolate in the right crystal habit In practice this means we want 1-2% solids at ~32 o C which will act as seeds when the melt is cooled

17. Why 32 o C?

18. Tempering Why temper? –Demolding –Snap –Gloss –Resistance to bloom Temperature and time control

19. Tempering Sequence 50 o C 32 o C 27 o C 30-32 o C time temperature Melt Cool - no crystallization Form mix of crystals Melt out unstable polymorphs

20. Tempering Practice Hand tempering Batch tempering Continuous tempering Temper meters

21. Hand Tempering Melt fat Pour melt onto slab and work with spatulas Return semicrystalline batch back to warm melt Mold chocolate Melt Cool - no crystallization Form mix of crystals Melt out unstable polymorphs

22. Kettle Tempering Melt Cool - no crystallization Form mix of crystals Melt out unstable polymorphs

23. 3-stage Tempering Machine

24. Tempering Tempering is a process to ensure the formation of stable crystals Tempering is a time-temperature process Tempering can be done as a batch or continuous process Degree of temper can be measured from a cooling curve

25. What is bloom? White “moldy” appearance at the surface Major reason for product failure NOT a health hazard Often caused by large fat crystals growing from the surface and scattering light

27. Types of Bloom High temperature bloom Low temperature bloom Fat migration bloom

28. High Temperature Bloom Fat is stored hot enough to melt (~35 o C) Fat resolidifies and is no longer tempered Untempered chocolate rapidly grows bloom Use a high melting fat if you can’t be certain of distribution temperature

29. Low Temperature Bloom In well tempered chocolate stored below its melting point Associated with V to VI transition Occurs faster at high temperatures (esp. if temp. cycles) Reduce storage temperature

30. Migration Bloom The movement of fat from an enrobed center to the surface Dissolves some cocoa butter and carries it to the surface Cocoa butter recrystalizes at the surface

31. How to avoid bloom Temper the chocolate properly Store cool Add butter-fat Add emulsifier (e.g. sorbitan monostearate)

32. Bloom A moldy white deposit on the surface Large fat crystals formed by migration and recrystallization Not a health hazard but it is a cause for product rejection Avoid by good tempering and controlled storage