Cocoa Butter
crystallization, tempering, bloom
Plan
• Lipid structure, crystallization &
polymorphism
• Tempering theory & practice
• Bloom
Fatty Acids
Stearic acid
18 carbon carboxylic acid
linear molecule
Oleic Acid
16 carbon carboxylic acid
single double bond puts a “kink”
O
C
HO
Fatty Acids in Cocoa Butter
26 wt%
16:0
Palmitic acid
34 wt%
18:0
Stearic acid
35 wt%
18:1
Oleic acid
…plus about 5 others
Triglycerides take on a tuning fork configuration
Homogeneous Nucleation
T>Tmelt
True melt
T=Tmelt
T<<Tmelt
supercooling
Crystal embryos
Crystal lattice
Heterogeneous Nucleation
T>Tmelt
True melt
T=Tmelt
Nucleation
T<Tmelt
less supercooling
Crystal lattice
Solid Fat Content
100% solid
• 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
100% liquid
cold
Temperature
hot
Polymorphism
Molecular packing can vary by angle of tilt...
…and by chain packing
Consequently there are several
types of triglyceride crystal
I
sub-
17.3oC
II

23.3oC
III
'2
25.5oC
IV
More dense
'1
V

VI

Higher MP
o
27.3 C
o
33.8 C
o
36.3 C
More
desirable
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
• 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
Rapid cooling leads to a less well ordered structure!
Cocoa butter
• Cocoa butter is largely triglycerides
• There has several stable crystal polymorphs
• Good chocolate can only be made from the
stable crystals
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 ~32oC which will act as
seeds when the melt is cooled
Why
o
32 C?
I
sub-
17.3oC
II

23.3oC
III
'2
25.5oC
IV
'1
V

VI

o
27.3 C
o
33.8 C
o
36.3 C
Tempering
• Why temper?
–
–
–
–
Demolding
Snap
Gloss
Resistance to bloom
• Temperature and time control
Tempering Sequence
temperature
50oC
Melt
Cool - no crystallization
Form mix of crystals
Melt out unstable polymorphs
32oC
30-32oC
27oC
time
Tempering Practice
• Hand tempering
• Batch tempering
• Continuous tempering
• Temper meters
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
Kettle Tempering
Melt
Cool - no crystallization
Form mix of crystals
Melt out unstable polymorphs
3-stage Tempering Machine
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
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
Types of Bloom
• High temperature bloom
• Low temperature bloom
• Fat migration bloom
High Temperature Bloom
• Fat is stored hot enough to melt (~35oC)
• Fat resolidifies and is no longer tempered
• Untempered chocolate rapidly grows bloom
U se a high melting fat if you can’t be certain
of distribution temperature
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
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
How to avoid bloom
•
•
•
•
Temper the chocolate properly
Store cool
Add butter-fat
Add emulsifier (e.g. sorbitan monostearate)
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