Cocoa Butter

crystallization, tempering, bloom

Plan

• Lipid structure, crystallization & polymorphism

• Tempering theory & practice

• Bloom

Fatty Acids

Stearic acid18 carbon carboxylic acid

linear molecule

Oleic Acid16 carbon carboxylic acid

single double bond puts a “kink”

CO

HO

Fatty Acids in Cocoa Butter

…plus about 5 others

26 wt% 16:0 Palmitic acid

34 wt% 18:0 Stearic acid

35 wt% 18:1 Oleic acid

Triglycerides take on a tuning fork configuration

True melt Crystal embryos Crystal lattice

T>Tmelt T=Tmelt T<<Tmelt

supercooling

Homogeneous Nucleation

True melt Nucleation Crystal lattice

T>Tmelt T=Tmelt T<Tmelt

less supercooling

Heterogeneous Nucleation

Temperaturecold hot

100% liquid

100% solidS

olid

Fat

Con

tent

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

Molecular packing can vary by angle of tilt...

Polymorphism

…and by chain packing

Consequently there are several types of triglyceride crystal

I sub- 17.3oC

II 23.3oC

III '2 25.5oC

IV '1 27.3oC

V 33.8oC

VI 36.3oC

Higher MPMore dense

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 32oC?

I sub- 17.3oC

II 23.3oC

III '2 25.5oC

IV '1 27.3oC

V 33.8oC

VI 36.3oC

Tempering

• Why temper?– Demolding– Snap– Gloss– Resistance to bloom

• Temperature and time control

Tempering Sequence50oC

32oC

27oC

30-32oC

time

tem

pera

ture

MeltCool - no crystallizationForm mix of crystalsMelt out unstable polymorphs

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 MeltCool - no crystallizationForm mix of crystalsMelt out unstable polymorphs

Kettle Tempering

MeltCool - no crystallizationForm mix of crystalsMelt 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

Use 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