Cocoa Butter crystallization tempering bloom Plan Lipid structure

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 …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

• SFC is a function of temperature history • SFC is a function of time • SFC is a function of composition ing l coo ting hea Solid Fat Content 100% solid 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 More dense Higher MP 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 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

Why o 32 C?

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

Tempering Sequence temperature 50 o. C Melt Cool - no crystallization Form mix of crystals Melt out unstable polymorphs 32 o. C 30 -32 o. C 27 o. C 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 (~35 o. C) • 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