Effect of processing on the microstructural properties of water-in-cocoa butter emulsions

• A margarine line allows controlling the microstructure of fat continuous emulsions.
• Using a scraped surface heating exchanger (SSHE) smaller droplets are obtained.
• The use of a SSHE allows tempering cocoa butter on emulsification.
• At low residence time, when using the SSHE only, bigger droplets are produced.

A bench scale margarine line (a scraped surface heating exchanger followed by a pin stirrer) was used to produce stable tempered water-in-cocoa butter emulsions. A wide set of processing parameters was explored and correlated to the microstructural properties (d3,2 and main crystal polymorphic form) of emulsions containing 10% or 20% (w/w) aqueous phase. The droplets size (d3,2) was evaluated using pulsed field gradient NMR measurements and related to the applied shear profile. In particular, the effect of each mixer on the final d3,2 values was examined. Results obtained from DSC analysis of fast cooled emulsions were used to understand the effect of continuous shear on the main polymorphic form of cocoa butter. The behaviour of this fat in an emulsified system is still mostly unknown. The results allow us to better understand the mechanism of the emulsifying process occurring in the margarine line, and show a clear dependence of the crystallising behaviour on the applied mechanical shear. Finally, droplets size data was fitted with a power law model used in literature for high shear mixers.