Author: Herr Dr. Amoneit
Last saved by: Saritas, Sevim
Company: Loughborough University

The Effect of Hazelnut Oil on the Crystallisation of Cocoa Butter Observed via Hot Stage Microscopy
David I. Stewart^1, Andrew G. F. Stapley^1, Zoltan K. Nagy^1, and Peng S. Chong^2
^1Department of Chemical Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, U.K.,
and ^2Nestlé Product Technology Centre, York, YO31 8FZ, U.K.

The crystallisation and melting behaviour of cocoa butter (CB) and an 80:20 mixture of CB in hazelnut (HZ) oil was investigated using hot stage microscopy (HSM). Samples were melted at 60°C, cooled at various rates to 0°C, and then remelted at various rates. Images were taken in order to ascertain induction temperatures and observe polymorphic and melting behaviour, which were also studied by DSC. Crystals first appeared when temperatures were in the range 18-23°C, with more rapid cooling rates giving lower induction temperatures. In pure CB samples, very few high-melting (β) crystals were apparent upon remelting. However, in CB-HZ samples the β form was much more prevalent, particularly when faster cooling rates had been used. This shows that liquid oil content is an important variable for polymorphic transformation, aiding the transition to the β form. Fast cooling rates are more likely to produce lower polymorphic forms and these appear to transform relatively easily into the β form. Slower cooling rates generally produced the β‘ form, which was less likely to then transform to β. HSM is shown to be an excellent technique for visualising crystal growth and polymorphic transformation.