Flexible chocolate

Chocolate is a complex soft solid that undergoes a series of physical transformations in the mouth during consumption. Normally chocolate products are manufactured by liquid processing techniques that include 'melting and casting' liquid chocolate into moulds as well as enrobing sweet centres with a chocolate outer shell. There is however another method of shape forming chocolate and this review discusses the key elements of a so called 'cold extrusion' process. This process involves a combination of pressure and flow, which results in a product with a temporary flexibility. The review covers the basic aspects of the composition and microstructure of chocolate together with experimental observations on the cold extrusion process and the subsequent post extrusion flexibility of the extrudate. Finally some physical insight into the unusual behaviour of chocolate during and after cold extrusion is presented.