Cold Extrusion of Flexible Chocolate
Cold extrusion of flexible chocolate is concerned with pressure driven extrusion processing of chocolate in the semi-solid state. Contrary to the traditional liquid melt processing of chocolate, Beckett et al.  showed that the semi solid ram extrusion processing of chocolate below the melting point of the material was feasible. The fresh extrudate was found to have a temporary flexibility before becoming brittle with storage time. This short term flexibility of the extrudate enables for instance complex shape formation immediately after extrusion.
Wide Sheet Extrusion
The wide sheet extrusion of flexible chocolate was performed using a converging diverging die and a Betol ram extruder.
After extrusion, the flexible chocolate sheet was further shape formed by stamping using a male and female mould. The desired quality of the final product (e.g. shape definition, surface gloss) could be controlled by careful adjustments of both extrusion processing and stamping parameters.
The stamping process was modelled using Forge 2D, which is commonly used to study plastic flow in metal processes such as extrusion and forging. This allowed useful predictions of the stress (shown in the diagram to the left) and strain distributions during material deformation as well as the amount of mould fill and stamping load involved.
1. Beckett, S.T., Craig, M.A., Gurney, R.J., Ingleby, B.S., Mackley, M.R. and Parsons, T.C.L., The cold extrusion of chocolate, Trans IChemE, Vol. 72, Part C, p. 47-54 (1994).