The influence of process parameters on gas assisted mechanical expression (GAME) of cocoa nibs

It is known that increased cocoa butter yields can be achieved with Gas Assisted Mechanical Expression (GAME) of cocoa nibs when compared to conventional expression of cocoa nibs [Venter, M.J., Willems, P., Kuipers, N.J.M. & de Haan, A.B. (2006). Gas Assisted Mechanical Expression of cocoa butter from cocoa nibs and edible oils from oilseeds. Journal of Supercritical Fluids, 37 (3), 350]. In a hydraulic press the GAME operation consists of a CO2 dissolution stage, a pressing stage and a depressurisation stage. In this work the influence of the process parameters involved with the pressing stage on the final cocoa butter yield is investigated. All GAME experiments were performed with 10 MPa of CO2. It is shown that neither the mass of cocoa nibs used, the duration of the pressing stage nor the mechanical pressure profile has a significant influence on the final cocoa butter yield. The moisture content of the nibs determines the behaviour of the solid structure during the pressing stage, thereby determining the cocoa butter yield that can be achieved as well as the speed with which it can be obtained. The maximum yield is obtained at a moisture content of 1.3 wt.% (wet basis). Lower moisture contents result in a faster compression of the cake. It is impossible to recover cocoa butter with GAME at 100 °C when nibs with moisture contents higher than 5.5 wt.% are used due to the extrusion of the cocoa solids through the filter medium. Similar yields were obtained when cocoa liquor and cocoa nibs were used in GAME experiments at the same conditions. Lastly it is shown that higher yields can be achieved when multi-stage GAME is used instead of single stage GAME. An absolute increase in cocoa butter yield of 7–10% was achieved when two-stage GAME was used instead of single stage GAME