Search

Abstract: The ability of the Shirato model to describe the expression of dry cocoa nibs in a hydraulic press at pressures of 20–80MPa was compared with that of a numerically solved conservation laws model based on mass and momentum balances. Experimental data were used to determine the material constants involved in both models at 40, 80 and 100°C. The Shirato model more accurately describes the final average porosity at different pressures. The Shirato model was therefore used to calculate the influence of the pressure, pressing time and mass of nibs used on the expression process. The calculation results followed the experimentally observed trends. The Shirato model was also used to describe the expression behaviour of cocoa liquor (finely grinded cocoa nibs) at 100°C and pressures of 20–70MPa. It was calculated that the filtration stage is absent at these pressures. However, the behaviour of cocoa liquor can only be accurately described with the Shirato model for the last part of the expression process (>100s). [Copyright &y& Elsevier]

Abstract: The effect of temperature (40–110°C), applied mechanical pressure (20–80MPa), applied pressure profile (constant/linearly increasing) and moisture content (0–8wt.%, wet basis) on the expression of cocoa nibs were investigated. The maximum cocoa butter yield is achieved at 100°C. The optimum moisture content with respect to cocoa butter yield is 1.3wt.%. The cocoa butter yield increases with pressure up till 60MPa where it has a value of 80% when dry cocoa beans are used. Neither the use of higher pressures nor the use of a linearly increasing pressure profile causes any further increases in the cocoa butter yield when the total pressing time is kept constant. The rate of expression increases with an increase in temperature or a decrease in moisture content. Higher cocoa butter yields (up to 89%) were achieved when cocoa liquor was pressed instead of cocoa nibs. [Copyright &y& Elsevier]