Thermal inactivation of Salmonella spp. during conching

Although chocolate is a microbiologically stable product it has been described as a vehicle for Salmonella spp. Because of the low water activity (aw) and the high fat content of chocolate Salmonella spp. shows an increased heat resistance, even during the thermal process of chocolate making. The aim of this study was to evaluate the thermal inactivation of Salmonella spp. during conching in various masses of chocolate and cocoa butter at different temperatures (50–90 °C). The effect of thermal treatment on Salmonella spp. was determined with the MPN (Most-Probable-Number) method. Results of thermal treatment showed approximate D-values for cocoa butter from D50°C = 245 min to D60°C = 306 min, for cocoa liquor from D50°C = 999 min to D90°C = 26 min and for dark chocolate of D50°C = 1574 min. z-values were found to be z = 20 °C in cocoa liquor and z = 14 °C in dark chocolate. This study demonstrates that the conching process alone does not ensure the inactivation of Salmonella spp. in different chocolate masses and that an additional decontamination step at the beginning of the process as well as an HACCP concept is necessary during chocolate production to guarantee the absence of Salmonella spp. in chocolates and related products.