Purpose: To determine the inactivation kinetics of BC and GB on cocoa nibs and beans at 110, 125 and 140ºC.
Methods: Spores suspensions of five different strains of each BC and GB were used. Cocoa beans and nibs were put in sterile steel trays and separately inoculated with spores of BC and GB, respectively. The roasting process was carried out at three temperatures (110, 125 and 140 ± 2ºC). Samples were collected in different time periods and survivors were enumerated on MYP (BC) and DTA (GB). Data on survivors (CFU/g) were plotted against time and inactivation kinetic parameters were determined by fitting predictive models to data using the add-in Ginafit.
Results: The inactivation kinetics of BC and GB were estimated using Weibull-type models. The δ-values (time for the first decimal reduction; min) for BC in cocoa nibs at 110, 125 and 140ºC were 79.2±16.7, 47.9±1.2, and 24.1±0.1, whereas for cocoa beans these values were 166.2±24.1, 702±26.3, and 31.3±3.2, respectively. The δ-values (min) for GB in cocoa nibs at 110, 125 and 140ºC were 117.8±27.1, 212±0.4 and 69.9±13.5, while in cocoa beans these values were 278.2±66.0, 58.4±8.5 and 61.6±13.8, respectively. The 4D-values (time for 4 log CFU reduction; min) for BC in cocoa nibs at 110, 125 and 140ºC were 281.1±7.3, 107.2±0.9 and 59.6±4.7; whereas, in cocoa beans, 4D-values were 389.2.±9.5, 143.1±19.0 and 65.2±2.8. The 4D-values for GB in cocoa nibs were 427.8±18.5, 153.0±4.2 and 137.6±6.8, while for cocoa beans were 564.3±23.3, 228.6±12.7 and 156.0±8.5.
Significance: These data suggest that the temperature conditions applied during cocoa roasting will not impact on BC and BG spores.