Kinetics of aflatoxin degradation during peanut roasting.

This study investigated aflatoxin degradation during peanut roasting. First, peanuts contaminated with three initial aflatoxin concentrations (35, 332 and 695µg/kg) were roasted at 180°C for up to 20min. The percentage of aflatoxin degradation after 20min were 55, 64 and 81% for peanuts contaminated with aflatoxin at 35, 332 and 695µg/kg, respectively. This difference was statistically significant (p<0.05), showing that initial concentration influences aflatoxin reduction. Thereafter, peanut samples contaminated with an initial aflatoxin concentration of 85µg/kg were roasted at 160, 180 and 200°C for 5, 10, 15, 20 and 25min, then residual concentrations of aflatoxin were determined. Roasting at 160, 180 and 200°C resulted in an aflatoxin reduction of 61.6, 83.6 and 89.7%, respectively. This study has provided quantitative data reinforcing the fact that roasting alone is not enough to control aflatoxins in peanuts.

Inactivation of Salmonella during cocoa roasting and chocolate conching.

The high heat resistance of Salmonella in foods with low water activity raises particular issues for food safety, especially chocolate, where outbreak investigations indicate that few colony-forming units are necessary to cause salmonellosis. This study evaluated the efficiency of cocoa roasting and milk chocolate conching in the inactivation of Salmonella 5-strain suspension. Thermal resistance of Salmonella was greater in nibs compared to cocoa beans upon exposure at 110 to 130°C. The D-values in nibs were 1.8, 2.2 and 1.5-fold higher than those calculated for cocoa beans at 110, 120 and 130°C. There was no significant difference (p>0.05) between the matrices only at 140°C. Since in the conching of milk chocolate the inactivation curves showed rapid death in the first 180 min followed by a lower inactivation rate, and two D-values were calculated. For the first time interval (0-180 min) the D-values were 216.87, 102.27 and 50.99 min at 50, 60 and 70°C, respectively. The other D-values were determined from the second time interval (180-1440 min), 1076.76 min at 50°C, 481.94 min at 60°C and 702.23 min at 70°C. The results demonstrated that the type of matrix, the process temperature and the initial count influenced the Salmonella resistance.