Purpose: This study validated a simulated commercial tortilla cooking process to control a seven-serotype Salmonella (Hartford, Newport, Senftenberg, Tennessee, Typhimurium, and two isolates from pet food) cocktail, and determined D- and z-values of the cocktail in tortilla dough.
Methods: Wheat flour was mist inoculated with the Salmonella cocktail, dried to the pre-inoculation weight to achieve ~7.5 log CFU/g, and used for preparing tortilla dough. For the cooking validation, dough was pressed in a standard tortilla press (top and bottom plates at ~93 and 43°C, respectively), heated on a pan (preset at 240°C) for 30, 45, or 60 s on each side, followed by 10 min of ambient cooling. D-values of the Salmonella cocktail were determined at 55, 58, and 61°C using thermal-death-time disks. Both studies utilized a randomized complete block (three replications) design and analyses were conducted at P≤0.05.
Results: After cooking for 30, 45, or 60 s on each side, the Salmonella population decreased by >7.5 log CFU/g in flour tortillas; however, Salmonella was detected by enrichment plating at the end of each cooking time. D-values of the Salmonella cocktail in tortilla dough at 55, 58, and 61°C were 22.19, 13.48, and 4.59 min, respectively; the z-value was 8.85°C.
Significance: This study validated that >7.5 log reduction of Salmonella in flour tortillas is achieved after cooking for ≥30 s on each side at a 240°C pan temperature. The calculated D- and z-values in this study can help the flatbread industry design appropriate parameters to control Salmonella contamination in ready-to-eat tortillas.