Thermal Inactivation of Salmonella on Sesame-topped Bread during Baking Using High and Low Oven Humidity

Unpasteurized ingredients, such as contaminated sesame seeds or flour, may introduce Salmonella into bakery products. Therefore, the use of a validated baking process is critical to eliminate this pathogen. This study compared the effect of oven relative humidity (RH) on the reduction of Salmonella and yeast during baking of inoculated bread dough topped with inoculated sesame seeds. Salmonella was injected into individual portions of bun dough to yield populations of 7.0–8.0 log CFU/g; dough was proofed and then topped with dry, inoculated sesame seeds (6.0–7.0 log CFU Salmonella/g seed). The seeded buns and seeds alone were baked in dry (average ~3% RH) or moist (average 20% RH after wet bulb spike) oven conditions for 7 and 9 min, respectively, to match a “bun-color standard,” as suggested by a commercial bakery. After complete baking, Salmonella and yeast populations in the bun had decreased > 5-log for both methods. In contrast, differences in oven RH affected inactivation on the surface seeds, with reductions of 3.6 and > 6.0 log Salmonella at the end of dry and moist baking, respectively. This study demonstrates that maintaining an average 20% relative humidity during baking enhances the lethality on the product surface, compared to ≤ 3% RH, while also maintaining quality.