Validation of the baking process as a kill-step for controlling Salmonella in muffins

- A muffin baking process was validated to eliminate Salmonella introduced via flour.
- Baking at 190.6 °C oven temperature for 17 min reduced 5 log cycles of Salmonella.
- Salmonella D-values at 55, 58 and 61 °C were 62.2, 40.1 and 16.5 min, respectively.
- Salmonella z-value in muffin batter was 10.4 °C.

This research investigates the potential risk of Salmonella in muffins when contamination is introduced via flour, the main ingredient. Flour was inoculated with a 3-strain cocktail of Salmonella serovars (Newport, Typhimurium, and Senftenberg) and re-dried to achieve a target concentration of ~ 8 log CFU/g. The inoculated flour was then used to prepare muffin batter following a standard commercial recipe. The survival of Salmonella during and after baking at 190.6 °C for 21 min was analyzed by plating samples on selective and injury-recovery media at regular intervals. The thermal inactivation parameters (D and z values) of the 3-strain Salmonella cocktail were determined. A ≥ 5 log CFU/g reduction in Salmonella population was demonstrated by 17 min of baking, and a 6.1 log CFU/g reduction in Salmonella population by 21 min of baking. The D-values of Salmonella serovar cocktail in muffin batter were 62.2 ± 3.0, 40.1 ± 0.9 and 16.5 ± 1.7 min at 55, 58 and 61 °C, respectively; and the z-value was 10.4 ± 0.6 °C. The water activity (aw) of the muffin crumb (0.928) after baking and 30 min of cooling was similar to that of pre-baked muffin batter, whereas the aw of the muffin crust decreased to (0.700). This study validates a typical commercial muffin baking process utilizing an oven temperature of 190.6 °C for at least 17 min as an effective kill-step in reducing a Salmonella serovar population by ≥ 5 log CFU/g.