Purpose: This study validated a simulated commercial muffin baking process against E. coli O121 (flour outbreak isolate), and determined D- and z-values of E. coli O121 (four-isolate cocktail) and Salmonella (three-serovar cocktail of Newport, Typhimurium, and Senftenberg) in muffin batter.
Methods: Batter were prepared using spray inoculated flour containing ~7 log CFU E. coli O121 or Salmonella/g. For the baking validation, batter was baked at 190.6°C oven temperature for 21 min followed by 30 min of ambient cooling. D-values of E. coli O121 and Salmonella cocktails in batter were determined using thermal-death-time disks. Randomized complete block designs were used for each study, with three replications as blocks (a=0.05).
Results: Escherichia coli O121 populations decreased by >7 log CFU/g in muffins at 17 min, and were completely eliminated at 21 min of baking. D-values of E. coli O121 and Salmonella cocktails in muffin batter at 60, 65, and 70°C were 42.03 and 38.38, 7.49 and 7.17, and 0.42 and 0.47 min, respectively. The z-values of E. coli O121 and Salmonella were 5.01 and 5.22°C, respectively.
Significance: Survival of E. coli O121 in muffins during oven baking was slightly lower than observed for Salmonella, as determined in a previous study by these authors. The validated baking process against Salmonella would effectively control similar levels of E. coli O121. Both organism cocktails demonstrated similar D- and z-values in batter and can be used by the bakery industry to establish safe baking protocols; however, specific validation studies may be appropriate if the baking parameters or muffin recipe are modified.