Validation of the baking step for brownies to control Salmonella

Primary author: Phoebe Unger
Co-author(s): Arshdeep Singh; Amninder Singh Sekhon; Monipel Ansong; Lakshmikantha H. Channaiah; Minto Michael
Faculty sponsor: Minto Michael

Primary college/unit: Agricultural, Human and Natural Resource Sciences
Campus: Pullman


Salmonella can survive under dry environment of flour for extended periods of time. Salmonella can flourish when flour is hydrated while preparing batter or dough, and could cause serious foodborne illnesses if the product is improperly baked. The main goal of this study was to validate a simulated commercial baking process for brownies that has ~7 log CFU/g Salmonella population. The study was conducted in a randomized complete block design with three replications. All-purpose flour was spray inoculated with a 5-serovar Salmonella (Enteritidis, Montevideo, Newport, Senftenberg and Typhimurium) cocktail, and dried back to original pre-inoculation water activity. Brownie batter was prepared from inoculated flour and baked in a conventional oven at 176.7°C for 40 min in a 12″ by 12″ pan. Samples were taken at five-minute intervals during baking. Microbial populations were enumerated using injury-recovery media (brain heart infusion agar overlaid with xylose lysine deoxycholate agar). The initial Salmonella population in brownie batter was 6.9 log CFU/g. The Salmonella population was below the detection limit (0.60 log CFU/g) after 30 minutes of baking. The bacterial population at 5, 10, 15, 20, and 25 minutes were calculated as 6.7, 6.5, 5.5,4.4 and 2.6 log CFU/g, respectively. As expected, the water activity of brownies decreased during baking. This study validated that a typical commercial brownie baking process utilizing an oven temperature of 176.7°C and baking for at least 40 min would achieve >5-log reductions in Salmonella populations. However, validation studies should be individually conducted for brownie products with different baking parameters.