Survival of Salmonella during Baking of Peanut Butter Cookies

Introduction: Peanuts and peanut-based products have been the source of recent Salmonella outbreaks worldwide. Since peanut butter is widely used as an ingredient in baked goods, the risk of Salmonella remaining in these products after baking needs to be assessed.

Purpose: This research examines the potential hazard of Salmonella in peanut butter cookies when it is introduced via the peanut-derived ingredient. The objective was to determine the survival of Salmonella during the baking process.

Methods: Commercial, creamy-style peanut butter was artificially inoculated with a 5-strain Salmonella cocktail at a high (10⁸ CFU/g) and a low (10⁵ CFU/g) target concentration. Peanut butter cookies were prepared using a standard recipe and the inoculated peanut butter. Initial Salmonella concentrations in the dough made with the high and low inoculated peanut butter were 6.5 and 2.5 log CFU/g, respectively. Dough was baked at 350 °F for 15 minutes. After baking, the survival of Salmonella was determined either by plating or enrichment. Temperature profiles of the cookies were monitored during baking. Cookie moisture content, water activity and pH were measured before and after baking.

Results: Salmonella survived in 13 of the 24 samples prepared with the high inocula peanut butter. In positive samples, Salmonella populations decreased an average of 5.0 log CFU/g. No Salmonella was detected in the 24 baked samples made with the low Salmonella contaminated peanut butter, resulting in a decrease greater than 3.9 log CFU/g.

Significance: Results of this study indicate that the risk of Salmonella in peanut butter cookies prepared with contaminated peanut butter is greatly reduced during baking.