Heat Resistance of Salmonella Species in Confections Containing Sensitive Ingredients during Candy Processing

Introduction: Candy making is an artisanal process with some modern recipes dating back decades and even centuries; long before the advent of modern food safety techniques. Candy processes are assumed to produce microbiologically safe foods due their high processing temperatures, generally greater than 100°C. However, this assumption is dangerous as candies often contain sensitive ingredients like, chocolate, flour, or whey, which are known vectors for Salmonella and the low water activity of confections can contribute to the heat resistance of Salmonella. Since thermal processes vary between products and facilities these processes must be validated as a biological control step to ensure food safety.

Purpose: This study investigated the heat resistance of Salmonella spp. during typical confectionary thermal processing in model caramel and licorice matrices.

Methods: The model caramel and licorice ingredients were heated and mixed to mimic a pre-processed product. The caramel and licorice were then dry inoculated with two different Salmonella cocktails made on whey and wheat flour, respectively. Aliquots were sealed in Whirlpak bags which underwent thermal processing in an oil or water bath. Caramel and licorice samples were treated at temperatures between 80°C and 105°C. The data was analyzed to determine D-values and z-values.

Results: The water activities of caramel and licorice were between 0.4 - 0.6.  The caramel D_85°C and D_90°C of Salmonella spp. were 196 and 98 seconds. The licorice D_80°C and D_85°C of Salmonella spp. were 29 and 24 seconds respectively. In both candies, regardless of A_w or inoculum type, instantaneous multi-log reductions of the Salmonella spp. at 100°C were observed.

Significance: The data suggests that if a minimum temperature of 100°C is reached in a confectionary process then the process can be can be considered a pathogen control step for caramel and licorice.