Inactivation of desiccation-resistant salmonella on apple slices following treatment with e-polylysine, sodium bisulfate or peracetic acid and subsequent dehydration

Authors: Gurtler, Joshua; Garner, Christina; GRASSO-KELLEY, ELIZABETH - Food And Drug Administration(FDA); Fan, Xuetong; Jin, Zhonglin

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2024
Publication Date: 5/9/2024
Citation: Gurtler, J., Garner, C.M., Grasso-Kelley, E., Fan, X., Jin, Z.T. 2024. Inactivation of desiccation-resistant salmonella on apple slices following treatment with e-polylysine, sodium bisulfate or peracetic acid and subsequent dehydration. Journal of Food Protection. 87:100297. https://doi.org/10.1016/j.jfp.2024.100297.
DOI: https://doi.org/10.1016/j.jfp.2024.100297

Interpretive Summary: Salmonella can survive during drying of apple slices, which has caused caused at least one dried apple recall. This study examined the death of Salmonella on apple slices after washing for 2 minutes in three antibacterial solutions (epsilon-polylysine [EP], sodium bisulfate [SBS] or peracetic acid [PAA]), and then drying apple slices at 60 degrees Celsius. After 0.1 percent EP and 0.3 percent SBS washes and then drying apple slices, 3.87 and 6.2 log of Salmonella died. Washing with either 18 or 42 parts per million of PAA killed 4.62 and 5.63 log of Salmonella, after drying. These results may provide solutions to help kill Salmonella during commercial or consumer hot-air drying of apple slices.

Technical Abstract: Salmonella is capable of surviving dehydration within various foods, such as dried fruit. Dried fruit, including apple slices, have been the subject of product recalls due to contamination with Salmonella. A study was conducted to determine the fate of Salmonella on apple slices, following immersion in three antimicrobial solutions (viz., epsilon-polylysine [EP], sodium bisulfate [SBS] or peracetic acid [PAA]), and subsequent hot-air dehydration. Gala apples were aseptically cored and sliced into 0.4 cm thick rings, bisected, and inoculated with a five-strain composite of desiccation-resistant Salmonella to a population of 8.28 log CFU/slice. Slices were then immersed for 2 min in various concentrations of antimicrobial solutions, including EP (0.005, 0.02, 0.05 and 0.1 percent), SBS (0.05, 0.1, 0.2 and 0.3 percent), PAA (18 or 42 ppm), or varying concentrations of PAA plus EP, and then dehydrated at 60 degrees Celsius for 5 h. Salmonella populations in positive-control samples (inoculated slices washed in sterile water) declined by 2.64 log CFU after drying. Previous studies have demonstrated that a two-minute, 0.5 percent SBS wash, prior to dehydration, inactivated greater than 5.0 log CFU of Salmonella on Gala apple slices. In the present study, inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.2 log (at 0.10 and 0.30 percent of the two compounds), respectively. Based on preliminary studies, EP concentrations greater than 0.1 percent did not result in lower populations of Salmonella. Pretreatment washes with either 18 or 42 ppm of PAA inactivated Salmonella populations by 4.62 and 5.63 log, respectively, following desiccation. Combining PAA with up to 0.1 percent EP induced no greater reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, effectively reducing its biocidal efficacy. These results may provide pre-drying treatment alternatives to promote the reduction of Salmonella during commercial or consumer home hot-air drying of apple slices.