Comparison of Peracetic Acid and Chlorine Effectiveness during Fresh-Cut Vegetable Processing at Industrial Scale

Inactivation of Desiccation-Resistant Salmonella on Apple Slices Following Treatment with ε-Polylysine, Sodium Bisulfate, or Peracetic Acid and Subsequent Dehydration

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., ε-polylysine [epsilon-polylysine or 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%), SBS (0.05, 0.1, 0.2, and 0.3%), PAA (18 or 42 ppm), or varying concentrations of PAA + EP, and then dehydrated at 60°C for 5 h. Salmonella populations in positive control samples (inoculated apple slices washed in sterile water) declined by 2.64 log after drying. In the present study, the inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.20 log (with 0.1 and 0.3% of the two compounds, respectively). Based on preliminary studies, EP concentrations greater than 0.1% 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% EP induced no greater population reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, reducing its biocidal efficacy. These results may provide antimicrobial predrying treatment alternatives to promote the reduction of Salmonella during commercial or consumer hot air drying of apple slices.

Disinfection efficiency of chlorine dioxide and peracetic acid against MNV-1 and HAV in simulated soil-rich wash water

Wash water from fresh vegetables and root vegetables is an important vehicle for foodborne virus transmission. However, there is lack of assessing rapid viral inactivation strategies in wash water characterized by a high soil content at the post-harvest stage. Considering the significance of food safety during the washing stage for fresh and root vegetable produce prior to marketing, we assessed the inactivation efficacy by using chlorine dioxide (ClO2) and peracetic acid (PAA) against a surrogate of human norovirus (murine norovirus 1, MNV-1) and hepatitis A virus (HAV), in wash water containing black soil and clay loam. The results indicated that MNV-1 and HAV were reduced to the process limit of detection (PLOD), with reductions ranging from 4.89 to 6.35 log10 PFU, and 4.63 to 4.96 log10 PFU when treated with ClO2 at 2.5 ppm for 10 mins. Comparatively, when treated with 500 ppm of PAA for 10 mins, MNV-1 and HAV were maximum reduced to 1.75 ± 0.23 log10 PFU (4.50 log10 PFU reduction) and 2.13 ± 0.12 log10 PFU (2.72 log10 PFU reduction). This demonstrated the efficacy of ClO2 in eliminating foodborne viruses in soil-rich wash water. When we validated the recovery of the virus from two types of wash water, the pH (9.24 ± 0.33 and 5.95 ± 0.05) had no impact on the recovery of MNV-1, while the recovery of HAV was less than 1 %. By adjusting the pH to a neutral level, recovery of HAV and its RNA levels was increased to 15.94 and 3.89 %. Thus, this study emphasized the critical role of pH in the recovery of HAV from the complex soil-rich aqueous environment, and the efficacy of ClO2 serving as a pivotal reference for the development of control strategies against foodborne viruses in the supply chain of fresh and root vegetables.

Exploring Peracetic Acid and Acidic pH Tolerance of Antibiotic-Resistant Non-Typhoidal Salmonella and Enterococcus faecium from Diverse Epidemiological and Genetic Backgrounds

Acid stress poses a common challenge for bacteria in diverse environments by the presence of inorganic (e.g., mammals' stomach) or organic acids (e.g., feed additives; acid-based disinfectants). Limited knowledge exists regarding acid-tolerant strains of specific serotypes, clonal lineages, or sources in human/animal pathogens: namely, non-typhoidal Salmonella enterica (NTS) and Enterococcus faecium (Efm). This study evaluated the acidic pH (Mueller-Hinton acidified with HCl) and peracetic acid (PAA) susceptibility of Efm (n = 72) and NTS (n = 60) from diverse epidemiological/genetic backgrounds and with multiple antibiotic resistance profiles. Efm minimum growth/survival pH was 4.5-5.0/3.0-4.0, and for NTS it was 4.0-4.5/3.5-4.0. Efm distribution among acidic pH values showed that only isolates of clade-non-A1 (non-hospital associated) or the food chain were more tolerant to acidic pH compared to clade-A1 (hospital-associated clones) or clinical isolates (p < 0.05). In the case of NTS, multidrug-resistant (MDR) isolates survived better in acidic pH (p < 0.05). The PAA MIC/MBC for Efm was 70-120/80-150 mg/L, and for NTS, it was 50-70/60-100 mg/L. The distribution of Efm among PAA concentrations showed that clade-A1 or MDR strains exhibited higher tolerance than clade-non-A1 or non-MDR ones (p < 0.05). NTS distribution also showed higher tolerance to PAA among non-MDR and clinical isolates than food chain ones (p < 0.05) but there were no differences among different serogroups. This unique study identifies specific NTS or Efm populations more tolerant to acidic pH or PAA, emphasizing the need for further research to tailor controlled measures of public health and food safety within a One Health framework.