Evaluation and validation of the efficacy of peroxyacetic acid and chlorine as antimicrobial treatments for agricultural surface water to be used post-harvest

Master of ScienceFood Science InstituteSara E GraggThe recent increase in food-borne illness cases associated with produce threatens public health, the produce industry, and the national economy. Water used in produce washing is one of the routes of microbial contamination, hence the increasing interest and importance of finding efficient antimicrobial disinfectants to treat wash water to ensure that it is potable and safe for produce washing. Objective one evaluated peroxyacetic acid and chlorine as treatments for simulated surface water inoculated with a non-pathogenic Escherichia coli cocktail (ca. 5 log colony forming units (CFU/ml) to determine their efficacy at achieving ‘no detectable generic E. coli in 100 mL of post-harvest agricultural water. Simulated surface water was prepared to turbidity levels of two and 100 NTU using PTI Arizona Test Dust. Each of the two turbidities was adjusted to both pH 6.5 and 8.4, and the turbid water was equilibrated to 32 and 12C. Each sample was inoculated with ca. 5 log CFU/ml of non-pathogenic E. coli and treated with either free chlorine (C) 252 ppm, peroxyacetic acid (PAA) 755 ppm, or a sterile water control (W), with a 10 second (s) contact time. Following the 10 s contact time, samples were neutralized in Dey-Engley Broth, and E. coli were enumerated using E. coli/Coliform (EC) Petrifilm at 0, 5, 10, 60, 1440, and 2880 minutes (min). At each time point, samples were also enriched in 2X brain heart infusion (BHI) broth to be streaked on MacConkey agar plates to confirm the absence of E. coli. All C and PAA treated samples were below the limit of detection on EC (5 CFU/ml) and negative for E. coli on MacConkey plates starting from the 0 min time point. This suggests the achievement of no detectable levels of E. coli by both C and PAA after a 10 s contact time. Objective two validated the efficacy of C and PAA at reducing E. coli in surface water sources to the ‘no detectable generic E. coli’ for agricultural water that will have post-harvest contact with the produce, as required by the Food Safety Modernization Act for post-harvest use. Rain barrel and creek water sources obtained from two different farms were inoculated with ca. 5 log CFU/ml of a non-pathogenic E. coli cocktail and equilibrated at temperatures 32 and 12C. Samples were treated as described in objective one and enumerated at 0, 5, 10-, 60-, 1440-, and 2880-min post-treatment using the FDA- approved IDEXX Quanti-Tray/2000 Colilert method and EC Petrifilm. Samples were enriched in 2X BHI and streaked on MacConkey agar to test for the absence or presence of E. coli. Using Colilert, E. coli was detected until 60 min contact time in samples treated with C, while E. coli was not detected in samples treated with PAA at the 0 min (10 sec contact time) sampling point. When enumerating with EC Petrifilm, the W sample harbored 5 logs of E. coli, which was statistically different than C and PAA (P<0.05), both of which were negative for E. coli following enrichment in 2X BHI. Data collected during objectives one and two suggest that at the evaluated dosage levels and water conditions, chlorine and peroxyacetic acid effectively achieve no detectable E. coli in surface water sources in less than 60 min post-treatment

Evaluation of Peroxyacetic Acid and Chlorine as Treatments for Surface Water for Post-Harvest Uses in the Produce Industry

Nearly half of foodborne illnesses are linked to produce and nuts, and water used for produce post-harvest activities can contribute to contamination. Surface water serves as an economical source for agricultural activities; however, exposure to the environment increases microbial risks and impacts its physicochemical characteristics. In this study, peroxyacetic acid (PAA) and chlorine (Cl) were evaluated as treatments for simulated surface water to determine their efficacy at achieving ‘no detectable generic Escherichia coli’ in 100 mL. Simulated surface water was prepared to turbidities of 2 and 100 NTU, adjusted to pH 6.5 or 8.4, equilibrated to 32 or 12 °C, inoculated with 5 logs per mL of non-pathogenic (generic) E. coli, and treated with Cl 25 ± 2 ppm, PAA 75 ± 5 ppm, or sterile water control (W). Dey-Engley neutralization was followed by enumeration on E. coli/Coliform Petrifilm at times (t) 0 to 2880 min (48 h) post-treatment. When not detected, treatments were further evaluated through enrichment in 2X Brain Heart Infusion (BHI) broth. Enrichments were streaked on MacConkey agar (MAC) to confirm E. coli absence. All Cl and PAA treated samples were below the test limit of detection (E. coli was not detected in 5 mL enrichments even at t = 0 (shortly after treatment). These data suggest that Cl and PAA interventions may be effective for treating surface water for post-harvest uses

Evaluation of Peroxyacetic Acid and Chlorine as Treatments for Surface Water for Post-Harvest Uses in the Produce Industry

Nearly half of foodborne illnesses are linked to produce and nuts, and water used for produce post-harvest activities can contribute to contamination. Surface water serves as an economical source for agricultural activities; however, exposure to the environment increases microbial risks and impacts its physicochemical characteristics. In this study, peroxyacetic acid (PAA) and chlorine (Cl) were evaluated as treatments for simulated surface water to determine their efficacy at achieving &lsquo;no detectable generic Escherichia coli&rsquo; in 100 mL. Simulated surface water was prepared to turbidities of 2 and 100 NTU, adjusted to pH 6.5 or 8.4, equilibrated to 32 or 12 &deg;C, inoculated with 5 logs per mL of non-pathogenic (generic) E. coli, and treated with Cl 25 &plusmn; 2 ppm, PAA 75 &plusmn; 5 ppm, or sterile water control (W). Dey-Engley neutralization was followed by enumeration on E. coli/Coliform Petrifilm at times (t) 0 to 2880 min (48 h) post-treatment. When not detected, treatments were further evaluated through enrichment in 2X Brain Heart Infusion (BHI) broth. Enrichments were streaked on MacConkey agar (MAC) to confirm E. coli absence. All Cl and PAA treated samples were below the test limit of detection (&lt;5 CFU/mL), and E. coli was not detected in 5 mL enrichments even at t = 0 (shortly after treatment). These data suggest that Cl and PAA interventions may be effective for treating surface water for post-harvest uses