Evaluating the efficacy of peroxyacetic acid in preventing Salmonella cross-contamination on tomatoes in a model flume system

Abstract

The use of flume tanks for tomato processing has been identified as a potential source of cross-contamination, which could result in foodborne illness. This study's objective was to assess the efficacy of peroxyacetic acid (PAA) at a concentration of ≤80 mg/L in preventing Salmonella enterica cross-contamination under various organic loads in a benchtop model tomato flume tank. The stability of 80 mg/L PAA at different chemical oxygen demand (COD) levels was also tested. Tomatoes were spot inoculated with a five-serovar rifampin-resistant (rif+) Salmonella cocktail (10⁶ or 10⁸ colony forming unit (CFU)/tomato). Inoculated (n = 3) and uninoculated (n = 9) tomatoes were introduced into the flume system containing 0-80 mg/L PAA and 0 or 300 mg/L COD. After washing for 30, 60, or 120 s, uninoculated tomatoes were sampled and analyzed for cross-contamination. All experiments were conducted in triplicate. Increasing the organic load (measured as COD) affected the stability of PAA in water with significantly faster dissociation when exposed to 300 mg/L COD. The concentration of PAA, inoculum level, COD levels, and time intervals were all significant factors that affected cross-contamination. Cross-contamination occurred at the high inoculum level (10⁸ CFU/tomato) even when 80 mg/L PAA was present in the model flume tank, regardless of the organic load level. When the tomatoes were contaminated at a level of 10⁶ CFU/tomato, concentrations as low as 5 mg/L of PAA were effective in preventing cross-contamination at 0 mg/L COD; however, 100 % tomatoes (9/9) were positive when the organic load increased to 300 mg/L COD. When the PAA concentration was increased to 10 mg/L, it effectively prevented cross-contamination in the tank, regardless of the presence of organic load. These results suggest that using PAA at concentrations below the maximum limit remains effective in limiting bacterial cross-contamination and offers a more environment-friendly option for tomato packinghouse operators.

Keywords: Chemical oxygen demand; Fresh produce; Pathogen inactivation; Post-harvest processing; Sanitizer efficacy.

Fig. 1

Residual concentration of components of an 80 mg/L peroxyacetic acid (PAA): peroxyacetic acid and hydrogen peroxide over 48 h at three different chemical oxygen demand (COD) levels: (A) 0, (B) 100, and (C) 300 mg/L in the module flume tank. The experiment was conducted in triplicate (n = 3).