Purpose: This experiment aims to validate the use of antimicrobial solutions in a spray cabinet to inactivate E. coli O157:H7 surrogate organisms on jalapeno peppers.
Methods: Jalapeno peppers, inoculated with a 5-strain mixture of rifampin-resistant (100 µg/ml) E. coli O157:H7 pathogenic surrogates (7.0 log CFU/ml, ATCC BAA-1427, BAA-1428, BAA-1429, BAA-1430, BAA-1431), were passed through a commercial antimicrobial cabinet containing a top and bottom bar spraying (20 psi and 2 l/min) water, sodium hypochlorite (SH; 50 ppm), SH with pH adjusted to 6.7 (ASH), peroxyacetic acid (PAA; 80 ppm), PAA with pH adjusted to 6.7 (APAA), a lactic and citric acid blend (LCA; 1%), and chlorine dioxide (CD; 5 ppm). Surviving bacteria were recovered in 0.1% buffered peptone water (60 s shake) followed by spread plating onto tryptic soy agar plus rifampicin (100 µg/ml). Data (2 replicates/3 samples per replicate) were analyzed using the ANOVA of SAS.
Results: There were no significant difference (P ≥ 0.05) in recovered E. coli populations between untreated peppers (3.9 ± 0.3 log CFU/g) and those treated with water and CD (3.7 ± 0.3 and 3.6 ± 0.4, respectively). Significantly fewer (P < 0.05) E. coli were on the peppers after treatment with all other antimicrobials applied in the commercial antimicrobial cabinet with the fewest E. coli recovered (2.9 log CFU/g) on peppers sprayed with PAA and APAA. Interestingly in a single spray application when applying SH or PAA to peppers, pH adjustment made no difference (P ≥ 0.05) in recovered E. coli populations.
Significance: These results validate the use of a commercial antimicrobial spray cabinet and are useful for developing application protocols for antimicrobials to control E. coli O157:H7 during post-harvest processing of jalapeno peppers.