Reductions in natural microbial flora, nonpathogenic Escherichia coli, and pathogenic Salmonella on jalapeno peppers processed in a commercial antimicrobial cabinet: A pilot plant trial

Abstract

This experiment aimed to validate the use of antimicrobial solutions in a spray cabinet to inactivate natural microbial flora, nonpathogenic Escherichia coli, and Salmonella on jalapeno peppers. Jalapeno peppers, uninoculated or inoculated with a five-strain mixture of rifampin-resistant E. coli (3.9 log CFU/g) or novobiocin- and nalidixic acid-resistant Salmonella (4.2 log CFU/g), were passed through a commercial antimicrobial cabinet containing both a top and bottom bar spraying (1.38 bar and 2 liters/min) water, sodium hypochlorite (50 ppm), sodium hypochlorite with pH adjusted to 6.7, peroxyacetic acid (PAA; 80 ppm), PAA with pH adjusted to 6.7, lactic with citric acid (1%), lactic with citric acid with sodium lauryl sulfate (1,200 ppm), or chlorine dioxide (5 ppm). Bacteria were recovered in 0.1% buffered peptone water plus 0.1% sodium thiosulfate, which was followed by spread plating onto tryptic soy agar (TSA), TSA plus rifampin (100 μg/ml), and TSA plus novobiocin (25 μg/ml) and nalidixic acid (20 μg/ml). There were no significant differences (P ≥ 0.05) in recovered natural microbial flora, E. coli, and Salmonella populations between untreated peppers (3.5 to 4.2 log CFU/g) and peppers treated with water (3.4 to 3.8 log CFU/g). Significantly fewer (P < 0.05) natural microbial flora, E. coli, and Salmonella populations were recovered on the peppers after they were treated with a majority of the antimicrobials applied in the commercial antimicrobial cabinet. The largest population reduction was observed on peppers sprayed with PAA. Interestingly, the pH adjustment did not make a difference (P ≥ 0.05) in the recovered bacterial populations. These results validate the use of a commercial antimicrobial spray cabinet, and they are useful for developing application protocols for antimicrobials to control Salmonella during the postharvest processing of jalapeno peppers.