Inactivation of Listeria monocytogenes , Escherichia coli O157:H7, and Salmonella spp. on dates by antimicrobial washes

Abstract

Dates are a low moisture ready-to-eat fruit that are popular both globally and in the United States. The harvesting and post-harvest handling of dates could result in the contamination of common produce-associated foodborne pathogens including E. coli O157:H7, Listeria monocytogenes, and Salmonella spp. In this study, the efficacy of antimicrobial washes for the reduction of foodborne pathogen populations was evaluated as a post-harvest mitigation step. Peracetic acid (PAA, 75 ppm), ethanol (EtOH, 70%), lactic acid (LA, 2.5%), trans-cinnamaldehyde (TC, 2%), and pomegranate peel extract (1%, PPE) were used to develop five antimicrobial washes: 75 ppm PAA; 75 ppm PAA + 70% EtOH; 75 ppm PAA + 2.5% LA; 75 ppm PAA + 70% EtOH + 2% trans-cinnamaldehyde (TC); and 75 ppm PAA + 1% PPE. For whole dried dates, a 60 s treatment with 75 ppm PAA significantly reduced pathogen populations by 4.08 to 4.96 log CFU/g. Specifically, for E. coli O157:H7, populations were reduced by 7.25 log CFU/g on dates when treated for 60 s with either 75 ppm PPA + 70% EtOH or with 75 ppm PPA + 70% EtOH + 2% TC. No significant reductions in pathogen populations were observed on the fresh whole dates for any of the sanitizer treatments. In addition, all three pathogens were capable of survival on pitted date pieces during storage at 4°C for 31 days; no significant reduction for any pathogen was observed. The results of this study provide data on the survival of these three foodborne pathogens on fresh and dried dates and can aid in the risk assessment of this food product. Practical applications This study provides the basis for a preventive control with the ability to reduce foodborne pathogenic bacteria populations between 1.34 and 7.25 log CFU/g on fresh and dried dates. An antimicrobial wash implemented as a preventative control will greatly increase the confidence a manufacturer may have in date products used in RTE foods. Survival of foodborne pathogens on dates can aid in its risk assessment.