Inactivation of Escherichia coli O157:H7 and Salmonella and Native Microbiota on Fresh Strawberries by Antimicrobial Washing and Coating

Abstract

Antimicrobial washing (AW), antimicrobial coating (AC), and a combination of washing followed by coating (AW+AC) were evaluated for their ability to inactivate artificially inoculated foodborne pathogens and native microbiota on strawberries stored at 4°C. Strawberries were inoculated with a six-strain composite of Escherichia coli O157:H7 and Salmonella; treated by AW, AC, or AW+AC; and stored at 4°C for 3 weeks. The washing solution contained 90 ppm of peracetic acid, and the coating solution consisted of chitosan (1%, w/v), allyl isothiocyanate (1%, v/v), and corn-bio fiber gum (5%, w/v). The effectiveness of the antimicrobial treatments against E. coli O157:H7 and Salmonella pathogens and native microflora on strawberries and their impact on fruit quality (appearance, weight loss, color, and firmness) were determined. By the end of storage, pathogen populations on strawberries were 2.5 (AW+AC), 2.9 (AC), 3.8 (AW), and 4.2 log CFU for the positive (untreated) control. AW+AC treatments also inactivated the greatest population of native microflora, followed by the AC treatment alone. AW+AC treatments showed additional antimicrobial effectiveness against these two pathogens and native microflora. Both AW+AC and AC treatments preserved the color, texture, and appearance of strawberries throughout storage. The coating treatments (AW+AC and AC alone) further reduced the loss of moisture throughout storage. The AW treatment was the least effective in reducing populations of pathogens and native microflora and in maintaining the quality of strawberries throughout storage. This study demonstrates a method to improve the microbiological safety, shelf life, and quality of strawberries.