Purpose: To develop an effective multicomponent antimicrobial system for fresh produce based on rational combinations of interactive natural components.
Methods: Antimicrobials examined included Grape Seed Extract (GSE; Kikkoman), long-chain sodium polyphosphate (BEKAPLUS FS; ICL Performance Products) and various organic acids, including citric, malic and tartaric acids. The efficacy of individual antimicrobials and their combinations against E. coli O157:H7 ATCC 35150 and S. enterica ser. Typhimurium ATCC 14028 was evaluated using a Bioscreen C Microbiological Reader (Growth Curves USA). One antimicrobial system was also evaluated against Salmonella Typhimurium in a lettuce extract system with plating on selective (XLT-4) and non-selective (Tryptic Soy Agar) media after 12 and 24 h exposure.
Results: A combination of GSE (0.5%), BEKAPLUS FS (1%) and tartaric acid (0.125%) showed the best inhibitory effect against two pathogens in our Bioscreen tests. This system reduced Salmonella Typhimurium by ~4 logs within 12 h, and by > 6 logs after 24 h in the lettuce extract system. Selective and non-selective plating revealed cellular injury by GSE. Higher levels of BEKAPLUS FS (5%) resulted in buffering and reduced system efficacy.
Significance: Our work indicates that natural antimicrobial systems composed of phenolic compounds, metal chelators and organic acids may have promise for control of E. coli and Salmonella on minimally processed fruits and vegetables. By using a systems approach, effective levels of individual components may be minimized, potentially reducing negative organoleptic impacts of the treatment on produce.