Antimicrobial effect of synergistic interaction between UV-A light and gallic acid against Escherichia coli O157: H7 in fresh produce wash water and biofilm

Andrea Cossu, Duygu Ercan, Qingyang Wang, Wendy Ann Peer, Nitin Nitin, Rohan V. Tikekar

Research output: Contribution to journalArticle

20 Scopus citations


A synergistic interaction between gallic acid (GA) and UV-A light (UV-A + GA) to inactivate E. coli O157:H7 in spinach wash water and in biofilm was evaluated. A 30-min exposure to UV-A light in presence of 10 mM GA had relevant biological effect in the inactivation of E. coli O157:H7 in suspension in the absence (> 5 log(CFU/mL)) and the presence of organic content (> 3-log(CFU/mL) in 2000 mg O2/L COD (Chemical Oxygen Demand) organic load), and resulted in ~ 80% decrease in the metabolic activity of E. coli O157:H7 biofilm. GA solutions could be recycled through at least 3-cycles of UV-A treatment without a significant loss in antibacterial effect. Catalase reduced the extent of E. coli O157:H7 inactivation from the UV-A + GA treatment suggesting that generation of hydrogen peroxide was partially responsible for the observed antimicrobial effect. The UV-A + GA treatment was also found to be effective in causing > 3 log(CFU/mL) reductions in E. coli O157:H7 on the surface of spinach leaves. UV-A + GA treatment can serve as an effective intervention in the fresh produce sanitation. Industrial relevance The results of this study show that a synergistic interaction between gallic acid (GA) and UV-A (365 nm) light is an effective treatment for sanitation of fresh produce and water used to wash fresh produce. It was also found to be effective against the E.coli O157:H7 biofilm. The attractive attributes of this technology include a relatively low cost; specific, light-triggered activity; non-toxic nature and scalability. Thus, this technology has potential to replace conventional chemical sanitizer-based sanitation approaches.

Original languageEnglish (US)
Pages (from-to)44-52
Number of pages9
JournalInnovative Food Science and Emerging Technologies
StatePublished - Oct 1 2016



  • Biofilm
  • Escherichia coli O157:H7
  • Gallic acid
  • Photodynamic treatment
  • Photosensitization
  • Wash water

ASJC Scopus subject areas

  • Food Science
  • Chemistry(all)
  • Industrial and Manufacturing Engineering

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