Purpose: The purpose of this study was to evaluate the effect of Wuweizi extracts on the survival of major foodborne pathogenic bacteria in synthetic and food models.
Methods: Ten grams of Wuweizi were boiled in 200 ml of distilled water for 45 min. Various dilutions of the extract were tested against Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium via the agar well diffusion assay as well as in nutrient broth. In addition, pasteurized orange juice supplemented with 5% Wuweizi extract was separately inoculated at 6 log CFU/ml with the three pathogens and stored at 7°C or 21°C. Over time the pathogens in the juice were enumerated on plate count agar. Finally, chemical analysis was conducted on the extract to determine its acidity, and total phenolic, flavonoid and anthocyanin contents.
Results: Wuweizi extract generated inhibition zones of 1.58, 2.78, and 1.63 cm against E. coli O157:H7, L. monocytogenes, and Salmonella Typhimurium, respectively. L. monocytogenes and Salmonella Typhimurium in nutrient broth containing 2.5% Wuweizi extract were killed within 6 h. At 21°C, the extract at 5% inactivated all three pathogens in orange juice within 24 h. At 7°C, L. monocytogenes in orange juice was killed within 2 d; whereas, E. coli O157:H7 or Salmonella Typhimurium did not survive longer than 4 d. The pH of Wuweizi extract was 2.51. The total phenolic, flavonoid, and anthocyanin contents were measured at 851 mg GAE/l, 64.3 mg quercetin/l, and 22.9 mg cyd 3-glu/l, respectively.
Significance: The antimicrobial property of Wuweizi extract may be attributed to its high contents of organic acids and phenolic compounds. The extract provides an alternative and green solution to enhance the microbiological safety of food.