Effect of Antimicrobial Coatings on the Radiosensitization of Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes in Fresh Broccoli

Abstract

Radiosensitization of Listeria monocytogenes, Escherichia coli, Salmonella Typhimurium, and aerobic microflora was evaluated in broccoli florets coated by antimicrobial coatings and treated with different doses of γ-radiation. Broccoli florets were inoculated with aerobic microflora isolated from broccoli and with pathogenic bacteria (L. monocytogenes, E. coli, and Salmonella Typhimurium) at 10(6) CFU/ml. Inoculated florets were then coated with methylcellulose-based coating containing various mixtures of antimicrobial agents: organic acids plus lactic acid bacteria (LAB metabolites), organic acids plus citrus extract, organic acids plus citrus extract plus spice mixture, and organic acids plus rosemary extract. Coated florets were irradiated with various doses (0 to 3.3 kGy), and microbial analyses were conducted to calculate the D(10)-value and relative sensitivity. All antimicrobial coatings had almost the same effect of increasing the radiosensitivity of L. monocytogenes (from 1.31 to 1.45 times) to γ-irradiation. The coating containing organic acid plus citrus extract was the most efficient formulation for increasing the radiosensitization of E. coli and aerobic microflora, by 2.40 and 1.76 times, respectively, compared with the control without the antimicrobial coating. The coating containing organic acids plus LAB metabolites was the most effective formulation for increasing the radiosensitization (by 2.4 times) of Salmonella Typhimurium. Results suggest that the spice extract, when mixed with organic acids and citrus extract, might protect E. coli and aerobic microflora from the effects of γ-irradiation.

Antimicrobial effects of combined UV-C or gamma radiation with natural antimicrobial formulations against Listeria monocytogenes, Escherichia coli O157: H7, and total yeasts/molds in fresh cut cauliflower

“…The obtained results with gamma irradiation treatments showed that L. monocytogenes was more resistant to gamma irradiation than E. coli O157:H7, which is consistent with several previous studies (Takala et al, 2011;Yun et al, 2011). Cauliflower samples treated with gamma rays showed the best visual quality among all samples (data not shown), indicating that this type of treatment had a very negligible impact on vegetables.…”

“…These results indicated that application of irradiation treatment after applying natural antimicrobial formulations, could have the antimicrobial effect in short term, as shown by several studies (Takala et al, 2011;Turgis et al, 2011;Yun et al, 2011), but the long-term antimicrobial effect might be diminished. Therefore, spraying of natural antimicrobial formulations on products, followed by the irradiation (UV-C or gamma) treatment on products, prevents interferences between these two methods.…”

“…It has been demonstrated that irradiation on vegetables in the presence of various natural or synthetic active compounds can result in reduction of required doses for bacterial lethality (Takala, Vu, Salmieri, & Lacroix, 2011;Turgis, Millette, Salmieri, & Lacroix, 2011). However, the gamma irradiation or UV-C treatments on vegetables, followed by application of natural antimicrobials has not been investigated.…”

Combination irradiation treatments for food safety and phytosanitary uses

“…The molecular characterization revealed the interaction between alginate-CNC and nisin which also demonstrated the better retention activity of microencapsulated nisin during storage. The radiosensitization of L. monocytogens, Escherichia coli, S. Typhimurium and aerobic microflora in broccoli florets coated by antimicrobial coatings immobilized in methylcellulosebased coating was evaluated by Takala et al [69]. The coating contained different mixtures of antimicrobial agents such as organic acids/lactic acid bacteria (LAB metabolites), organic acids/citrus extract, organic acids/citrus extract/spice mixture and organic acids/rosemary extract, and coated florets were treated with different doses of γ-irradiation.…”

Antimicrobial Effects of Nisin, Essential Oil, and γ‐Irradiation Treatments against High Load of Salmonella typhimurium on Mini‐carrots

“…Several authors in previous works on γ‐irradiation treatment combined with other nonthermal treatments reported that the survival microorganisms after irradiation treatment are more sensitive to nonthermal treatments than untreated cells to adverse environmental conditions, such as in the presence of antimicrobial compounds or modified atmosphere (Severino and others , 2015). Takala and others () showed the antimicrobial effect of coatings containing citrus and rosemary extracts, spice mixture, and lactic acid increases the radiosensitization of E. coli, S . Typhimurium, and L. monocytogenes in broccoli florets.…”