Abstract
Efficiencies of various treatments for UVC photolysis (ultraviolet light-C at 254 nm), VUV photolysis (vacuum ultraviolet light at 254 nm and 185 nm), UVC-assisted titanium dioxide photocatalysis (UVC-TiO2), and VUV-assisted titanium dioxide photocatalysis (VUV-TiO2) were investigated for the degradation of pesticides including pyraclostrobin, boscalid, fludioxonil, and azoxystrobin and inactivation of microorganisms Escherichia coli K12 as a surrogate for E. coli O157:H7 and Saccharomyces cerevisiae in aqueous solutions and on the surface of fresh cut carrots. The degradation efficiencies of VUV were higher than for UVC on pesticides in aqueous solutions. However, there was no significant difference between degradation efficiencies for UVC and UVC-TiO2 treatments, and between VUV and VUV-TiO2 treatments. UVC, VUV, UVC-TiO2, and VUV-TiO2 showed similar inactivation effects against E. coli K12 and S. cerevisiae in aqueous solutions. The combined use of UVC and VUV treatments (combined UV) and combined use of UVC-TiO2 and VUV-TiO2 treatments (combined UV-TiO2) showed higher efficiencies (72–94% removal) for the removal of residual pesticides on fresh cut carrots than bubble water washing (53–73% removal). However, there was no significant difference in removal efficiency between combined UV and combined UV-TiO2 treatments. For E. coli K12 and S. cerevisiae on fresh cut carrots, the combined UV-TiO2 treatment (1.5 log and 1.6 log reduction, respectively) showed slightly higher inactivation effects than combined UV (1.3 log and 1.2 log reduction, respectively). Photolysis and TiO2 photocatalytic treatments under UV irradiation, including VUV as a light source, showed potential for the simultaneous degradation of pesticides and microorganisms as a non-chemical and residue-free technique for surface disinfection of fresh produce.
Highlights
An increased consumption of fresh fruits and vegetables has led to an increased risk of foodborne illnesses that are associated with pathogens and toxic chemical residues [1,2]
Pesticides are representative of chemical hazards and their use has increased for controlling diseases and pest insect infestation for increasing crop yields
VUV was more effective than UVC for pesticide degradation in single solutions (20 ppm) of each pesticide (Figure 2)
Summary
An increased consumption of fresh fruits and vegetables has led to an increased risk of foodborne illnesses that are associated with pathogens and toxic chemical residues [1,2]. Pesticides are representative of chemical hazards and their use has increased for controlling diseases and pest insect infestation for increasing crop yields. Pesticides may have toxic effects on humans who consume fresh produce [3,4,5,6,7]. The toxicities of pesticides to organisms, including beneficial insects and non-target plants, can change the natural balance of the ecosystem by altering the environment to favor the pests [8]. Four pesticides (pyraclostrobin, boscalid, fludioxonil, and azoxystrobin) that are widely used during the growth of various vegetables and fruits were chosen for the degradation experiment [9,10,11,12]
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