Title Page
Abstract
Contents
Ⅰ. INTRODUCTION 15
Ⅱ. MATERIALS AND METHODS 20
2.1. VUV-amalgam lamp system 20
2.1.1. VUV-amalgam lamp and LP Hg lamp system for water and surface disinfection 20
2.1.2. Simultaneous VUV-amalgam lamp and NIR lamp system for black peppercorn disinfection 23
2.2. Irradiance measurement 25
2.3. Inactivation of foodborne pathogenic bacteria on water and stainless steel surfaces by vacuum-UV amalgam lamp and low-pressure mercury UV lamp irradiation 26
2.3.1. Bacterial cultures and cell suspensions 26
2.3.2. Sample inoculation and treatment for surface and water 27
2.3.3. Microbial enumeration 28
2.3.4. Modeling of survival curves 29
2.3.5. Bacterial mechanism 29
2.3.6. Ozone concentration measurement 32
2.3.7. Determination of ROS in water 34
2.4. Simultaneous vacuum ultra violet-amalgam lamp radiation and near- infrared radiation heating for a synergistic bactericidal effect against Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in black peppercorn 35
2.4.1. Bacterial cultures and cell suspensions 35
2.4.2. Sample preparation and inoculation 36
2.4.3. VUV-amalgam and NIR treatment 36
2.4.4. Microbial enumeration 38
2.4.5. Temperature measurement 39
2.4.6. Color and moisture content measurement 39
2.4.7. Volatile flavor component measurement by HPLC 40
2.4.8. Ozone and hydrogen peroxide concentration measurement 41
2.5. Statistical analysis. 42
Ⅲ. RESULTS 43
3.1. Inactivation of foodborne pathogenic bacteria on water and stainless steel surfaces by vacuum-UV amalgam lamp and low-pressure mercury UV lamp irradiation 43
3.1.1. Inactivation of foodborne pathogens by VUV-amalgam and LP lamps 43
3.1.2. Kinetics modeling of pathogen inactivation on the stainless steel surface 48
3.1.3. Analysis of inactivation mechanisms on the stainless steel surfaces 50
3.1.4. Analysis of ozone concentration generated by VUV-amalgam lamp treatment 53
3.1.5. Determination of ROS produced by LP and VUV-amalgam lamp treatment in water 56
3.2. Simultaneous vacuum ultra violet-amalgam lamp radiation and near-infrared radiation heating for a synergistic bactericidal effect against Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in black peppercorn 58
3.2.1. Average temperature-time histories of the black peppercorn surface 58
3.2.2. Inactivation of pathogenic bacteria by simultaneous treatment with NIR and VUV-amalgam lamp irradiation 61
3.2.3. Recovery of injured cells 63
3.2.4. Effect of NIR and VUV-amalgam lamp treatment on product quality 66
3.2.5. Determination of ozone and hydrogen peroxide concentrations generated by VUV-amalgam lamp treatment 68
3.2.6. Effect of NIR and VUV-amalgam lamp treatment on the moisture content of black peppercorn 70
3.2.7. Inactivation of pathogenic bacteria by sequential treatment of NIR and VUV-amalgam lamp irradiation 72
Ⅳ. DISCUSSION 74
4.1. Inactivation of foodborne pathogenic bacteria on water and stainless steel surfaces by vacuum-UV amalgam lamp and low-pressure mercury UV lamp irradiation 74
4.2. Simultaneous vacuum ultra violet-amalgam lamp radiation and near-infrared radiation heating for a synergistic bactericidal effect against Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in black peppercorn 80
Ⅴ. Conclusion 85
Ⅵ. REFERENCES 87
Ⅶ. 국문초록 94
Table 1. Survival populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes suspended in DW after treatment with the VUV-amalgam lamp and LP lamp 46
Table 2. Parameters of the Weibull model for inactivation of E. coli O157:H7, S. Typhimurium, and L. monocytogenes on the stainless steel surface treated with the LP lamp and VUV-amalgam lamp corresponding to irradiation dose (mJ/cm²) profiles and the calculated... 49
Table 3. DNA integrity values of E. coli O157:H7, S. Typhimurium, and L. monocytogenes from the DNA quantification assay by SYBR green Ⅰ. The values were calculated by dividing the obtained fluorescence (F) by the control value (F₀) 52
Table 4. Ozone concentration of DW treated by VUV-amalgam lamp. The data was measured by the indigo method. The lower detection limit for spectrophotometric determinations is 2 μg/L ozone 55
Table 5. Absorbance of XTT and GSH assay values by VUV-amalgam lamp and LP lamp irradiation. Treatments without UV treatment was used as negative control 57
Table 6. Log reductions of E. coli O157:H7 in black peppercorn treated with VUV-amalgam lamp (Amalgam), NIR radiant heating (NIR) heating, and both technologies simultaneously (NIR-VUV). The initial populations are 8.21±0.10 and 8.33±0.30, respectively... 64
Table 7. Log reductions of S. Typhimurium in black peppercorn treated with VUV-amalgam lamp (amalgam), NIR radiant heating (NIR) heating, and both technologies simultaneously (NIR-VUV). The initial populations are 8.29±0.11 and 8.27±0.34, respectively... 65
Table 8. Color values and piperine content of treated and untreated black peppercorn 67
Table 9. Ozone concentration generated by the VUV-amalgam lamp and simultaneous NIR-amalgam lamp in the treatment chamber. The concentration was measured by the Gastec method after the warm-up time (3 min) of the VUV-amalgam lamp 69
Table 10. Hydrogen peroxide concentration generated by the simultaneous NIR combined amalgam lamp in the treatment chamber. The concentration was measured by the Gastec method after the warm-up time (3 min) of the VUV-amalgam lamp 69
Table 11. Moisture content of treated and untreated black peppercorn 71
Table 12. Log reductions of E. coli O157:H7 and S. Typhimurium in black peppercorn treated with the sum of both single treatments, sequential, and simultaneous treatment of VUV-amalgam lamp and NIR radiant heating. The initial populations are 8.21±0.10 and... 73
Fig. 1. Schematic diagram (a) and photograph (b) of the experimental set-up used in this study. 22
Fig. 2. Schematic diagram (a) and photograph (b) of the simultaneous NIR and amalgam treatment system used in this study. 24
Fig. 3. Comparison of 254 nm UV irradiance rate between the amalgam lamp and LP lamp 45
Fig. 4. Log reductions of E. coli O157:H7 (A), S. Typhimurium (B), and L. monocytogenes (C) inoculated on stainless steel surface after treatment with the VUV-amalgam lamp and LP lamp. The initial populations are 6.02±0.20, 5.55±0.05, and 6.46±0.20 log... 47
Fig. 5. Membrane damage values were obtained by measuring propidium iodide (PI) uptake values of E. coli O157:H7, S. Typhimurium, and L.... 51
Fig. 6. Ozone concentration is generated by the VUV-amalgam lamp in the chamber. The data was measured by the Gastec method. Values with the... 54
Fig. 7. Average temperature-time histories of black peppercorn surfaces during NIR heating and simultaneous NIR combined amalgam treatment. The... 59
Fig. 8. Average temperature-time histories of black peppercorn surfaces during sequential treatment of NIR heating following VUV-amalgam... 60
Fig. 9. Log reductions of E. coli O157:H7 (A) and S. Typhimurium (B) in black peppercorn treated in VUV-amalgam lamp irradiation, NIR heating, and... 62