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Application of Radio-Frequency Heating for Inactivation of Foodborne Pathogen : 식중독균 제어를 위한 고주파 가열의 활용
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | Dong-Hyun Kang | - |
dc.contributor.author | 정슬기 | - |
dc.date.accessioned | 2017-10-27T16:49:14Z | - |
dc.date.available | 2017-10-27T16:49:14Z | - |
dc.date.issued | 2017-08 | - |
dc.identifier.other | 000000145920 | - |
dc.identifier.uri | https://hdl.handle.net/10371/136888 | - |
dc.description | 학위논문 (박사)-- 서울대학교 대학원 농업생명과학대학 농생명공학부, 2017. 8. Dong-Hyun Kang. | - |
dc.description.abstract | The specific objectives of this study were, ( i ) to evaluate the efficacy of RF heating for inactivating foodborne pathogens, such as Salmonella enterica serovar Enteritidis, Typhimurium, and Senftenberg in raw shelled almonds compared to conventional convective heating as well as its effect on product quality, ( ii ) investigate the effect of salt content of samples, packaging material, and electrode gap on the antimicrobial efficacy of RF heating, ( iii ) evaluate the antimicrobial effects of the combination treatment of RF heating with ultraviolet (UV) radiation and organic acid spray against foodborne pathogens on dried foods, ( iv ) develop a computer simulation model and predict the behavior of RF heating in spice products.
RF heating can be applied to control internalized pathogens as well as surface-adhering pathogens in raw almonds without affecting product quality. As the salt content of pistachios increased, treatment time required to achieve 4-log reduction of S. enterica decreased and then was maintained when the salt content exceeded a level corresponding to the peak heating rate. PEI film reduced the treatment time required to reduce S. Typhimurium and E. coli O157:H7 by more than 7 log CFU/g (below the detection limit, 1 log CFU/g) in red and black pepper powders. The dielectric constant of PEI film was similar to that of target sample, and the dielectric loss factor of PEI film was relatively low. The heating rate of the sample increased with decreasing electrode gap. RF heating for the treatment time required to reach 90 °C achieved 2.85-, 2.17-, and 2.09-log reductions of C. sakazakii without generating heat-injured cells at the electrode gaps of 8 cm, 10 cm, and 12 cm, respectively. The RF-UV combined treatment showed synergistic effects: the total microbial log unit reduction of the combined treatment was significantly (P < 0.05) different from the sum of the reductions obtained from individual treatments. Qualitative (transmission electron microscopy) and quantitative (leakage of intracellular substances and propidium iodide uptake) analyses provide evidence that damage to the cell membrane was identified as the main factor contributing to the synergistic lethal effect of the combination treatment of RF heating and UV irradiation. RF-UV combined treatment for 60 s did not significantly (P > 0.05) affect the color, moisture content, and sulfhydryl activities of powdered infant formula. As another available hurdle combination, combined treatment of RF heating and LA sprays for 40 s caused 4.94 and 5.48 reductions of S. Enteritidis PT 30 and S. Typhimurium, respectively. The RF-LA combined treatment did not change color and oxidative rancidity of almonds significantly (P > 0.05). A computer simulation was studied to predict the influence of various factors on the inactivation of foodborne pathogens on food samples by RF heating. A finite element-based commercial software, COMSOL Multiphysics, were used to predict electric potential, electric field distribution, and temperature distribution of red pepper powder during RF heating. The computer simulation model was validated by comparing with the experimental temperature profiles of powdered red pepper spices and applied to predict the effect of frequency, electrode gap, and dielectric properties of packaging materials on the antimicrobial effect of RF heating. The simulated results demonstrated that the efficacy of RF heating in reducing foodborne pathogens could be improved using a higher frequency, a bigger electrode area, a similar dielectric constant of packaging material as target sample, and a lower dielectric loss factor of packaging material. The results of this thesis are helpful to establish treatment conditions for maximizing the antimicrobial efficacy of RF treatment, and by extension, to commercial practical application of RF heating. The combination treatment of RF heating with other technology suggest alternatives to conventional decontamination treatments. In conclusion, application of RF heating in the food industry is expected to represent a novel and innovative thermal process for the production of safe foods. | - |
dc.description.tableofcontents | Chapter I. Evaluation of radio-frequency heating in controlling foodborne pathogens in raw shelled almonds 1
I-1.Introduction 2 I-2. Materials and Methods 6 Bacterial strains 6 Preparation of pathogen inocula 6 Sample preparation and inoculation 7 Experimental apparatus 10 RF heating and conventional convective heating treatment 12 Temperature measurement 12 Bacterial enumeration 13 Enumeration of heat-injured cells 13 Quality measurement 14 Statistical analysis 15 I-3. Results 16 Temperature curves of almonds 16 Survival curves of foodborne pathogens 18 Recovery of heat-injured cells 22 Effect of RF heating on product quality 24 I-4. Discussion 27 Chapter II. Intrinsic and extrinsic factors affecting antimicrobial effect of RF heating against foodborne pathogens 32 Chapter II-1. Effect of salt content on inactivation of foodborne pathogens in pistachios by RF heating 33 II-1.1. Introduction 34 II-1.2. Materials and Methods 37 Bacterial strains 37 Preparation of pathogen inocula 37 Sample preparation and inoculation 38 Experimental apparatus 40 RF heating treatment 40 Dielectric properties measurement 41 Bacterial enumeration 42 Enumeration of heat-injured cells 42 Quality measurement 43 Statistical analysis 44 II-1.3. Results 45 Temperature curves of pistachios with different salt contents 45 Effect of salt content on dielectric properties of pistachios 47 Relationships between heating rate, dielectric loss factor, and salt content of pistachios 49 Effect of salt content on inactivation of pathogenic bacteria in pistachio 51 Recovery of heat-injured cells 53 Effect of RF heating within different salt range on product quality 55 II-1.4. Discussion 58 Chapter II-2. Effect of packaging materials on inactivation of foodborne pathogens in red and black pepper spices by RF heating 62 II-2.1. Introduction 63 II-2.2. Materials and Methods 66 Bacterial strains 66 Preparation of pathogen inocula. 66 Sample preparation and inoculation 67 RF heating treatment 67 Temperature measurement 68 Dielectric properties measurement 68 Bacterial enumeration 68 Enumeration of heat-injured cells 69 Color measurement 70 Volatile flavor component measurement 70 Statistical analysis 72 II-2.3. Results 73 Temperature curves of powdered red and black pepper spice surrounded with different packaging materials 73 Dielectric properties of different packaging materials 76 Effect of packaging materials on inactivation of foodborne pathogens in powdered red and black pepper spice 78 Recovery of heat-injured cells 84 Effect of RF heating on product quality during post-packaging pasteurization 87 II-2.4. Discussion 90 Chapter II-3. Effect of electrode gap on inactivation of Cronobacter sakazakii in powdered infant formula by RF heating 94 II-3.1. Introduction 95 II-3.2. Materials and Methods 98 Bacterial strains 98 Preparation of pathogen inocula 98 Sample preparation and inoculation 99 RF heating treatment 99 Temperature measurement 102 Bacterial enumeration 102 Enumeration of injured cells 103 Quality measurement 103 Modeling of survival curves 104 Statistical analysis 105 II-3.3. Results 106 Average temperature-time histories of powdered infant formula with different electrode gaps 106 Inactivation of pathogenic bacteria by RF heating with various electrode gap 108 Recovery of heat-injured cells 110 Effect of RF heating with different electrode gaps on product quality 112 Suitable model of survival curves 115 II-3.4. Discussion 117 Chapter III. Combination treatments of RF heating with various sanitizing technologies 120 Chapter III-1. Enhanced inactivation of Cronobacter sakazakii in powdered infant formula by RF heating combined with UV radiation and mechanism of the synergistic bactericidal action 121 III-1.1. Introduction 122 III-1.2. Materials and Methods 125 Bacterial strains 125 Preparation of pathogen inocula 125 Sample preparation and inoculation 126 Combined treatment of RF heating and UV radiation 126 Bacterial enumeration 127 Enumeration of injured cells 128 Transmission electron microscopy analysis 128 Measurement of extracellular UV-absorbing substances and propidium iodine uptake 130 Quality measurement 130 Statistical analysis 131 III-1.3. Results 132 Synergistic bactericidal effect of combined UV-RF treatment 132 Recovery of UV-RF-injured cells 134 Microscopic evaluation of damages 136 Determination of cell membrane damage by leakage of bacterial intracellular substances and PI uptake 138 Effect of UV-RF combined treatment on product quality 140 III-1.4. Discussion 143 Chapter III-2. Combination treatment of RF heating and organic acid spray for inactivating foodborne pathogens on raw shelled almonds 147 III-2.1. Introduction 148 III-2.2. Materials and Methods 151 Bacterial strains 151 Preparation of pathogen inocula 151 Sample preparation and inoculation 152 Preparation of lactic acid solution 152 Combined treatment of RF heating and LA sprays 153 Bacterial enumeration 155 Enumeration of heat-injured cells 155 Measurement of extracellular UV-absorbing substances and propidium iodine uptake 156 Quality measurement 157 Statistical analysis 158 III-2.3. Results 159 Survival curves of foodborne pathogens 159 Recovery of injured cells 162 Determination of cell membrane damage by leakage of bacterial intracellular substances and PI uptake 164 Effect of RF-LA combined treatment on product quality 166 III-2.4. Discussion 169 Chapter IV. Computer simulation model development and prediction for RF heating of dry food materials 173 IV-1. Introduction 174 IV-2. Materials and Methods 177 Sample preparation 177 Dielectric and thermal properties measurement 177 Physical model 177 Governing equations 180 Initial and boundary conditions 181 Solving methodology 182 Model parameters 183 Model validation 186 Model applications 186 IV-3. Results 188 Simulated electric potential and electric field distribution for powdered red pepper 188 Simulated temperature profiles for powdered red pepper 191 Model validation 194 Effect of processing parameters on inactivation of foodborne pathogen in powdered red pepper 196 Effect of packaging materials around powdered red pepper on inactivation of foodborne pathogen 199 IV-4. Discussion 202 References 205 국문초록 235 | - |
dc.format | application/pdf | - |
dc.format.extent | 2533075 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | radio-frequency heating | - |
dc.subject | salt content | - |
dc.subject | dielectric properties | - |
dc.subject | packaging material | - |
dc.subject | electrode gap | - |
dc.subject | ultraviolet irradiation | - |
dc.subject | organic acid | - |
dc.subject | lactic acid | - |
dc.subject | spray | - |
dc.subject | foodborne pathogen | - |
dc.subject | computer simulation | - |
dc.subject | dry powdered food | - |
dc.subject | nut kernel | - |
dc.subject.ddc | 630 | - |
dc.title | Application of Radio-Frequency Heating for Inactivation of Foodborne Pathogen | - |
dc.title.alternative | 식중독균 제어를 위한 고주파 가열의 활용 | - |
dc.type | Thesis | - |
dc.description.degree | Doctor | - |
dc.contributor.affiliation | 농업생명과학대학 농생명공학부 | - |
dc.date.awarded | 2017-08 | - |
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