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Application of near-infrared heating as an antimicrobial intervention for food safety
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.advisor | 강동현 | - |
| dc.contributor.author | 하재원 | - |
| dc.date.accessioned | 2017-07-13T08:23:25Z | - |
| dc.date.available | 2017-07-13T08:23:25Z | - |
| dc.date.issued | 2015-08 | - |
| dc.identifier.other | 000000066660 | - |
| dc.identifier.uri | https://hdl.handle.net/10371/119501 | - |
| dc.description | 학위논문 (박사)-- 서울대학교 대학원 : 농생명공학부, 2015. 8. 강동현. | - |
| dc.description.abstract | The application of infrared (IR) radiation heating to food processing has gained momentum due to its inherent advantages over the conventional heating systems. Certain characteristics of IR heating such as emissivity and transmissivity set it apart from and make it more effective for industrial applications than others. IR radiation transfers thermal energy in the form of an electromagnetic wave and can be classified into 3 regions, near IR (NIR | - |
| dc.description.abstract | 0.76 to 2 μm), medium IR (MIR | - |
| dc.description.abstract | 2 to 4 μm), and far IR (FIR | - |
| dc.description.abstract | 4 to 1,000 μm). Among them, NIR heating has been gaining wider acceptance because of its higher heat transfer capacity and high energy efficiency compared with MIR and FIR heating. This thesis explored the potential and utilization of NIR heating as an alternative antimicrobial intervention for food safety.
The specific objectives of this study were, (ⅰ) to investigate the efficacy of NIR heating to reduce major foodborne pathogens, such as Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes in ready-to-eat (RTE) food (focused on deli meat product) compared to conventional convective heating as well as its effect on product quality, (ⅱ) develop and validate the inactivation kinetic models of the three major pathogens on RTE sliced ham by NIR heating, as a function of the processing parameter, radiation intensity, (ⅲ) investigate the effect of the simultaneous application of NIR heating and ultraviolet (UV) irradiation on inactivation of these pathogens in RTE sliced ham, (ⅳ) elucidate the underlying mechanisms of the synergistic bactericidal action of NIR heating and UV irradiation, (ⅴ) extensively apply the combined treatment to other food systems (dry powdered foods) with a mild NIR heat, and (ⅵ) evaluate the efficacy of organic acid spray along with NIR heating for inactivating Salmonella Enteritidis on dry nut kernel products. A cocktail of three pathogens was inoculated on the exposed or protected surfaces of ham slices, followed by NIR or conventional convective heating at identical conditions (1.8 kW). NIR heating for 50 s achieved 4.1-, 4.19-, and 3.38-log reductions in surface-inoculated S. Typhimurium, E. coli O157: H7, and L. monocytogenes, respectively, without affecting product quality whereas convective heating needed 180 s to attain comparable reductions for each pathogen. There were no statistically significant (P > 0.05) differences in reduction between surface- and internally inoculated pathogens at the end of NIR treatment (50 s). However, when treated with conventional heating, significant (P < 0.05) differences were observed at the final stages of the treatment (150 and 180 s). Thus, NIR heating can be applied to control internalized pathogens as well as surface-adhering pathogens in RTE sliced meats as an alternative to conventional heat treatment. For investigation of the inactivation kinetics as a function of radiation intensity, precooked ham slices inoculated with the three pathogens were treated at different NIR intensities (ca. 100, 150, and 200 μW/cm2/nm). The survival curves of the three pathogens exhibited both shoulder and tailing behavior at all light intensities. Among nonlinear models, the relationship between the scale & shape parameters (α & β values) of the Weibull model and applied radiation intensity was almost a straight line, and single linear equations for the three pathogens were obtained. The final predictive models (tertiary models) for the three pathogens were developed by substituting the secondary linear models into the Weibull primary model and allowed us to predict survival curves at NIR intensities different from those used in this study. The tertiary models were validated with data obtained from further experiments within the range of the experimental domain. The R2, RMSE, Bf, and Af values were within the acceptable range indicating the suitability of the model for predictive purposes. These results would be beneficial to the deli meat industry in selecting the optimum processing conditions of NIR heating to meet the desired target level of pathogen inactivation. Simultaneous application of NIR heating and UV irradiation at ca. 0.9 kW (half of NIR treatment alone) for 70 s achieved 4.17, 3.62, and 3.43 log CFU reductions of S. Typhimurium, E. coli O157:H7, and L. monocytogenes, respectively. For all three pathogens, the simultaneous application of both technologies resulted in an additional log unit reduction as a result of their synergism compared to the sum of the reductions obtained after the individual treatments. To investigate the mechanisms of NIR-UV synergistic injury for a particular microorganism in a food base, I evaluated the effect of four types of metabolic inhibitors using the overlay method and confirmed that damage to cellular membranes and the inability of cells to repair these structures due to ribosomal damage were the primary factors related to the synergistic lethal effect. The NIR-UV combined treatment for a maximum of 70 s did not alter the color values or texture parameters of ham slices significantly (P > 0.05). Additionally, simultaneous NIR-UV combined processing was employed for decontaminating red pepper powder (target pathogens: S. Typhimurium and E. coli O157:H7) and powdered infant formula (target pathogen: Cronobacter sakazakii). Many pathogens have been known to be more resistant in low-water-activity environments. Due to its ability to survive in dry food matrices, controlling pathogens in the final dehydrated product is of great concern to the food industry. NIR-UV combined treatment for 5 min achieved 3.34- and 2.78-log CFU reductions in S. Typhimurium and E. coli O157:H7 in powdered red pepper, respectively, and for 7 min achieved a 2.79-log CFU reduction of C. sakazakii in powdered infant formula without causing any deterioration in product quality due to the lower intensity of NIR. The sum of NIR and UV inactivation was lower than that obtained by the simultaneous application of both technologies due to their synergism. Through qualitative (transmission electron microscopy) and quantitative (propidium iodide uptake) analyses, disruption of the bacterial cell membrane was identified again as the main factor contributing to the synergistic lethal effect of NIR-UV combined treatment. The results of these extensive studies suggest that a NIR-UV decontaminating system can be applied as an alternative to other interventions in various kinds of powdered/granulated foods. As an another available hurdle combination, the efficacy of NIR heating combined with 2% lactic acid (LA) sprays for decontaminating dry nut kernels (almonds and pine nuts) was investigated. Although surface temperatures of nuts treated with NIR were higher than those subjected to NIR-distilled water spray (DW) or NIR-LA treatment, more S. Enteritidis survived after NIR treatment alone. The effectiveness of NIR-DW and NIR-LA was similar, but significantly more sublethally injured cells were recovered from NIR-DW treated samples. I confirmed that the enhanced bactericidal effect of the NIR-LA combination may not be attributed to cell membrane damage per se. NIR heat treatment might allow S. Enteritidis cells to become permeable to applied LA solution. Due to the lower levels of NIR and applied LA, combined NIR-LA treatments did not change quality attributes of nut kernels significantly (P > 0.05). Thus, the NIR-LA treatment may be a potential intervention for controlling food-borne pathogens on nut kernel products. The simultaneous NIR-UV or NIR-LA combinations have some advantages not only regarding the germicidal effect but also in terms of simplified handling, environmental preservation, and reduced costs through lower inputs of energy. Furthermore, the NIR or combined processing techniques can easily be expanded to practical industrial scale on a continuous basis. In conclusion, application of NIR heating in the food industry is expected to represent a novel and innovative antimicrobial process for the production of high-quality & safe foods at low cost. | - |
| dc.description.tableofcontents | Chapter I. Evaluation of Near-Infrared Pasteurization in Controlling Food-Borne Pathogens in Ready-To-Eat Deli Meat....................................................................................................1
I-1. Introduction.............................................................................................2 I-2. Materials and Methods............................................................................6 Bacterial strains......................................................................................6 Preparation of pathogen inocula............................................................6 Sample preparation and inoculation.......................................................7 Near-infrared heating and conventional convective heating..................8 Temperature measurement...................................................................10 Bacterial enumeration..........................................................................11 Enumeration of heat-injured cells........................................................12 Color and texture measurement...........................................................13 Statistical analysis................................................................................13 I-3. Results...................................................................................................15 Average temperature-time histories of ham slices...............................15 Survival curves of food-borne pathogens............................................18 Comparison of pathogen populations between surface- and internally inoculated ham slices...........................................................................21 The recovery of heat-injured cells.......................................................21 The effect of near-infrared heating on product quality........................24 I-4. Discussion.............................................................................................27 Chapter II. Modeling Inactivation of Food-Borne Pathogens in Ready-To-Eat Deli Meat by NIR Heating at Different Radiation Intensities.........................................................................................33 II-1. Introduction..........................................................................................34 II-2. Materials and Methods.........................................................................37 Bacterial strains and inoculum preparation..........................................37 Sample preparation and inoculation.....................................................37 NIR heating and radiation intensity measurement...............................38 Temperature measurement...................................................................41 Bacterial enumeration..........................................................................41 Modeling of survival curves................................................................42 Tertiary model and validation..............................................................43 II-3. Results and Discussion........................................................................45 Average temperature-time histories of ham slices at different radiation intensities.............................................................................................45 Inactivation of pathogenic bacteria by NIR heating at various radiation intensities.............................................................................................47 Suitable model of survival curves........................................................50 Secondary and tertiary models.............................................................56 Model validation..................................................................................58 Chapter III. Enhanced Inactivation of Food-Borne Pathogens in Ready-To-Eat Deli Meat by NIR Heating Combined with UV-C Irradiation and Mechanism of the Synergistic Bactericidal Action................................................................................................63 III-1. Introduction........................................................................................64 III-2. Materials and Methods.......................................................................67 Bacterial strains....................................................................................67 Preparation of pathogen inocula..........................................................67 Sample preparation and inoculation.....................................................68 Near-infrared heating and UV-C irradiation........................................68 Temperature measurement...................................................................71 Bacterial enumeration..........................................................................71 Enumeration of injured cells................................................................72 Investigation of the bactericidal mechanism........................................73 Color and texture measurement...........................................................75 Statistical analysis................................................................................76 III-3. Results................................................................................................77 Inactivation of pathogenic cells by simultaneous NIR-UV treatment..............................................................................................77 Resuscitation of NIR-UV-injured cells................................................82 Average temperature-time histories of ham slices...............................82 Determination of injury sites in NIR-UV-treated cells........................85 Effect of simultaneous NIR-UV treatment on product quality............87 III-4. Discussion...........................................................................................89 Chapter IV. Simultaneous NIR Radiant Heating and UV Radiation for Inactivating Food-Borne Pathogens in Powdered Red Pepper.......................................................................................96 IV-1. Introduction.........................................................................................97 IV-2. Materials and Methods.....................................................................101 Bacterial strains..................................................................................101 Preparation of pathogen inocula........................................................101 Sample preparation and inoculation...................................................102 Near-infrared heating and UV irradiation..........................................102 Bacterial enumeration........................................................................105 Enumeration of injured cells..............................................................105 Temperature measurement.................................................................106 Transmission electron microscopy analysis.......................................107 Measurement of propidium iodine uptake.........................................108 Color and capsaicinoid measurement................................................109 Statistical analysis..............................................................................110 IV-3. Results...............................................................................................111 Inactivation of pathogenic bacteria by NIR-UV simultaneous treatment.............................................................................................111 Recovery of NIR-UV-injured cells....................................................114 Average temperature-time histories of red pepper powder................114 Microscopic evaluation of damages...................................................117 Determination of membrane damage by PI uptake............................120 Effect of NIR-UV simultaneous treatment on product quality..........122 IV-4. Discussion.........................................................................................125 Chapter V. Synergistic Bactericidal Effect of Simultaneous NIR Radiant Heating and UV Radiation against Cronobacter sakazakii in Powdered Infant Formula........................................131 V-1. Introduction........................................................................................132 V-2. Materials and Methods.......................................................................136 Bacterial strains..................................................................................136 Preparation of pathogen inocula........................................................136 Sample preparation and inoculation...................................................137 Near-infrared heating and UV irradiation..........................................137 Temperature measurement.................................................................140 Bacterial enumeration........................................................................140 Enumeration of injured cells..............................................................141 Assessment of propidium iodide uptake............................................142 Color measurement and sensory evaluation......................................142 Statistical analysis..............................................................................143 V-3. Results................................................................................................144 Synergistic bactericidal effect of simultaneous NIR-UV treatment............................................................................................144 Recovery of NIR-UV-injured cells....................................................146 Average temperature-time histories of powdered infant formula......146 Determination of cell membrane damage by PI uptake.....................149 Effect of simultaneous NIR-UV treatment on product quality..........151 V-4. Discussion..........................................................................................154 Chapter VI. Combining Organic Acid Spray with NIR Radiant Heating to Inactivate Food-Borne Pathogens on Dry Nut Kernels............................................................................................160 VI-1. Introduction......................................................................................161 VI-2. Materials and Methods.....................................................................165 Bacterial strains..................................................................................165 Preparation of pathogen inocula........................................................165 Sample preparation and inoculation...................................................166 Preparation of lactic acid solution......................................................166 Spraying with LA and near-infrared heating......................................167 Bacterial enumeration........................................................................170 Enumeration of injured cells..............................................................170 Temperature measurement.................................................................171 Measurement of extracellular UV-absorbing substances.................. 171 Acid value, peroxide value, and total phenolic content measurement......................................................................................172 Color / post-treatment moisture content measurement and sensory evaluation...........................................................................................173 Statistical analysis..............................................................................174 VI-3. Results..............................................................................................175 Survival curves of food-borne pathogens..........................................175 Resuscitation of injured cells.............................................................179 Average temperature-time histories of nut kernels............................182 Leakage of bacterial intracellular substances....................................184 Effect of NIR-LA combined treatment on product quality................186 VI-4. Discussion........................................................................................190 References......................................................................................195 국문 초록.......................................................................................213 List of Figures Fig. I-1. Schematic diagram of the NIR heating system used in this study.......................................................................................................................9 Fig. I-2. Average temperature-time histories of ham slice surfaces during conventional convective and NIR heating...........................................................16 Fig. I-3. Average temperature-time histories of insides of two contiguous ham slices during conventional convective and NIR heating......................................17 Fig. I-4. Survival curves of Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes on ham slice surfaces treated with NIR or conventional convective heating..........................................................................19 Fig. I-5. Survival curves of Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes inside two contiguous ham slices treated with NIR or conventional convective heating.....................................................................20 Fig. II-1. Schematic view of the NIR heating system used in this study.....................................................................................................................40 Fig. II-2. Average temperature-time histories of ham slice surfaces during NIR heating at different radiation intensities...............................................................46 Fig. II-3. Survival curves for Salmonella enterica serovar Typhimurium (a), Escherichia coli O157:H7 (b), and Listeria monocytogenes (c) on ham slice surfaces treated at different NIR intensities.........................................................49 Fig. II-4. Plot of the observed and estimated data obtained with the models developed for Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes on ham slices.........................................62 Fig. III-1. Schematic diagram of the NIR-UV combined treatment system used in this study..........................................................................................................70 Fig. III-2. Average temperature-time histories of ham slice surfaces during NIR heating and simultaneous NIR-UV treatment......................................................84 Fig. IV-1. Combined NIR-UV treatment system used in this study..................104 Fig. IV-2. Average temperature-time histories of the treatment chamber and red pepper powder cores during simultaneous NIR heating and UV-C irradiation...........................................................................................................116 Fig. IV-3. Comparison of damage induced by UV-C irradiation, NIR heating, and their combination (for 3 min) in S. Typhimurium cells, observed by TEM...................................................................................................................118 Fig. IV-4. Comparison of damage induced by UV-C irradiation, NIR heating, and their combination (for 3 min) in Escherichia coli O157:H7 cells, observed by TEM..............................................................................................................119 Fig. V-1. Schematic diagram of the combined NIR-UV treatment system used in this study............................................................................................................139 Fig. V-2. Average temperature-time histories for treatment chamber and infant formula powder cores during simultaneous NIR heating and UV-C irradiation...........................................................................................................148 Fig. VI-1. Schematic diagram of the NIR-LA combined treatment system used in this study............................................................................................................169 Fig. VI-2. Survival curves of Salmonella Enteritidis PT 30 on almond kernels treated with single NIR or 2 % lactic acid sprays and NIR heating combined with distilled water or 2 % lactic acid sprays.............................................................177 Fig. VI-3. Survival curves of Salmonella enterica serovar Enteritidis on pine nut kernels treated with single NIR or 2 % lactic acid sprays and NIR heating combined with distilled water or 2 % lactic acid sprays....................................178 Fig. VI-4. Average temperature-time histories of almond and pine nut surfaces during single NIR heating and NIR heating combined with distilled water or 2 % lactic acid sprays................................................................................................183 List of Tables Table I-1. Comparison of pathogen populations between surface- and internally inoculated ham slices following NIR (A) or conventional convective heating (B)........................................................................................................................22 Table I-2. Levels of surviving cells and cells including heat-injured Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes on the ham slices following NIR (A) or conventional convective heating (B)..............23 Table I-3. Surface color values of NIR-treated ham slices................................25 Table I-4. Maximum load values for quantifying texture of ham slices following treatment with NIR..............................................................................................26 Table II-1. Comparison of goodness of fit of the Weibull model and log-logistic model for the survival curves of S. Typhimurium, E. coli O157:H7, and L. monocytogenes on ready-to-eat sliced ham treated with near-infrared heating at different radiation intensities...............................................................................52 Table II-2. Kinetic parameters of the Weibull model for S. Typhimurium, E. coli O157:H7, and L. monocytogenes on ready-to-eat sliced ham treated with near-infrared heating at different radiation intensities.................................................55 Table II-3. Secondary models developed for α and β values of Weibull distribution...........................................................................................................57 Table II-4. The validation of developed tertiary models with the data measured at other radiation intensities for determining the goodness of prediction............61 Table III-1. Concentrations of metabolic inhibitors incorporated into TSA medium and targets of synthesis inhibition..........................................................74 Table III-2. Reductions in numbers of viable Salmonella Typhimurium cells on ham slice surfaces treated with UV, NIR, and NIR-UV.......................................79 Table III-3. Reductions in numbers of viable Escherichia coli O157:H7 cells on ham slice surfaces treated with UV, NIR, and NIR-UV.......................................80 Table III-4. Reductions in numbers of viable Listeria monocytogenes cells on ham slice surfaces treated with UV, NIR, and NIR-UV.......................................81 Table III-5. Effect of metabolic inhibitors on resuscitation of UV-, NIR-, and NIR-UV-injured Salmonella Typhimurium DT 104 cells....................................86 Table III-6. Surface color values and maximum load values for quantifying texture of ham slices simultaneously treated with NIR-UV.................................88 Table IV-1. Viable-count reductions of S. Typhimurium in red pepper powder treated with UV-C irradiation (UV), NIR radiant heating (NIR), and both technologies simultaneously (NIR-UV).............................................................112 Table IV-2. Viable-count reductions of E. coli O157:H7 in red pepper powder treated with UV-C irradiation (UV), NIR radiant heating (NIR), and both technologies simultaneously (NIR-UV).............................................................113 Table IV-3. Levels of membrane damage of NIR-, UV-, and NIR-UV treated cells obtained from the propidium iodine (PI) uptake test.................................121 Table IV-4. Color values of NIR-UV simultaneously treated red pepper powder................................................................................................................123 Table IV-5. Capsaicinoid content of NIR-UV-treated red pepper powder.......124 Table V-1. Reductions in numbers of viable C. sakazakii cells in powdered infant formula treated with UV-C irradiation, NIR radiant heating, and simultaneous application of both technologies..................................................145 Table V-2. Levels of membrane damage of UV-, NIR-, and simultaneously NIR-UV-treated cells obtained from the PI uptake test.................................... 150 Table V-3. Color values of simultaneously NIR-UV-treated infant formula powder............................................................................................................... 152 Table V-4. Sensory attributes of powdered infant formula following simultaneous NIR-UV treatment (at day 0)...................................................... 153 Table VI-1. Levels of surviving cells and cells including injured Salmonella Enteritidis PT 30 on almond kernels following NIR heating combined with distilled water or 2 % lactic acid sprays.............................................................180 Table VI-2. Levels of surviving cells and cells including injured Salmonella enterica serovar Enteritidis on pine nut kernels following NIR heating combined with distilled water or 2 % lactic acid sprays....................................................181 Table VI-3. Levels of membrane damage of LA-, NIR-, NIR-DW-, and NIR-LA-treated cells inferred from leakage of intracellular UV-absorbing substances..........................................................................................................185 Table VI-4. Acid value, peroxide value, and total phenolic contenta of NIR-LA treated almond kernels during storage under accelerated conditions................187 Table VI-5. Acid value, peroxide value, and total phenolic contenta of NIR-LA treated pine nut kernels during storage under accelerated conditions...............188 Table VI-6. Color values, moisture content, and sensory attributesa of nut kernels following 5 min of NIR-LA treatment (at day 0)..................................189 | - |
| dc.format | application/pdf | - |
| dc.format.extent | 2572973 bytes | - |
| dc.format.medium | application/pdf | - |
| dc.language.iso | en | - |
| dc.publisher | 서울대학교 대학원 | - |
| dc.subject | near-infrared heating | - |
| dc.subject | ultraviolet irradiation | - |
| dc.subject | organic acid | - |
| dc.subject | lactic acid | - |
| dc.subject | spray | - |
| dc.subject | inactivation | - |
| dc.subject | foodborne pathogen | - |
| dc.subject | radiation intensity | - |
| dc.subject | kinetics model | - |
| dc.subject | deli meat | - |
| dc.subject | dry powdered food | - |
| dc.subject | nut kernel | - |
| dc.subject.ddc | 630 | - |
| dc.title | Application of near-infrared heating as an antimicrobial intervention for food safety | - |
| dc.type | Thesis | - |
| dc.description.degree | Doctor | - |
| dc.citation.pages | XXII, 218 | - |
| dc.contributor.affiliation | 농업생명과학대학 농생명공학부 | - |
| dc.date.awarded | 2015-08 | - |
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