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Application of Superheated Steam-Based Technology for Inactivation of Foodborne Pathogens : 과열 수증기를 이용한 식품병원성균 제어 기술 연구
DC Field | Value | Language |
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dc.contributor.advisor | 강동현 | - |
dc.contributor.author | 반가희 | - |
dc.date.accessioned | 2017-07-13T08:23:49Z | - |
dc.date.available | 2018-10-25 | - |
dc.date.issued | 2015-08 | - |
dc.identifier.other | 000000067492 | - |
dc.identifier.uri | https://hdl.handle.net/10371/119509 | - |
dc.description | 학위논문 (박사)-- 서울대학교 대학원 : 농생명공학부(식품생명공학전공), 2015. 8. 강동현. | - |
dc.description.abstract | Superheated steam (SHS) is steam which is given additional heat to raise its temperature above the saturation temperature at a constant pressure. SHS has been known as a safe, non-polluting technology with low energy consumption and proven to be one of the most effective methods for the drying of biological or non-biological products, including foods. However, the inactivation of foodborne pathogens by SHS has rarely been studied. This study researched the effects of SHS treatment for inactivating foodborne pathogens including Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes by comparing and evaluating the effectiveness of SS and SHS.
Bacteria can attach to solid surfaces of food processing facilities and form slimy, slippery biofilms consisting of hydrated extracellular polymeric substances. Adhesion of bacteria to food processing facility surfaces leads to potential hygienic problems in the food processing industry. Biofilms were formed on PVC and stainless steel coupons by using a mixture of three strains each of three foodborne pathogens at 25°C. After biofilm development, PVC and stainless steel coupons were treated with saturated steam (SS) at 100°C and SHS at 125, 150, 175, and 200°C for 5, 10, 20, and 30 s on both sides. The viable cell numbers of biofilms were significantly (P < 0.05) reduced as SHS temperature and exposure time increased. For all biofilm cells, SHS treatment resulted in an additional log reduction compared to SS treatments. After exposure to 200°C steam for 30 s or 10 s on PVC or stainless steel, respectively, the numbers of biofilm cells were reduced to below the detection limit (1.48 log CFU/coupon). SHS treatment effectively reduced populations of biofilm cells and reduced disinfection time compared to SS treatments. Effectiveness of SHS on the inactivation of foodborne pathogens on agriculture produce including almonds, in-shell pistachios, cherry tomatoes, oranges, radish seeds, and alfalfa seeds and on quality by measuring color, texture, ascorbic acid contents, antioxidant capacity, and germination rate were evaluated. Exposure of almonds and pistachios to SHS for 15 or 30 s at 200˚C reduced all tested pathogens to below the detection limit (0.3 log CFU/g) without causing significant changes in color values or texture parameters (P > 0.05). For both almonds and pistachios, acid and peroxide values following SS and SHS treatment for up to 15 s and 30 s, respectively, were within the acceptable range. Exposure to SHS for 3 or 20 s at 200˚C reduced all tested pathogens on cherry tomatoes and oranges, respectively, to below the detection limit (1 and 1.7 log CFU/g, respectively) without causing significant changes in color values or texture parameters, ascorbic acid contents, and antioxidant capacity (P > 0.05). SHS treatment caused to an additional 0.79?2.05 and 0.78?1.77 log reductions of the three pathogens on radish seeds and alfalfa seeds treated continuous and intermittent (1 s heating followed by cooling at 25˚C for 2 min) steam treatment, respectively, compared to SS treatments. A continuous steam treatment for 3 and 2 s resulted in a considerably drop in percent germination compared to the water control for radish seeds and alfalfa seeds, respectively. However, 10 times intermittent SHS treatment at 200°C did not decrease germination rate of radish seeds and alfalfa seeds under the 90%. Simulation using computational fluid dynamics (CFD) was studied to evaluate the inactivation of foodborne pathogens on food samples by SHS treatment. COMSOL multi-physics software to predict temperature distribution and concentration of the live bacteria on an orange were used. The governing equations for continuity, compressible fluid flow, and energy are solved numerically together with bacteria concentration, using a finite element method. Arrhenius equation was used to describe bacteria deactivation kinetics. The simulations have provided flow pattern, live bacteria concentration, and temperature profiles from different periods of heating. The simulated results show the slowest heating and little effect zones, which are correlated to the concentration of the live bacteria. The simulations also show bacteria were eliminated during SHS treatment at 200°C for 20 s. Portable superheated steam generator for field application was developed and the ability of inactivation of foodborne pathogens biofilm cells on stainless steel evaluated. The populations of viable biofilm cells on stainless steel coupons were reduced below the detection limit when subjected to SHS treatment at 160°C for 30 s. Healthy cells and heat-injured cells on stainless steel coupons following SS or SHS heating were compared. There were no significant (P > 0.05) differences between the levels of cells enumerated on the appropriate selective agar (SMAC, XLD, and OAB) versus the agar for resuscitation (SPRAB, OV-XLD, and OV-OAB) during the whole SHS treatment time. Also, the results have revealed that the Weibull model, which had been mostly used for describing inactivation of the bacterial cells by heat treatment, could be successfully used to describe foodborne pathogens biofilm cells on stainless steel inactivation by SHS. This study demonstrated that SHS treatment effectively reduced populations of biofilm cells on materials and foodborne pathogens on agricultural produce compared to SS treatments. And inactivation of bacteria on food during SHS treatment using CFD and development of portable SHS generator can be used for application to feeding facilities. SHS treatment has potential as an excellent intervention for controlling foodborne pathogens and enhancing safety in the food industry. | - |
dc.description.tableofcontents | Contents
General introduction 1 Superheated steam 1 Inactivation methods of foodborne pathogens 4 Computational fluid dynamics for food industry 9 Objectives of this study 11 Chapter I. Inactivation of Foodborne Pathogens Biofilm Cells on Materials used in Food Processing Facilities 12 I(1). Effect of Chlorine, Hydrogen Peroxide, Quaternary Ammonium, and Iodophor Combined with Steam Heating on the Inactivation of Foodborne Pathogens in a Biofilm on Stainless Steel 13 I(1)-1. Introduction 14 I(1)-2. Materials and Methods 17 Bacterial strains and culture preparation 17 Preparation of stainless steel coupons 17 Biofilm formation 18 Sanitizer preparation 18 Combination treatment of sanitizer and steam 19 Bacterial enumeration 19 Confocal laser scanning microscopy 20 Statistical analysis 21 I(1)-3. Results 22 Inactivation of E. coli O157:H7 biofilms on stainless steel 22 Inactivation of S. Typhimurium biofilms on stainless steel 26 Inactivation of L. monocytogenes biofilms on stainless steel 29 Effect of sanitizer and steam treatment on membrane integrity 32 I(1)-4. Discussion 35 I(2). Synergistic Effect of Steam and Lactic Acid against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes Biofilms on Polyvinyl Chloride and Stainless Steel 40 I(2)-1. Introduction 41 I(2)-2. Materials and Methods 44 Bacterial strains and culture preparation 44 Preparation of PVC and stainless steel coupons 44 Biofilm formation 45 Preparation of acid 45 Combination treatment of steam and acid 45 Bacterial enumeration 46 Temperature monitoring 47 Confocal laser scanning microscopy 47 Statistical analysis 48 I(2)-3. Results 49 Inactivation of E. coli O157:H7 biofilm on PVC and stainless steel 49 Inactivation of S. Typhimurium biofilms on PVC and stainless steel 52 Inactivation of L. monocytogenes biofilms on PVC and stainless steel 54 Temperature monitoring 56 Effect of hyperthermia on membrane integrity 56 I(2)-4. Discussion 59 I(3). A Comparison of Saturated Steam and Superheated Steam for Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes Biofilms on Polyvinyl Chloride and Stainless Steel 64 I(3)-1. Introduction 65 I(3)-2. Materials and Methods 68 Bacterial strains and culture preparation 68 Preparation of PVC and stainless steel coupons 68 Biofilm formation 69 SS and SHS treatment 69 Bacterial enumeration 70 Temperature monitoring 70 Confocal laser scanning microscopy 71 Statistical analysis 71 I(3)-3. Results 72 Inactivation of E. coli O157:H7 biofilm on PVC and stainless steel 72 Inactivation of S. Typhimurium biofilms on PVC and stainless steel 75 Inactivation of L. monocytogenes biofilms on PVC and stainless steel 77 Temperature monitoring 79 Effect of hyperthermia on membrane integrity 79 I(3)-4. Discussion 83 Chapter II. Effectiveness of Superheated Steam to Inactivate Foodborne Pathogens on Agricultural Produce 89 II(1). Effectiveness of Superheated Steam for Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Salmonella Enteritidis phage type 30, and Listeria monocytogenes on Almonds and Pistachios 90 II(1)-1. Introduction 91 II(1)-2. Materials and Methods 93 Sample preparation 93 Bacterial strains and inoculum preparation 93 Inoculation procedure 94 SS and SHS treatment 94 Bacterial enumeration 95 Color and texture measurement 96 Acid value and peroxide value 97 Statistical analysis 97 II(1)-3. Results 98 Inactivation of pathogenic bacteria on almonds 98 Effect of SS and SHS treatment on color and texture of almonds and pistachios 104 Effect of SS and SHS treatment on lipid oxidation of almonds and pistachios 108 II(1)-4. Discussion 111 II(2). Effectiveness of Superheated Steam for Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on Cherry tomatoes and Oranges 116 II(2)-1. Introduction 117 II(2)-2. Materials and Methods 120 Bacterial strains and culture preparation 120 Sample preparation and inoculation procedure 120 SS and SHS treatment 121 Bacterial enumeration 122 Color and texture measurement 123 Vitamin C measurement 124 Determination of antioxidant capacity .125 Statistical analysis 125 II(2)-3. Results 126 Inactivation of bacteria on cherry tomatoes and oranges 126 Effect of SS and SHS treatment on color and texture of cherry tomatoes and oranges 132 Effect of SS and SHS treatment on vitamin C and antioxidant capacities of cherry Tomatoes, orange pulp, and orange peel 136 II(2)-4. Discussion 141 II(3). A Comparision of Continuous and Intermittent Superheated Steam for Inactivation of foodborne pathogens on Radish Seeds and Alfalfa Seeds 146 II(3)-1. Introduction 147 II(3)-2. Materials and Methods 150 Bacterial strains and culture preparation 150 Sample preparation and inoculation 150 SS and SHS treatment 151 Bacterial enumeration 152 Determination of seed germination percent. 153 Statistical analysis 153 II(3)-3. Results 154 Inactivation of pathogenic bacteria on radish seeds 154 Inactivation of pathogenic bacteria on alfalfa seeds 157 Effect of SS and SHS treatment on germination rate of radish seeds and alfalfa seeds 160 II(3)-4. Discussion 162 III. Analysis of Superheated Steam Treatment Using Computational Fluid Dynamics 165 III-1. Introduction 166 III-2. Mathematical Model and Simulation 169 SHS treatment system design 169 Temperature monitoring 171 Governing equation 171 Prediction of thermo-physical properties 173 Bacterial deactivation kinetics 174 Simulation procedure 175 III-3. Results and Discussion 177 Temperature distribution in chamber during SHS treatment 177 Flow pattern in chamber during SHS treatment 177 Bacteria deactivation in chamber during SHS treatment 177 Nomenclature 186 IV. Development of Portable Superheated Steam Generator and Inactivation Kinetics of Foodborne Pathogens Biofilm Cells 187 IV-1. Introduction 188 IV-2. Materials and Methods 191 Bacterial strains and culture preparation 191 Biofilm formation 191 SS and SHS treatment 192 Bacterial enumeration 194 Enumeration of heat-injured cells 194 First-order kinetics and Weibull model 195 Statistical analysis 196 IV-3. Results and Discussion 197 Development of superheated steam generator 197 Inactivation of E. coli O157:H7, S. Typhimurium, or L. monocytogenes biofilm on stainless steel 197 Recovery of heat-injured cells 202 Suitable model of survival curves 202 References 205 국문초록 237 | - |
dc.format | application/pdf | - |
dc.format.extent | 3192438 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | Superheated steam | - |
dc.subject | Escherichia coli O157:H7 | - |
dc.subject | Salmonella Typhimurium | - |
dc.subject | Listeria monocytogenes | - |
dc.subject | Biofilm | - |
dc.subject | Computational fluid dynamics | - |
dc.subject | Portable | - |
dc.subject.ddc | 630 | - |
dc.title | Application of Superheated Steam-Based Technology for Inactivation of Foodborne Pathogens | - |
dc.title.alternative | 과열 수증기를 이용한 식품병원성균 제어 기술 연구 | - |
dc.type | Thesis | - |
dc.description.degree | Doctor | - |
dc.citation.pages | XIV, 240 | - |
dc.contributor.affiliation | 농업생명과학대학 농생명공학부 | - |
dc.date.awarded | 2015-08 | - |
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