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Gędas A, Schmidt H, Weiss A. Identification and evaluation of Escherichia coli strain ATCC 8739 as a surrogate for thermal inactivation of enterohemorrhagic Escherichia coli in fruit nectars: Impact of applied techniques on the decimal reduction time. Food Microbiol 2024; 122:104544. [PMID: 38839230 DOI: 10.1016/j.fm.2024.104544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 04/12/2024] [Accepted: 04/13/2024] [Indexed: 06/07/2024]
Abstract
The objective of this study was to identify a suitable surrogate for E. coli O157:H7 strain 19685/91 and O113:H21 strain TS18/08, by assessing their thermal resistance at temperatures of 60 °C, 65 °C, and 72 °C in strawberry nectar. The influence of the matrix and the research methodology on the decimal reduction time (D-value) was investigated. Thermal kinetics and safety assessment demonstrated that E. coli ATCC 8739 is a suitable surrogate. The study demonstrated that the presence of fruit particles in the nectar increased thermal resistance of the tested strains. Variations in D-values were observed depending on the research method employed, with D-values in glass capillaries were up to 6.6 times lower compared to larger sample volumes. Encapsulation of E. coli ATCC 8739 exhibited high efficiency of 90.25 ± 0.26% and maintained stable viable counts after 26 days of storage in strawberry nectar at 4 °C. There were no significant differences in thermal resistance between surrogates directly inoculated into strawberry nectar and those encapsulated in alginate beads. Additionally, the encapsulated strains did not migrate outside the beads. Therefore, encapsulated E. coli ATCC 8739 in alginate beads can be effectively utilized in industrial settings to validate thermal treatments as a reliable and safe method.
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Affiliation(s)
- Astrid Gędas
- Food Microbiology, Hamburg School of Food Science, University of Hamburg, Ohnhorststrasse 18, 22609, Hamburg, Germany; Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany
| | - Agnes Weiss
- Food Microbiology, Hamburg School of Food Science, University of Hamburg, Ohnhorststrasse 18, 22609, Hamburg, Germany.
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2
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Özcan S, Işık S, Işık H, Güner S, Topalcengiz Z. Use of dishwashers fails to inactivate foodborne pathogens in home-canned model foods. Int J Food Microbiol 2024; 418:110739. [PMID: 38749263 DOI: 10.1016/j.ijfoodmicro.2024.110739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 03/15/2024] [Accepted: 05/06/2024] [Indexed: 05/27/2024]
Abstract
Risky home canning techniques are still performed for food preservation due to limited science-based recommendations. This study aimed to evaluate the inactivation of Shiga toxin-producing Escherichia coli O157:H7, Salmonella enterica (ser. Typhimurium, Enteritidis, and Infantis) and Listeria monocytogenes during home canning with a household dishwasher. The 450 mL of blended tomato (acidic liquid food) and potato puree (non-acidic solid food) were prepared with 1.5 % salt and 25 mL vinegar as model foods in glass jars (660 mL). The two model foods were sterilized, then inoculated with separate cocktails of each pathogen at 106-107 CFU/g. The prepared jars were placed in the bottom rack of a dishwasher and subjected to the following cycles: economic (50 °C, 122 min), express (60 °C, 54 min), and intensive (70 °C, 96 min). Temperature changes in jars were monitored by using thermocouples during heat treatment. Within the center of the jars, temperatures were measured as 45 to 53 °C in blended tomato and 44 to 52 °C in potato puree during all tested dishwasher cycles, respectively. The economic cycle treatment reduced S. enterica, E. coli O157:H7, and L. monocytogenes populations by 3.1, 4.6, and 4.2 log CFU/g in blended tomato (P ≤ 0.05), where a <1.0 log reduction was observed in potato puree (P > 0.05). All pathogens showed similar heat resistance during the express cycle treatment with a log reduction ranging from 4.2 to 5.0 log CFU/g in blended tomato and 0.6 to 0.7 log CFU/g in potato puree. Reduction in L. monocytogenes population was limited (0.6 log CFU/g) compared to E. coli O157:H7 (2.0 log CFU/g) and S. enterica (2.7 log CFU/g) in blended tomato during the intensive cycle treatment (P ≤ 0.05). Dishwasher cycles at manufacturer defined settings failed to adequately inactivate foodborne pathogens in model foods. This study indicates that home-canned vegetables may cause foodborne illnesses when dishwashers in home kitchens are used for heat processing.
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Affiliation(s)
- Seracettin Özcan
- Department of Food Safety, Graduate School of Natural and Applied Sciences, Muş Alparslan University, 49250 Muş, Türkiye
| | - Sefa Işık
- Department of Food Processing, Vocational School of Technical Sciences, Muş Alparslan University, 49250 Muş, Türkiye
| | - Hasan Işık
- Department of Food Processing, Vocational School of Technical Sciences, Muş Alparslan University, 49250 Muş, Türkiye
| | - Senem Güner
- Department of Food Engineering, Faculty of Engineering, Afyon Kocatepe University, 03200 Afyonkarahisar, Türkiye
| | - Zeynal Topalcengiz
- Department of Food Engineering, Faculty of Engineering and Architecture, Muş Alparslan University, 49250 Muş, Türkiye; Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR 72704, USA.
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3
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Yesil M, Kasler DR, Huang E, Yousef AE. Thermal Inactivation of Escherichia Phage OSYSP and Host Strain Escherichia coli O157:H7 EDL933: A Comparative Kinetic Analysis. J Food Prot 2024; 87:100215. [PMID: 38182094 DOI: 10.1016/j.jfp.2023.100215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 12/13/2023] [Accepted: 12/29/2023] [Indexed: 01/07/2024]
Abstract
Lytic bacteriophages are promising biocontrol agents against pathogenic bacteria for food and therapeutic applications. Investigating the feasibility of combining phage and physical lethal agents, such as heat, as an effective hurdle combination could lead to beneficial applications. The current research was initiated to compare the thermal inactivation kinetics of a lytic phage (Escherichia phage OSYSP) and its host (Shiga toxin-producing Escherichia coli O157:H7 EDL933), considering they have different critical thermal targets in their structures. To provide a basis for comparison, thermal inactivation kinetics were determined on suspensions of these agents in buffered peptone water using a thermally controlled circulating water bath. Results showed that the bacteriophage virions have a remarkable heat resistance (p < 0.05) compared to their host cells. The D-values of the populations of phage (PFU/mL) and EDL933 strain (CFU/mL) were 166.7 and 7.3 min at 55°C, compared to 44.4 and 0.3 min at 60°C, respectively. Additionally, D-values were significantly (p < 0.05) more influenced by temperature changes in the case of E. coli O157:H7 EDL933 (z-value 3.7°C) compared to that for phage OSYSP (z-value 7.7°C). When the phage suspension was heat-treated in a thermal cycler instead of a water bath, no significant differences between the two treatment procedures (p > 0.05) in estimating virus D- and z-values were observed. Based on these findings, it may be feasible to combine phage OSYSP with mild heat during processing of food to selectively inactivate E. coli O157:H7 EDL933 and subsequently maintain product safety during storage by the surviving phage population; however, the feasibility of this application needs to be investigated. Additionally, the relatively heat-resistant phage OSYSP could qualify as a biological indicator to validate thermal treatments of minimally processed foods in which E. coli O157:H7 EDL933 is the pathogen-of-concern.
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Affiliation(s)
- Mustafa Yesil
- Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA
| | - David R Kasler
- Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA
| | - En Huang
- Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA
| | - Ahmed E Yousef
- Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA; Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
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Liu S, Qiu Y, Su G, Sheng L, Qin W, Ye Q, Wu Q. Enhanced heat tolerance of freeze-dried Enterococcus faecium NRRL B-2354 as valid Salmonella surrogate in low-moisture foods. Food Res Int 2023; 173:113232. [PMID: 37803547 DOI: 10.1016/j.foodres.2023.113232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 06/30/2023] [Accepted: 07/03/2023] [Indexed: 10/08/2023]
Abstract
In microbial studies of low-moisture foods (LMFs, water activity less than 0.85), freeze-dried bacteria benefit us to inoculate LMFs without introducing extra water or altering food physiochemical properties. However, the freeze-drying process would bring unavoidable damage to bacterial cells and results in less-resistant inoculum that are unlikely to be qualified in microbial studies. Herein, we enhanced bacterial heat tolerance by subjecting the cells to mild heat (42-50 °C) to counteract the reduced heat tolerance and survivability of freeze-dried bacteria. Enterococcus faecium NRRL B-2354 (E. faecium), a Salmonella surrogate in LMFs, was used as the target microorganism because it was widely accepted in microbial validation of thermal pasteurizing LMFs. Three types of LMFs (peanut powder, protein powder, and onion powder) were used as LMFs models to validate the freeze-dried E. faecium in comparison with Salmonella enterica Enteritidis PT 30 (S. Enteritidis) prepared by the traditional aqueous method. The heat tolerance (D65℃ value) of E. faecium increased at all treatments and peaked (+31.48 ± 0.13%) at temperature-time combinations of 45 °C-60 min and 50 °C-5 min. Survivability of freeze-dried inoculum and its heat tolerance retained well within 50 d storage. The freeze-dried E. faecium was prepared in this study brought equal or higher heat tolerance (D85℃ or D75℃) than S. Enteritidis in tested LMFs models. For instance, the D85℃ of freeze-dried E. faecium (heat-treated at 50 °C for 5 min) and S. Enteritidis in whole egg powder are 35.56 ± 1.52 min and 28.41 ± 0.41 min, respectively. The freeze-dried E. faecium with enhanced heat tolerance appears to be a suitable Salmonella surrogate for dry-inoculating LMFs. Our protocol also enables industry-scale production of freeze-dried inoculum by broth-cultivation method combined with mild-heat treatment.
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Affiliation(s)
- Shuxiang Liu
- College of Food Science, Sichuan Agricultural University, Ya'an 625014, China; State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou 510070, China.
| | - Yan Qiu
- College of Food Science, Sichuan Agricultural University, Ya'an 625014, China
| | - Gehong Su
- College of Science, Sichuan Agricultural University, Ya'an 625014, China
| | - Lina Sheng
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Collaborative Innovation Center of Food Safety and Quality Control, Jiangnan University, Wuxi 214122, China
| | - Wen Qin
- College of Food Science, Sichuan Agricultural University, Ya'an 625014, China
| | - Qinghua Ye
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou 510070, China
| | - Qingping Wu
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou 510070, China.
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Liu S, Qiu Y, Ji K, Ozturk S, Erdoğdu F, Qin W, Yang R, Wu Q. Effect of oil exposure stages on the heat resistance of Salmonella enterica serovar Enteritidis phage type 30 in peanut flour. Food Microbiol 2023; 113:104275. [PMID: 37098433 DOI: 10.1016/j.fm.2023.104275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 04/03/2023] [Accepted: 04/03/2023] [Indexed: 04/08/2023]
Abstract
The oil in low-moisture foods (LMFs) shows protective effects on bacteria during thermal processing. However, the circumstances under which this protective effect strengthens remain unclear. This study aimed to understand which step of the oil exposure to bacterial cells (inoculation, isothermal inactivation, or recovery and enumeration step) in LMFs can enhance their heat resistance. Peanut flour (PF) and defatted PF (DPF) were selected as the oil-rich and oil-free LMF models. Salmonella enterica Enteritidis Phage Type 30 (S. Enteritidis) was inoculated into four designated PF groups representing different oil exposure stages. It was isothermally treated to obtain heat resistance parameters. At a constant moisture content (aw,25°C = 0.32 ± 0.02) and controlled aw,85°C (0.32 ± 0.02), S. Enteritidis exhibited significantly high (p < 0.05) D values in oil-rich sample groups. For instance, the heat resistance values of S. Enteritidis in the PF-DPF and DPF-PF groups were D80°C of 138.22 ± 7.45 min and 101.89 ± 7.82 min; however, the D80°C in the DPF-DPF group was 34.54 ± 2.07 min. The oil addition after the thermal treatment also helped injured bacterial recovery in the enumeration. For instance, the D80°C, D85°C, and D90°C values in the DFF-DPF oil groups were 36.86 ± 2.30, 20.65 ± 1.23, and 7.91 ± 0.52 min, respectively, which were higher than those in the DPF-DPF group at 34.54 ± 2.07, 17.87 ± 0.78, and 7.10 ± 0.52 min. We confirmed that the oil protected S. Enteritidis in PF in all three stages: desiccation process, heat treatment, and recovery of bacterial cells in plates.
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Qiu Y, Ozturk S, Cui X, Qin W, Wu Q, Liu S. Increased heat tolerance and transcriptome analysis of Salmonella enterica Enteritidis PT 30 heat-shocked at 42 ℃. Food Res Int 2023; 167:112636. [PMID: 37087231 DOI: 10.1016/j.foodres.2023.112636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 02/15/2023] [Accepted: 02/21/2023] [Indexed: 02/26/2023]
Abstract
In this study, we compared the heat tolerance parameter (D65℃) values of Salmonella enterica serovar Enteritidis PT 30 (S. Enteritidis ) heat adapted at different degrees (at 42 ℃ for 20-180 min) and cultivated using two methods. The treated group with the highest D65℃ value (LP-42 ℃-60 min) and the untreated groups (Control-TSB and Control-TSA) were subjected to transcriptome analysis. Heat-adaptation increased the D65℃ values of S. Enteritidis by 24.5-60.8%. The D65℃ values of the LP-42 ℃-60 min group (1.85 ± 0.13 min, 7.7% higher) was comparable to that of the Control-TSA. A total of 483 up- and 443 downregulated genes of S. enteritidis were identified in the LP-42 ℃-60 min group (log2fold change > 1, adjusted p-value < 0.05). Among these genes, 5 co-expressed and 15 differentially expressed genes in the LP-42 ℃-60 min and Control-TSA grops possibly contributed to the high D65℃ values of S. Enteritidis . The Rpo regulon was involved in the heat adaptation of S. Enteritidis , as evidenced by the significant upregulation of rpoS, rpoN, and rpoE. KEGG enrichment pathways, such as biosynthesis of secondary metabolites, tricarboxylic acid, and ribosomes were identified and mapped to reveal the molecular mechanisms of S. enteritidis during heat adaptation. This study quantified the enhanced heat tolerance of S. Enteritidis heat adapted at different degrees of heat-adaptation. The results of this study may serve as a basis for elucidating the molecular mechanisms underlying the enhanced heat tolerance at the transcriptome level.
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Affiliation(s)
- Yan Qiu
- College of Food Science, Sichuan Agricultural University, Ya'an, China
| | - Samet Ozturk
- Department of Food Engineering, Gümüşhane University, Gümüşhane, Turkey
| | - Xinyao Cui
- College of Food Science, Sichuan Agricultural University, Ya'an, China
| | - Wen Qin
- College of Food Science, Sichuan Agricultural University, Ya'an, China; Food Processing and Safety Institute, Sichuan Agricultural University, Ya'an, China
| | - Qingping Wu
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou 510070, China
| | - Shuxiang Liu
- College of Food Science, Sichuan Agricultural University, Ya'an, China; Food Processing and Safety Institute, Sichuan Agricultural University, Ya'an, China; State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou 510070, China.
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Yang R, Fleischman GJ, Shazer A, Li H. Experimentally Implementing the Linear Nonisothermal Equation for Simultaneously Obtaining D- and z-Values of Salmonella Senftenberg in Skim Milk with a Differential Scanning Calorimeter. J Food Prot 2022; 85:1410-1417. [PMID: 35775995 DOI: 10.4315/jfp-22-009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 06/29/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT For bacteria with log-linear thermal inactivation kinetics in food, D-values are obtained in multiple isothermal inactivation experiments at different temperatures, and the z-value is obtained from these D-values. In a previous work, the cumulative lethality integral was mathematically solved in closed form when temperature in the food increased linearly with time. The solution revealed that each nonisothermal experiment could yield both D- and z-values, eliminating the need for getting multiple D-values to get a z-value. The present study reports on the first experimental implementation of this method of obtaining D- and z-values for Salmonella Senftenberg suspended in skim milk for which a differential scanning calorimeter (DSC) provided the required constant heating rate. The resulting D- and z-values were compared with those obtained from an isothermal method with capillary tubes. No significant differences in z-values were found between the two methods. The D-values also agreed but only after correcting the nonisothermal value for temperature lag in the DSC caused by the large sample size required. A 5 K/min heating rate was used in this comparison. Other rates were also investigated: 1, 3, 7.5, and 10 K/min. Although D- and z-values should be independent of DSC heating rate, heating rates of 1 and 10 K/min yielded values that were significantly different from the others; therefore, these rates cannot be recommended for use in this nonisothermal method. HIGHLIGHTS
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Affiliation(s)
- Ren Yang
- Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, Illinois 60501
| | - Gregory J Fleischman
- Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, Illinois 60501.,U.S. Food and Drug Administration, Bedford Park, Illinois 60501
| | - Arlette Shazer
- Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, Illinois 60501.,U.S. Food and Drug Administration, Bedford Park, Illinois 60501
| | - Haiping Li
- U.S. Department of Agriculture, 1400 Independence Avenue S.W., Washington, DC 20250, USA
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Recent development in low-moisture foods: Microbial safety and thermal process. Food Res Int 2022; 155:111072. [DOI: 10.1016/j.foodres.2022.111072] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/22/2022] [Accepted: 02/24/2022] [Indexed: 11/17/2022]
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9
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Modeling the effect of protein and fat on the thermal resistance of Salmonella enterica Enteritidis PT 30 in egg powders. Food Res Int 2022; 155:111098. [DOI: 10.1016/j.foodres.2022.111098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/23/2022] [Accepted: 03/02/2022] [Indexed: 11/23/2022]
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10
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Eisner MD. Direct and indirect heating of milk – A technological perspective beyond time–temperature profiles. Int Dairy J 2021. [DOI: 10.1016/j.idairyj.2021.105145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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11
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Cheng T, Tang J, Yang R, Xie Y, Chen L, Wang S. Methods to obtain thermal inactivation data for pathogen control in low-moisture foods. Trends Food Sci Technol 2021. [DOI: 10.1016/j.tifs.2021.03.048] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Dhowlaghar N, Zhu MJ. Control of Salmonella in low-moisture foods: Enterococcus faecium NRRL B-2354 as a surrogate for thermal and non-thermal validation. Crit Rev Food Sci Nutr 2021; 62:5886-5902. [PMID: 33798006 DOI: 10.1080/10408398.2021.1895055] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Salmonella has been implicated in multiple foodborne outbreaks and recalls associated with low water activity foods (LawF). To verify the effectiveness of a process against Salmonella in LawF, validation using a nonpathogenic surrogate strain is essential. Enterococcus faecium NRRL B-2354 strain has been used as a potential surrogate of Salmonella in different processing of LawF. However, the survival of Salmonella and E. faecium in LawF during food processing is a dynamic function of aw, food composition and structure, processing techniques, and other factors. This review assessed pertinent literature on the thermal and non-thermal inactivation of Salmonella and its presumable surrogate E. faecium in various LawF and provided an overview of its suitibility in different LawF. Overall, based on the D-values, survival/reduction, temperature/time to obtain 4 or 5-log reductions, most studies concluded that E. faecium is a suitable surrogate of Salmonella during LawF processing as its magnitude of resistance was slightly greater or equal (i.e., statistical similar) as compared to Salmonella. Studies also showed its unsuitability which either does not provide a proper margin of safety or being overly resistant and may compromise the quality and organoleptic properties of food. This review provides useful information and guidance for future validation studies of LawF.
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Affiliation(s)
- Nitin Dhowlaghar
- School of Food Science, Washington State University, Pullman, Washington, USA
| | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, Washington, USA
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Lau SK, Wei X, Kirezi N, Panth R, See A, Subbiah J. A Comparison of Three Methods for Determining Thermal Inactivation Kinetics: A Case Study on Salmonella enterica in Whole Milk Powder. J Food Prot 2021; 84:521-530. [PMID: 33159446 DOI: 10.4315/jfp-20-232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/30/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Different methods for determining the thermal inactivation kinetics of microorganisms can result in discrepancies in thermal resistance values. In this study, thermal resistance of Salmonella in whole milk powder was determined with three methods: thermal death time (TDT) disk in water bath, pouches in water bath, and the TDT Sandwich system. Samples from three production lots of whole milk powder were inoculated with a five-strain Salmonella cocktail and equilibrated to a water activity of 0.20. The samples were then subjected to three isothermal treatments at 75, 80, or 85°C. Samples were removed at six time points and cultures were enumerated for survivors. The inactivation data were fitted to two consolidated models: two primary models (log linear and Weibull) and one secondary model (Bigelow). Normality testing indicated that all the model parameters were normally distributed. None of the model parameters for both consolidated models were significantly different (α = 0.05). The amount of inactivation during the come-up time was also not significantly different among the methods (α = 0.05). However, the TDT Sandwich resulted in less inactivation during the come-up time and overall less variation in model parameters. The survivor data from all three methods were combined and fitted to both consolidated models. The Weibull had a lower root mean square error and a better fit, according to the corrected Akaike's information criterion. The three thermal treatment methods produced results that were not significantly different; thus, the methods are interchangeable, at least for Salmonella in whole milk powder. Comparisons with more methods, other microorganisms, and larger varieties of food products using the same framework presented in this study could provide guidance for standardizing thermal inactivation kinetics studies for microorganisms in foods. HIGHLIGHTS
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Affiliation(s)
- Soon Kiat Lau
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.]).,Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68583
| | - Xinyao Wei
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.])
| | - Nina Kirezi
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.])
| | - Rajendra Panth
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.])
| | - Arena See
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.])
| | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (ORCID: https://orcid.org/0000-0001-8264-7761 [S.K.L.]; https://orcid.org/0000-0002-1746-2653 [X.W.]; https://orcid.org/0000-0002-8512-0735 [J.S.]).,Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68583.,Department of Food Science, University of Arkansas, System Division of Agriculture, Fayetteville, Arkansas 72704, USA
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14
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Zhang S, Lan R, Zhang L, Wang S. Computational modelling of survival of Aspergillus flavus in peanut kernels during hot air-assisted radio frequency pasteurization. Food Microbiol 2020; 95:103682. [PMID: 33397605 DOI: 10.1016/j.fm.2020.103682] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 11/08/2020] [Accepted: 11/18/2020] [Indexed: 10/22/2022]
Abstract
In recent years, radio frequency (RF) heating is getting popular as an alternative pasteurization method for agricultural commodities and low moisture foods. Computer simulation is an effective way to help understand RF interactions with food components and predict temperature distributions among food samples after RF treatments. In this study, a computer model based on Joule heating and thermal inactivation kinetic of A. flavus was established to predict both temperature distribution and microbial reduction among peanut kernels after RF processing. For the process validation, three 2-g peanut samples inoculated with 40 μL A. flavus were placed at three representative locations among 2.17 kg peanut kernels and subjected to various processing conditions in a 27.12 MHz, 6 kW RF heating unit together with hot air system. Results showed that the average difference of the sample temperature and microbial reduction between simulation and experiment was small with RMSE values of 0.009 °C and 0.012 °C, and 0.31 log CFU/g and 0.42 log CFU/g for peanut moisture contents of 7.56% and 12.02% w. b., respectively. Nonuniform RF heating resulted in the least lethality of A. flavus at the cold spot. The validated computer model was further used to estimate microbial reduction distributions at other target temperatures based on predicted temperature profiles. This computer model may help design the RF pasteurization protocols for peanut kernels without extensive experiments in food industry.
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Affiliation(s)
- Shuang Zhang
- Northwest A&F University, College of Mechanical and Electronic Engineering, Yangling, Shaanxi, 712100, China
| | - Ruange Lan
- Northwest A&F University, College of Mechanical and Electronic Engineering, Yangling, Shaanxi, 712100, China
| | - Lihui Zhang
- Northwest A&F University, College of Mechanical and Electronic Engineering, Yangling, Shaanxi, 712100, China
| | - Shaojin Wang
- Northwest A&F University, College of Mechanical and Electronic Engineering, Yangling, Shaanxi, 712100, China; Department of Biological Systems Engineering, Washington State University, 213 L.J. Smith Hall, Pullman, WA, 99164-6120, USA.
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15
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Lau SK, Subbiah J. TDT Sandwich: An open source dry heat system for characterizing the thermal resistance of microorganisms. HARDWAREX 2020; 8:e00114. [PMID: 35498246 PMCID: PMC9041244 DOI: 10.1016/j.ohx.2020.e00114] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/03/2020] [Accepted: 06/04/2020] [Indexed: 06/14/2023]
Abstract
The determination of the thermal death kinetics of microorganisms has traditionally been performed with liquid baths which have some disadvantages such as liquid spillage and liquid infiltration into samples. The TDT Sandwich was developed as a free, open source alternative that utilizes dry heat. The system is capable of heating samples up to 140 °C and maintaining it within 0.2 °C of the target temperature. Other features of the TDT Sandwich include adjustable heating rates up to approximately 100 °C/min, real-time display and recording of temperature readings at a nominal rate of 5 Hz, an optional thermocouple for acquiring temperature of samples, built-in heating timer, and customizable operating parameters. The modular nature of the TDT Sandwich allows multiple units to be connected to a computer or laptop. Operation of the TDT Sandwich is done through a computer program which, along with the build instructions and microcontroller program, are open source and are available for free to the public at https://doi.org/10.17605/OSF.IO/5Q3Y7.
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Affiliation(s)
- Soon Kiat Lau
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, USA
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, USA
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA
- Department of Food Science, University of Arkansas, Fayetteville, AR, USA
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16
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Mugampoza D, Gkatzionis K, Swift BMC, Rees CED, Dodd CER. Diversity of Lactobacillus Species of Stilton Cheese Relates to Site of Isolation. Front Microbiol 2020; 11:904. [PMID: 32477308 PMCID: PMC7236593 DOI: 10.3389/fmicb.2020.00904] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 04/16/2020] [Indexed: 11/15/2022] Open
Abstract
This study has characterized the dominant non-starter Lactobacillus species isolated from different sites in a Stilton cheese to establish its diversity, stress-tolerance, anti-microbial activity and potential contribution to quality of cheese. Fifty-nine Lactobacillus isolates were cultured from the outer crust, blue veins and white core of the cheese and were speciated phenotypically and by 16S rDNA sequence analysis. Lactobacillus plantarum was the dominant species detected with only two isolates identified as Lactobacillus brevis. Strains were typed by pulse-field gel electrophoresis (PFGE) using the enzyme NotI to examine their genomic diversity. Cluster analysis of PFGE patterns produced five major clusters which associated isolates with their sites of isolation within the cheese. One L. plantarum isolate from each cheese site was selected and evaluated for salt, acid, relative humidity, and heat tolerance to determine whether stress conditions within the isolation site selected their phenotype. D72°C values were 6, 13, and 17 s for strains from the crust, veins and core, respectively, suggesting strains on the crust may not have been able to survive pasteurization and therefore had been added post-pasteurization. All strains recovered from heat injury within 24–48 h at 4°C. pH values of 3, 3.5, and 4 suppressed growth but strains showed a varying ability to grow at pH 4.5 and 5; isolates from the core (which has the lowest pH) were the most acid-tolerant. All strains grew at 3.5 and 5% salt but were suppressed at 10%; those from the crust (which has a lower water activity) were the most halo-tolerant, growing at 8% salt whereas strains from the core were sensitive to this salt concentration. All 57 L. plantarum isolates were examined for antimicrobial activity and variable activity against Lactobacillus pentosus and other genera was demonstrated; plantaricin EF genes were present in 65% of strains. It was concluded that there are varied phenotypes and genotypes of Lactobacillus in a Stilton cheese according to site of isolation. Occurrence of different L. plantarum genotypes could contribute to variation in the cheese quality from batch to batch and provides criteria for selecting isolates as potential adjunct cultures.
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Affiliation(s)
- Diriisa Mugampoza
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom.,Department of Food Technology, Kyambogo University, Kampala, Uganda
| | - Konstantinos Gkatzionis
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom.,Department of Food Science and Nutrition, School of the Environment, University of the Aegean, Lemnos, Greece
| | - Benjamin M C Swift
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom.,Pathobiology and Population Sciences, Royal Veterinary College, Hertfordshire, United Kingdom
| | - Catherine E D Rees
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom
| | - Christine E R Dodd
- School of Biosciences, University of Nottingham, Nottingham, United Kingdom
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17
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Wei X, Lau SK, Reddy BS, Subbiah J. A microbial challenge study for validating continuous radio-frequency assisted thermal processing pasteurization of egg white powder. Food Microbiol 2020; 85:103306. [DOI: 10.1016/j.fm.2019.103306] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 08/16/2019] [Accepted: 08/19/2019] [Indexed: 10/26/2022]
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18
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de Souza Figueiredo EE, Yang X, Zhang P, Reuter T, Stanford K. Comparison of heating block and water bath methods to determine heat resistance in Shiga-toxin producing Escherichia coli with and without the locus of heat resistance. J Microbiol Methods 2019; 164:105679. [PMID: 31351872 DOI: 10.1016/j.mimet.2019.105679] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 07/24/2019] [Accepted: 07/24/2019] [Indexed: 10/26/2022]
Abstract
This study found variability in the time required for tubes of media in heating block wells to reach 60 °C, resulting in significant effects on heat resistance measurements. To determine the extent that methodology changed heat resistance measurements, we compared the heat resistance of Shiga-toxin producing Escherichia coli (STEC) strains with and without the locus of heat resistance (LHR) using both heating block and water bath methods. A total of 34 strains of STEC were used along with a generic E. coli which has been identified as heat-resistant and used as a positive control. The E. coli strains were incubated in a water bath and a heating block set at 60 °C to determine come up time to 60 °C (T0) and for 6 additional minutes (T6) to calculate the D60 value. After incubation, the colony forming units (CFU) were enumerated and mean log CFU/mL from biological replicates was calculated. To compare reductions from T0 to T6, standard deviations among replicates within heating method and correlation of the D60 values generated across methods were determined using Mixed model and Correlation analyses. Our findings indicate that the method chosen to evaluate heat resistance of E. coli can dramatically influence results as there was not a significant correlation between D60 values for the same isolate determined by water bath and heating block methods. The water bath method generates more reliable and consistent heat resistance data and should be used in future evaluations of heat resistance in E. coli. Moreover, PCR screening for the LHR would only be moderately useful for predicting phenotypic heat-resistance of E. coli. Considering water bath data only, LHR-positive STEC isolates were either moderately heat-resistant (1 to 5 log reduction) or heat-sensitive (> 5 log reduction). As LHR-negative STEC were also moderately heat-resistant, prediction of phenotypic heat resistance from genotype requires further refinement.
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Affiliation(s)
| | - Xianqin Yang
- Agriculture and Agri-Food Canada, Lacombe Research and Development Centre, Lacombe, AB T4L 1W1, Canada
| | - Peipei Zhang
- Agriculture and Agri-Food Canada, Lacombe Research and Development Centre, Lacombe, AB T4L 1W1, Canada
| | - Tim Reuter
- Alberta Agriculture and Forestry, Agriculture Centre, Lethbridge, AB T1J 4V6, Canada
| | - Kim Stanford
- Alberta Agriculture and Forestry, Agriculture Centre, Lethbridge, AB T1J 4V6, Canada.
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19
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A 3D-CFD-heat-transfer-based model for the microbial inactivation of pasteurized food products. INNOV FOOD SCI EMERG 2019. [DOI: 10.1016/j.ifset.2019.04.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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20
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Kou X, Li R, Zhang L, Ramaswamy H, Wang S. Effect of heating rates on thermal destruction kinetics of Escherichia coli ATCC25922 in mashed potato and the associated changes in product color. Food Control 2019. [DOI: 10.1016/j.foodcont.2018.10.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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21
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Zhang S, Zhang L, Lan R, Zhou X, Kou X, Wang S. Thermal inactivation of Aspergillus flavus in peanut kernels as influenced by temperature, water activity and heating rate. Food Microbiol 2018; 76:237-244. [DOI: 10.1016/j.fm.2018.05.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 05/27/2018] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
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22
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Ghadirzad S, Yavarmanesh M, Habibi Najafi MB. Survival of male-specific coliphage (MS2) as a surrogate for enteric viruses in the production process of traditional ice cream. J Food Saf 2018. [DOI: 10.1111/jfs.12450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sheila Ghadirzad
- Department of Food Science and Technology, Faculty of Agriculture; Ferdowsi University of Mashhad; Mashhad Iran
| | - Masoud Yavarmanesh
- Department of Food Science and Technology, Faculty of Agriculture; Ferdowsi University of Mashhad; Mashhad Iran
| | - Mohammad B. Habibi Najafi
- Department of Food Science and Technology, Faculty of Agriculture; Ferdowsi University of Mashhad; Mashhad Iran
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23
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A New Chemical Marker-Model Food System for Heating Pattern Determination of Microwave-Assisted Pasteurization Processes. FOOD BIOPROCESS TECH 2018. [DOI: 10.1007/s11947-018-2097-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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24
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Li R, Kou X, Zhang L, Wang S. Inactivation kinetics of food-borne pathogens subjected to thermal treatments: a review. Int J Hyperthermia 2018; 34:177-188. [DOI: 10.1080/02656736.2017.1372643] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Affiliation(s)
- Rui Li
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, China
| | - Xiaoxi Kou
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, China
| | - Lihui Zhang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, China
| | - Shaojin Wang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, China
- Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
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25
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Kou X, Li R, Hou L, Zhang L, Wang S. Identifying possible non-thermal effects of radio frequency energy on inactivating food microorganisms. Int J Food Microbiol 2018; 269:89-97. [DOI: 10.1016/j.ijfoodmicro.2018.01.025] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 01/18/2018] [Accepted: 01/30/2018] [Indexed: 11/17/2022]
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26
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Cheng T, Li R, Kou X, Wang S. Influence of controlled atmosphere on thermal inactivation of Escherichia coli ATCC 25922 in almond powder. Food Microbiol 2017; 64:186-194. [DOI: 10.1016/j.fm.2017.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/03/2017] [Accepted: 01/15/2017] [Indexed: 12/29/2022]
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27
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Topalcengiz Z, Danyluk MD. Thermal inactivation responses of acid adapted and non-adapted stationary phase Shiga toxin-producing Escherichia coli (STEC), Salmonella spp. and Listeria monocytogenes in orange juice. Food Control 2017. [DOI: 10.1016/j.foodcont.2016.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Monteagudo JM, Durán A, Martín IS, Acevedo AM. A novel combined solar pasteurizer/TiO 2 continuous-flow reactor for decontamination and disinfection of drinking water. CHEMOSPHERE 2017; 168:1447-1456. [PMID: 27923504 DOI: 10.1016/j.chemosphere.2016.11.142] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/23/2016] [Accepted: 11/28/2016] [Indexed: 06/06/2023]
Abstract
A new combined solar plant including an annular continuous-flow compound parabolic collector (CPC) reactor and a pasteurization system was designed, built, and tested for simultaneous drinking water disinfection and chemical decontamination. The plant did not use pumps and had no electricity costs. First, water continuously flowed through the CPC reactor and then entered the pasteurizer. The temperature and water flow from the plant effluent were controlled by a thermostatic valve located at the pasteurizer outlet that opened at 80 °C. The pasteurization process was simulated by studying the effect of heat treatment on the death kinetic parameters (D and z values) of Escherichia coli K12 (CECT 4624). 99.1% bacteria photo-inactivation was reached in the TiO2-CPC system (0.60 mg cm-2 TiO2), and chemical decontamination in terms of antipyrine degradation increased with increasing residence time in the TiO2-CPC system, reaching 70% degradation. The generation of hydroxyl radicals (between 100 and 400 nmol L-1) was a key factor in the CPC system efficiency. Total thermal bacteria inactivation was attained after pasteurization in all cases. Chemical degradation and bacterial photo-inactivation in the TiO2-CPC system were improved with the addition of 150 mg L-1 of H2O2, which generated approximately 2000-2300 nmol L-1 of HO● radicals. Finally, chemical degradation and bacterial photo-inactivation kinetic modelling in the annular CPC photoreactor were evaluated. The effect of the superficial liquid velocity on the overall rate constant was also studied. Both antipyrine degradation and E. coli photo-inactivation were found to be controlled by the catalyst surface reaction rate.
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Affiliation(s)
- José María Monteagudo
- Department of Chemical Engineering, Grupo IMAES, Escuela Técnica Superior de Ingenieros Industriales, Instituto de Investigaciones Energéticas y Aplicaciones Industriales (INEI), University of Castilla-La Mancha, Avda. Camilo José Cela 3, 13071 Ciudad Real, Spain.
| | - Antonio Durán
- Department of Chemical Engineering, Grupo IMAES, Escuela Técnica Superior de Ingenieros Industriales, Instituto de Investigaciones Energéticas y Aplicaciones Industriales (INEI), University of Castilla-La Mancha, Avda. Camilo José Cela 3, 13071 Ciudad Real, Spain
| | - Israel San Martín
- Department of Chemical Engineering, Grupo IMAES, Escuela Técnica Superior de Ingenieros Industriales, Instituto de Investigaciones Energéticas y Aplicaciones Industriales (INEI), University of Castilla-La Mancha, Avda. Camilo José Cela 3, 13071 Ciudad Real, Spain
| | - Alba María Acevedo
- Department of Chemical Engineering, Grupo IMAES, Escuela Técnica Superior de Ingenieros Industriales, Instituto de Investigaciones Energéticas y Aplicaciones Industriales (INEI), University of Castilla-La Mancha, Avda. Camilo José Cela 3, 13071 Ciudad Real, Spain
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29
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Li H, Gänzle M. Some Like It Hot: Heat Resistance of Escherichia coli in Food. Front Microbiol 2016; 7:1763. [PMID: 27857712 PMCID: PMC5093140 DOI: 10.3389/fmicb.2016.01763] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 10/20/2016] [Indexed: 11/13/2022] Open
Abstract
Heat treatment and cooking are common interventions for reducing the numbers of vegetative cells and eliminating pathogenic microorganisms in food. Current cooking method requires the internal temperature of beef patties to reach 71°C. However, some pathogenic Escherichia coli such as the beef isolate E. coli AW 1.7 are extremely heat resistant, questioning its inactivation by current heat interventions in beef processing. To optimize the conditions of heat treatment for effective decontaminations of pathogenic E. coli strains, sufficient estimations, and explanations are necessary on mechanisms of heat resistance of target strains. The heat resistance of E. coli depends on the variability of strains and properties of food formulations including salt and water activity. Heat induces alterations of E. coli cells including membrane, cytoplasm, ribosome and DNA, particularly on proteins including protein misfolding and aggregations. Resistant systems of E. coli act against these alterations, mainly through gene regulations of heat response including EvgA, heat shock proteins, σE and σS, to re-fold of misfolded proteins, and achieve antagonism to heat stress. Heat resistance can also be increased by expression of key proteins of membrane and stabilization of membrane fluidity. In addition to the contributions of the outer membrane porin NmpC and overcome of osmotic stress from compatible solutes, the new identified genomic island locus of heat resistant performs a critical role to these highly heat resistant strains. This review aims to provide an overview of current knowledge on heat resistance of E. coli, to better understand its related mechanisms and explore more effective applications of heat interventions in food industry.
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Affiliation(s)
- Hui Li
- Department of Agricultural, Food and Nutritional Science, University of Alberta, EdmontonAB, Canada
| | - Michael Gänzle
- Department of Agricultural, Food and Nutritional Science, University of Alberta, EdmontonAB, Canada
- College of Bioengineering and Food Science, Hubei University of TechnologyHubei, China
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30
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Hildebrandt IM, Marks BP, Ryser ET, Villa-Rojas R, Tang J, Garces-Vega FJ, Buchholz SE. Effects of Inoculation Procedures on Variability and Repeatability of Salmonella Thermal Resistance in Wheat Flour. J Food Prot 2016; 79:1833-1839. [PMID: 28221914 DOI: 10.4315/0362-028x.jfp-16-057] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Limited prior research has shown that inoculation methods affect thermal resistance of Salmonella in low-moisture foods; however, these effects and their repeatability have not been systematically quantified. Consequently, method variability across studies limits utility of individual data sets and cross-study comparisons. Therefore, the objective was to evaluate the effects of inoculation methodologies on stability and thermal resistance of Salmonella in a low-moisture food (wheat flour), and the repeatability of those results, based on data generated by two independent laboratories. The experimental design consisted of a cross-laboratory comparison, both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 water activity, 80°C), utilizing five different inoculation methods: (i) broth-based liquid inoculum, (ii) lawn-based liquid inoculum, (iii) lawn-based pelletized inoculum, (iv) direct harvest of lawn culture with wheat flour, and (v) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 water activity and then was subjected to isothermal treatment (80°C) in aluminum test cells. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α = 0.05), regardless of laboratory. Salmonella inoculated with the broth-based liquid inoculum method and the fomite transfer of a lawn culture method exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, the method using direct harvest of lawn culture with wheat flour yielded different D-values across the laboratories (α = 0.05), which was attributed to larger potential impact of operator variability. The lawn-based liquid inoculum and the lawn-based pelletized inoculum methods yielded stable inoculation levels and repeatable D-values (~250 and ~285 s, respectively). Also, inoculation level (3 to 8 log CFU/g) did not affect D-values (using the lawn-based liquid inoculum method). Overall, the results demonstrate that inoculation methods significantly affect Salmonella population kinetics and subsequent interpretation of thermal inactivation data for low-moisture foods.
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Affiliation(s)
- Ian M Hildebrandt
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
| | - Bradley P Marks
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
| | - Elliot T Ryser
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824
| | - Rossana Villa-Rojas
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington 99164, USA
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington 99164, USA
| | - Francisco J Garces-Vega
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
| | - Sarah E Buchholz
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
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31
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Kou XX, Li R, Hou LX, Huang Z, Ling B, Wang SJ. Performance of a Heating Block System Designed for Studying the Heat Resistance of Bacteria in Foods. Sci Rep 2016; 6:30758. [PMID: 27465120 PMCID: PMC4964582 DOI: 10.1038/srep30758] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 07/08/2016] [Indexed: 11/09/2022] Open
Abstract
Knowledge of bacteria's heat resistance is essential for developing effective thermal treatments. Choosing an appropriate test method is important to accurately determine bacteria's heat resistances. Although being a major factor to influence the thermo-tolerance of bacteria, the heating rate in samples cannot be controlled in water or oil bath methods due to main dependence on sample's thermal properties. A heating block system (HBS) was designed to regulate the heating rates in liquid, semi-solid and solid foods using a temperature controller. Distilled water, apple juice, mashed potato, almond powder and beef were selected to evaluate the HBS's performance by experiment and computer simulation. The results showed that the heating rates of 1, 5 and 10 °C/min with final set-point temperatures and holding times could be easily and precisely achieved in five selected food materials. A good agreement in sample central temperature profiles was obtained under various heating rates between experiment and simulation. The experimental and simulated results showed that the HBS could provide a sufficiently uniform heating environment in food samples. The effect of heating rate on bacterial thermal resistance was evaluated with the HBS. The system may hold potential applications for rapid and accurate assessments of bacteria's thermo-tolerances.
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Affiliation(s)
- Xiao-xi Kou
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Rui Li
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Li-xia Hou
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zhi Huang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Bo Ling
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Shao-jin Wang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
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32
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Hildebrandt IM, Marks BP, Juneja VK, Osoria M, Hall NO, Ryser ET. Cross-Laboratory Comparative Study of the Impact of Experimental and Regression Methodologies on Salmonella Thermal Inactivation Parameters in Ground Beef. J Food Prot 2016; 79:1097-106. [PMID: 27357028 DOI: 10.4315/0362-028x.jfp-15-496] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Isothermal inactivation studies are commonly used to quantify thermal inactivation kinetics of bacteria. Meta-analyses and comparisons utilizing results from multiple sources have revealed large variations in reported thermal resistance parameters for Salmonella, even when in similar food materials. Different laboratory or regression methodologies likely are the source of methodology-specific artifacts influencing the estimated parameters; however, such effects have not been quantified. The objective of this study was to evaluate the effects of laboratory and regression methodologies on thermal inactivation data generation, interpretation, modeling, and inherent error, based on data generated in two independent laboratories. The overall experimental design consisted of a cross-laboratory comparison using two independent laboratories (Michigan State University and U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center [ERRC] laboratories), both conducting isothermal Salmonella inactivation studies (55, 60, 62°C) in ground beef, and each using two methodologies reported in prior studies. Two primary models (log-linear and Weibull) with one secondary model (Bigelow) were fitted to the resultant data using three regression methodologies (two two-step regressions and a one-step regression). Results indicated that laboratory methodology impacted the estimated D60°C- and z-values (α = 0.05), with the ERRC methodology yielding parameter estimates ∼25% larger than the Michigan State University methodology, regardless of the laboratory. Regression methodology also impacted the model and parameter error estimates. Two-step regressions yielded root mean square error values on average 40% larger than the one-step regressions. The Akaike Information Criterion indicated the Weibull as the more correct model in most cases; however, caution should be used to confirm model robustness in application to real-world data. Overall, the results suggested that laboratory and regression methodologies have a large influence on resultant data and the subsequent estimation of thermal resistance parameters.
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Affiliation(s)
- Ian M Hildebrandt
- Department of Biosystems and Agricultural Engineering, Michigan State University, 524 South Shaw Lane, East Lansing, Michigan 48824-1323, USA
| | - Bradley P Marks
- Department of Biosystems and Agricultural Engineering, Michigan State University, 524 South Shaw Lane, East Lansing, Michigan 48824-1323, USA;
| | - Vijay K Juneja
- Eastern Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA
| | - Marangeli Osoria
- Eastern Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA
| | - Nicole O Hall
- Department of Biosystems and Agricultural Engineering, Michigan State University, 524 South Shaw Lane, East Lansing, Michigan 48824-1323, USA
| | - Elliot T Ryser
- Department of Food Science and Human Nutrition, Michigan State University, 524 South Shaw Lane, East Lansing, Michigan 48824-1323, USA
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El Jaam O, Fliss I, Aider M. Application of electro-activated potassium acetate and potassium citrate solutions combined with moderate heat treatment on the inactivation of Clostridium sporogenes PA 3679 spores. INNOV FOOD SCI EMERG 2016. [DOI: 10.1016/j.ifset.2015.11.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Bozkurt H, D'Souza DH, Davidson PM. Thermal Inactivation of Foodborne Enteric Viruses and Their Viral Surrogates in Foods. J Food Prot 2015; 78:1597-617. [PMID: 26219377 DOI: 10.4315/0362-028x.jfp-14-487] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Foodborne viruses, in particular human norovirus and hepatitis A virus, are the most common causes of food-associated infections and foodborne illness outbreaks around the world. Since it is currently not possible to cultivate human noroviruses and the wild-type strain of hepatitis A virus in vitro, the use of a variety of viral surrogates is essential to determine appropriate thermal processing conditions to reduce the risk associated with their contamination of food. Therefore, the objectives of this review are to (i) present pertinent characteristics of enteric foodborne viruses and their viral surrogates, (ii) discuss the viral surrogates currently used in thermal inactivation studies and their significance and value, (iii) summarize available data on thermal inactivation kinetics of enteric viruses, (iv) discuss factors affecting the efficacy of thermal treatment, (v) discuss suggested mechanisms of thermal inactivation, and (vi) provide insights on foodborne enteric viruses and viral surrogates for future studies and industrial applications. The overall goal of this review is to contribute to the development of appropriate thermal processing protocols to ensure safe food for human consumption.
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Affiliation(s)
- Hayriye Bozkurt
- Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA
| | - Doris H D'Souza
- Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA
| | - P Michael Davidson
- Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
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Jiao Y, Shi H, Tang J, Li F, Wang S. Improvement of radio frequency (RF) heating uniformity on low moisture foods with Polyetherimide (PEI) blocks. Food Res Int 2015; 74:106-114. [DOI: 10.1016/j.foodres.2015.04.016] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 04/06/2015] [Accepted: 04/12/2015] [Indexed: 10/23/2022]
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36
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Hamoud-Agha MM, Curet S, Simonin H, Boillereaux L. Holding time effect on microwave inactivation of Escherichia coli K12: Experimental and numerical investigations. J FOOD ENG 2014. [DOI: 10.1016/j.jfoodeng.2014.06.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ling B, Tang J, Kong F, Mitcham EJ, Wang S. Kinetics of Food Quality Changes During Thermal Processing: a Review. FOOD BIOPROCESS TECH 2014. [DOI: 10.1007/s11947-014-1398-3] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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38
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Shi Y, Tang J, Yue T, Rasco B, Wang S. Pasteurizing Cold Smoked Salmon (Oncorhynchus nerka): Thermal Inactivation Kinetics ofListeria monocytogenesandListeria innocua. JOURNAL OF AQUATIC FOOD PRODUCT TECHNOLOGY 2014. [DOI: 10.1080/10498850.2013.808303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Bozkurt H, D'Souza DH, Davidson PM. Determination of thermal inactivation kinetics of hepatitis A virus in blue mussel (Mytilus edulis) homogenate. Appl Environ Microbiol 2014; 80:3191-7. [PMID: 24632250 PMCID: PMC4018912 DOI: 10.1128/aem.00428-14] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 03/07/2014] [Indexed: 02/04/2023] Open
Abstract
Hepatitis A virus (HAV) is a food-borne enteric virus responsible for outbreaks of hepatitis associated with shellfish consumption. The objectives of this study were to determine the thermal inactivation behavior of HAV in blue mussels, to compare the first-order and Weibull models to describe the data, to calculate Arrhenius activation energy for each model, and to evaluate model efficiency by using selected statistical criteria. The times required to reduce the population by 1 log cycle (D-values) calculated from the first-order model (50 to 72°C) ranged from 1.07 to 54.17 min for HAV. Using the Weibull model, the times required to destroy 1 log unit (tD = 1) of HAV at the same temperatures were 1.57 to 37.91 min. At 72°C, the treatment times required to achieve a 6-log reduction were 7.49 min for the first-order model and 8.47 min for the Weibull model. The z-values (changes in temperature required for a 90% change in the log D-values) calculated for HAV were 15.88 ± 3.97°C (R(2), 0.94) with the Weibull model and 12.97 ± 0.59°C (R(2), 0.93) with the first-order model. The calculated activation energies for the first-order model and the Weibull model were 165 and 153 kJ/mol, respectively. The results revealed that the Weibull model was more appropriate for representing the thermal inactivation behavior of HAV in blue mussels. Correct understanding of the thermal inactivation behavior of HAV could allow precise determination of the thermal process conditions to prevent food-borne viral outbreaks associated with the consumption of contaminated mussels.
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Affiliation(s)
- Hayriye Bozkurt
- Department of Food Science and Technology, The University of Tennessee, Knoxville, Tennessee, USA
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Bozkurt H, D'Souza DH, Davidson PM. A comparison of the thermal inactivation kinetics of human norovirus surrogates and hepatitis A virus in buffered cell culture medium. Food Microbiol 2014; 42:212-7. [PMID: 24929739 DOI: 10.1016/j.fm.2014.04.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 04/03/2014] [Accepted: 04/05/2014] [Indexed: 02/01/2023]
Abstract
Human noroviruses and hepatitis A virus (HAV) are considered as epidemiologically significant causes of foodborne disease. Therefore, studies are needed to bridge existing data gaps and determine appropriate parameters for thermal inactivation of human noroviruses and HAV. The objectives of this research were to compare the thermal inactivation kinetics of human norovirus surrogates (murine norovirus (MNV-1), and feline calicivirus (FCV-F9)) and HAV in buffered medium (2-ml vials), compare first-order and Weibull models to describe the data, calculate Arrhenius activation energy for each model, and evaluate model efficiency using selected statistical criteria. The D-values calculated from the first-order model (50-72 °C) ranged from 0.21-19.75 min for FCV-F9, 0.25-36.28 min for MNV-1, and 0.88-56.22 min for HAV. Using the Weibull model, the tD = 1 (time to destroy 1 log) for FCV-F9, MNV-1 and HAV at the same temperatures ranged from 0.10-13.27, 0.09-26.78, and 1.03-39.91 min, respectively. The z-values for FCV-F9, MNV-1, and HAV were 9.66 °C, 9.16 °C, and 14.50 °C, respectively, using the Weibull model. For the first order model, z-values were 9.36 °C, 9.32 °C, and 12.49 °C for FCV-F9, MNV-1, and HAV, respectively. For the Weibull model, estimated activation energies for FCV-F9, MNV-1, and HAV were 225, 278, and 182 kJ/mol, respectively, while the calculated activation energies for the first order model were 195, 202, and 171 kJ/mol, respectively. Knowledge of the thermal inactivation kinetics of norovirus surrogates and HAV will allow the development of processes that produce safer food products and improve consumer safety.
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Affiliation(s)
- Hayriye Bozkurt
- Department of Food Science and Technology, The University of Tennessee, 2600 River Drive, Knoxville, TN 37996-4591, USA
| | - Doris H D'Souza
- Department of Food Science and Technology, The University of Tennessee, 2600 River Drive, Knoxville, TN 37996-4591, USA.
| | - P Michael Davidson
- Department of Food Science and Technology, The University of Tennessee, 2600 River Drive, Knoxville, TN 37996-4591, USA
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Bozkurt H, D'souza DH, Davidson PM. Thermal inactivation of human norovirus surrogates in spinach and measurement of its uncertainty. J Food Prot 2014; 77:276-83. [PMID: 24490922 DOI: 10.4315/0362-028x.jfp-13-289] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Leafy greens, including spinach, have potential for human norovirus transmission through improper handling and/or contact with contaminated water. Inactivation of norovirus prior to consumption is essential to protect public health. Because of the inability to propagate human noroviruses in vitro, murine norovirus (MNV-1) and feline calicivirus (FCV-F9) have been used as surrogates to model human norovirus behavior under laboratory conditions. The objectives of this study were to determine thermal inactivation kinetics of MNV-1 and FCV-F9 in spinach, compare first-order and Weibull models, and measure the uncertainty associated with the process. D-values were determined for viruses at 50, 56, 60, 65, and 72 °C in 2-ml vials. The D-values calculated from the first-order model (50 to 72 °C) ranged from 0.16 to 14.57 min for MNV-1 and 0.15 to 17.39 min for FCV-9. Using the Weibull model, the tD for MNV-1 and FCV-F9 to destroy 1 log (D ≈ 1) at the same temperatures ranged from 0.22 to 15.26 and 0.27 to 20.71 min, respectively. The z-values determined for MNV-1 were 11.66 ± 0.42 °C using the Weibull model and 10.98 ± 0.58 °C for the first-order model and for FCV-F9 were 10.85 ± 0.67 °C and 9.89 ± 0.79 °C, respectively. There was no difference in D- or z-value using the two models (P > 0.05). Relative uncertainty for dilution factor, personal counting, and test volume were 0.005, 0.0004, and ca. 0.84%, respectively. The major contribution to total uncertainty was from the model selected. Total uncertainties for FCV-F9 for the Weibull and first-order models were 3.53 to 7.56% and 11.99 to 21.01%, respectively, and for MNV-1, 3.10 to 7.01% and 13.14 to 16.94%, respectively. Novel and precise information on thermal inactivation of human norovirus surrogates in spinach was generated, enabling more reliable thermal process calculations to control noroviruses. The results of this study may be useful to the frozen food industry in designing blanching processes for spinach to inactivate or control noroviruses.
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Affiliation(s)
- Hayriye Bozkurt
- Department of Food Science and Technology, University of Tennessee-Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA
| | - Doris H D'souza
- Department of Food Science and Technology, University of Tennessee-Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA
| | - P Michael Davidson
- Department of Food Science and Technology, University of Tennessee-Knoxville, 2605 River Drive, Knoxville, Tennessee 37996-4591, USA.
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Thermal inactivation kinetic modeling of human norovirus surrogates in blue mussel (Mytilus edulis) homogenate. Int J Food Microbiol 2013; 172:130-6. [PMID: 24412376 DOI: 10.1016/j.ijfoodmicro.2013.11.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 11/20/2022]
Abstract
Control of seafood-associated norovirus outbreaks has become an important priority for public health authorities. Due to the absence of human norovirus infectivity assays, cultivable surrogates such as feline calicivirus (FCV-F9) and murine norovirus (MNV-1) have been used to begin to understand their thermal inactivation behavior. In this study, the effect of thermal treatment on inactivation of human norovirus surrogates in blue mussels was investigated at 50, 56, 60, 65, and 72 °C for various times (0-6 min). The results obtained were analyzed using the Weibull and first-order models. The Theil error splitting method was used for model comparison. This method splits the error in the predicted data into fixed and random error. This method was applied to select satisfactory models for determination of thermal inactivation of norovirus surrogates and kinetic modeling. The D-values calculated from the first-order model (50-72 °C) were in the range of 0.07 to 5.20 min for FCV-F9 and 0.18 to 20.19 min for MNV-1. Using the Weibull model, the t(D=1) for FCV-F9 and MNV-1 to destroy 1 log (D=1) at the same temperatures were in the range of 0.08 to 4.03 min and 0.15 to 19.80 min, respectively. The z-values determined for MNV-1 were 9.91±0.71 °C (R²=0.95) using the Weibull model and 11.62±0.59 °C (R²=0.93) for the first-order model. For FCV-F9 the z-values were 12.38±0.68 °C (R²=0.94) and 11.39±0.41 °C (R²=0.97) for the Weibull and first-order models, respectively. The Theil method revealed that the Weibull model was satisfactory to represent thermal inactivation data of norovirus surrogates and that the model chosen for calculation of thermal inactivation parameters is important. Knowledge of the thermal inactivation kinetics of norovirus surrogates will allow development of processes that produce safer shellfish products and improve consumer safety.
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Whole-genome transcriptional analysis of Escherichia coli during heat inactivation processes related to industrial cooking. Appl Environ Microbiol 2013; 79:4940-50. [PMID: 23770902 DOI: 10.1128/aem.00958-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli K-12 was grown to the stationary phase, for maximum physiological resistance, in brain heart infusion (BHI) broth at 37°C. Cells were then heated at 58°C or 60°C to reach a process lethality value \[\mathbf{\left(}{{\mathit{F}}^{\mathit{o}}}_{\mathbf{70}}^{\mathbf{10}}\mathbf{\right)} \] of 2 or 3 or to a core temperature of 71°C (control industrial cooking temperature). Growth recovery and cell membrane integrity were evaluated immediately after heating, and a global transcription analysis was performed using gene expression microarrays. Only cells heated at 58°C with F(o) = 2 were still able to grow on liquid or solid BHI broth after heat treatment. However, their transcriptome did not differ from that of bacteria heated at 58°C with F(o) = 3 (P value for the false discovery rate [P-FDR] > 0.01), where no growth recovery was observed posttreatment. Genome-wide transcriptomic data obtained at 71°C were distinct from those of the other treatments without growth recovery. Quantification of heat shock gene expression by real-time PCR revealed that dnaK and groEL mRNA levels decreased significantly above 60°C to reach levels similar to those of control cells at 37°C (P < 0.0001). Furthermore, despite similar levels of cell inactivation measured by growth on BHI media after heating, 132 and 8 genes were differentially expressed at 71°C compared to 58°C and 60°C at F(o) = 3, respectively (P-FDR < 0.01). Among them, genes such as aroA, citE, glyS, oppB, and asd, whose expression was upregulated at 71°C, may be worth investigating as good biomarkers for accurately determining the efficiency of heat treatments, especially when cells are too injured to be enumerated using growth media.
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44
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Hamoud-Agha MM, Curet S, Simonin H, Boillereaux L. Microwave inactivation of Escherichia coli K12 CIP 54.117 in a gel medium: Experimental and numerical study. J FOOD ENG 2013. [DOI: 10.1016/j.jfoodeng.2012.11.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Affiliation(s)
- Kirk D. Dolan
- Department of Food Science and Nutrition, Michigan State University, East Lansing, Michigan 48824;
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
| | - Dharmendra K. Mishra
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
- Nestlé Nutrition, Fremont, Michigan 49412
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Pleitner A, Zhai Y, Winter R, Ruan L, McMullen LM, Gänzle MG. Compatible solutes contribute to heat resistance and ribosome stability in Escherichia coli AW1.7. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1351-7. [PMID: 22841996 DOI: 10.1016/j.bbapap.2012.07.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 07/19/2012] [Accepted: 07/19/2012] [Indexed: 11/27/2022]
Abstract
This study investigated the mechanisms of heat resistance in Escherichia coli AW1.7 by quantification of cytoplasmic solutes, determination of ribosome denaturation, and by determination of protein denaturation. To assess the contribution of heat shock proteins and compatible solutes, experiments were conducted after exposure to sublethal heat shock, and with cultures grown at NaCl concentrations ranging from 0 to 6%. Heat resistance of E. coli AW1.7 was compared to the heat sensitive E. coli GGG10 and a plasmid-cured, heat sensitive derivative of E. coli AW1.7 named E. coli AW1.7ΔpHR1. Sublethal heat shock improved survival at 60°C of E. coli GGG10 and AW1.7ΔpHR1 but not of E. coli AW1.7. Addition of NaCl increased the heat resistance of all three strains, but only E. coli AW1.7 exhibited high heat resistance when grown in NaCl concentrations ranging from 2 to 6%. E. coli AW1.7 and GGG10 accumulated 16.1 ± 0.8 and 8.8 ± 0.8mmolL⁻¹ amino acids when grown at 0% NaCl, and 1.47 ± 0.07 and 0.78 ± 0.06mmolL⁻¹ carbohydrates when grown at 6% NaCl, respectively. Ribosome denaturation was determined by differential scanning calorimetry. After growth in the presence of 0% NaCl, the 30S subunit denatured at 63.7 ± 0.8°C and 60.7 ± 0.3°C in E. coli AW1.7 and GGG10, respectively. Fourier-transformed-infrared-spectroscopy did not indicate differences in protein denaturation between the strains during heating. In conclusion, heat resistance in E. coli AW1.7 correlates to ribosome stability at 60°C and is dependent on accumulation of cytoplasmic solutes.
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Affiliation(s)
- Aaron Pleitner
- University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Canada T6G 2P5
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47
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Büchner C, Thomas S, Jaros D, Rohm H. Fast-responding thermal-death-time tubes for the determination of thermal bacteria inactivation. Eng Life Sci 2011. [DOI: 10.1002/elsc.201100041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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48
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Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock. Food Sci Biotechnol 2011. [DOI: 10.1007/s10068-011-0105-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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49
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Dlusskaya EA, McMullen LM, Gänzle MG. Characterization of an extremely heat-resistant Escherichia coli obtained from a beef processing facility. J Appl Microbiol 2011; 110:840-9. [PMID: 21219555 DOI: 10.1111/j.1365-2672.2011.04943.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AIMS This study aimed to determine the survival of Escherichia coli strains during steam and lactic acid decontamination interventions currently used by the beef-processing industry, and to determine their heat resistance. METHODS AND RESULTS Strains were grouped into cocktails of five strains each differing in their RAPD patterns for subsequent identification. Steam and lactic acid treatments on meat reduced cell counts of E. coli strain cocktails by 90-99%. The 20 slaughter plant isolates exhibited only minor variation in their resistance to steam and lactic acid treatments but were more resistant than reference strains (three strains) or isolates from live cattle (seven strains). D(60) values of strains from live cattle, and reference strains ranged from 0·1 to 0·5 min, in keeping with literature data. However, D(60) values of current slaughter plant isolates ranged between 15 for E. coli DM18.3 and 71 min AW 1.7. Cell counts of E. coli AW 1.7 were reduced by <5 log(10) CFU g(-1) in ground beef patties cooked to an internal temperature of 71°C. CONCLUSIONS Strains of E. coli that survive cooking of ground beef to the recommended internal temperature of 71°C can be isolated from beef-processing facilities. SIGNIFICANCE AND IMPACT OF THE STUDY Pathogen interventions in current commercial beef slaughter may select for extremely heat-resistant strains of E. coli.
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Affiliation(s)
- E A Dlusskaya
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada
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50
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GURTLER JOSHUAB, RIVERA REBECCAB, ZHANG HOWARDQ, SOMMERS CHRISTOPHERH. BEHAVIOR OF AVIRULENT YERSINIA PESTISIN LIQUID WHOLE EGG AS AFFECTED BY STORAGE TEMPERATURE, ANTIMICROBIALS AND THERMAL PASTEURIZATION. J Food Saf 2010. [DOI: 10.1111/j.1745-4565.2010.00224.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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