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Hildebrandt IM, Riddell LM, Hall NO, James MK, Marks BP. Demonstration of Inappropriate Validation Method for a Cracker Baking Process Using Predictive Modeling. J Food Prot 2024; 87:100298. [PMID: 38734415 DOI: 10.1016/j.jfp.2024.100298] [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: 07/31/2023] [Revised: 05/01/2024] [Accepted: 05/06/2024] [Indexed: 05/13/2024]
Abstract
Validation of baking processes for the inactivation of Salmonella is complicated by the combined effects of product heating and drying. The goal of this study was to quantitatively evaluate a previously disseminated approach to validating baking processes utilizing a predictive model developed using only isothermal and single-moisture inactivation data for the initially formulated dough. A simple cracker dough was formulated using flour inoculated with a five-strain cocktail of Salmonella. Side-by-side isothermal and baking experiments were performed to estimate Salmonella inactivation kinetics and to quantify survivors in a dynamic environment, respectively. Isothermal, single-moisture inactivation experiments were performed with cracker dough (water activity, aw = 0.956 ± 0.002; moisture content = 0.50 ± 0.01 dry basis) at three temperatures (56, 60, or 63°C) with ≥6 time intervals. Baking experiments were performed in a convection oven at 177°C with samples pulled every 30 s up to 360 s, with an endpoint product aw (25°C) of 0.45. The Salmonella isothermal, single-moisture inactivation kinetics in cracker dough resulted in D60°C and z-values of 4.6 min and 4.9°C, respectively; this model was then integrated over the dynamic product temperature profiles from the baking experiments. In the baking experiments, an average of 5-log reductions of Salmonella was achieved by 150 s of treatment; however, >100-log reductions were predicted by the dough-based models at that time point. This fail-dangerous overestimation of Salmonella lethality in crackers explicitly demonstrated that single-level moisture-based prediction models are inappropriate for describing inactivation in a process with both dynamic temperature and moisture, and that model-based validations must incorporate moisture/aw. Furthermore, end-users should exercise caution when utilizing unvalidated models to validate preventive control processes.
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Affiliation(s)
- Ian M Hildebrandt
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Linnea M Riddell
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Nicole O Hall
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Michael K James
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Bradley P Marks
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan, USA.
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2
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Hines IS, Jurkiw T, Nguyen E, Ferguson M, Solaiman S, Reed E, Hoffmann M, Zheng J. Persistence comparison of two Shiga-toxin producing Escherichia coli (STEC) serovars during long-term storage and thermal inactivation in various wheat flours. PLoS One 2024; 19:e0299922. [PMID: 38457435 PMCID: PMC10923466 DOI: 10.1371/journal.pone.0299922] [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: 10/05/2023] [Accepted: 02/16/2024] [Indexed: 03/10/2024] Open
Abstract
Foodborne outbreaks associated with Shiga toxin-producing Escherichia coli (STEC) contaminated wheat flour have been an increasing food safety concern in recent decades. However, there is little literature aimed at investigating the impact of different flour types on the persistence of STEC during storage and thermal inactivation. Therefore, two serovars of STEC, O121 and O157, were selected to inoculate each of five different types of common wheat flours: whole wheat, bleached, unbleached, bread, and self-rising. Inoculated flours were examined for the stability of STEC during storage for up to 42 days at room temperature (RT) and aw ~0.56. Additionally, the thermal resistance of O121 and O157 under isothermal conditions at 60, 70, 80, and 90°C was analyzed for the inoculated flours. STEC storage persistence at RT was generally not affected by flour type, however, decreases of 1.2 and 2.4 log CFU/day within whole wheat flour for O121 and O157, respectively, were significantly lower than other flours. Though few differences were identified in relation to flour type, O121 exhibited significantly better survival rates than O157 during both equilibrium and storage periods. Compared to an approximate 6 log reduction in the population of O157, O121 population levels were reduced by a significantly lower amount (~3 log) during the entire storage period at RT. At each isothermal temperature, the impact of flour type on the thermal resistance capabilities of O121 or O157 was not a significant factor and resulted in similar survival curves regardless of serovar. Instead of exhibiting linear survival curves, both O121 and O157 displayed nonlinear curves with some shoulder/tail effect. Similar for both O121 and O157, the predicted decimal reduction time (D-value) decreased from approximately 25 min to around 8 min as the isothermal temperature increased from 60°C to 90°C. Results reported here can contribute to risk assessment models concerning contamination of STEC in wheat flour and add to our understanding of the impacts of flour type and STEC serovar on desiccation stability during storage and isothermal inactivation during thermal treatment.
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Affiliation(s)
- Ian S. Hines
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Tom Jurkiw
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Emily Nguyen
- Joint Institute of Food Safety and Applied Nutrition, College Park, MD, United States of America
| | - Martine Ferguson
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Sultana Solaiman
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Elizabeth Reed
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Maria Hoffmann
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
| | - Jie Zheng
- Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, United States of America
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3
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Chen L, Snyder AB. Surface inoculation method impacts microbial reduction and transfer of Salmonella Enteritidis PT 30 and potential surrogates during dry sanitation. Int J Food Microbiol 2023; 406:110405. [PMID: 37734279 DOI: 10.1016/j.ijfoodmicro.2023.110405] [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: 03/13/2023] [Revised: 07/31/2023] [Accepted: 09/17/2023] [Indexed: 09/23/2023]
Abstract
Dry sanitation methods are often limited to physical removal strategies such as brushing or wiping with sanitary cleaning tools. However, the relative efficacy of these approaches to remove microbiota on surfaces, and the risk of transferring cells to other surfaces via the cleaning tool, is unclear. The effect of dry wiping with a single-use towel on the removal of four different bacteria (Salmonella Enteritidis, Enterococcus faecium, Listeria innocua, Escherichia coli) was investigated. We also quantified the number of cells transferred to the towel itself during dry cleaning. Three different surface inoculation methods (spot, glass bead, contaminated milk powder) were assessed and significantly impacted initial surface microbial load. Higher initial counts corresponded to lower transfer coefficients (e.g., proportion of transferred cells). The effect of bacterial identity was significant on reduction after dry wiping for all three inoculation methods. Moreover, both bacterial identity and inoculation method had significant effects on the number of cells transferred to the towel. In most scenarios, dry wiping resulted in a reduction <1.0 log CFU/coupon. Although, on surfaces inoculated via contaminated milk powder, reductions of up to 1.6 ± 0.3 log CFU/coupon were obtained. Overall, E. faecium transferred more readily to the towel. These results may help guide experimental design for future research on dry sanitation.
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Affiliation(s)
- Long Chen
- College of Mechanical and Electronic Engineering, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Abigail B Snyder
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
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4
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Liu S, Xue R, Qin W, Yang X, Ye Q, Wu Q. Performance and transcriptome analysis of Salmonella enterica serovar Enteritidis PT 30 under persistent desiccation stress: Cultured by lawn and broth methods. Food Microbiol 2023; 115:104323. [PMID: 37567618 DOI: 10.1016/j.fm.2023.104323] [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: 02/13/2023] [Revised: 06/04/2023] [Accepted: 06/13/2023] [Indexed: 08/13/2023]
Abstract
Lawn-harvest method uses a solid medium (e.g., tryptic soy agar, TSA) to produce bacterial lawns and is widely accepted for the culture of microorganisms in microbial studies of low-moisture foods (LMFs, foods with water activity less than 0.85). It produces desiccation-tolerant cells with higher D-values in LMFs; however, little is known about the molecular mechanisms underlying bacterial resistance. Salmonella enterica Enteritidis PT 30 (S. Enteritidis), the most pertinent pathogen in LMFs, was cultured in TSA and tryptic soy broth (TSB). Cells were harvested and inoculated on filter papers to assess their performance under a relative humidity of 32 ± 2%. Transcriptome analysis of cultured cells during long-term desiccation (24, 72, and 168 h) was conducted in TruSeq PE Cluster Kit (Illumina) by paired-end methods. Lawn-cultured S. Enteritidis cells have stronger survivability (only decreased by 0.78 ± 0.12 log after 130 d of storage) and heat tolerance (higher D/β value) than those from the broth method. More desiccation genes of lawn-cultured cells were significantly upregulated from growth to long-term desiccation. Differentially expressed genes were the most enriched in the ribosome and sulfur metabolism pathways in the lawn- and broth-cultured groups. This study tracked the transcriptomic differences between two cultured groups in response to long-term desiccation stress and revealed some molecular mechanisms underlying their different suitability in microbial studies of LMFs.
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Affiliation(s)
- Shuxiang Liu
- College of Food Science, Sichuan Agricultural University, Ya'an, 625014, China; Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, 510070, China.
| | - Ruimin Xue
- College of Food Science, Sichuan Agricultural University, Ya'an, 625014, China
| | - Wen Qin
- College of Food Science, Sichuan Agricultural University, Ya'an, 625014, China
| | - Xiaojuan Yang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, 510070, China
| | - Qinghua Ye
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, 510070, China
| | - Qingping Wu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, 510070, China.
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Sun S, Xie Y, Zhou X, Zhu MJ, Sablani S, Tang J. Survival and thermal resistance of Salmonella in chocolate products with different water activities. Food Res Int 2023; 172:113209. [PMID: 37689954 DOI: 10.1016/j.foodres.2023.113209] [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: 02/24/2023] [Revised: 06/27/2023] [Accepted: 06/29/2023] [Indexed: 09/11/2023]
Abstract
Contamination of Salmonella in chocolate products has caused worldwide outbreaks and recalls. There is a lack of information on the impact of water activity (aw) on the stability of Salmonella in chocolate products during storage and thermal treatments. In this research, the survival and thermal resistance of a Salmonella cocktail (S. Enteritidis PT30, S. Tennessee K4643, S. Typhimurium S544) was examined in different chocolate products (dark chocolate, white chocolate, milk chocolate) at two aw levels (0.25, 0.50) over 12 months at 22 °C. A reduction of 4.19 log10 CFU/gof Salmonella was obtained in dark chocolate after 12 months (aw = 0.50, at 22 °C); less reductions were observed in white and milk chocolates. In all three products, more reductions were observed ataw = 0.50 than at aw = 0.25 over the 12-months storage. When treated at 80 °C, the D-values (time required to cause 1 log reduction) of the Salmonella cocktail in the chocolate samples with initial aw of 0.25 were 35.7, 25.2 and 11.6 min in dark, white and milk chocolate, respectively, before the storage. The D80°C -values of Salmonella cocktail in the samples with initial aw of 0.50 were 6.45, 7.46, and 3.98 min in dark, white and milk chocolate, respectively. After 12 months of storage at 22 °C, the D80°C-value of Salmonella cocktail decreased to 9.43 min (p < 0.05) in milk chocolate but remained 22.7 min in white chocolate with an aw of 0.25 at 22 °C. The data suggests that Salmonella can survive in chocolate products for up to 12 months, and its thermal resistance remained relatively stable. Thus, Salmonella is resistant to desiccation in chocolates, particularly in milk and white chocolates, and its thermal resistance remains during one-year storage, which could pose a potential threat for future outbreaks.
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Affiliation(s)
- Sicheng Sun
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA
| | - Yucen Xie
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA
| | - Xu Zhou
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA
| | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, WA 99164, USA
| | - Shyam Sablani
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA.
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6
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Xu S, Chen H. The influence of almond's water activity and storage temperature on Salmonella survival and thermal resistance. Food Microbiol 2023; 113:104269. [PMID: 37098429 DOI: 10.1016/j.fm.2023.104269] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/21/2023] [Accepted: 03/21/2023] [Indexed: 03/29/2023]
Abstract
This study investigated the effects of inoculation method, water activity (aw), packaging method, and storage temperature and duration on the survival of Salmonella on almonds as well as their resistance to subsequent thermal treatments. Whole almond kernels were inoculated with a broth-based or agar-based growth Salmonella cocktail and conditioned to aw of 0.52, 0.43 or 0.27. Inoculated almonds with aw of 0.43 were treated with a previously validated treatment (4 h of dry heat at 73 °C) to determine the potential differences in heat resistance resulted from the two inoculation methods. The inoculation method did not significantly (P > 0.05) impact the thermal resistance of Salmonella. Inoculated almonds at aw of 0.52 and 0.27 were either vacuum packaged in moisture-impermeable mylar bags or non-vacuum packaged in moisture-permeable polyethylene bags before stored at 35, 22, 4, or -18 °C for up to 28 days. At selected storage intervals, almonds were measured for aw, analyzed for Salmonella population level, and subjected to dry heat treatment at 75 °C. Over the month-long storage of almonds, Salmonella populations remained almost unchanged (<0.2 log CFU/g) at 4 °C and -18 °C and declined slightly (<0.8 log CFU/g) at 22 °C and more substantially (1.6-2.0 log CFU/g) at 35 °C regardless of the inoculation method, packaging method, and almond aw. When stored at 35 °C, almonds with initial aw of 0.52 had significantly higher (P < 0.05) Salmonella reductions than those with initial aw of 0.27. Prior storage of almonds vacuum packaged in mylar bags at temperatures between -18 °C and 35 °C for 28 days affected their aw levels but did not significantly (P > 0.05) affect the subsequent thermal resistance of Salmonella at 75 °C regardless of almond aw and storage duration. Salmonella on almonds with higher aw was more sensitive to heat treatment than those with lower aw. To achieve >5 log CFU/g reductions of Salmonella, a dry heat treatment at 75 °C for 4 and 6 h was needed for almonds with initial aw of 0.52 and 0.27, respectively. When applying the dry heating technology for almond decontamination, the processing time needs to be determined based on initial aw of almonds regardless of storage condition or age of almonds within the current design frame.
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7
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Jung J, Harris LJ. Survival of Salmonella and Shiga toxin–producing Escherichia coli during tempering of wheat berries. Food Control 2023. [DOI: 10.1016/j.foodcont.2022.109343] [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]
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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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Ahmad NH, Marks BP, Ryser ET. Effect of Lactose and Milk Protein on Thermal Resistance of Enterococcus faecium NRRL B-2354 and Salmonella in Dairy Powders. J Food Prot 2022; 85:1865-1874. [PMID: 36173901 DOI: 10.4315/jfp-22-111] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 09/26/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT Microbial challenge studies using nonpathogenic surrogates provide a practical means for validating thermally based pathogen controls for low-moisture foods. Because the relative thermal resistance, or kill ratio, of Enterococcus faecium NRRL B-2354 (a nonpathogenic surrogate) to Salmonella is greatly influenced by food composition, this study assessed relative thermal resistance of a five-strain Salmonella cocktail and E. faecium in skim milk powder (SMP), lactose-free skim milk powder (LSMP), 90% milk protein isolate (MPI), and lactose powder (LP). The impact of sugar composition (lactose versus glucose-galactose) on resuscitation of bacterial survivors, by using SMP and LSMP, was also determined. Dairy powders were inoculated with agar-grown cultures, mixed, preequilibrated at 0.25 water activity (aw), ground to achieve homogeneity, reequilibrated, and subjected to isothermal treatment. After enumeration on nonselective differential media, log-linear and Bigelow models were fit to the survivor data via one-step global regression. The aw changes and glass transition temperature were assessed at elevated temperatures by using uninoculated, equilibrated powder samples. Estimated D90°C-values were approximately two times higher for E. faecium (P < 0.05) than for Salmonella in SMP, LP, and MPI, but statistically similar (P > 0.05) in LSMP. Addition of sugars to recovery media did not influence survivor resuscitation from heat-treated SMP and LSMP, confirming that microbial inactivation was impacted primarily by the thermal treatment, not the recovery step. Thermally induced changes in aw were seen only for LP and MPI, with the glass transition temperature observed only for SMP and MPI. In conclusion, rather than always requiring greater lethality of E. faecium than Salmonella, these findings suggest that sufficient pathogen controls for low-moisture foods can also be validated by thoroughly documenting the appropriate kill ratios of E. faecium to Salmonella. HIGHLIGHTS
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Affiliation(s)
- Nurul Hawa Ahmad
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA
| | - Bradley P Marks
- Department of Biosystem and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA
| | - Elliot T Ryser
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA
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A comparative study for determination of thermal inactivation parameters of Salmonella in high gel and standard egg white powder using three methods. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2022.114185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Ahmad NH, Hildebrandt IM, Pickens SR, Vasquez S, Jin Y, Liu S, Halik LA, Tsai HC, Lau SK, D'Souza RC, Kumar S, Subbiah J, Thippareddi H, Zhu MJ, Tang J, Anderson NM, Grasso-Kelley EM, Ryser ET, Marks BP. Interlaboratory Evaluation of Enterococcus faecium NRRL B-2354 as a Salmonella Surrogate for Validating Thermal Treatment of Multiple Low-Moisture Foods. J Food Prot 2022; 85:1538-1552. [PMID: 35723555 DOI: 10.4315/jfp-22-054] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 06/16/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision. HIGHLIGHTS
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Affiliation(s)
- Nurul Hawa Ahmad
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824
| | - Ian M Hildebrandt
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824.,U.S. Food Drug Administration, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Shannon R Pickens
- U.S. Food Drug Administration, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Sabrina Vasquez
- Department of Food Science and Technology, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Yuqiao Jin
- Department of Biological Systems Engineering, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Shuxiang Liu
- Department of Biological Systems Engineering, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Lindsay A Halik
- Illinois Institute of Technology, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Hsieh-Chin Tsai
- School of Food Science, Washington State University, Pullman, Washington 99164
| | - Soon Kiat Lau
- Department of Food Science and Technology, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501.,Department of Biological System Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
| | - Roshan C D'Souza
- Department of Poultry Science, University of Georgia, Athens, Georgia 30602, USA
| | - Sanjay Kumar
- Department of Poultry Science, University of Georgia, Athens, Georgia 30602, USA
| | - Jeyamkondan Subbiah
- Department of Food Science and Technology, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501.,Department of Biological System Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
| | | | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, Washington 99164
| | - Juming Tang
- Department of Biological Systems Engineering, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Nathan M Anderson
- U.S. Food Drug Administration, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Elizabeth M Grasso-Kelley
- U.S. Food Drug Administration, Institute of Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Elliot T Ryser
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824
| | - Bradley P Marks
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824
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12
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Wang Y, Yang H. Metabolomics elucidating the effect of water activity on the thermal resistance of Salmonella in wheat flour. Food Res Int 2022; 162:112203. [DOI: 10.1016/j.foodres.2022.112203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 11/12/2022] [Accepted: 11/15/2022] [Indexed: 11/21/2022]
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13
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Jung J, Schaffner DW. Thermal Inactivation of Salmonella enterica and Nonpathogenic Bacterial Surrogates in Wheat Flour by Baking in a Household Oven. J Food Prot 2022; 85:1431-1438. [PMID: 35880899 DOI: 10.4315/jfp-22-107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 07/05/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT Wheat flour has been implicated in recalls and outbreaks linked to Salmonella and pathogenic Escherichia coli. An instructional online video posted on a popular YouTube channel with over 20 million subscribers claimed that safe raw cookie dough could be made from flour baked in a household oven at 177°C (350°F) for 5 min, but no evidence in support of that claim was provided. This study was conducted to assess thermal inactivation of two Salmonella strains, as well as Enterobacter aerogenes and Pantoea dispersa in wheat flour during home oven baking. Wheat flour was inoculated with Salmonella Enteritidis PT 30, Salmonella Typhimurium PT 42, or their potential surrogates at high concentrations (4.8 to 6.1 log CFU/g) before baking in a consumer-style convection oven (toaster oven) at 149, 177, and 204°C (300, 350, or 400°F) for up to 7 min. Flour was heated in an aluminum tray, with a maximum depth of ∼2 cm. Heated wheat flour samples (5 g each) were enumerated in triplicate, and the microbial concentration was expressed in log CFU per gram. Thermal profiles of the geometric center of the wheat flour pile and air in the oven during the baking were recorded. Water activity of wheat flour samples was also measured before and after baking. The water activity of wheat flour decreased, as baking temperature and time increased. Water activity values ranged from 0.30 to 0.06 after 7 min, as oven temperature increased from 149 to 204°C. Thermal inactivation kinetics were linear until counts approached the limit of detection for all microorganisms. D-values for Salmonella and potential surrogate strains ranged from 1.86 to 2.13 min at 149°C air temperature, 1.66 to 1.92 min at 177°C air temperature, and 1.12 to 1.38 min at 204°C air temperature. Both Salmonella strains and surrogates showed similar inactivation patterns. Baking of wheat flour in household toaster ovens has potential as an inactivation treatment of pathogenic bacteria in consumer homes, despite its low water activity. HIGHLIGHTS
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Affiliation(s)
- Jiin Jung
- Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, USA
| | - Donald W Schaffner
- Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901-8520, USA
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Lin Y, Simsek S, Bergholz TM. Impact of Chlorinated Water on Pathogen Inactivation during Wheat Tempering and Resulting Flour Quality. J Food Prot 2022; 85:1210-1220. [PMID: 35653628 DOI: 10.4315/jfp-22-076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 05/21/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT Outbreaks of enteric pathogens linked to wheat flour have led the wheat milling industry to seek solutions addressing this food safety concern. Chlorinated water at 400 to 700 ppm has been used in the flour milling industry as a tempering aid to control growth of yeast and mold in tempering bins. However, the effectiveness of chlorinated water for inactivating enteric pathogens on wheat kernels was unknown. Five strains of Shiga toxin-producing Escherichia coli and two strains of Salmonella were inoculated onto hard red spring wheat at 7 log CFU/g and stored at room temperature for 1 month. Inoculated wheat was tempered with four concentrations (0, 400, 800, and 1,200 ppm) of chlorinated water (pH 6.5). The reduction due to chlorine was determined by calculating change in microbial loads at each chlorine level by using the response at 0 ppm as a reference. Uninoculated wheat tempered with chlorinated water was used to measure flour quality parameters. Changes in pathogen population over 18 h ranged from -2.35 to -0.30 log CFU/g with 800 ppm of chlorinated water and were not significantly different from changes at 400 and 1,200 ppm. Significant (P < 0.05) differences in the extent of reduction were observed among strains. However, the effect of chlorinated water at reducing native microbes on wheat kernels was minimal, with an average reduction of 0.39 log CFU/g for all concentrations. No significant (P > 0.05) changes occurred in flour quality and gluten functionality or during bread making for grains tempered at 400 and 800 ppm of chlorinated water. There were small but significant (P < 0.05) changes in flour protein content, final viscosity, and water absorption when tempered with 1,200 ppm of chlorinated water. The data showed that the level of chlorinated water currently used in industry for tempering could reduce enteric pathogen numbers by 1.22 log CFU/g for Shiga toxin-producing Escherichia coli and 2.29 log CFU/g for Salmonella, with no significant effects on flour quality and gluten functionality. HIGHLIGHTS
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Affiliation(s)
- Yawei Lin
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824
| | - Senay Simsek
- Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, Indiana 47907, USA
| | - Teresa M Bergholz
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824
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15
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Thermal death kinetics of Salmonella Enteritidis PT30 in peanut butter as influenced by water activity. Food Res Int 2022; 157:111288. [DOI: 10.1016/j.foodres.2022.111288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 04/20/2022] [Accepted: 04/21/2022] [Indexed: 11/22/2022]
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16
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Yang R, Cheng T, Hong Y, Wei L, Tang J. The effect of dry headspace on the thermal resistance of bacteria in peanut oil and peanut butter in thermal treatments. Food Control 2022. [DOI: 10.1016/j.foodcont.2022.108851] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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17
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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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18
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Wason S, Verma T, Wei X, Mauromoustakos A, Subbiah J. Thermal inactivation kinetics of Salmonella enterica and Enterococcus faecium NRRL B- 2354 as a function of temperature and water activity in fine ground black pepper. Food Res Int 2022; 157:111393. [DOI: 10.1016/j.foodres.2022.111393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 05/11/2022] [Accepted: 05/19/2022] [Indexed: 11/29/2022]
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19
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Thermal resistance for Salmonella enterica strains in Sous-vide chicken-and-vegetable patties. Int J Gastron Food Sci 2022. [DOI: 10.1016/j.ijgfs.2022.100540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Metabolic Responses of "Big Six" Escherichia coli in Wheat Flour to Thermal Treatment Revealed by Nuclear Magnetic Resonance Spectroscopy. Appl Environ Microbiol 2022; 88:e0009822. [PMID: 35285244 DOI: 10.1128/aem.00098-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Escherichia coli outbreaks linked to wheat flour consumption have kept emerging in recent years, which necessitated an antimicrobial step being incorporated into the flour production process. The objectives of this in vivo study were to holistically evaluate the sanitizing efficacy of thermal treatment at 60 and 70°C against the "big six" E. coli strains (O26:H11, O45:H2, O103:H11, O111, O121:H19, and O145) in wheat flour and to assess the strain-specific metabolic responses using nuclear magnetic resonance (NMR) spectroscopy. The 70°C treatment temperature indiscriminatingly inactivated all strains by over 4.3-log CFU/g within 20 min, suggesting the high sanitization effectiveness of this treatment temperature, whereas the treatment at 60°C inactivated the strains to various degrees during the 1-h process. The most resistant strains at 60°C, O26 and O45, were characterized by amino acid and sugar depletion, and their high resistance was attributed to the dual effects of activated heat shock protein (HSP) synthesis and promoted glycolysis. O121 also demonstrated these metabolic changes, yet its thermal resistance was largely impaired by the weakened membrane structure and diminished osmotic protection due to phosphorylcholine exhaustion. In contrast, O111, O145, and O103 presented a substantial elevation of metabolites after stress at 60°C; their moderate thermal resistance was mainly explained by the accumulation of amino acids as osmolytes. Overall, the study enhanced our understanding of the metabolic responses of big six E. coli to heat stress and provided a model for conducting NMR-based metabolomic studies in powdered food matrices. IMPORTANCE "Big six" Escherichia coli strains have caused several outbreaks linked to wheat flour consumption in the last decade, revealing the vital importance of adopting an antimicrobial treatment during the flour production process. Therefore, the present study was carried out to evaluate the efficacy of a typical sanitizing approach, thermal treatment, against the big six strains in wheat flour along with the underlying antimicrobial mechanisms. Findings showed that thermal treatment at 60 and 70°C could markedly mitigate the loads of all strains in wheat flour. Moreover, activated heat shock protein synthesis combined with expedited glycolysis and enhanced osmotic protection were identified as two major metabolic alteration patterns in the E. coli strains to cope with the heat stress. With the responses of big six in wheat flour to thermal treatment elucidated, scientific basis for incorporating a thermal inactivation step in wheat flour production was provided.
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Liu S, Wei X, Tang J, Qin W, Wu Q. Recent developments in low-moisture foods: microbial validation studies of thermal pasteurization processes. Crit Rev Food Sci Nutr 2021:1-16. [PMID: 34927484 DOI: 10.1080/10408398.2021.2016601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Outbreaks associated with low-moisture foods (e.g., wheat flour, nuts, and cereals) have urged the development of novel technologies and re-validation of legacy pasteurization process. For various thermal pasteurization processes, they share same scientific facts (e.g., bacterial heat resistance increased at reduced water activity) and guidelines. However, they also face specific challenges because of their different heat transfer mechanisms, processing conditions, or associated low-moisture foods' formulations. In this article, we first introduced the general structural for validating a thermal process and the shared basic information that would support our understanding of the key elements of each thermal process. Then, we reviewed the current progress of validation studies of 7 individual heating technologies (drying roasting, radiofrequency-assisted pasteurization, superheated steam, etc.) and the combined treatments (e.g., infrared and hot air). Last, we discussed knowledge gaps that require more scientific data in the future studies. We aimed to provide a process-centric view point of thermal pasteurization studies of low-moisture foods. The information could provide detailed protocol for process developers, operators, and managers to enhance low-moisture foods safety.
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Affiliation(s)
- Shuxiang Liu
- 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, China.,Institute of Food Processing and Safety, School of Food Science, Sichuan Agricultural University, Sichuan, China
| | - Xinyao Wei
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, China
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
| | - Wen Qin
- Institute of Food Processing and Safety, School of Food Science, Sichuan Agricultural University, Sichuan, 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, China
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22
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Lauer JR, Simsek S, Bergholz TM. Fate of Salmonella and Enterohemorrhagic Escherichia coli on Wheat Grain. J Food Prot 2021; 84:2109-2115. [PMID: 34347868 DOI: 10.4315/jfp-21-076] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 08/01/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Wheat flour has been connected to outbreaks of foodborne illnesses with increased frequency in recent years, specifically, outbreaks involving Salmonella enterica and enterohemorrhagic Escherichia coli (EHEC). However, there is little information regarding the survival of these pathogens on wheat grain during long-term storage in a low-moisture environment. This study aims to evaluate the long-term survival of these enteric pathogens on wheat grain over the course of a year. Hard red spring wheat was inoculated with strains of four serovars of Salmonella (Enteritidis, Agona, Tennessee, and Montevideo) and six serotypes of EHEC (O157:H7, O26:H11, O121:H19, O45:NM, O111:H8, and O103:H2) in triplicate, sealed in Mylar bags to maintain the water activity, and stored at room temperature (22 ± 1°C). The survival of each pathogen was evaluated by plating onto differential media. Viable counts of strains from all four serovars of Salmonella (Enteritidis, Agona, Tennessee, and Montevideo) were detected on wheat grain stored at room temperature (22 ± 1°C) for the duration of the study (52 weeks). Viable counts of strains from EHEC serotypes O45:NM, O111:H8, and O26:H11 were only detected for 44 weeks, and strains from serotypes O157:H7, O121:H19, and O103:H2 were only detected for 40 weeks until they passed below the limit of detection (2.0 log CFU/g). The D-values were found to be significantly different between Salmonella and EHEC (adjusted P ≤ 0.05) with Salmonella D-values ranging from 22.9 ± 2.2 weeks to 25.2 ± 1.0 weeks and EHEC D-values ranging from 11.4 ± 0.6 weeks to 13.1 ± 1.8 weeks. There were no significant differences among the four Salmonella strains or among the six EHEC strains (adjusted P > 0.05). These observations highlight the wide range of survival capabilities of enteric pathogens in a low-moisture environment and confirm these pathogens are a food safety concern when considering the long shelf life of wheat grain and its products. HIGHLIGHTS
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Affiliation(s)
- Jessica R Lauer
- Department of Microbiological Sciences, North Dakota State University, Fargo, North Dakota 58108
| | - Senay Simsek
- Department of Plant Sciences, North Dakota State University, Fargo, North Dakota 58108
| | - Teresa M Bergholz
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA
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23
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Suehr QJ, Liu X, Grasso-Kelley EM, Anderson NM. Predictive Microbial Modeling of Enterococcus faecium NRRL B-2354 Inactivation during Baking of a Multicomponent Low-Moisture Food. J Food Prot 2021; 84:1990-2001. [PMID: 34189582 DOI: 10.4315/jfp-21-036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 06/28/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT The use of baking ovens as a microbial kill step should be validated based on results of thermal inactivation models. Although traditional isothermal models may not be appropriate for these dynamic processes, they are being used by the food industry. Previous research indicates that the impact of additional process conditions, such as humidity, should be considered when validating thermal processes for the control of microbial hazards in low-moisture foods. In this study, the predictive performance of traditional and modified thermal inactivation kinetic models accounting for process humidity were assessed for predicting inactivation of Enterococcus faecium NRRL B-2354 in a multi-ingredient composite food during baking. Ingredients (milk powder, protein powder, peanut butter, and whole wheat flour) were individually inoculated to achieve ∼6 log CFU/g, equilibrated to a water activity of 0.25, and then mixed to form a cookie dough. An isothermal inactivation study was conducted for the dough to obtain traditional D- and z-values (n = 63). In a separate experiment, cookies were baked under four dynamic heating conditions: 135°C, high humidity; 135°C, low humidity; 150°C, high humidity; and 150°C, low humidity. Process humidity measurements; time-temperature profiles for the product core, surface, and bulk air; and microbial survivor ratios were collected for the four conditions at six residence times (n = 144). The traditional isothermal model had a high root mean square error (RMSE) of 856.51 log CFU/g, significantly overpredicting bacterial inactivation during the process. The modified model accounting for the dynamic time-temperature profile and process humidity data was a better predictor with an RMSE of 0.55 log CFU/g. These results indicate the importance of accounting for additional process parameters in baking inactivation models and that model performance can be improved by utilizing model parameters obtained directly from industrial-scale experimental data. HIGHLIGHTS
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Affiliation(s)
- Quincy J Suehr
- U.S. Food and Drug Administration, Illinois Institute of Technology, Institute for Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
| | - Xiyang Liu
- Department of Food Science and Nutrition, Illinois Institute of Technology, Institute for Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
| | - Elizabeth M Grasso-Kelley
- Department of Food Science and Nutrition, Illinois Institute of Technology, Institute for Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
| | - Nathan M Anderson
- U.S. Food and Drug Administration, Illinois Institute of Technology, Institute for Food Safety and Health, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
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24
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Wei X, Verma T, Danao MGC, Ponder MA, Subbiah J. Gaseous chlorine dioxide technology for improving microbial safety of spices. INNOV FOOD SCI EMERG 2021. [DOI: 10.1016/j.ifset.2021.102783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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25
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Girbal M, Strawn LK, Murphy CM, Schaffner DW. Wet versus Dry Inoculation Methods Have a Significant Effect of Listeria monocytogenes Growth on Many Types of Whole Intact Fresh Produce. J Food Prot 2021; 84:1793-1800. [PMID: 34115865 DOI: 10.4315/jfp-21-187] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/08/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Listeria monocytogenes causes relatively few outbreaks linked to whole fresh produce but triggers recalls each year in the United States. There are limited data on the influence of wet versus dry inoculation methods on pathogen growth on whole produce. A cocktail of five L. monocytogenes strains that included clinical, food, and environmental isolates associated with foodborne outbreaks and recalls was used. Cultures were combined to target a final wet inoculum concentration of 4 to 5 log CFU/mL. The dry inoculum was prepared by mixing wet inoculum with 100 g of sterile sand and drying for 24 h. Produce investigated belonged to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Rosaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). Whole intact, inoculated fruit and vegetable commodities were incubated at 2, 12, 22, and 35 ± 2°C. Commodities were sampled for up to 28 days, and the experiment was replicated six times. The average maximum growth increase was obtained by measuring the maximum absolute increase for each replicate within a specific commodity, temperature, and inoculation method. Data for each commodity, replicate, and temperature were used to create primary growth or survival models describing the lag phase and growth or shoulder and decline as a function of time. Use of a liquid inoculum (versus dry inoculum) resulted in a markedly increased L. monocytogenes growth rate and growth magnitude on whole produce surfaces. Temperature highly influenced this difference: a greater effect seen with more commodities at higher temperatures (22 and 35°C) versus lower temperatures (2 and 12°C). These findings need to be explored for other commodities and pathogens. The degree to which wet or dry inoculation techniques more realistically mimic contamination conditions throughout the supply chain (e.g., production, harvest, postharvest, transportation, or retail) should be investigated. HIGHLIGHTS
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Affiliation(s)
- Marina Girbal
- Department of Food Science, 65 Dudley Road, Rutgers University, New Brunswick, New Jersey 08901
| | - Laura K Strawn
- Department of Food Science & Technology, 1230 Washington Street S.W., Blacksburg, Virginia 24061, USA
| | - Claire M Murphy
- Department of Food Science & Technology, 1230 Washington Street S.W., Blacksburg, Virginia 24061, USA
| | - Donald W Schaffner
- Department of Food Science, 65 Dudley Road, Rutgers University, New Brunswick, New Jersey 08901
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Lau SK, Panth R, Chaves BD, Weller CL, Subbiah J. Thermal Inactivation Kinetics of Salmonella and Enterococcus faecium NRRL-B2354 on Whole Chia Seeds (Salvia hispanica L.). J Food Prot 2021; 84:1357-1365. [PMID: 33852729 DOI: 10.4315/jfp-20-468] [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: 11/27/2020] [Accepted: 04/12/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Intervention technologies for inactivating Salmonella on whole chia seeds are currently limited. Determination of the thermal inactivation kinetics of Salmonella on chia seeds and selection of an appropriate nonpathogenic surrogate will provide a foundation for selecting and optimizing thermal pasteurization processes for chia seeds. In this study, chia seed samples from three separate production lots were inoculated with a five-strain Salmonella cocktail or Enterococcus faecium NRRL-B2354 and equilibrated to a water activity of 0.53 at room temperature (25°C). After equilibration for at least 3 days, the inoculated seeds were subjected to isothermal treatments at 80, 85, or 90°C. Samples were removed at six time points, and surviving bacteria were enumerated. Whole chia seeds were diluted in a filter bag at 1:30 because bacterial recovery with this method was similar to that obtained from ground seeds. Survivor data were fitted to consolidated models: one primary model (log linear or Weibull) and one secondary model (Bigelow). E. faecium had higher thermal resistance than did Salmonella, suggesting that E. faecium may be a suitable conservative nonpathogenic surrogate for Salmonella. The Weibull model was a better fit for the survivor data than was the log-linear model for both bacteria based on the lower root mean square error and corrected Akaike's information criterion values. Lipid oxidation measurements and fatty acid concentrations were significantly different from those of the control samples, but the overall magnitude of the differences was relatively small. The thermal inactivation kinetics of Salmonella and E. faecium on chia seeds may be used as a basis for developing thermal pasteurization processes for chia seeds. HIGHLIGHTS
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Affiliation(s)
- Soon Kiat Lau
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583.,Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68583
| | - Rajendra Panth
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583
| | - Byron D Chaves
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583
| | - Curtis L Weller
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583.,Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68583
| | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68583.,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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Wei X, Agarwal S, Subbiah J. Heating of milk powders at low water activity to 95°C for 15 minutes using hot air-assisted radio frequency processing achieved pasteurization. J Dairy Sci 2021; 104:9607-9616. [PMID: 34176627 DOI: 10.3168/jds.2021-20449] [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: 03/13/2021] [Accepted: 05/13/2021] [Indexed: 11/19/2022]
Abstract
Salmonella persistence in milk powders has caused several multistate foodborne disease outbreaks. Therefore, ways to deliver effective thermal treatment need to be identified and validated to ensure the microbial safety of milk powders. In this study, a process of hot air-assisted radio frequency (HARF) followed by holding at high temperatures in a convective oven was developed for pasteurization of milk powders. Heating times were compared between HARF and a convection oven for heating milk powders to a pasteurization temperature, and HARF has been shown to considerably reduce the come-up time. Whole milk powder (WMP) and nonfat dry milk (NFDM) were inoculated with a 5-serotype Salmonella cocktail and equilibrated to a water activity of 0.10 to simulate the worst case for the microbial challenge study. After heating the sample to 95°C using HARF, followed by 10 and 15 min of holding in the oven, more than 5 log reduction of Salmonella was achieved in WMP and NFDM. This study validated a HARF-assisted thermal process for pasteurization of milk powder based on previously collected microbial inactivation kinetics data and provides valuable insights to process developers to ensure microbial safety of milk powder. This HARF process may be implemented in the dairy industry to enhance the microbial safety of milk powders.
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Affiliation(s)
- Xinyao Wei
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588
| | | | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588; Department of Food Science, University of Arkansas System Division of Agriculture, Fayetteville 72704.
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29
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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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30
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Wei X, Chen L, Chaves BD, Ponder MA, Subbiah J. Modeling the effect of temperature and relative humidity on the ethylene oxide fumigation of Salmonella and Enterococcus faecium in whole black peppercorn. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2020.110742] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Yan R, Pinto G, Taylor-Roseman R, Cogan K, D'Alesandre G, Kovac J. Evaluation of the Thermal Inactivation of a Salmonella Serotype Oranienburg Strain During Cocoa Roasting at Conditions Relevant to the Fine Chocolate Industry. Front Microbiol 2021; 12:576337. [PMID: 33763036 PMCID: PMC7982832 DOI: 10.3389/fmicb.2021.576337] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 02/04/2021] [Indexed: 12/31/2022] Open
Abstract
Cocoa roasting produces and enhances distinct flavor of chocolate and acts as a critical control point for inactivation of foodborne pathogens in chocolate production. In this study, the inactivation kinetics of Salmonella enterica subsp. enterica serotype Oranienburg strain was assessed on whole cocoa beans using roasting protocols relevant to the fine chocolate industry. Beans were inoculated with 107-108 log10 CFU/bean of Salmonella Oranienburg and roasted at 100-150°C for 2-100 min. A greater than 5 log10 reduction of S. Oranienburg was experimentally achieved after 10-min roasting at 150°C. Data were fitted using log-linear and Weibull models. The log-linear models indicated that the roasting times (D) needed to achieve a decimal reduction of Salmonella at 100, 110, 115, 120, 130, and 140°C were 33.34, 18.57, 12.92, 10.50, 4.20, and 1.90 min, respectively. A Weibull model indicated a decrease in the Salmonella inactivation rate over time (β < 1). Statistical analysis indicated that the Weibull model fitted the data better compared to a log-linear model. These data demonstrate the efficacy of cocoa roasting in inactivation of Salmonella and may be used to guide food safety decision-making.
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Affiliation(s)
- Runan Yan
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States
| | - Gabriella Pinto
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States
| | | | - Karen Cogan
- Dandelion Chocolate Inc., San Francisco, CA, United States
| | | | - Jasna Kovac
- Department of Food Science, The Pennsylvania State University, University Park, PA, United States
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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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Wei X, Vasquez S, Thippareddi H, Subbiah J. Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella in ground black pepper at different water activities. Int J Food Microbiol 2021; 344:109114. [PMID: 33652336 DOI: 10.1016/j.ijfoodmicro.2021.109114] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/08/2021] [Accepted: 02/14/2021] [Indexed: 10/22/2022]
Abstract
Thermal inactivation kinetics of Salmonella in low moisture foods are necessary for developing proper thermal processing parameters for pasteurization. The effect of water activity on thermal inactivation kinetics of Salmonella and Enterococcus faecium NRRL B-2354 in ground black pepper has not been studied previously. Identification of a suitable surrogate assists in conducting in-plant process validations. Ground black pepper was inoculated with a 5-serotype Salmonella cocktail or E. faecium NRRL B-2354, equilibrated to water activities of 0.25, 0.45 or 0.65 in a humidity-controlled chamber, and isothermally treated at different temperatures. The survivor data were used for fitting the log-linear models to obtain the D and z-values of Salmonella and E. faecium in ground black pepper. Modified Bigelow models were developed to evaluate the effects of temperature and water activity on the thermal inactivation kinetics of Salmonella and E. faecium. Water activity and temperature showed significant negative effects on the thermal resistance of Salmonella and E. faecium in ground black pepper. For example, significantly higher D values of Salmonella were observed at water activity of 0.45 (D70°C = 20.5 min and D75°C = 7.8 min) compared to water activity of 0.65 (D70°C = 3.9 min and D75°C = 2.0 min). D-values of E. faecium were significantly higher than those of Salmonella at all three water activities, indicating that E. faecium is a suitable surrogate for Salmonella in thermal processing validation.
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Affiliation(s)
- Xinyao Wei
- Department of Food Science and Technology, University of Nebraska-Lincoln, NE, USA
| | - Sabrina Vasquez
- Department of Food Science and Technology, University of Nebraska-Lincoln, NE, USA
| | | | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Nebraska-Lincoln, NE, USA; Department of Food Science, University of Arkansas System Division of Agriculture, Fayetteville, AR, USA.
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Liu S, Wang H, Ma S, Dai J, Zhang Q, Qin W. Radiofrequency-assisted hot-air drying of Sichuan pepper (Huajiao). Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2020.110158] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Wei X, Agarwal S, Subbiah J. Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella enterica in milk powders at different storage times and temperatures. J Dairy Sci 2021; 104:198-210. [DOI: 10.3168/jds.2020-19190] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 09/02/2020] [Indexed: 01/15/2023]
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Lin B, Zhu Y, Zhang L, Xu R, Guan X, Kou X, Wang S. Effect of Physical Structures of Food Matrices on Heat Resistance of Enterococcus faecium NRRL-2356 in Wheat Kernels, Flour and Dough. Foods 2020; 9:foods9121890. [PMID: 33352900 PMCID: PMC7765854 DOI: 10.3390/foods9121890] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 12/10/2020] [Accepted: 12/16/2020] [Indexed: 02/07/2023] Open
Abstract
Nonpathogenic surrogate microorganisms, with a similar or slightly higher thermal resistance of the target pathogens, are usually recommended for validating practical pasteurization processes. The aim of this study was to explore a surrogate microorganism in wheat products by comparing the thermal resistance of three common bacteria in wheat kernels and flour. The most heat-resistant Enterococcus faecium NRRL-2356 rather than Salmonella cocktail and Escherichia coli ATCC 25922 was determined when heating at different temperature-time combinations at a fixed heating rate of 5 °C/min in a heating block system. The most heat-resistant pathogen was selected to investigate the influences of physical structures of food matrices. The results indicated that the heat resistance of E. faecium was influenced by physical structures of food matrices and reduced at wheat kernel structural conditions. The inactivation of E. faecium was better fitted in the Weibull distribution model for wheat dough structural conditions while in first-order kinetics for wheat kernel and flour structural conditions due to the changes of physical structures during heating. A better pasteurization effect could be achieved in wheat kernel structure in this study, which may provide technical support for thermal inactivation of pathogens in wheat-based food processing.
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Affiliation(s)
- Biying Lin
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
| | - Yufei Zhu
- College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China;
| | - Lihui Zhang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
| | - Ruzhen Xu
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
| | - Xiangyu Guan
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
| | - Xiaoxi Kou
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
| | - Shaojin Wang
- College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; (B.L.); (L.Z.); (R.X.); (X.G.); (X.K.)
- Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA
- Correspondence: ; Tel.: +86-29-87092391; Fax: +86-29-87091737
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Thermal inactivation kinetics of Salmonella and Enterococcus faecium NRRL B-2354 on dried basil leaves. Food Microbiol 2020; 96:103710. [PMID: 33494891 DOI: 10.1016/j.fm.2020.103710] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 11/27/2020] [Accepted: 11/30/2020] [Indexed: 01/14/2023]
Abstract
The enhanced heat resistance of Salmonella developed at low water activity makes it a serious challenge to eliminate them during thermal processing. The objectives of this research are to (i) investigate the effect of water activity on thermal inactivation of Salmonella cocktail (Agona, Tennessee, Mbandaka, Montevideo, and Reading) in dried basil leaves, and (ii) evaluate Enterococcus faecium NRRL B-2354 as an appropriate surrogate for Salmonella in dried basil leaves. Dried basil leaves, inoculated with a Salmonella cocktail and E. faecium separately, were equilibrated to different water activities (aw: 0.40, 0.55, and 0.70) in a humidity-controlled chamber. The basil samples were packed (1.6 ± 0.1 g) in aluminum pouches and thermally treated at 70, 75, and 80 °C using a dry heating method for 0-180 min to obtain the thermal death curve. The microbial survival data was fit using two primary models (Log-linear and Weibull model). Results from AICc showed that the log-linear model fits well for thermal inactivation of both microorganisms. As the aw decreases from 0.70 to 0.40 at 75 °C, the D-value increases from 3.30 to 9.14 min for Salmonella and 6.53 to 14.07 min for E. faecium. Based on the AICc values, the modified Bigelow model fits the D-values better than the response surface model for both the microorganisms. The kill ratio of surrogate to pathogen ranged from 1.4 to 2.8, indicating that it is a conservative surrogate for Salmonella for performing validation of the thermal pasteurization process. The identification of suitable surrogate and development of modified Bigelow model will help the spice industry in developing the thermal processes for improving the safety of basil leaves.
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Yadav B, Roopesh M. In-package atmospheric cold plasma inactivation of Salmonella in freeze-dried pet foods: Effect of inoculum population, water activity, and storage. INNOV FOOD SCI EMERG 2020. [DOI: 10.1016/j.ifset.2020.102543] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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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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Pérez-Reyes ME, Jie X, Zhu MJ, Tang J, Barbosa-Cánovas GV. Influence of low water activity on the thermal resistance of Salmonella Enteritidis PT30 and Enterococcus faecium as its surrogate in egg powders. FOOD SCI TECHNOL INT 2020; 27:184-193. [DOI: 10.1177/1082013220937872] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Egg powders are increasingly popular ingredients, due to their functionality and compactness, in industrial food production and preparation at homes. However, there is a lack of studies that evaluate the thermal resistance of Salmonella Enteritidis PT30 and its potential surrogate Enterococcus faecium NRRL B-2354 in egg powders. This study examined the log-linear relationship between the thermal resistance of Salmonella Enteritidis (D-value) and the water activity (aw) of egg powders. The changes of aw in the egg powders with temperature were measured using a Vapor Sorption Analyzer and a high-temperature cell. The D80 ℃-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, and 0.6) at 20 ℃ were determined using aluminum thermal death test cells. The aw values increased (P < 0.05) in all three egg powders when the temperature of the samples was raised from room temperature to 80 ℃. The D80 ℃-values ranged from 5.3 ± 0.1 to 25.9 ± 0.2 min for S. Enteritidis while 10.4 ± 0.4 to 43.8 ± 0.4 for E. faecium in samples of the three different aw levels. S. Enteritidis PT30 showed a log-linear relationship between D80 ℃-values and aw80 ℃ for the egg powders. This study contributes to our understanding of the impact of aw on the development of thermal treatments for low-moisture foods.
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Affiliation(s)
- Marco E Pérez-Reyes
- Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
| | - Xu Jie
- Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
| | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, WA, USA
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
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Yang R, Xu J, Lombardo SP, Ganjyal GM, Tang J. Desiccation in oil protects bacteria in thermal processing. Food Res Int 2020; 137:109519. [PMID: 33233153 DOI: 10.1016/j.foodres.2020.109519] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/30/2020] [Accepted: 07/02/2020] [Indexed: 11/30/2022]
Abstract
Edible oils have long been considered to have a protective effect on bacteria from thermal inactivation, but the mechanism for this effect remains unclear. Our recent study suggests that the water activity (aw) of oil decreases exponentially with increasing temperature. Therefore, in thermal processing, the aw of the bacteria inside oil may also decrease making the bacteria more resistant to heat. To validate this hypothesis, the equilibrium aw of bacteria (Enterococcus faecium NRRL B2354, or E. faecium) in peanut oil samples, with different initial aw (0.93, 0.75, 0.52 & 0.33) at room temperature, were measured at elevated temperatures up to 80 °C. Meanwhile, the thermal resistances of E. faecium in these samples were also tested at 80 °C. Results indicate that the aw of the bacteria-in-oil systems changed in the same manner as that of pure peanut oil; it decreased exponentially with temperature from 0.93, 0.75, 0.52 & 0.33 (at ~23 °C) to 0.36, 0.30, 0.21 & 0.13 (at 80 °C), respectively. This confirmed that bacterial cells experienced desiccation in oil during the thermal treatments. The thermal death rates of E. faecium in peanut oil samples followed first-order kinetics. The D80 value (time needed to achieve 1-log reduction at 80 °C) increased exponentially with the reduced aw at 80 °C, from 87 min at aw 0.36 to 1539 min at aw 0.13. A graphical comparison (logD80 vs. high-temperature aw) showed a similarity between the thermal resistance of E. faecium in oil and that in dry air, which supports the hypothesis that oil protects bacteria from thermal treatments through desiccation.
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Affiliation(s)
- Ren Yang
- Department of Biological Systems Engineering, Washington State University, P.O. Box 646120, Pullman, WA 99164-6120, USA
| | - Jie Xu
- Department of Biological Systems Engineering, Washington State University, P.O. Box 646120, Pullman, WA 99164-6120, USA
| | - Stephen P Lombardo
- Technical Innovation Center, McCormick & Company, Inc., Hunt Valley, MD 21031, USA
| | - Girish M Ganjyal
- School of Food Science, Washington State University, P.O. Box 646376, Pullman, WA 99164-6376, USA
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, P.O. Box 646120, Pullman, WA 99164-6120, USA.
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Wei X, Lau SK, Chaves BD, Danao MGC, Agarwal S, Subbiah J. Effect of water activity on the thermal inactivation kinetics of Salmonella in milk powders. J Dairy Sci 2020; 103:6904-6917. [PMID: 32475668 DOI: 10.3168/jds.2020-18298] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 03/22/2020] [Indexed: 12/20/2022]
Abstract
Persistence of Salmonella in milk powders has caused several foodborne outbreaks. The determination of proper pasteurization processing conditions requires an understanding of the thermal inactivation kinetics of Salmonella in milk powders. However, there is a lack of knowledge related to the effects of water activity (aw) and fat content on Salmonella inactivation in milk powder during thermal processing. Two types of milk powders, nonfat dry milk and whole milk powder, with different fat contents (0.62 and 29.46% wt/wt, respectively) were inoculated with a 5-strain cocktail of Salmonella and equilibrated to 3 aw levels (0.10, 0.20, and 0.30) for isothermal treatments at 75, 80, and 85°C to obtain D-values (the time required to achieve a 10-fold reduction of the bacteria at the isothermal treatment temperature) and z-values (the increase in temperature required to achieve a 90% reduction of the decimal reduction time D). Stability tests showed that the inoculation method used in this study provided a high and stable population of Salmonella for thermal inactivation studies. A moisture sorption isotherm was measured to understand the relationship between aw and moisture content of milk powders. The thermal resistance of Salmonella was found to significantly increase as aw decreased, which suggested that a higher temperature or longer processing time would be required at low aw to achieve the desired inactivation of Salmonella. The microbial inactivation kinetics were not significantly different for the 2 milk powders; therefore, data were combined to develop a universal model. A response surface model was compared with a modified Bigelow model. The modified Bigelow model performed well to predict D-values [root mean square error (RMSE) = 1.47 min] and log reductions (RMSE = 0.48 log cfu/g). The modified Bigelow model developed here could be used to estimate D-value as a function of water activity and temperature to design a thermal pasteurization system for milk powders.
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Affiliation(s)
- Xinyao Wei
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588
| | - Soon Kiat Lau
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588; Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln 68583
| | - Byron D Chaves
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588
| | - Mary-Grace C Danao
- Department of Food Science and Technology, University of Nebraska, Lincoln 68588; The Food Processing Center, University of Nebraska, Lincoln 68588
| | | | - Jeyamkondan Subbiah
- Department of Food Science and Technology, University of Arkansas, Fayetteville 72704.
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Hildebrandt IM, Marks BP, Anderson NM, Grasso-Kelley EM. Reproducibility of Salmonella Thermal Resistance Measurements via Multilaboratory Isothermal Inactivation Experiments. J Food Prot 2020; 83:609-614. [PMID: 32221564 DOI: 10.4315/0362-028x.jfp-19-343] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 12/03/2019] [Indexed: 11/11/2022]
Abstract
ABSTRACT Isothermal inactivation experiments often are used to investigate the thermal resistance of pathogens, such as Salmonella, in foods; however, little is known about the reproducibility of such experimental methodologies. The objective of this study was to quantify the reproducibility of Salmonella isothermal resistance results via a six-laboratory comparison. Inoculation was performed at a single location and then distributed to each laboratory for isothermal analysis. Salmonella Agona 447967 was inoculated into oat flour, re-equilibrated to a water activity (aw) of 0.45, and then packaged and distributed to each laboratory. Before conducting the inactivation trials, each laboratory was required to verify the inoculated product's aw, enumerate Salmonella population levels, and verify that the isothermal treatment medium was at the target temperature (80°C). All laboratories were required to process at least three replications, collect at least six sample time points with three subsamples at each sampling point, enumerate survivors using an identical plating methodology and media, and verify that the temperature did not substantially change during isothermal treatment. The log-linear model was fit to the Salmonella survivor data, and the resultant D-values were statistically compared via Welch's t test (α = 0.05). Two significant differences in thermal inactivation kinetics were identified as potentially resulting from suspected methodology deviations. Two of the inoculated batches distributed for analysis yielded significantly lower D-values, which likely resulted from a deviation in the inoculation procedures. One laboratory yielded significantly lower D-values, which was likely the result of temperature deviations. Overall, excluding the D-values resulting from deviations, the inactivation results were reproducible, yielding D-values of 30.2 ± 3 min. These results indicate that isothermal inactivation results can be reproducible but that even minor methodology deviations can substantially affect measured Salmonella thermal resistance. HIGHLIGHTS
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Affiliation(s)
- Ian M Hildebrandt
- U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Bradley P Marks
- Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 43824
| | - Nathan M Anderson
- U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501
| | - Elizabeth M Grasso-Kelley
- Department of Food Science and Nutrition/Institute for Food Safety and Health, Illinois Institute of Technology, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
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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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Evaluation of Enterococcus faecium NRRL B-2354 as a potential surrogate of Salmonella in packaged paprika, white pepper and cumin powder during radio frequency heating. Food Control 2020. [DOI: 10.1016/j.foodcont.2019.106833] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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48
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Xu J, Yang R, Jin Y, Barnett G, Tang J. Modeling the temperature-dependent microbial reduction of Enterococcus faecium NRRL B-2354 in radio-frequency pasteurized wheat flour. Food Control 2020. [DOI: 10.1016/j.foodcont.2019.106778] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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49
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Suehr QJ, Anderson NM, Keller SE. Desiccation and Thermal Resistance of Escherichia coli O121 in Wheat Flour. J Food Prot 2019; 82:1308-1313. [PMID: 31310172 DOI: 10.4315/0362-028x.jfp-18-544] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Non-O157 Shiga toxin-producing Escherichia coli infections have recently been associated with wheat flour on two separate accounts in the United States and Canada. However, there is little information regarding the thermal resistance and longevity of non-O157 Shiga toxin-producing Escherichia coli during storage in low-moisture environments. The objectives of this study were to determine the thermal inactivation kinetics of E. coli O121 in wheat flour and to compare the thermal inactivation rates with those of other pathogens. Wheat flour, inoculated with E. coli O121, was equilibrated at 25°C to a water activity of 0.45 in a humidity-controlled conditioning chamber. Inoculated samples were treated isothermally at 70, 75, and 80°C, and posttreatment population survivor ratios were determined by plate counting. D- and z-values calculated with a log-linear model, were compared with those obtained in other studies. At 70, 75, and 80°C, the D-values for E. coli O121 were 18.16 ± 0.96, 6.47 ± 0.50, and 4.58 ± 0.40 min, respectively, and the z-value was 14.57 ± 2.21°C. Overall, E. coli O121 was observed to be slightly less thermally resistant than what has been previously reported for Salmonella Enteritidis PT30 in wheat flour as measured under the same conditions with the same methods.
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Affiliation(s)
- Quincy J Suehr
- U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
| | - Nathan M Anderson
- U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
| | - Susanne E Keller
- U.S. Food and Drug Administration, 6502 South Archer Road, Bedford Park, Illinois 60501, USA
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50
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Ahmad NH, Öztabak C, Marks BP, Ryser ET. Effect of Talc as a Dry-Inoculation Carrier on Thermal Resistance of Enterococcus faecium NRRL B-2354 in Almond Meal. J Food Prot 2019; 82:1110-1115. [PMID: 31210547 DOI: 10.4315/0362-028x.jfp-18-543] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
HIGHLIGHTS E. faecium was more thermally resistant in dry- than in wet-inoculated almond meal. Presence of talc affected thermal resistance of E. faecium in almond meal. Use of dry inoculum carriers for thermal validation studies requires further work.
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Affiliation(s)
- Nurul Hawa Ahmad
- 1 Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, Michigan 48824, USA (ORCID: https://orcid.org/0000-0003-1337-2658 [E.T.R.])
| | - Cemre Öztabak
- 2 Sakarya University, Esentepe Campus, Serdivan, Sakarya, Turkey 54187
| | - Bradley P Marks
- 3 Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA
| | - Elliot T Ryser
- 1 Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, Michigan 48824, USA (ORCID: https://orcid.org/0000-0003-1337-2658 [E.T.R.])
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