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Li Z, Zhao W, Wang P, Zhao S, Wang D, Zhao X. Evolution of microbial community and the volatilome of fresh-cut chili pepper during storage under different temperature conditions: Correlation of microbiota and volatile organic compounds. Food Chem 2024; 451:139401. [PMID: 38685178 DOI: 10.1016/j.foodchem.2024.139401] [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: 11/07/2023] [Revised: 03/07/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024]
Abstract
The effect of temperature conditions on the evolution of microbial communities and volatile organic compounds (VOCs) in fresh-cut chili peppers during storage was investigated. Results showed that Proteobacteria and Actinobacteriota were the dominant phyla in fresh-cut chili peppers. During storage, bacterial communities changed more dramatically than fungi. Different temperature conditions significantly affected the shift of bacteria at the genus level. At the beginning of storage, Rhodococcus, Pantoea, and Pseudomonas dominated the bacteria. However, on day 8, Pantoea and Enterobacter became the predominant genera at 5 °C and high temperatures (10, 15 °C, dynamic temperature), respectively. No significant variability in bacterial species was observed between different batches. Additionally, 140 VOCs were determined in fresh-cut chili peppers. Twenty-two VOCs were screened and could be recommended as potential spoilage markers. Based on Spearman's correlation analysis results, Enterobacter and Enterococcus were the most positive microorganisms correlated with spoilage markers.
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Affiliation(s)
- Zudi Li
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, China; Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China
| | - Wenting Zhao
- Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China.
| | - Pan Wang
- Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China.
| | - Shuang Zhao
- Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China.
| | - Dan Wang
- Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China.
| | - Xiaoyan Zhao
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, China; Institute of Agri-food Processing and Nutrition, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing 100097, China.
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2
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Sunil S, Walsky T, Henry M, Kemmerling L, Pajor M, Guo X, Murphy SI, Ivanek R, Wiedmann M. A longitudinal study on the bacterial quality of baby spinach cultivated in Arizona and California. Appl Environ Microbiol 2024:e0055324. [PMID: 38995040 DOI: 10.1128/aem.00553-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 06/17/2024] [Indexed: 07/13/2024] Open
Abstract
In the U.S., baby spinach is mostly produced in Arizona (AZ) and California (CA). Characterizing the impact of growing region on the bacterial quality of baby spinach can inform quality management practices in industry. Between December 2021 and December 2022, baby spinach was sampled after harvest and packaging for microbiological testing, including shelf-life testing of packaged samples that were stored at 4°C. Samples were tested to (i) determine bacterial concentration, and (ii) obtain and identify bacterial isolates. Packaged samples from the Salinas, CA, area (n = 13), compared to those from the Yuma, AZ, area (n = 9), had a significantly higher bacterial concentration, on average, by 0.78 log10 CFU/g (P < 0.01, based on aerobic, mesophilic plate count data) or 0.67 log10 CFU/g (P < 0.01, based on psychrotolerant plate count data); the bacterial concentrations of harvest samples from the Yuma and Salinas areas were not significantly different. Our data also support that an increase in preharvest temperature is significantly associated with an increase in the bacterial concentration on harvested and packaged spinach. A Fisher's exact test and linear discriminant analysis (effect size), respectively, demonstrated that (i) the genera of 2,186 bacterial isolates were associated (P < 0.01) with growing region and (ii) Pseudomonas spp. and Exiguobacterium spp. were enriched in spinach from the Yuma and Salinas areas, respectively. Our findings provide preliminary evidence that growing region and preharvest temperature may impact the bacterial quality of spinach and thus could inform more targeted strategies to manage produce quality. IMPORTANCE In the U.S., most spinach is produced in Arizona (AZ) and California (CA) seasonally; typically, spinach is cultivated in the Yuma, AZ, area during the winter and in the Salinas, CA, area during the summer. As the bacterial quality of baby spinach can influence consumer acceptance of the product, it is important to assess whether the bacterial quality of baby spinach can vary between spinach-growing regions. The findings of this study provide insights that could be used to support region-specific quality management strategies for baby spinach. Our results also highlight the value of further evaluating the impact of growing region and preharvest temperature on the bacterial quality of different produce commodities.
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Affiliation(s)
- Sriya Sunil
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Tamara Walsky
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Mikayla Henry
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Leonie Kemmerling
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Magdalena Pajor
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Xiaodong Guo
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Sarah I Murphy
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Renata Ivanek
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, New York, USA
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3
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Woodford L, Fellows R, White HL, Ormsby MJ, Quilliam RS. Salmonella Typhimurium and Vibrio cholerae can be transferred from plastic mulch to basil and spinach salad leaves. Heliyon 2024; 10:e31343. [PMID: 38818200 PMCID: PMC11137414 DOI: 10.1016/j.heliyon.2024.e31343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 05/14/2024] [Accepted: 05/14/2024] [Indexed: 06/01/2024] Open
Abstract
Plastic pollution is increasingly found in agricultural environments, where it contaminates soil and crops. Microbial biofilms rapidly colonise environmental plastics, such as the plastic mulches used in agricultural systems, which provide a unique environment for microbial plastisphere communities. Human pathogens can also persist in the plastisphere, and enter agricultural environments via flooding or irrigation with contaminated water. In this study we examined whether Salmonella Typhimurium and Vibrio cholerae can be transferred from the plastisphere on plastic mulch to the surface of ready-to-eat crop plants, and subsequently persist on the leaf surface. Both S. Typhimurium and V. cholerae were able to persist for 14 days on fragments of plastic mulch adhering to the surface of leaves of both basil and spinach. Importantly, within 24 h both pathogens were capable of dissociating from the surface of the plastic and were transferred onto the surface of both basil and spinach leaves. This poses a further risk to food safety and human health, as even removal of adhering plastics and washing of these ready-to-eat crops would not completely remove these pathogens. As the need for more intensive food production increases, so too does the use of plastic mulches in agronomic systems. Therefore, there is now an urgent need to understand the unquantified co-pollutant pathogen risk of contaminating agricultural and food production systems with plastic pollution.
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Affiliation(s)
- Luke Woodford
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Rosie Fellows
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Hannah L. White
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Michael J. Ormsby
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Richard S. Quilliam
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
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4
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Gu G, Ding Q, Redding M, Yang Y, O'Brien R, Gu T, Zhang B, Zhou B, Micallef SA, Luo Y, Fonseca JM, Nou X. Differential microbiota shift on whole romaine lettuce subjected to source or forward processing and on fresh-cut products during cold storage. Int J Food Microbiol 2024; 416:110665. [PMID: 38457887 DOI: 10.1016/j.ijfoodmicro.2024.110665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 02/28/2024] [Accepted: 03/05/2024] [Indexed: 03/10/2024]
Abstract
Romaine lettuce in the U.S. is primarily grown in California or Arizona and either processed near the growing regions (source processing) or transported long distance for processing in facilities serving distant markets (forward processing). Recurring outbreaks of Escherichia coli O157:H7 implicating romaine lettuce in recent years, which sometimes exhibited patterns of case clustering in Northeast and Midwest, have raised industry concerns over the potential impact of forward processing on romaine lettuce food safety and quality. In this study, freshly harvested romaine lettuce from a commercial field destined for both forward and source processing channels was tracked from farm to processing facility in two separate trials. Whole-head romaine lettuce and packaged fresh-cut products were collected from both forward and source facilities for microbiological and product quality analyses. High-throughput amplicon sequencing targeting16S rRNA gene was performed to describe shifts in lettuce microbiota. Total aerobic bacteria and coliform counts on whole-head lettuce and on fresh-cut lettuce at different storage times were significantly (p < 0.05) higher for those from the forward processing facility than those from the source processing facility. Microbiota on whole-head lettuce and on fresh-cut lettuce showed differential shifting after lettuce being subjected to source or forward processing, and after product storage. Consistent with the length of pre-processing delays between harvest and processing, the lettuce quality scores of source-processed romaine lettuce, especially at late stages of 2-week storage, was significantly higher than of forward-processed product (p < 0.05).
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Affiliation(s)
- Ganyu Gu
- Environmental Microbial and Food Safety Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Qiao Ding
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742, United States of America
| | - Marina Redding
- Environmental Microbial and Food Safety Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Yishan Yang
- Environmental Microbial and Food Safety Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Regina O'Brien
- Food Quality Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Tingting Gu
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, United States of America
| | - Boce Zhang
- Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, United States of America
| | - Bin Zhou
- Food Quality Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Shirley A Micallef
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742, United States of America; Centre for Food Safety and Security Systems, University of Maryland, College Park, MD 20742, United States of America
| | - Yaguang Luo
- Environmental Microbial and Food Safety Laboratory, USDA ARS, Beltsville, MD 20705, United States of America; Food Quality Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Jorge M Fonseca
- Food Quality Laboratory, USDA ARS, Beltsville, MD 20705, United States of America
| | - Xiangwu Nou
- Environmental Microbial and Food Safety Laboratory, USDA ARS, Beltsville, MD 20705, United States of America.
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5
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Sunil S, Murphy SI, Orsi RH, Ivanek R, Wiedmann M. Strain-specific Growth Parameters are Important to Accurately Model Bacterial Growth on Baby Spinach in Simulation Models. J Food Prot 2024; 87:100270. [PMID: 38552796 DOI: 10.1016/j.jfp.2024.100270] [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: 11/29/2023] [Revised: 03/04/2024] [Accepted: 03/23/2024] [Indexed: 04/14/2024]
Abstract
Digital tools to predict produce shelf life have the potential to reduce food waste and improve consumer satisfaction. To address this need, we (i) performed an observational study on the microbial quality of baby spinach, (ii) completed growth experiments of bacteria that are representative of the baby spinach microbiota, and (iii) developed an initial simulation model of bacterial growth on baby spinach. Our observational data showed that the predominant genera found on baby spinach were Pseudomonas, Pantoea and Exiguobacterium. Rifampicin-resistant mutants (rifR mutants) of representative bacterial subtypes were subsequently generated to obtain strain-specific growth parameters on baby spinach. These experiments showed that: (i) it is difficult to select rifR mutants that do not have fitness costs affecting growth (9 of 15 rifR mutants showed substantial differences in growth, compared to their corresponding wild-type strain) and (ii) based on estimates from primary growth models, the mean (geometric) maximum population of rifR mutants on baby spinach (7.6 log10 CFU/g, at 6°C) appears lower than that of the spinach microbiota (9.6 log10 CFU/g, at 6°C), even if rifR mutants did not have substantial growth-related fitness costs. Thus, a simulation model, parameterized with the data obtained here as well as literature data on home refrigeration temperatures, underestimated bacterial growth on baby spinach. The root mean square error of the simulation's output, compared against data from the observational study, was 1.11 log10 CFU/g. Sensitivity analysis was used to identify key parameters (e.g., strain maximum population) that impact the simulation model's output, allowing for prioritization of future data collection to improve the simulation model. Overall, this study provides a roadmap for the development of models to predict bacterial growth on leafy vegetables with strain-specific parameters and suggests that additional data are required to improve these models.
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Affiliation(s)
- Sriya Sunil
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA
| | - Sarah I Murphy
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Renato H Orsi
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA
| | - Renata Ivanek
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
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6
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Stanosheck JA, Castell-Perez ME, Moreira RG, King MD, Castillo A. Oversampling methods for machine learning model data training to improve model capabilities to predict the presence of Escherichia coli MG1655 in spinach wash water. J Food Sci 2024; 89:150-173. [PMID: 38051016 DOI: 10.1111/1750-3841.16850] [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: 06/09/2023] [Revised: 10/16/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023]
Abstract
We assessed the efficacy of oversampling techniques to enhance machine learning model performance in predicting Escherichia coli MG1655 presence in spinach wash water. Three oversampling methods were applied to balance two datasets, forming the basis for training random forest (RF), support vector machines (SVMs), and binomial logistic regression (BLR) models. Data underwent method-specific centering and standardization, with outliers replaced by feature-specific means in training datasets. Testing occurred without these preprocessing steps. Model hyperparameters were optimized using a subset of testing data via 10-fold cross-validation. Models were trained on full datasets and tested on newly acquired spinach wash water samples. Synthetic Minority Oversampling Technique (SMOTE) and Adaptive Synthetic Sampling approach (ADASYN) achieved strong results, with SMOTE RF reaching an accuracy of 90.0%, sensitivity of 93.8%, specificity of 87.5%, and an area under the curve (AUC) of 98.2% (without data preprocessing) and ADASYN achieving 86.55% accuracy, 87.5% sensitivity, 83.3% specificity, and a 92.4% AUC. SMOTE and ADASYN significantly improved (p < 0.05) SVM and RF models, compared to their non-oversampled counterparts without preprocessing. Data preprocessing had a mixed impact, improving (p < 0.05) the accuracy and specificity of the BLR model but decreasing the accuracy and specificity (p < 0.05) of the SVM and RF models. The most influential physiochemical feature for E. coli detection in wash water was water conductivity, ranging from 7.9 to 196.2 µS. Following closely was water turbidity, ranging from 2.97 to 72.35 NTU within this study.
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Affiliation(s)
- Jacob A Stanosheck
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas, USA
| | - M Elena Castell-Perez
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas, USA
| | - Rosana G Moreira
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas, USA
| | - Maria D King
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas, USA
| | - Alejandro Castillo
- Department of Food Science and Technology, Texas A&M University, College Station, Texas, USA
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7
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Shang H, Tan BZ, Dakwa V, D'Agnese E, Stanley RA, Sassi H, Lai YW, Deaker R, Bowman JP. Effect of pre-harvest sanitizer treatments on Listeria survival, sensory quality and bacterial community dynamics on leafy green vegetables grown under commercial conditions. Food Res Int 2023; 173:113341. [PMID: 37803650 DOI: 10.1016/j.foodres.2023.113341] [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: 03/23/2023] [Revised: 07/19/2023] [Accepted: 07/31/2023] [Indexed: 10/08/2023]
Abstract
Leafy green vegetables (LGVs) have large surface areas and can be colonized by various microorganisms including pathogens. In this study, we investigated the effect of pre-harvest sanitizer treatments on the survival of inoculated proxy pathogen Listeria innocua ATCC 33090 and the natural microbial community of mizuna, rocket (arugula), red chard and spinach grown under commercial conditions. Electrolyzed water (e-water), peracetic acid (PAA), and 1-bromo-3-chloro-5-dimethylhydantoin (BCDMH) were tested against water controls. We also observed the subsequent sensorial changes of harvested, bagged LGV leaves over a period of 12 days within chill storage alongside the growth, diversity and structure of bacterial populations determined using 16S rRNA gene amplicon sequencing and total viable counts (TVC). Treatment with PAA resulted in the highest reductions of L. innocua (2.4-5.5 log units) compared to the other treatments (0.25-2.5 log units). On day 0 (24 h after sanitizer application), the TVC on sanitizer treated LGVs were significantly reduced compared to water controls, except for rocket. During storage at 4.5 (±0.5)°C sanitisers only hindered microbial growth on LGVs initially and did not influence final bacterial population levels, growth rates or changes in LGV sample colour, decay, odour and texture compared to water controls. Shelf-life was not extended nor was it reduced. The community structure on LGV types differed though a core set of bacterial amplicon sequence variants (ASV) were present across all samples. No significant differences were observed in bacterial diversity between sanitizer treatments, however sanitizer treated LGV samples had initially reduced diversity compared to water treated samples. The bacterial compositions observed at the end point of storage considerably differed from what was observed at initial point owing to the increase in abundance of specific bacterial taxa, mainly Pseudomonas spp., the abundance and growth responses differing between LGV types studied. This study provides a better understanding on the microbiology and sensory impact of pre-harvest applied sanitiser treatments on different LGVs destined for commercial food use.
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Affiliation(s)
- Hongshan Shang
- School of Life and Environmental Sciences, F22 - LEES Building, The University of Sydney, NSW 2006, Australia; Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia
| | - Bi Zheng Tan
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia
| | - Vongai Dakwa
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia
| | - Erin D'Agnese
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia
| | - Roger A Stanley
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia
| | - Hannah Sassi
- School of Life and Environmental Sciences, F22 - LEES Building, The University of Sydney, NSW 2006, Australia
| | - Yu-Wen Lai
- School of Life and Environmental Sciences, F22 - LEES Building, The University of Sydney, NSW 2006, Australia
| | - Rosalind Deaker
- School of Life and Environmental Sciences, F22 - LEES Building, The University of Sydney, NSW 2006, Australia
| | - John P Bowman
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005, Australia.
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Siripongvutikorn S, Usawakesmanee W, Pisuchpen S, Khatcharin N, Rujirapong C. Nutritional Content and Microbial Load of Fresh Liang, Gnetum gnemon var. tenerum Leaves. Foods 2023; 12:3848. [PMID: 37893741 PMCID: PMC10605991 DOI: 10.3390/foods12203848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 10/10/2023] [Accepted: 10/12/2023] [Indexed: 10/29/2023] Open
Abstract
Liang (Gnetum gnemon var. tenerum) leaves are widely consumed as a green vegetable in Southern Thailand, and the plant is valued for its nutritional benefits. However, like other leafy greens, liang is vulnerable to microbial contamination, generating foodborne illnesses. This study examined the nutritional content and microbial load of liang leaves at different maturity stages and the effects of washing with chlorinated water. Various growth stages were analysed for proximate composition, amino acids, vitamins, and minerals. Results revealed distinct nutritional profiles, with tip leaves rich in protein and fat and intermediate leaves high in dietary fibre. Liang leaves are abundant in essential amino acids and proteins. Washing with chlorinated water increased leaf weight due to water retention but also caused physical damage, fostering microbial growth and spoilage. Microbiological analysis showed marginal reductions in total viable counts after washing with chlorinated water and significant decreases in coliform and Escherichia coli counts. However, stem detachment during washing increased the coliform and E. coli counts. Liang leaves exhibited favourable nutritional content, especially in the intermediate stage. Proper handling and storage of liang leaves are crucial to preventing physical damage and microbial contamination. Improved food safety measures, including appropriate post-harvest washing and handling of leafy vegetables, will ensure that consumers can safely enjoy the nutritional benefits of liang leaves.
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Affiliation(s)
- Sunisa Siripongvutikorn
- Centre of Excellence in Functional Foods and Gastronomy, Faculty of Agro-Industry Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand; (W.U.); (N.K.); (C.R.)
| | - Worapong Usawakesmanee
- Centre of Excellence in Functional Foods and Gastronomy, Faculty of Agro-Industry Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand; (W.U.); (N.K.); (C.R.)
| | - Supachai Pisuchpen
- Centre of Excellence in Bio-Based Materials and Packaging Innovation, Faculty of Agro-Industry Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand;
| | - Nicha Khatcharin
- Centre of Excellence in Functional Foods and Gastronomy, Faculty of Agro-Industry Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand; (W.U.); (N.K.); (C.R.)
| | - Chanonkarn Rujirapong
- Centre of Excellence in Functional Foods and Gastronomy, Faculty of Agro-Industry Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand; (W.U.); (N.K.); (C.R.)
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9
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Brandl MT, Mammel MK, Simko I, Richter TKS, Gebru ST, Leonard SR. Weather factors, soil microbiome, and bacteria-fungi interactions as drivers of the epiphytic phyllosphere communities of romaine lettuce. Food Microbiol 2023; 113:104260. [PMID: 37098420 DOI: 10.1016/j.fm.2023.104260] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 02/16/2023] [Accepted: 03/07/2023] [Indexed: 03/16/2023]
Abstract
Lettuce is associated with seasonal outbreaks of Shiga toxin-producing Escherichia coli (STEC) infections. Little is known about how various biotic and abiotic factors affect the lettuce microbiome, which in turn impacts STEC colonization. We characterized the lettuce phyllosphere and surface soil bacterial, fungal, and oomycete communities at harvest in late-spring and -fall in California using metagenomics. Harvest season and field type, but not cultivar, significantly influenced the microbiome composition of leaves and surface soil near plants. Phyllosphere and soil microbiome compositions were correlated with specific weather factors. The relative abundance of Enterobacteriaceae, but not E. coli, was enriched on leaves (5.2%) compared to soil (0.4%) and correlated positively with minimum air temperature and wind speed. Co-occurrence networks revealed seasonal trends in fungi-bacteria interactions on leaves. These associations represented 39%-44% of the correlations between species. All significant E. coli co-occurrences with fungi were positive, while all negative associations were with bacteria. A large proportion of the leaf bacterial species was shared with those in soil, indicating microbiome transmission from the soil surface to the canopy. Our findings provide new insight into factors that shape lettuce microbial communities and the microbial context of foodborne pathogen immigration events in the lettuce phyllosphere.
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Affiliation(s)
- Maria T Brandl
- Produce Safety and Microbiology Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA, USA
| | - Mark K Mammel
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Ivan Simko
- Crop Improvement and Protection Research Unit, US Department of Agriculture, Agricultural Research Service, Salinas, CA, USA
| | - Taylor K S Richter
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Solomon T Gebru
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Susan R Leonard
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA.
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10
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Smalla K, Kabisch J, Fiedler G, Hammerl JA, Tenhagen BA. [Health risks from crop irrigation with treated wastewater containing antibiotic residues, resistance genes, and resistant microorganisms]. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2023:10.1007/s00103-023-03710-7. [PMID: 37233812 DOI: 10.1007/s00103-023-03710-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 04/25/2023] [Indexed: 05/27/2023]
Abstract
This review describes the effects and potential health risks of resistant microorganisms, resistance genes, and residues of drugs and biocides that occur when re-using wastewater for crop irrigation. It focusses on specific aspects of these contaminants and their interactions, but does not provide a general risk assessment of the microbial load when using reclaimed water.Antimicrobial residues, antimicrobial resistant microorganisms, and resistance genes are frequently detected in treated wastewater. They have effects on the soil and plant-associated microbiota (total associated microorganisms) and can be taken up by plants. An interaction of residues with microorganisms is mainly expected before using the water for irrigation. However, it may also occur as a combined effect on the plant microbiome and all the abundant resistance genes (resistome). Special concerns are raised as plants are frequently consumed raw, that is, without processing that might reduce the bacterial load. Washing fruits and vegetables only has minor effects on the plant microbiome. On the other hand, cutting and other processes may support growth of microorganisms. Therefore, after such process steps, cooling of the foods is required.Further progress has to be made in the treatment of wastewater that will be used for crop irrigation with respect to removing micropollutants and microorganisms to minimize the risk of an increased exposure of consumers to transferable resistance genes and resistant bacteria.
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Affiliation(s)
- Kornelia Smalla
- Institut für Epidemiologie und Pathogendiagnostik, Julius Kühn-Institut (JKI), Braunschweig, Deutschland
| | - Jan Kabisch
- Institut für Mikrobiologie und Biotechnologie, Max Rubner-Institut (MRI), Kiel, Deutschland
| | - Gregor Fiedler
- Institut für Mikrobiologie und Biotechnologie, Max Rubner-Institut (MRI), Kiel, Deutschland
| | - Jens Andre Hammerl
- Abteilung Biologische Sicherheit, Bundesinstitut für Risikobewertung (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Deutschland
| | - Bernd-Alois Tenhagen
- Abteilung Biologische Sicherheit, Bundesinstitut für Risikobewertung (BfR), Max-Dohrn-Str. 8-10, 10589, Berlin, Deutschland.
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11
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Possas A, Pérez-Rodríguez F. New insights into Cross-contamination of Fresh-Produce. Curr Opin Food Sci 2022. [DOI: 10.1016/j.cofs.2022.100954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Modeling the effect of Croton blanchetianus Baill essential oil on pathogenic and spoilage bacteria. Arch Microbiol 2022; 204:618. [PMID: 36098860 DOI: 10.1007/s00203-022-03235-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 08/26/2022] [Accepted: 09/01/2022] [Indexed: 11/02/2022]
Abstract
This study aimed to evaluate and model the antimicrobial action of different concentrations of Croton blanchetianus essential oil (CBEO) on the behavior of six bacterial species in vitro. CBEO extraction was performed by hydrodistillation and characterized by CG-MS. CBEO solutions in culture media were tested at 0.90, 1.80, 2.71, and 4.51 mg of CBEO/mL, against foodborne bacteria: pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes and Salmonella Enteritidis at 35 °C), a non-pathogenic Escherichia coli (at 35 °C), and spoilage bacteria (Weissella viridescens and Leuconostoc mesenteroides at 30 °C). The CBEO major compounds were eucalyptol, α-pinene, sativene, E-caryophyllene, bicyclogermacrene, and spatulenol. Baranyi and Roberts (growth) and Weibull (inactivation) primary models, along with power and hyperbolic secondary models, were able to describe the data. CBEO inactivated L. monocytogenes, S. aureus, L. mesenteroides and W. viridescens at all applied concentrations. CBEO did not inactivate S. Enteritidis and E. coli, but their growth rates were reduced.
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13
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Sudarsan A, Keener K. Inactivation of spoilage organisms on baby spinach leaves using high voltage atmospheric cold plasma (HVACP) and assessment of quality. INNOV FOOD SCI EMERG 2022. [DOI: 10.1016/j.ifset.2022.103023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Uhlig E, Kjellström A, Oscarsson E, Nurminen N, Nabila Y, Paulsson J, Lupan T, Velpuri NSBP, Molin G, Håkansson Å. The live bacterial load and microbiota composition of prepacked "ready-to-eat" leafy greens during household conditions, with special reference to E. coli. Int J Food Microbiol 2022; 377:109786. [PMID: 35716582 DOI: 10.1016/j.ijfoodmicro.2022.109786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 06/05/2022] [Accepted: 06/09/2022] [Indexed: 10/18/2022]
Abstract
Ready-to-eat (RTE) leafy greens are popular products that unfortunately have been associated with numerous foodborne illness outbreaks. Since the influence of consumer practices is essential for their quality and safety, the objective of this study was to analyze the microbiota of RTE products throughout shelf life during simulated household conditions. Products from different companies were analyzed in terms of plate counts, and resealed and unopened packages were compared. High bacterial loads were found, up to a total plate count of 9.6 log10 CFU/g, and Enterobacteriaceae plate counts up to 6.0 CFU/g on the expiration date. The effect of consumer practice varied, thus no conclusions regarding resealed or unopened bags could be drawn. The tested products contained opportunistic pathogens, such as Enterobacter homaechei, Hafnia paralvei and Pantoea agglomerans. Amplicon sequencing revealed that the relative abundance of major taxonomic groups changed during shelf life; Pseudomonadaceae and Xanthomonadaceae decreased, while Flavobacteriaceae and Marinomonadaceae inceased. Inoculation with E. coli CCUG 29300T showed that the relative abundance of Escherichia-Shigella was lower on rocket than on other tested leafy greens. Inoculation with E. coli strain 921 indicate growth at the beginning of shelf-life time, while E. coli 731 increases at the end, seemingly able to adapt to cold storage conditions. The high levels of live microorganisms, the detection of opportunistic pathogens, and the ability of E. coli strains to grow at refrigeration temperature raise concerns and indicate that the shelf life may be shortened to achieve a safer product. Due to variations between products, further studies are needed to define how long the shelf-life of these products should be, to ensure a safe product even at the end of the shelf-life period.
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Affiliation(s)
- E Uhlig
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden.
| | - A Kjellström
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - E Oscarsson
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - N Nurminen
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - Y Nabila
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - J Paulsson
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - T Lupan
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - N S B P Velpuri
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - G Molin
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
| | - Å Håkansson
- Department of Food Technology, Engineering and Nutrition, Lund University, PO box 124, SE-221 00 Lund, Sweden
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15
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Tongwanichniyom S, Kitjaruwankul S, Phornphisutthimas S. Production of biomaterials from seafood waste for application as vegetable wash disinfectant. Heliyon 2022; 8:e09357. [PMID: 35574197 PMCID: PMC9095745 DOI: 10.1016/j.heliyon.2022.e09357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 02/26/2022] [Accepted: 04/27/2022] [Indexed: 11/18/2022] Open
Affiliation(s)
| | - Sunan Kitjaruwankul
- Faculty of Science at Sriracha, Kasetsart University, Chonburi, 20230, Thailand
| | - Somkiat Phornphisutthimas
- Department of Biology, and Research Unit on Science, Technology and Environment for Learning, Faculty of Science, Srinakharinwirot University, Bangkok, 10110, Thailand
- Corresponding author.
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16
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Yin Y, Zhu D, Yang G, Su J, Duan G. Diverse antibiotic resistance genes and potential pathogens inhabit in the phyllosphere of fresh vegetables. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 815:152851. [PMID: 34990692 DOI: 10.1016/j.scitotenv.2021.152851] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/28/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
Fresh vegetables are considered as a reservoir of pathogenic bacteria and antibiotic resistance genes (ARGs), which are the emerging environmental contaminants, posing increasing concerned risk to human health. However, the prevalence of pathogens in phyllosphere of fresh vegetables, as well as the association of ARGs with pathogenic bacteria, have not been well elaborated. In this study, we explored the structure of microbial communities and ARGs through high-throughput quantitative PCR and 16S rRNA gene Illumina sequencing, and characterized the microorganisms resisting to antibiotics by pure culture. From phyllosphere of six different kinds of vegetables, 205 ARGs were detected and genes for multidrug resistance was the most abundant. The predominant potential pathogens were classified to Pseudomonas, Klebsiella, and Acinetobacter genera, which carried various ARGs such as multidrug and beta-lactam resistance genes presumedly. Among six kinds of vegetables, Lactuca sativa var. asparagina carried the highest abundance of potential pathogens and ARGs, while Allium sativum L harbored the lowest abundance of pathogens and ARGs. In addition, various culturable bacteria resisting to colistin or meropenem could be isolated from all vegetables, remarkably, all the isolates resistant to both antibiotics are potential pathogens. Our study highlighted the risks of pathogens and ARGs from raw vegetables to consumers, characterized their structure patterns among different vegetables, and analyzed the potential mechanisms regulating phyllosphere pathogens and resistome of fresh vegetables, which would be helpful for reducing the microbial risk from vegetable ingestion.
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Affiliation(s)
- Yue Yin
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dong Zhu
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guang Yang
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jianqiang Su
- University of Chinese Academy of Sciences, Beijing 100049, China; Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Guilan Duan
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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17
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Madamba T, Moreira RG, Castell‐Perez E, Banerjee A, Silva D. Agent‐based simulation of cross‐contamination of
Escherichia coli
O157
:
H7
On lettuce during processing with temperature fluctuations during storage in a produce facility. Part 1: Model development. J FOOD PROCESS ENG 2022. [DOI: 10.1111/jfpe.14002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Tonderai Madamba
- Biological & Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Rosana G. Moreira
- Biological & Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Elena Castell‐Perez
- Biological & Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Amarnath Banerjee
- Industrial and Systems Engineering Department Texas A&M University College Station Texas USA
| | - Dilma Silva
- Computer Science and Engineering Department Texas A&M University College Station Texas USA
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18
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Murphy SI, Chen R, Belias AM, Chen W, Zhang LQ, Sunil S, Bulut E, Li Y, Wiedmann M, Ivanek R. Growth and survival of aerobic and Gram-negative bacteria on fresh spinach in a Chinese supply chain from harvest through distribution and refrigerated storage. Int J Food Microbiol 2022; 370:109639. [DOI: 10.1016/j.ijfoodmicro.2022.109639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 03/09/2022] [Accepted: 03/23/2022] [Indexed: 11/17/2022]
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19
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Madamba T, Moreira RG, Castell‐Perez E, Banerjee A, Silva D. Agent‐based simulation of cross‐contamination of
Escherichia coli
O157
:
H7
on lettuce during processing and temperature fluctuations during storage in a produce facility. Part 2: Model implementation. J FOOD PROCESS ENG 2022. [DOI: 10.1111/jfpe.13983] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tonderai Madamba
- Biological and Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Rosana G. Moreira
- Biological and Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Elena Castell‐Perez
- Biological and Agricultural Engineering Department Texas A&M University College Station Texas USA
| | - Amarnath Banerjee
- Industrial and Systems Engineering Department Texas A&M University College Station Texas USA
| | - Dilma Silva
- Computer Science and Engineering Department Texas A&M University College Station Texas USA
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20
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Leonard SR, Simko I, Mammel MK, Richter TKS, Brandl MT. Seasonality, shelf life and storage atmosphere are main drivers of the microbiome and E. coli O157:H7 colonization of post-harvest lettuce cultivated in a major production area in California. ENVIRONMENTAL MICROBIOME 2021; 16:25. [PMID: 34930479 PMCID: PMC8686551 DOI: 10.1186/s40793-021-00393-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 11/30/2021] [Indexed: 05/10/2023]
Abstract
BACKGROUND Lettuce is linked to recurrent outbreaks of Shiga toxin-producing Escherichia coli (STEC) infections, the seasonality of which remains unresolved. Infections have occurred largely from processed lettuce, which undergoes substantial physiological changes during storage. We investigated the microbiome and STEC O157:H7 (EcO157) colonization of fresh-cut lettuce of two cultivars with long and short shelf life harvested in the spring and fall in California and stored in modified atmosphere packaging (MAP) at cold and warm temperatures. RESULTS Inoculated EcO157 declined significantly less on the cold-stored cultivar with short shelf life, while multiplying rapidly at 24 °C independently of cultivar. Metagenomic sequencing of the lettuce microbiome revealed that the pre-storage bacterial community was variable but dominated by species in the Erwiniaceae and Pseudomonadaceae. After cold storage, the microbiome composition differed between cultivars, with a greater relative abundance (RA) of Erwiniaceae and Yersiniaceae on the cultivar with short shelf life. Storage at 24 °C shifted the microbiome to higher RAs of Erwiniaceae and Enterobacteriaceae and lower RA of Pseudomonadaceae compared with 6 °C. Fall harvest followed by lettuce deterioration were identified by recursive partitioning as important factors associated with high EcO157 survival at 6 °C, whereas elevated package CO2 levels correlated with high EcO157 multiplication at 24 °C. EcO157 population change correlated with the lettuce microbiome during 6 °C storage, with fall microbiomes supporting the greatest EcO157 survival on both cultivars. Fall and spring microbiomes differed before and during storage at both temperatures. High representation of Pantoea agglomerans was a predictor of fall microbiomes, lettuce deterioration, and enhanced EcO157 survival at 6 °C. In contrast, higher RAs of Erwinia persicina, Rahnella aquatilis, and Serratia liquefaciens were biomarkers of spring microbiomes and lower EcO157 survival. CONCLUSIONS The microbiome of processed MAP lettuce evolves extensively during storage. Under temperature abuse, high CO2 promotes a lettuce microbiome enriched in taxa with anaerobic capability and EcO157 multiplication. In cold storage, our results strongly support a role for season and lettuce deterioration in EcO157 survival and microbiome composition, suggesting that the physiology and microbiomes of fall- and spring-harvested lettuce may contribute to the seasonality of STEC outbreaks associated with lettuce grown in coastal California.
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Affiliation(s)
- Susan R Leonard
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Ivan Simko
- Crop Improvement and Protection Research Unit, US Department of Agriculture, Agricultural Research Service, Salinas, CA, USA
| | - Mark K Mammel
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Taylor K S Richter
- Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, USA
| | - Maria T Brandl
- Produce Safety and Microbiology Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA, USA.
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