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Gomez-Galindo M, Serra-Castelló C, Bover-Cid S, Truchado P, Gil MI, Allende A. The Gamma concept approach as a tool to predict fresh produce supporting or not the growth of L. monocytogenes. Food Microbiol 2024; 122:104554. [PMID: 38839220 DOI: 10.1016/j.fm.2024.104554] [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: 01/26/2024] [Revised: 04/19/2024] [Accepted: 04/22/2024] [Indexed: 06/07/2024]
Abstract
Challenge tests are commonly employed to evaluate the growth behavior of L. monocytogenes in food matrices; they are known for being expensive and time-consuming. An alternative could be the use of predictive models to forecast microbial behavior under different conditions. In this study, the growth behavior of L. monocytogenes in different fresh produce was evaluated using a predictive model based on the Gamma concept considering pH, water activity (aw), and temperature as input factors. An extensive literature search resulted in a total of 105 research articles selected to collect growth/no growth behavior data of L. monocytogenes. Up to 808 L. monocytogenes behavior values and physicochemical characteristics were extracted for different fruits and vegetables. The predictive performance of the model as a tool for identifying the produce commodities supporting the growth of L. monocytogenes was proved by comparing with the experimental data collected from the literature. The model provided satisfactory predictions on the behavior of L. monocytogenes in vegetables (>80% agreement with experimental observations). For leafy greens, a 90% agreement was achieved. In contrast, the performance of the Gamma model was less satisfactory for fruits, as it tends to overestimate the potential of acid commodities to inhibit the growth of L. monocytogenes.
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Affiliation(s)
- Marisa Gomez-Galindo
- Research Group on Microbiology and Quality of Fruit and Vegetables, CEBAS-CSIC, Murcia, Spain
| | | | - Sara Bover-Cid
- IRTA, Food Safety and Functionality Program, Finca Camps i Armet s/n, 17121, Monells, Spain
| | - Pilar Truchado
- Research Group on Microbiology and Quality of Fruit and Vegetables, CEBAS-CSIC, Murcia, Spain
| | - Maria I Gil
- Research Group on Microbiology and Quality of Fruit and Vegetables, CEBAS-CSIC, Murcia, Spain
| | - Ana Allende
- Research Group on Microbiology and Quality of Fruit and Vegetables, CEBAS-CSIC, Murcia, Spain.
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Xie Y, Long X, Kim Y, Harris LJ, Nitin N. Survival of Salmonella enterica and Enterococcus faecium on Abiotic Surfaces During Storage at Low Relative Humidity. J Food Prot 2024; 87:100292. [PMID: 38718984 DOI: 10.1016/j.jfp.2024.100292] [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: 02/29/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 05/23/2024]
Abstract
Currently, there is limited knowledge on the survival of bacteria on surfaces during postharvest handling of dry products such as onions. Extended survival of microorganisms, coupled with a lack of established and regular, validated cleaning or sanitation methods could enable cross-contamination of these products. The aim of the study was to evaluate the survival of a potential surrogate, Enterococcus faecium, and Salmonella enterica on typical onion handling surfaces, polyurethane (PU), and stainless steel (SS), under low relative humidity. The influence of onion extract on the survival of E. faecium and Salmonella on PU and SS was also investigated. Rifampin-resistant E. faecium NRRL B-2354 and a five-strain cocktail of Salmonella suspended in 0.1% peptone or onion extract were separately inoculated onto PU and SS coupons (2 × 2 cm), at high, moderate, or low (7, 5, or 3 log CFU/cm2) levels. The inoculated surfaces were stored at ∼34% relative humidity and 21°C for up to 84 days. Triplicate samples were enumerated at regular intervals in replicate trials. Samples were enriched when populations fell below the limit of detection by plating (0.48 log CFU/cm2). Scanning electron microscopy was used to observe the cell distribution on the coupons. Reductions of E. faecium of less than ∼2 log were observed on PU and SS over 12 weeks at all inoculum levels and with both inoculum carriers. In 0.1% peptone, Salmonella populations declined by 2 to 3 log over 12 weeks at the high and moderate inoculum levels; at the low inoculum level, Salmonella could not be recovered by enrichment at 84 days. Survival of E. faecium and Salmonella was significantly (P < 0.05) enhanced over 84 days of storage when suspended in onion extract, where cells were covered by a layer of onion extract. E. faecium might have utility as a conservative surrogate for Salmonella when evaluating microbial survival on dry food-contact surfaces.
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Affiliation(s)
- Yucen Xie
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Xiaonuo Long
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Yoonbin Kim
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Linda J Harris
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Western Center for Food Safety, University of California, Davis, CA 95616, USA.
| | - Nitin Nitin
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Department of Agricultural and Biological Engineering, University of California, Davis, CA 95616, USA.
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Wang L, Teplitski M. Microbiological food safety considerations in shelf-life extension of fresh fruits and vegetables. Curr Opin Biotechnol 2023; 80:102895. [PMID: 36689852 DOI: 10.1016/j.copbio.2023.102895] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 12/11/2022] [Accepted: 12/23/2022] [Indexed: 01/22/2023]
Abstract
There are a number of opportunities for reducing loss and waste, and extending shelf life of fresh produce that go beyond cold chain optimization. For example, plant genotype (including ripening-related genes), presence of phytopathogens, maturity at harvest, and environmental conditions close to the harvest time, storage conditions, and postharvest treatments (washing, cutting, and waxing) all impact both shelf life of produce and food safety outcomes. Therefore, loss can be reduced and shelf life of fresh produce can be extended with plant breeding to manipulate ripening-related traits, or with pre- and postharvest treatments delaying senescence and decay. Food safety considerations of these applications are discussed.
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Affiliation(s)
- Luxin Wang
- Department of Food Science and Technology, University of California Davis, Davis, CA 95616, United States
| | - Max Teplitski
- International Fresh Produce Association, Washington, DC, United States.
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Moyne AL, Waite-Cusic J, Harris LJ. Water Application Method Influences Survival or Growth of Escherichia coli on Bulb Onions during Field Curing. J Food Prot 2022; 85:961-972. [PMID: 35333326 DOI: 10.4315/jfp-21-394] [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: 10/20/2021] [Accepted: 03/19/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT The impact of water application method on bacterial survival at or after the final irrigation was evaluated in bulb onions during commercially relevant field drying (curing). A three-strain rifampin-resistant cocktail of Escherichia coli was introduced to onions via a single overhead spray application in two separate trials (5.22 [trial 1] or 2.40 [trial 2] log CFU per onion) 2 to 3 days after the final irrigation. Onions were lifted from the soil 8 days after spray inoculation and, in some cases, foliage was removed (topping); onions remained in the field for an additional ca. 2 weeks (total ca. 3 weeks of curing). E. coli populations declined on the onions in the first 4 h after spray inoculation. E. coli was recovered from 38 (48%) or 28 (35%) of 80 whole-onion enrichments at the end of curing in trials 1 or 2, respectively. Topping did not significantly impact the percentage of E. coli-positive onions detected at the end of curing. From 8 h to 21 days, E. coli populations on positive onions ranged from 1 CFU per onion to 7 log CFU per onion in both trials, representing a potential risk of E. coli growth with overhead application of contaminated water at the end of onion production. In trial 2, additional rows of onions were inoculated via a 22-cm subsurface or surface drip irrigation line (1.94 log CFU/mL for 2.5 h). E. coli was detected in 0 (subsurface) and 4 (surface) of 50 whole-onion enrichments 3 h after the initiation of drip irrigation. Positive onions were detected at days 1 (4 of 50) and 7 (1 of 50) with subsurface drip inoculation, and at days 1 (7 of 50), 7 (2 of 50), and 14 (2 of 50) with surface drip inoculation. E. coli was not detected in whole-onion enrichments at the end of curing when inoculated by subsurface (0 of 50) or surface (0 of 50) drip irrigation. Application of contaminated water through drip irrigation, when coupled with field curing, results in low rates of contamination of bulb onions at the time of harvest. HIGHLIGHTS
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Affiliation(s)
- Anne-Laure Moyne
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, California 95616-5270.,Western Center for Food Safety, University of California, Davis, One Shields Avenue, Davis, California 95618
| | - Joy Waite-Cusic
- Department of Food Science and Technology, Oregon State University, Corvallis, Oregon, USA
| | - Linda J Harris
- Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, California 95616-5270.,Western Center for Food Safety, University of California, Davis, One Shields Avenue, Davis, California 95618
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Lieberman VM, Morgan EW, Harris LJ. Reduction of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella on Whole Yellow Onions (Allium cepa) Exposed to Hot Water. J Food Prot 2021; 84:1965-1972. [PMID: 34265051 DOI: 10.4315/jfp-21-242] [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: 06/09/2021] [Accepted: 07/13/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT In-home or food service antimicrobial treatment options for fresh produce are limited. Hot water treatments for whole (unpeeled) produce have been proposed, but data to support this practice for onions are not available. Separate cocktails of rifampin-resistant Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella were cultured on agar and suspended in sterile water. The outer papery skin at the equator or root or stem ends of the whole yellow onions was spot inoculated at 6 log CFU per onion. After drying for 30 min and, in some cases, storage at 4°C for 6 days, onions were immersed in water at ca. 100°C for 5 s or 85°C for 10 to 180 s. No significant difference (P > 0.05) in the mean decline of Salmonella was found on onions that were exposed to hot water after drying the inoculum for 30 min or after storage at 4°C for 6 days. Exposure of whole onions at 100°C for 5 s reduced E. coli O157:H7 and L. monocytogenes populations by >5 log CFU per onion at all inoculum sites and Salmonella populations by >5 log CFU per onion at the stem end and equator but not consistently at the root end. Mean root-end reductions of ≥5 log CFU per onion of E. coli O157:H7, L. monocytogenes, and Salmonella were achieved consistently when the root end was fully immersed in 85°C hot water for 45 or 60 s except in a small number of cases (4 of 57; 7%) when the root end was oriented upward and above the water line during treatment. When onions were held at 85°C for 180 s with the root end above the water line in an uncovered water bath, no significant declines in Salmonella populations were observed; significant mean declines in Salmonella were achieved (mean, 5 log CFU per onion; range, 3.49 to 6.25 log CFU per onion) when the water bath was covered. Short exposure to hot water can significantly reduce pathogens on the surface of whole onions. Reductions are more consistent when the root end is submerged and when the water bath is covered. HIGHLIGHTS
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Affiliation(s)
- Vanessa M Lieberman
- Department of Food Science and Technology and Western Center for Food Safety, University of California-Davis, One Shields Avenue, Davis, California 95616-8598, USA
| | - Ethan W Morgan
- Department of Food Science and Technology and Western Center for Food Safety, University of California-Davis, One Shields Avenue, Davis, California 95616-8598, USA
| | - Linda J Harris
- Department of Food Science and Technology and Western Center for Food Safety, University of California-Davis, One Shields Avenue, Davis, California 95616-8598, USA
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