Survival of Campylobacter jejuni and Salmonella enterica Typhimurium in vacuum-packed, moisture-enhanced pork

Salmonella Behavior in Meat during Cool Storage: A Systematic Review and Meta-Analysis

The aim of the present study was to investigate Salmonella behavior in meat stored in cool conditions (between 0 °C and 7.5 °C), by employing a systematic review and meta-analysis. The data were obtained from research articles published in SciELO, PubMed, the Web of Science, and Scopus databases. The results of the retrieved studies were obtained from meat (beef, chicken, pork, poultry, and turkey), fish, shellfish, and broth media samples The data were extracted as sample size (n), initial concentration (Xi), final concentration (Xf), standard deviation (SD), standard error (SE), and microbial behavior effects (reduction or growth). A meta-analysis was carried out using the metaphor package from R software. A total of 654 articles were initially retrieved. After applying the exclusion criteria, 83 articles were selected for the systematic review, and 61 of these were used for the meta-analysis. Most studies were conducted at 0 °C to 4.4 °C storage temperatures under normal atmosphere package conditions. Salmonella Typhimurium, S. Enteritidis, and a cocktail (strain mixture) were inoculated at 5.0 and 6.0 log CFU mL−1. Articles both with and without the addition of antimicrobial compounds were found. Salmonella concentration decreases were observed in most studies, estimated for all study combinations as −0.8429 ± 0.0931 log CFU g−1 (95% CI; −1.0254, −0.6604) (p < 0.001), varying for each subgroup analysis. According to this survey, Salmonella concentration decreases are frequent during cool storage, although concentration increases and no bacterial inactivation were observed in some studies.

Building “First Expire, First Out” models to predict food losses at retail due to cold chain disruption in the last mile

Current less-than-truckload (LTL) shipping practices allow for temperature abuse (TA) in the last segment (last mile) of the food supply chain. When this TA is combined with “First In, First Out” product rotation methods, it could lead to food spoilage and food waste; therefore, data-based decision models are needed to aid retail managers. An experiment was designed using pallets (4 layers/pallet × 5 boxes/layer) of commercially produced boneless chicken breast filet trays. The pallets were exposed to 24 h of simulated LTL TA (cyclic 2 h at 4°C, then 2 h at 23 ± 2°C). Filet temperatures were recorded for all 20 boxes using dataloggers with thermocouple wires. Additionally, microbiological sampling of filets [aerobic plate counts (APC) and psychrotrophic plate counts (PSY)] was conducted before (0 h of LTL TA) and after (24 h of LTL TA) the TA experiment for select boxes of the pallet and compared to control filets (maintained at 4°C). After TA, a shelf-life experiment was conducted by storing filets from predetermined boxes at 4°C until spoilage (7 log CFU/ml). Temperature and microbiological data were augmented using Monte Carlo simulations (MC) to build decision making models using two methods; (1) the risk of each box on the pallet reaching the bacterial “danger zone” (&gt;4°C) was determined; and (2) the risk-of-loss (shelf-life &lt; 4 days; minimum shelf-life required to prevent food waste) was determined. Temperature results indicated that boxes on the top and bottom layers reached 4°C faster than boxes comprising the middle layers while the perimeter boxes of each layer reached 4°C faster than centrally located boxes. Shelf-life results indicate simulated LTL TA reduced shelf-life by 2.25 and 1.5 days for APC and PSY, respectively. The first MC method showed the average risk of boxes reaching 4°C after 24 h of simulated LTL TA were 94.96%, 43.20%, 27.20%, and 75.12% for layers 1–4, respectively. The second MC method indicated that exposure at &gt;4°C for 8 h results in a risk-of-loss of 43.8%. The findings indicate that LTL TA decreases shelf-life of chicken breast filets in a heterogenous manner according to location of boxes on the pallet. Therefore, predictive models are needed to make objective decisions so that a “First Expire, First Out” method can be implemented to reduce food wastes due to TA during the last mile.

Biofilm formation, phenotypic production of cellulose and gene expression in Salmonella enterica decrease under anaerobic conditions

Salmonella enterica subsp. enterica is one of the main food-borne pathogens. This microorganism combines an aerobic life outside the host with an anaerobic life within the host. One of the main concerns related to S. enterica is biofilm formation and cellulose production. In this study, biofilm formation, morphotype, cellulose production and transcription of biofilm and quorum sensing-related genes of 11 S. enterica strains were tested under three different conditions: aerobiosis, microaerobiosis, and anaerobiosis. The results showed an influence of oxygen levels on biofilm production. Biofilm formation was significantly higher (P<0.05) in aerobiosis than in microaerobiosis and anaerobiosis. Cellulose production and RDAR (red, dry, and rough) were expressed only in aerobiosis. In microaerobiosis, the strains expressed the SAW (smooth and white) morphotype, while in anaerobiosis the colonies appeared small and red. The expression of genes involved in cellulose synthesis (csgD and adrA) and quorum sensing (sdiA and luxS) was reduced in microaerobiosis and anaerobiosis in all S. enterica strains tested. This gene expression levels were less reduced in S. Typhimurium and S. Enteritidis compared to the tested serotypes. There was a relationship between the expression of biofilm and quorum sensing-related genes. Thus, the results from this study indicate that biofilm formation and cellulose production are highly influenced by atmospheric conditions. This must be taken into account as contamination with these bacteria can occur during food processing under vacuum or modified atmospheres.

Survival and Risk Comparison of Campylobacter jejuni on Various Processed Meat Products

The objective of this study was to investigate survival kinetics of Campylobacter jejuni on various processed meat products (dry-cured ham, round ham with/without sodium nitrite, garlic seasoned ham with/without sodium nitrite, and sausage without sodium nitrite). Additionally, a semi-quantitative risk assessment of C. jejuni on various processed meat products was conducted using FDA-iRISK 1.0. Inoculated processed meat products with 6.0 ± 0.5 log CFU/g of C. jejuni were vacuum packed and stored at 4, 10, 17, 24, 30, and 36 °C. Survival curves were fitted to the Weibull model to obtain the delta values of C. jejuni on various processed meat products. The most rapid death of C. jejuni was observed on dry-cured ham, followed by sausage without sodium nitrite. The results of semi-quantitative risk assessment indicate that dry-cured ham represented the lowest risk among all samples. C. jejuni on processed meats presented a greater risk at 4 °C than at 10 °C. The risk of ham was greater than the risk of sausage, regardless of type. Among all samples, the highest risk of C. jejuni was observed in round ham without sodium nitrite. Overall, our data indicates that risk of processed meat products due to C. jejuni is relatively low.

Lateral transfer, vertical translocation, and survival of inoculated bacteria during moisture enhancement of pork

Lateral transfer, vertical translocation, and survival of bacteria during moisture enhancement of pork were investigated under laboratory conditions. In the first experiment, a pork loin was surface inoculated with Escherichia coli biotype I and moisture enhanced with brine to 10%. After the inoculated loin had been injected, four uninoculated loins were processed in the same manner, without cleaning or sanitizing the injector equipment. Samples were collected from both the surface and the interior tissues of the pork loins. E. coli biotype I was transferred from the inoculated loins to both the exterior and interior of the uninoculated loins in this process. In the second experiment, pork loins were surface inoculated with E. coli biotype I and injected to 10, 20, and 30% of initial weight. After injection, E. coli biotype I was recovered from both the surface and the interior tissues in the pork loins, although there were no significant differences between injection levels. The third experiment was performed to examine the survival of Salmonella enterica Typhimurium and Campylobacter jejuni in recirculating brines. The brine used for injecting pork loins was inoculated with Salmonella Typhimurium or C. jejuni and then recirculated for 48 h at 4 or 10 °C. Samples were collected at specific time intervals, and the surviving populations of the organisms were determined. The populations of both bacteria declined by <1 log over 48 h, and there was no significant difference in populations between temperatures. The present study indicates the potential for cross-contamination of pork during moisture enhancement.