Thermal inactivation of Salmonella Typhimurium in chicken shawirma (gyro)

Evaluation of the effect of active essential oil components added to pickled-based marinade on beef stored under vacuum packaging: Insight into physicochemical and microbiological quality

This research aimed to evaluate the effects of the addition of active essential oil components (linalool and/or eugenol) to a pickle-based marinade on controlling spoilage and extending the shelf life of fresh beef stored under vacuum packaging at 4 °C. Linalool and eugenol were used either separately at a concentration of 0.2 % (w/w) or together (1:1 ratio) to preserve marinated beef under vacuum packaging for 15 days. Samples were assessed for pH, color, texture, oxidative degradation, and microbiological parameters. All marinades exhibited significantly lower TBARS values than the control sample. The addition of linalool or eugenol to the marinate showed a significant antibacterial effect on total aerobic mesophilic bacteria (TAMB), lactic acid bacteria (LAB), Pseudomonas spp., and total coliform, and the reductions in microbial counts are as follows: TAMB: 1.563 log CFU/g and 1.46 log CFU/g; Pseudomonas spp.: 1.303 log CFU/g and 1.08 log CFU/g; LAB: 0.323 log CFU/g and 0.357 log CFU/g. Marinated beef with linalool and/or eugenol was found to be effective against the growth of yeast and mold. The use of eugenol presented the most effective inhibition activity against yeast and mold by reducing the number of yeast and molds to an uncountable level on the 12th and 15th days of storage. Physicochemical analysis also showed that the addition of active essential oils to marinade did not cause any undesirable effects on the color and texture properties of beef samples. Therefore, the findings revealed that eugenol and linalool could be suitable alternatives for beef marination.

Modeling Salmonella spp. inactivation in chicken meat subjected to isothermal and non-isothermal temperature profiles

Salmonella genus has foodborne pathogen species commonly involved in many outbreaks related to the consumption of chicken meat. Many studies have aimed to model bacterial inactivation as a function of the temperature. Due to the large heterogeneity of the results, a unified description of Salmonella spp. inactivation behavior is hard to establish. In the current study, by evaluating the root mean square errors, mean absolute deviation, and Akaike and Bayesian information criteria, the double Weibull model was considered the most accurate primary model to fit 61 datasets of Salmonella inactivation in chicken meat. Results can be interpreted as if the bacterial population is divided into two subpopulations consisting of one more resistant (2.3% of the total population) and one more sensitive to thermal stress (97.7% of the total population). The thermal sensitivity of the bacteria depends on the fat content of the chicken meat. From an adapted version of the Bigelow secondary model including both temperature and fat content, 90% of the Salmonella population can be inactivated after heating at 60 °C of chicken breast, thigh muscles, wings, and skin during approximately 2.5, 5.0, 9.5, and 57.4 min, respectively. The resulting model was applied to four different non-isothermal temperature profiles regarding Salmonella growth in chicken meat. Model performance for the non-isothermal profiles was evaluated by the acceptable prediction zone concept. Results showed that >80% of the predictions fell in the acceptable prediction zone when the temperature changes smoothly at temperature rates lower than 20 °C/min. Results obtained can be used in risk assessment models regarding contamination with Salmonella spp. in chicken parts with different fat contents.

Antimicrobial effect of thymol and carvacrol added to a vinegar-based marinade for controlling spoilage of marinated beef (Shawarma) stored in air or vacuum packaging

Controlling spoilage of the popular ethnic marinated beef "Shawarma" is crucial to achieve high quality, extend shelf-life, reduce food waste and meet the need of the globalized supply chain. Active essential oil (EO) components (thymol and carvacrol) were added at 0.4% and 0.8% (w/w) to preserve marinated beef, stored under aerobic or vacuum packaging. Microbiological and sensory (odor) parameters were assessed during 21 days at 4 °C. The treatments with higher EO concentration achieved higher antimicrobial activity than the lower ones and significantly reduced the mesophilic total viable count (TVC), lactic acid bacteria (LAB), Brochothrix thermosphacta, Pseudomonas spp., total coliforms, Escherichia coli, yeasts and molds. The higher EO concentration extended the microbiological shelf-life by 6 days, as judged by TVC and compared to the controls (aerobic and vacuum packaging) but was unacceptable sensorially. The lower EO concentration increased the microbiological shelf-life by 3 days and the sensorial shelf-life by 9 and > 12 days, under aerobic and vacuum conditions, respectively.

Neural Network Model for Thermal Inactivation of Salmonella Typhimurium to Elimination in Ground Chicken: Acquisition of Data by Whole Sample Enrichment, Miniature Most-Probable-Number Method

Predictive models are valuable tools for assessing food safety. Existing thermal inactivation models for Salmonella and ground chicken do not provide predictions above 71°C, which is below the recommended final cooked temperature of 73.9°C for chicken. They also do not predict when all Salmonella are eliminated without extrapolating beyond the data used to develop them. Thus, a study was undertaken to develop a model for thermal inactivation of Salmonella to elimination in ground chicken at temperatures above those of existing models. Ground chicken thigh portions (0.76 cm³) in microcentrifuge tubes were inoculated with 4.45 ± 0.25 log most probable number (MPN) of a single strain of Salmonella Typhimurium (chicken isolate). They were cooked at 50 to 100°C in 2 or 2.5°C increments in a heating block that simulated two-sided pan frying. A whole sample enrichment, miniature MPN (WSE-mMPN) method was used for enumeration. The lower limit of detection was one Salmonella cell per portion. MPN data were used to develop a multiple-layer feedforward neural network model. Model performance was evaluated using the acceptable prediction zone (APZ) method. The proportion of residuals in an APZ (pAPZ) from -1 log (fail-safe) to 0.5 log (fail-dangerous) was 0.911 (379 of 416) for dependent data and 0.910 (162 of 178) for independent data for interpolation. A pAPZ ≥0.7 indicated that model predictions had acceptable bias and accuracy. There were no local prediction problems because pAPZ for individual thermal inactivation curves ranged from 0.813 to 1.000. Independent data for interpolation satisfied the test data criteria of the APZ method. Thus, the model was successfully validated. Predicted times for a 1-log reduction ranged from 9.6 min at 56°C to 0.71 min at 100°C. Predicted times for elimination ranged from 8.6 min at 60°C to 1.4 min at 100°C. The model will be a valuable new tool for predicting and managing this important risk to public health.

Thermal treatment for pathogen inactivation as a risk mitigation strategy for safe recycling of organic waste in agriculture

Thermal treatment at temperatures between 46.0°C and 55.0°C was evaluated as a method for sanitization of organic waste, a temperature interval less commonly investigated but important in connection with biological treatment processes. Samples of dairy cow feces inoculated with Salmonella Senftenberg W775, Enterococcus faecalis, bacteriophage ϕX174, and porcine parvovirus (PPV) were thermally treated using block thermostats at set temperatures in order to determine time-temperature regimes to achieve sufficient bacterial and viral reduction, and to model the inactivation rate. Pasteurization at 70°C in saline solution was used as a comparison in terms of bacterial and viral reduction and was proven to be effective in rapidly reducing all organisms with the exception of PPV (decimal reduction time of 1.2 h). The results presented here can be used to construct time-temperature regimes in terms of bacterial inactivation, with D-values ranging from 0.37 h at 55°C to 22.5 h at 46.0°C and 0.45 h at 55.0°C to 14.5 h at 47.5°C for Salmonella Senftenberg W775 and Enterococcus faecalis, respectively and for relevant enteric viruses based on the ϕX174 phage with decimal reduction times ranging from 1.5 h at 55°C to 16.5 h at 46°C. Hence, the study implies that considerably lower treatment temperatures than 70°C can be used to reach a sufficient inactivation of bacterial pathogens and potential process indicator organisms such as the ϕX174 phage and raises the question whether PPV is a valuable process indicator organism considering its extreme thermotolerance.

Prevalence of Salmonella serovars, Listeria monocytogenes, and Escherichia coli O157:H7 in Mediterranean ready-to-eat meat products in Jordan

The presence of Salmonella, Listeria monocytogenes, and Escherichia coli O157:H7 in ready-to-eat (RTE) meat products is considered a major concern for food control authorities worldwide. The aims of this study were to determine (i) the prevalence of Salmonella, L. monocytogenes, and E. coli O157:H7 in Mediterranean RTE chicken and beef (CB) products sold in Jordanian restaurants and (ii) the susceptibility of the isolates to antibiotics. A total of 1,028 samples of various types of RTE CB products (550 RTE chicken and 478 RTE beef products) were analyzed by methods described by the International Organization for Standardization followed by molecular confirmation of the isolates. The VITEK2 automated system was used for testing antibiotic susceptibility of the isolates. The overall prevalence of Salmonella serovars in RTE CB products was 0.5%, with 0.8 and 0.2% in RTE chicken and RTE beef, respectively. The overall prevalence of L. monocytogenes in RTE CB products was 2%, with 2.7 and 1.5% in RTE chicken and RTE beef products, respectively. E. coli O157:H7 was not isolated from any of the tested samples. Multidrug-resistant Salmonella and L. monocytogenes isolates were found. The majority of Salmonella isolates were sensitive to most of the tested antibiotics, and all of the isolates were resistant to more than one antibiotic. Similarly, more than 85% of L. monocytogenes isolates were sensitive to nine antibiotics, and the majority of L. monocytogenes isolates were resistant to fosfomycin and oxacillin.