Validation of mathematical models for Salmonella growth in raw ground beef under dynamic temperature conditions representing loss of refrigeration

Fate of Listeria monocytogenes , Pathogenic Yersinia enterocolitica , and Escherichia coli O157:H7 gfp+ in Ready-to-Eat Salad during Cold Storage: What Is the Risk to Consumers?

In this study, we investigated the fate of Listeria monocytogenes , pathogenic Yersinia enterocolitica , and Escherichia coli O157:H7 gfp⁺ inoculated in low numbers into ready-to-eat baby spinach and mixed-ingredient salad (baby spinach with chicken meat). Samples were stored at recommended maximum refrigerator temperature (8°C in Sweden) or at an abuse temperature (15°C) for up to 7 days. Mixed-ingredient salad supported considerable growth when stored at 15°C during shelf life (3 days), with populations of L. monocytogenes , pathogenic Y. enterocolitica , and E. coli O157:H7 gfp⁺ increasing from less than 2.0 log CFU/g on day 0 to 7.0, 4.0, and 5.6 log CFU/g, respectively. However, when mixed-ingredient salad was stored at 8°C during shelf life, only L. monocytogenes increased significantly, reaching 3.0 log CFU/g within 3 days. In plain baby spinach, only pathogenic Y. enterocolitica populations increased significantly during storage for 7 days, and this was exclusively at an abuse temperature (15°C). Thus, mixing ready-to-eat leafy vegetables with chicken meat strongly influenced levels of inoculated strains during storage. To explore the food safety implications of these findings, bacterial numbers were translated into risks of infection by modeling. The risk of listeriosis (measured as probability of infection) was 16 times higher when consuming a mixed-ingredient salad stored at 8°C at the end of shelf life, or 200,000 times higher when stored at 15°C, compared with when consuming it on the day of inoculation. This indicates that efforts should focus on preventing temperature abuse during storage to mitigate the risk of listeriosis. The storage conditions recommended for mixed-ingredient salads in Sweden (maximum 8°C for 3 days) did not prevent growth of L. monocytogenes in baby spinach mixed with chicken meat. Manufacturers preparing these salads should be aware of this, and recommended storage temperature should be revised downwards to reduce the risk of foodborne disease.

Application of Antimicrobial Agents via Commercial Spray Cabinet To Inactivate Salmonella on Skinless Chicken Meat

Salmonella enterica subsp. enterica serovar Typhimurium is a food safety concern for raw poultry products. New and innovative application methods of antimicrobials for the reduction of Salmonella in poultry and poultry products are essential. The aim of this study was to determine the efficacy of three antimicrobial compounds against Salmonella on raw chicken meat when applied individually and in combination using a commercial spray cabinet. Raw chicken thigh meat inoculated with 5 log CFU/g Salmonella Typhimurium ATCC 53647 was passed through a spray cabinet while being sprayed with 5% lauric arginate (LAE), 0.8% vinegar solution (VS), near-neutral electrolyzed water, or deionized water. The following three experiments were carried out: (i) exposure times of 0, 15, 30, 45, and 60 s, (ii) storage at 4°C for 0, 1, 2, and 3 days after a 60-s exposure, and (iii) a combination of treatment with LAE and VS followed by storage at 4°C for 0, 1, 2, and 3 days. Analysis of variance and the Tukey test were used to determine mean significant differences (P < 0.05). The experiment was carried out in duplicate for each replicate (n = 3 × 2). In comparing individual antimicrobials, the 60-s treatment time resulted in the greatest reduction of Salmonella Typhimurium, with LAE achieving the greatest reduction (2.07 log), followed by VS, near-neutral electrolyzed water, and deionized water (0.63, 0.56, and 0.53 log, respectively). After 3 days of storage, LAE significantly (P < 0.05) reduced Salmonella Typhimurium, by 1.28 log. The combination of VS and then LAE resulted in a significantly (P < 0.05) greater reduction than using LAE followed by VS (1.61 and 0.93 log, respectively). The results of this study suggest that LAE is a viable compound to reduce Salmonella Typhimurium on raw chicken meat and that the order of application of antimicrobial agents plays a vital role.

Predictive model for the growth kinetics of Staphylococcus aureus in raw pork developed using Integrated Pathogen Modeling Program (IPMP) 2013

A predictive model was performed to describe the growth of Staphylococcus aureus in raw pork by using Integrated Pathogen Modeling Program 2013 and a polynomial model as a secondary predictive model. S. aureus requires approximately 180 h to reach 5-6 log CFU/g at 10 °C. At 15 °C and 25 °C, approximately 48 and 20 h, respectively, are required to cause food poisoning. Predicted data using the Gompertz model was the most accurate in this study. For lag time (LT) model, bias factor (Bf) and accuracy factor (Af) values were both 1.014, showing that the predictions were within a reliable range. For specific growth rate (SGR) model, Bf and Af were 1.188 and 1.190, respectively. Additionally, both Bf and Af values of the LT and SGR models were close to 1, indicating that IPMP Gompertz model is more adequate for predicting the growth of S. aureus on raw pork than other models.