Posts Tagged “bagged salads”
There have been recent E. coili outbreaks associated with leafy greens such as lettuce and spinach and researchers in Tennessee, along with scientists at the U.S. Centers for Disease Control and Prevention (CDC) have released a study published in Foodborne Pathogens and Disease about the risk of E. coli O157:H7 in bagged salads. An estimated 63,000 STEC O157 infections occur every year in the United States.
A look at an outbreak of STEC O157 that was associated with bagged salads in institutional settings has been taken by researchers. The outbreak was in schools, and the case-control study was made up of controls matched by school and grade.
Seventeen patients from three states were identified. The median age of a cases was 23 years. 76 percent of the cases were female. Six people were hospitalized and two died in this particular outbreak. The illness onset dates ranged from April 29 to May 12, 2012.
The analytical epidemiology analysis identified a single significant food service exposure: lettuce provided by a school cafeteria. The bagged salad was traced back to a single facility. Growing areas were scheduled for more inspection during the upcoming growing season to see if a source of the contamination, whether runoff from animals farms, problems in harvest or shipping, or some other source could be found.
A new study in the Journal of Food Protection’s February issue details that temperature abuse during commercial transport and retail sale of leafy greens negatively impacts both microbial safety and product quality. Consequently, the effect of fluctuating temperatures on Escherichia coli O157:H7 and Listeria monocytogenes growth in commercially-bagged salad greens was assessed during transport, retail storage, and display.
Thus, proper tempertures in-transit of bagged salads is very important.
Over a 16-month period, a series of time-temperature profiles for bagged salads were obtained from five transportation routes covering four geographic regions (432 profiles), as well as during retail storage (4,867 profiles) and display (3,799 profiles). Five different time-temperature profiles collected during 2 to 3 days of transport, 1 and 3 days of retail storage, and 3 days of retail display were then duplicated in a programmable incubator to assess E. coli O157:H7 and L. monocytogenes growth in commercial bags of romaine lettuce mix.
Microbial growth predictions were validated by comparing the root mean square error (RMSE), bias, and the acceptable prediction zone between the laboratory growth data and model predictions. Simulations were performed to calculate the probability distribution of microbial growth from 8,122,127,472 scenarios during transport, cold room storage, and retail display.
Using inoculated bags of retail salad, E. coli O157:H7 and L. monocytogenes populations increased a maximum of 3.1 and 3.0 at retail storage. Both models yielded acceptable and biases within the acceptable prediction zone for E. coli O157:H7.
Based on the simulation, both pathogens generally increased <2 log CFU/g during transport, storage, and display. However, retail storage duration can significantly impact pathogen growth. This large-scale U.S. study—the first using commercial time/temperature profiles to assess the microbial risk of leafy greens—should be useful in filling some of the data gaps in current risk assessments for leafy greens.