@article{walker_sun_lau_phebus_subbiah_thippareddi_2024, title={Modeling the growth/no growth response of Non-O157 Shiga toxin-producing<i> Escherichia</i><i> coli</i> to temperature, pH and water activity}, volume={202}, ISSN={["1096-1127"]}, url={https://doi.org/10.1016/j.lwt.2024.116292}, DOI={10.1016/j.lwt.2024.116292}, abstractNote={The objective of this study was to model the effect of temperature, pH and water activity (aw) on the growth/no growth response of non-O157 Shiga toxin-producing E. coli (STEC). A cocktail of six-serogroup STEC was inoculated into brain heart infusion broth (BHI) with 48 combinations of different pH and aw, and the inoculated medium was incubated at one of ten temperatures. After 62 days of incubation, growth was determined by turbidity and plating on tryptic soy agar. Binary data (0 [no growth] or 1 [growth]) were fitted into a nonlinear logistic regression and the parameters were estimated. The model was validated with independently produced data from seven serogroups of non-O157 STEC, a cocktail of E. coli O157:H7, and two panels of six-serogroup of STEC. The non-O157 STEC did not grow at temperatures ≤ 6 °C and ≥ 47 °C, and the highest tolerance to pH and aw occurred at 25 °C. Although slight difference in the growth/no growth response was observed among different groups of STEC, the developed model can be applied to all the STECs with an average concordance of 92.3%. This work provides valuable insight into the growth/no-growth response of STEC under various environmental conditions.}, journal={LWT-FOOD SCIENCE AND TECHNOLOGY}, author={Walker, Lin and Sun, Shengqian and Lau, Soon Kiat and Phebus, Randall K. and Subbiah, Jeyamkondan and Thippareddi, Harshavardhan}, year={2024}, month={Jun} }
 @article{walker_sun_thippareddi_2023, title={Growth comparison and model validation for growth of Shiga toxin-producing Escherichia coli (STEC) in ground beef}, volume={182}, ISSN={["1096-1127"]}, url={https://doi.org/10.1016/j.lwt.2023.114823}, DOI={10.1016/j.lwt.2023.114823}, abstractNote={The aim of this study was to compare the growth of non-O157 Shiga toxin-producing Escherichia coli (STEC) with E. coli O157:H7 in ground beef and modified Tryptic Soy Broth (TSB). Additionally, the performance of three available models (ComBase, Huang et al. model, and Cepeda et al. model), for predicting STEC growth in ground beef was evaluated. To achieve this, eleven groups of STEC, including E. coli O157:H7, were inoculated into irradiated ground beef (7% or 27% fat) or modified TSB, and then subjected to programmed water baths to follow time-varying sinusoidal temperature profiles for 300 h (low temperature, 5–15 °C) and 25 h (high temperature, 10–40 °C). The growth data of STEC in ground beef were fitted to the three models, and model performance indices such as mean relative percentage error (MRPE), mean absolute relative error (MARE), root mean squared error (RMSE), bias factor (BF) and accuracy factor (AF) were calculated to assess their accuracy in predicting STEC growth. The study found that the growth of non-O157 STEC was similar to that of E. coli O157:H7, indicating that growth models for E. coli O157:H7 can be used to predict the growth of non-O157 STEC. The fat content did not significantly affect STEC growth in ground beef. Among the three models tested, the Huang et al. model underestimated the growth of all STEC in ground beef, with an RMSE of up to 2.14 log CFU/g. The ComBase model also under-predicted STEC growth in ground beef at high temperatures (10–40 °C) and could not predict growth at temperatures below 10 °C, where STEC might grow slowly. In contrast, the Cepeda et al. model accurately predicted STEC growth in ground beef and is considered an conservative growth model for STEC in commercial ground beef products. In summary, this study provides important insights into the growth of non-O157 STEC and E. coli O157:H7 in ground beef and their modeling, which can aid in predicting the safety of commercial ground beef products.}, journal={LWT-FOOD SCIENCE AND TECHNOLOGY}, author={Walker, Lin and Sun, Shengqian and Thippareddi, Harshavardhan}, year={2023}, month={Jun} }
 @article{alig_anderson_malheiros_lowery_walker_2023, title={Impact of Stocking Densities on the Microbiota of the Cloaca, Eggshell, and Egg Content of White Egg Layers in Colony Cages}, url={https://doi.org/10.3390/poultry2030031}, DOI={10.3390/poultry2030031}, abstractNote={Food safety is a major concern for commercial poultry producers and consumers. Currently, there is also pressure from retailers and legislators to increase the space per hen in cages. Five different density treatments consisting of six (208 in2/bird), nine (139 in2/bird), twelve (104 in2/bird), fifteen (83 in2/bird), and eighteen birds (69 in2/bird) per cage were examined in colony cage environments. Microbiological tests were performed at 39, 55, and 68 weeks of age. The populations of total aerobic bacteria; E. coli/coliform; Enterobacteriaceae; and yeasts and molds from an eggshell rinse, egg content, and cloacal swabs were enumerated. The prevalence of Salmonella spp. in these samples was also monitored. Overall, no bacteria were detected in any of the egg content, and there were no differences (p > 0.05) between treatments for the shell rinse. Stocking density did not influence the eggshell microbiota of the hens. Hens housed at 104 in2 per hen showed higher levels of total aerobic bacterial counts from the cloaca compared to hens at 208 in2 and 69 in2 per hen. Hens housed at 139 in2 per hen had the highest level of cloacal molds. This research demonstrates that stocking density does not influence eggshell microbiota or Salmonella contamination of the eggshell or cloaca, thereby indicating that allowing more space per hen will not positively or negatively affect the prevalence or concentration of foodborne pathogen-associated bacteria in or on the eggs.}, journal={Poultry}, author={Alig, Benjamin and Anderson, Kenneth and Malheiros, Ramon and Lowery, Justin and Walker, Lin}, year={2023}, month={Sep} }
 @article{sun_anderson_walker_thippareddi_2022, title={A comparative study for determination of thermal inactivation parameters of Salmonella in high gel and standard egg white powder using three methods}, volume={172}, ISSN={["1096-1127"]}, DOI={10.1016/j.lwt.2022.114185}, journal={LWT-FOOD SCIENCE AND TECHNOLOGY}, author={Sun, Shengqian and Anderson, Nathan M. and Walker, Lin and Thippareddi, Harshavardha}, year={2022}, month={Dec} }