Impact of Storage Conditions on Salmonella enterica and Listeria monocytogenes in Pre- and Post-Printed 3D Food Ink

) of the food ink were measured at the initial and final timepoints. A significant four-way interaction effect was observed between microorganism type (L. monocytogenes/Salmonella), time, temperature, and storage method (capsule/print) (p = 0.014). Significant findings include (1) at -18 °C, concentrations of L. monocytogenes decreased between Day 0 and Day 1, (2) at 20 °C, concentrations of S. enterica were significantly higher in the capsule than in the printed food on Day 1 (p < 0.0001), and (3) at 4 °C, concentrations of S. enterica were significantly higher in the printed food on Day 5 compared to Day 1 (p < 0.0001) with a 0.9 (95% CI: 0.89, 0.91) log increase. In addition, a significant three-way interaction effect was found between microorganism type (yeast/aerobic counts), time, and temperature (p = 0.024). Yeast counts remained steady at all temperatures, while aerobic counts increased at 4 °C. Minimal differences were observed between Listeria and Salmonella and their responses to varying storage conditions over time indicating that storage method and temperature may be less important for a low-water activity product such as protein cookie food ink.