**4. Conclusions**

This study demonstrated the effectiveness of UV-C LED at reducing *Salmonella* on chicken breast samples and common food contact surfaces such as stainless steel and high-density polyethylene. At a minimum, a 1 Log CFU/cm<sup>2</sup> reduction for CB was noted in trials, with up to 3 Log CFU/cm<sup>2</sup> being reached. Further reductions seemed to be limited by the remaining *Salmonella* in the sample being shaded from the UV-C light. This is believed to occur by *Salmonella* sheltering within pores on the CB surface or behind neighboring bacterial cells, absorption of UV light by fluid present on the CB, or both effects simultaneously. *Salmonella* was also reduced on both food contact surfaces, yielding reductions up to 3.5 and 5.2 Log CFU/cm<sup>2</sup> on stainless steel and high-density polyethylene, respectively. An increase in irradiance yielded higher reductions of *Salmonella* on food and food contact surfaces with up to 99.999% in the case of HD.

A clumping cell factor, when large number of bacteria are accumulated on the surfaces, should be considered. Electron micrographs showed formation of layers of *Salmonella* that extended horizontally and accumulated vertically, which could protect cells beneath the top layer.

UV-C LED illumination could be an effective means to deactivate *Salmonella*, especially for nonporous surfaces which are not UV light absorbing.

By doubling the irradiance (mW/cm2) from 50 to 100%, the UV dose (J/cm2) deposited on each surface was also increased or duplicated. Larger UV doses were directly correlated with the *Salmonella* reduction (Log CFU/cm2) attained on each surface tested; however, such reduction did not necessarily double. In other words, *Salmonella* reductions were consistent with the intensity of exposure but not exactly proportional to the increase in the UV dose.

The majority of research studies investigating the effect of UV treatments to control bacterial pathogens from food or food contact surfaces focus on the use of conventional mercury UV lamps. Since the present investigation found the effectiveness of using UV-C LED light for food and environmental surface treatment, findings could be relevant particularly to the poultry industry. The advantages of UV-C LEDs over chemical treatments and conventional mercury UV should be highlighted when considering UV-C LEDs as an alternative for pathogen control. UV-C LEDs do not contain mercury, are environmentally friendly, robust, durable, energy efficient, and their full illumination power can be reached more rapidly, without time delay for warm-up [39].

**Author Contributions:** Conceptualization, A.C. and J.T.; methodology, A.C.; formal analysis, M.S.; investigation, M.F., B.M.; resources, A.C.; writing—original draft preparation, A.C. and J.T.; supervision, A.C.; funding acquisition, A.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Project data has been reported within this manuscript.

**Acknowledgments:** The authors want to acknowledge ICFIE laboratory personnel at Texas Tech University for their support during this research project, and Ilan Arvelo for overseeing some experiments conducted by research students. Special acknowledgment to Bo Zhao from CASM for processing samples and capturing SEM images. Acknowledgement of contribution of effort in no way formally implies endorsement of statements made within this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
