**5. Conclusions**

The selected Central Composite design and response surface methodology were effective tools to optimize and study the effects of LA and UV-C parameters on the *L. monocytogenes* and LAB reduction in vacuum packed beef. The combined application of LA and UV-C radiation under the tested conditions proved to be a useful strategy to reduce L. *monocytogenes* and LAB population in meat without significantly affecting meat color. The treatment had an effect over time by preventing *L. monocytogenes* growth and delaying LAB growth. The latter might have an impact on vacuum beef shelf life. The maximum reduction on *L. monocytogenes* obtained without significant changes in color was 1.55 log CFU/g. Considering that the usual amount of *L. monocytogenes* in fresh meat is low, this level of reduction is significant for meat safety purposes.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/foods10061217/s1, Table S1: Central composite experimental design matrix with L\*, a\* and b\* values for beef samples.

**Author Contributions:** Conceptualization, G.B. and C.R.; methodology, G.B. and C.R.; formal analysis, G.B., S.R. and J.R.; investigation, G.B., S.R. and J.R.; resources, C.R.; data curation, C.R.; writing— original draft preparation, C.R. and G.B.; writing—review and editing, C.R. and G.B.; supervision, C.R.; project administration, C.R.; funding acquisition, C.R. All authors have read and agreed to the published version of the manuscript.

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

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors thank Santiago Luzardo from INIA (Tacuarembó, Uruguay) for support for color measures, Eng. Alvaro Irigoyen and Eng. Juan Sanchez (Facultad de Ingeniería– UdelaR) for support with UV-C lamp intensity measures.

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