**4. Conclusions**

The fluorescence intensity measurement of microstructure images can be an indicator of the TPC and AC of the samples. Microstructure images showed that, with intense treatment, there is leaching of the polyphenolic substances into the milk because of cell structure breakage. For the microbiological inactivation, the results showed that the pomace had antimicrobial properties, but they were partially masked by the interactions between milk proteins and the polyphenols available, and that higher levels of inactivation were achieved at high pressures and long treatment times. The RSM results showed that TPC and AC were only affected by the pomace concentration added to the milkshake, because the high pomace concentration and the polyphenol–milk protein interactions could mask the effect of pressure and time.

Although the efficiency of HPP inactivation on *L. monocytogenes* has been proven, further research is needed for products without milk to study the effect of chokeberry pomace treated with HPP on the TPC, AC, and microbial inactivation.

**Author Contributions:** Formal analysis, D.R.; Investigation, E.D.-S.; Methodology, A.M.; Supervision, A.Q.; Writing–review & editing, I.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-Spain) through the "BERRYPOM. Adding value to processing waste: innovative ways to incorporate fibers from berry pomace in baked and extruded cereal-based foods" project included in the ERA-NET-SUSFOOD program, to Spanish Ministry of Science, Innovation and Universities through project AGL2017-86840-C2-2-R, and to FEDER funds from EU.

**Acknowledgments:** The authors are grateful to Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-Spain) for financial support through the BERRYPOM. Adding value to processing waste: innovative ways to incorporate fibers from berry pomace in baked and extruded cereal-based foods project included in the ERA-NET-SUSFOOD program, to Spanish Ministry of Science, Innovation and Universities through project AGL2017-86840-C2-2-R, and to FEDER funds from EU. They would also like to thank Phillip John Bentley for his assistance in correcting the manuscript's English.

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