**4. Conclusions**

Nowadays, consumers are more interested in sustainable food production due to the growing awareness of environmental pollution and the large amount of waste generated during conventional food processing. Moreover, consumers are more oriented toward the healthy aspects of food. Given that the food industry is facing the handling of thousands of tons of kiwi byproducts discarded each year, it is necessary to consider kiwi byproducts as good sources of functional ingredients. The present study is based on the formulation of multifunctional bio-ingredients based on kiwifruit pomace and peels, various flours, and cultures of lactic acid bacteria. These powders were obtained by freeze-drying and characterized in terms of phytochemical content, bioaccessibility of flavonoids after digestion, color, morphology, and structure, as well as the viability of *Lacticaseibacillus casei* 431® cells. In order to test the potential for food functionalization, the powder was added to protein bars, and the products were subsequently characterized in terms of added value. The results confirm that kiwi pomace has the potential to be used as a functional food ingredient with a beneficial effect on consumer health and a prebiotic effect on lactic acid bacteria. The results are also promising for the utilization of natural antioxidants in combination with lactic acid bacteria in order to develop multifunctional ingredients for food, pharmaceutical, and cosmetic applications.

**Author Contributions:** Conceptualization, N.S.; methodology, N.S. and S, .-A.M.; software, S, .-A.M.; validation, S, .-A.M., A.C., G.R. and N.S.; formal analysis, G.-I.I.; investigation, G.-I.I.; resources, G.R. and N.S.; writing—original draft preparation, G.-I.I.; writing—review and editing, S, .-A.M., G.R., A.C. and N.S.; visualization, N.S.; supervision, S, .-A.M. and N.S.; project administration, N.S.; funding acquisition, G.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financed by the Internal Grant financed by Dunarea de Jos University of Galati, Romania, contract no. 3637/30.09.2021.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article.

**Acknowledgments:** The Integrated Center for Research, Expertise and Technological Transfer in Food Industry is acknowledged for providing technical support.

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