**4. Conclusions**

In this study, 27 pine honeydew samples showed physicochemical and microscopic characteristics within the legal limits, except for diastase activity, a parameter known to be highly variable depending on many factors. The ability of pine honeydew samples to generate high levels of H2O2 is substantially higher than in other types of honeydew honey, whereas protein content was similar. Furthermore, due to their high polyphenol content, a strong antioxidant activity of honey samples was demonstrated. In addition, various correlations were identified among these parameters.

The antibacterial activity of pine honeydew honey samples was variable and MICs of honey solutions varied from 3.125 to 25% depending on the pathogen. The breakdown of H2O2 by catalase treatment into honey solution resulted in a significant decrease in antibacterial activity. Similarly, the digestion of honey proteins by proteinase K resulted in lower antibacterial efficacy among honey samples, again depending on specific bacteria. Interestingly, the antibacterial activity of proteinase K-treated honey samples against *A. baumannii* was not affected at all. Taken together, these observations sugges<sup>t</sup> multiple underlying mechanisms of antibacterial activity of pine honeydew honeys.

**Supplementary Materials:** The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/foods11070943/s1, Table S1: Full data of each tested honey, Table S2: Correlation coefficient (r, first value) and significance (second value) of physicochemical parameters of pine honey calculated by Spearman's correlation analysis, Figure S1: Sensory three −point scale evaluation of pine honey samples, Figure S2: Protein profile of pine honeydew honey samples (*n* = 27) from Greece, Figure S3: MIC values after proteinase K (MICp) and bovine catalase (MICc) treatment of honey samples.

**Author Contributions:** Conceptualization, D.M., P.G. and E.A.; methodology, D.K., S.G., M.B., J.G. and P.G.; validation, formal analysis, P.G., E.A., M.B., J.G., J.M., E.T., D.M. and T.G.D.; investigation, E.T., F.-P.V., E.S., A.K., D.K., M.D., S.L., I.R. and C.T. (Christina Tsadila); resources, D.M. and E.A.; data curation, P.G.; writing—original draft preparation, D.M., S.G., E.A., T.G.D. and J.M.; writing—review and editing, D.M., S.G., P.G., E.A., T.G.D. and J.M.; supervision, C.T. (Chrysoula Tananaki), S.G., P.G., E.A. and D.M.; project administration, C.T. (Chrysoula Tananaki); funding acquisition, C.T. (Chrysoula Tananaki), P.G., E.A., D.M. and J.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the General Secretariat for Research and Innovation (G.S.R.I.) under the national emblematic action "Honeybee Routes" and partially by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences VEGA 2/0022/22.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
