**4. Conclusions**

In terms of this research, the volatile fraction of 25 honey samples from indigenous monofloral autumn heather honey was investigated. The most important compounds indicating the botanical origin of this honey are benzaldehyde, 3,5,5- trimethylcclohex-2-en-1-one, 2,6,6-trimethylcyclohex-2-ene-1,4-dione, 2-hydroxy-3,5,5- trimethylcyclohex-2-en-1-one, 2,6,6-trimethylcyclohexa-1,3-diene-1-carbaldehyde, 4- methoxybenzaldehyde, 3,4,5-trimethylphenol, 1,1,5-trimethyl-1,2-dihydronaphthalene, (E)-1-(2,6,6-trimethylcyclohexa-1,3-dien-1-yl)but-2-en-1-one, (E)-1,6,6-trimethyl-7-(3- oxobut-1-en-1-yl)-3,8-dioxatricyclo[5.1.0.02,4]octan-5-one, ethyl 4-methoxybenzoate, (E)-4-(2,6,6-trimethylcyclohexa-1,3-dien-1-yl)but-3-en-2-one, and 4,6,10,10-tetramethyl-5-oxatricyclo[4.4.0.01,4]dec-2-en-7-ol. These compounds were identified in almost all samples in significant concentrations, with few exceptions. Obviously, the assessment of a quantitative reference value is very difficult to be set due to endogenous or exogenous factors. Some of the above volatiles were previously reported in heather honey. However, the autumn heather honey from *E. manipuliflora* has not been previously investigated. The main volatile compounds were analyzed using a well-suited RSM methodology and predictive models were created to evaluate each volatile separately. Moreover, preconized optimum conditions (A: 60 ◦C B: 30 min C: 15 min D: 100 rpm E: 6 mL F: 1:3 (*v*/*w*)) were proposed for all dominant volatiles. In addition, a validation set amplified the results by responsiveness. This study reinforces the more reliable characterization of the volatile profile of autumn heather honey, aiming at the assessment of its botanical origin. In addition, it investigates the most common isolation factors, in terms of their ability to isolate their aroma fraction with relative abundance.

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

**Funding:** This research was partly financed by the Emblematic Action "The Honeybee Roads" of the Greek Public Investments Program (P.I.P.) of General Secretariat for Research and Technology (GSRT) (project code: 2018 ΣE01300000).

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

**Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank the Laboratory of Sericulture and Apiculture of Aristotle University of Thessaloniki and the Laboratory of Analytical Chemistry of the Mediterranean Agronomic Institute of Chania (M.A.I.Ch.) for verifying the botanical origin of the samples.

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