# Construction of IsoVoc Database for the Authentication of Natural Flavours
## 4 Conclusions  
The falsification of natural flavours by either dilution, mixing with synthetic compounds, or false declaration of origin of natural ingredients creates a demand to control their authenticity. HS-SPME-GC-C-IRMS analysis of volatile fruit compounds is a valuable tool for differentiating between synthetic and naturally occurring aromas and, together with a database containing flavour compounds with well-defined origins, can be used for authenticity assessment. However, selecting suitable reference samples that need to be analysed to create such a database is critical. When comparing distillates with freshly prepared fruit juice, differences in isotope values in some of the investigated VOCs in apple and strawberry samples is observed. We needed to include both distillates and raw fruit samples to obtain maximal natural stable isotope variability of selected VOCs. A database of \(\delta^{13}\)C values for 39 aroma compounds present in fruit and distillate samples (apples, strawberries, blueberries, pears, raspberries, peaches, and sour cherries) and 31 VOC of synthetic origin were established. This study proves that samples of apple and strawberry are sufficient for database construction regarding the variability in \(\delta^{13}\)C values. The data are comparable with literature data, and despite some overlap between the natural and synthetic range of values, the method allows the successful separation of 25 of the 33 target VOCs. When testing commercial fruit distillates, the results show possible falsification for several fruit aroma compounds. However, extensive testing of flavoured products on the market is necessary to determine the extent of adulteration and evaluate the usefulness of IsoVoc for different flavoured products. Moreover, the development of an HS-SPME-GC-IRMS method for \({}^{2}\)H/\({}^{1}\)H ratio determination of fruit VOCs is required to upgrade the existing database, which could be more successfully used in fruit flavour authenticity studies. Conceptualisation, L.S. ; methodology, L.S., E.Z., D.K. ; software, L.S. and M.S. ([PERSON]); validation, L.S. ; formal analysis, L.S. ; investigation, L.S. ; resources, N.O., J.H., N.C.W., D.K., M.S. ([PERSON]); data curation, L.S. ; writing--original draft preparation, L.S. ; writing--review and editing, N.O. ; visualisation, L.S., M.S. ([PERSON]); supervision, N.O. ; project administration, N.O. ; funding acquisition, N.O. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. **Data Availability Statement:** No data available. The research was performed in the framework of the Slovenian Smart Specialisation Program: Food for Future, financially supported by the Ministry of Education, Science and Sport under GA no. C3330-16-529005 and takes part in MASSTWIN (H2020, GA no. 692241), ERA Chair ISO-FOOD (FP7, GA no. 621329) projects and P1-0143 program financially supported by Slovenian Research Agency. The authors would like to thank [PERSON] for technical support. The authors declare no conflict of interest. Supplementary data to this article can be found in Table A1.