# Comparison of Volatile Profiles of Meads and Related Uniflorl Honeys: Traceability Markers
## 2 Results and Discussion
### Traceability of Chemical Markers of Botanical Origin and Comparison with Control
Comparison between Volatile Profiles of Honey, Boiled and Not Boiled Meads-Principal Component Analysis (PCA)  
General observation of the volatile profiles demonstrated that the meads contain fewer terpene compounds than honey, but more aliphatic compounds. Depending on the method of preparation, different groups of compounds dominate the final product. Aliphatic acids are more abundant in the boiled meads and more aliphatic esters are present in the not boiled meads. As a result of fermentation, a number of compounds appear in the mead. Among them are mostly esters (DHLLE): 2-phenethyl acetate, ethyl acetate, isoamylacetate, ethyl octanoate, ethyl decanoate, ethyl dodecanoate, ethyl tetradecanoate, ethyl hexadecanoate (HS-SPME), ethyl decanoate, ethyl dodecanoate, ethyl tetradecanoate, ethyl hexadec-9-enoate, ethyl hexadecanoate, ethyl decadecanoate (DHLLE). The findings were similar for aliphatic acids: octanoic acid and decanoic acid (particularly abundant in boiled meads), acetic acid (HS-SPME), and octanoic acid. On the other hand, octadecanoic acid was most abundant in the analyzed honeys and its percentage was usually higher in the not boiled meads in comparison to the boiled ones. Other relevant differences were increases of 2-phenylethanol and 3-methylbutan-1-ol level (HS-SPME), increases of 2-phenylethyland and appearance of tryptophan (DHLLE) in the meads. 2-Phenylethanol and tryptophan are known to derive, respectively, from phenylalanine and tryptophan as _Saccharomyces cerevisiae_ catabolism products [23]. The esters are formed as a result of yeast fermentation and have high impact on the aroma of alcoholic beverages, providing fruity notes. The ester formation depends on different factors, but particularly on the concentration of nitrogen compounds and must solids [24; 25; 26]. Since preparation of boiled meads involves cooking and removal of solid impurities together with coagulated proteins before fermentation, it may be related with lower amounts of ester compounds in the final product. The datasets containing volatile compositions of honey and meads extracts obtained by DHLLE and HS-SPME were subjected to PCA analysis after mean-centering of the data (Figures 4 and 5). In the case of the data obtained for headspace volatiles, the first two factors explained 66.3% (and three 80.1%) of the variance among the samples and in the case of the data obtained for solvent extracts 75.3% (and three 85.5%). In both cases, natural clustering of honey, boiled and not boiled meads was observed regardless of the botanical origin. The variables providing the greatest contribution to the principal components and differentiation of the groups of samples, based on headspace, were: 2-phenylethanol, octanoic acid, benzaldehyde, 3-methylbutan-1-ol (accounting about 43%, 17%, 11% and 8% of PC1), octanoic acid, ethyl decanoate, decanoic acid, ethyl dodecanoate, 3-methylbutan-1-ol (accounting about 39%, 27%, 13%, 7% and 3% of PC2). The variables providing the greatest contribution to the principal components and differentiation of the groups of samples, based on DHLLE extracts, were: ethyl octadecanoate, ethyl hexadecanoate, octadecanoic acid, tricosane (accounting about 45%, 21%, 15% and 13% of PC1). In case of PC2, it was responsible for distinguishing between samples of linden origin from other samples and the major variables accounting for about 66% of PC2 in total were compounds characteristic for linden honey: 4-isopropylcyclohex-1,3-diene-1-carboxylic acid and 4-(2-hydroxy-2-propanyl)cyclohex-1,3-diene-1-carboxylic acid. The samples naturally formed three groups. In the case of DHLLE extracts, octadecanoic acid characterized honeys and ethyl hexadecanoate and ethyl octadecanoate characterized meads. Figure 4: Principal component analysis (PCA) scores (**left**) and loadings (**right**, only first five variables with the highest contributions are shown) plots based on the HS-SPME volatiles extract dataset.