## 3 Results and Discussion
### Classification Comparison of Volatile Compounds in Rose Beverage  
A comparative analysis was conducted on the heatmap of volatile organic compounds in rose beverages after fermentation. The heatmap provides a clear visualization of the volatile components. Significant variations in alcohols, esters, aldehydes, ketones, acids, phenols, and terpenes were identified, likely contributing to the flavor differences. In all samples, alcohols were the dominant class of flavor compounds, which was an important contributor to the fragrance of rose, and was also the highest content of aromatic compounds [54]. Despite the involvement of S. cerevisiae in the SFR and LSFR fermentations, ethanol was not detected. This absence may be attributed to its conversion into ethyl esters by the microorganisms [55]. Following fermentation, the content of inherent alcohols such as citroncellol (3,7-dimethyl-6-octen-1-ol), linalool (3,7-dimethylocta-1,6-dien-3-ol), and geraniol ((E)-3,7-dimethylocta-2,6-dien-1-ol) decreased in the _S. cerevisiae_ monoculture sample (SFR), while their types and content significantly increased in the samples associated with LAB fermentation (LFR and LSFR). This suggests that the presence of LAB is conducive to enhancing the alcohol-derived flavor characteristics of the rose beverage. Furthermore, LAB fermentation can also promote the conversion of certain low-abundance alcohols, including benzyl alcohol, 1-nonanol (nonan-1-ol), 2-undecanol (undecan-2-ol), 2-nonanol (nonan-2-ol), and 1-hexanol (hexan-1-ol). Benzyl alcohol, 1-nonanol, and 1-hexanol have been identified as critical volatile organic compounds influencing the flavor profiles of various fermented products, such as Pu'er tea [56], fermented oat beverage [57], and greenage wine [58]. The increase in these flavor compounds may be due to the hydrolysis activity of \(\beta\)-glucosidase produced by LAB [59]. This accumulation could contribute a richer aroma profile, including floral, fruity, and sweet notes, to the fermented rose beverages. Interestingly, the content of phenylethyl alcohol increased significantly in all fermented samples, with increases of 10.06-fold in LFR, 5.12-fold in LSFR, and 5.63-fold in SFR compared to the UFR. Phenylethyl alcohol is a key floral aroma compound and one of the most abundant aromatic alcohols in rose [60]. It is synthesized from L-phenylalanine via aromatic amino acid decarboxylase or aminotransferase, followed by reduction by phenylealdehyde reductase. Despite the presence of LAB, the increase in phenylethyl alcohol content in the LSFR sample was lower than in LFR, which might be a result of synergistic interactions influencing aromatic compound generation during the co-fermentation process. Figure 3: (**A**) Venn diagram. The numbers represent the quantities of volatile compounds; (**B**) Principal component analysis (PCA) of 245 volatile compounds in four rose beverage samples (\(n=4\)). UFR: rose beverage without fermentation; LFR: rose beverage fermentation by \(L\). _plantarum_; SFR: rose beverage fermentation by _S. cerevisiae_; LSFR: rose beverage fermentation by _L. plantarum_ and _S. cerevisiae_ collectively. Esters, typically formed through the esterification of short-chain acids with alcohols, contribute floral and fruity notes to rose beverages and can mitigate the harshness of fatty acids and the bitterness of amino acids [61]. In the present study, most ester compounds in the LAB monoculture sample (LFR) did not show significant changes, with the exception of 2-phenylethyll acetate, methyl salicate (methyl 2-hydroxybenzoic), pentanoic acid, (3,7-dimethyl-6-ocenyl) 4-methylpentanoate, and 2-isopropyl-5-methyl-4-hexen-1-yl acetate. Methyl salicate, characterized by a wintergreen aroma, can be released from glucoside precursors through glucosidase activity [62]. Several studies have reported that L. plantarum can produce glucosidase [63], suggesting that the increased content of methyl salicate in LFR samples is closely linked to this enzymatic hydrolysis.