## 3 Results and Discussion
### Dynamic Changes in Volatile Flavor Compounds
Statistical analysis showed that 20 out of 24 ketone compounds had statistically significant changes (\(p<0.05\)), reflecting active microbial metabolism during fermentation and further demonstrating the key role of microbes in flavor substance formation. Similarly, esters displayed significant alterations, emphasizing the impact of microbial activity on the formation of flavor compounds. Analyzing the changes in 61 ester compounds, various esters showed significant changes before and after fermentation. Ethyl Decanoate increased from 0.06 \(\upmu\)g/L before fermentation to 162.31 \(\upmu\)g/L after fermentation, contributing significantly to post-fermutation flavor. Ethyl Hexanoate increased from 0.10 \(\upmu\)g/L to 160.55 \(\upmu\)g/L, enhancing the fruity and sweet aromas of the juice. Octyl Acetateincreased from 0.35 \(\upmu\)g/L to 61.37 \(\upmu\)g/L, adding to the overall fruity aroma. 1-Methylbutyl Butanoate increased from 0.38 \(\upmu\)g/L to 69.98 \(\upmu\)g/L, and Ethyl Hexadecanoate increased from 0.56 \(\upmu\)g/L to 67.52 \(\upmu\)g/L, both contributing to the complex aroma profile. Ethyl Benzenepropanoate saw a significant increase from 0.86 \(\upmu\)g/L to 2088.29 \(\upmu\)g/L, with its floral and sweet aromas enhancing the overall flavor. Ethyl 4-Methylpentanoate increased from 0.59 \(\upmu\)g/L to 492.01 \(\upmu\)g/L, adding significantly to the fruity aroma. Geranyl Formate increased from 1.16 \(\upmu\)g/L to 138.01 \(\upmu\)g/L, known for its strong fruity aromas. Pentyl butanoate increased from 1.22 \(\upmu\)g/L to 279.13 \(\upmu\)g/L, adding banana and fruit aromas to the juice. 1-Isothiocyanato-2-Butene increased from 2.56 \(\upmu\)g/L to 311.28 \(\upmu\)g/L, and Butyl Butanoate increased from 12.14 \(\upmu\)g/L to 233.19 \(\upmu\)g/L, both significantly enhancing the aroma. 3-Methylbutyl Butanoate increased from 12.74 \(\upmu\)g/L to 1406.55 \(\upmu\)g/L, adding to the rich, fruity, and sweet aromas. Ethyl Butanoate increased from 189.73 \(\upmu\)g/L to 1056.87 \(\upmu\)g/L, contributing to the rich aroma profile. In contrast, some ester compounds showed a decrease during fermentation. (E)-Methyl 3-Hexanoate, Ethyl Tiglate, and Methyl 2-Octynoate saw reductions in their concentrations, indicating changes in the microbial metabolic pathways during fermentation and affecting the overall flavor profile. Most ester compounds significantly increased during fermentation, with the total ester content rising from 1190.37 \(\upmu\)g/L to 10,850.27 \(\upmu\)g/L. The substantial increase in ester compounds results from microbial esterification processes during fermentation, during which microbes convert alcohols and acids into esters, enhancing the juice's fruity aroma. Significance analysis showed that most of the 61 ester compounds had statistically significant changes (\(p<0.05\)), reflecting active microbial metabolism during fermentation and further demonstrating the key role of microbes in flavor substance formation. High-content ester compounds formed during fermentation, such as hexyl acetate and ethyl decanoate, contributed significantly to the overall aroma and flavor of the fermented product. During the spontaneous fermentation of Jerusalem artichoke juice, significant changes in various compounds were observed, reflecting complex biochemical reactions and microbial activities. Microbial diversity played a crucial role, with initial stages dominated by _Flavobacterium_, _Splingomonas_, and _Luteomonas_ breaking down complex substances like inulin, leading to flavor development [56]. As fermentation progressed, _Lactobacillus_ and _Pedicoccus_ became dominant, consuming organic acids and synthesizing flavor compounds [57; 58]. Fungal shifts from _Geosmithia_ and _Alternaria_ to _Pichia_ and _Penicillium_ also contributed significantly, particularly in producing alcohols and esters [59].