## 3 Results and Discussion
### Volatile Profiling Using HS-SPME/GC-MS  
Our investigation employed qualitative and quantitative analyses using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to evaluate the volatiles demonstrated using the electronic nose technique comprehensively. The findings presented in Tables S2 and 4 encompassed the identification of 80 volatile compounds with distinct aroma profiles in bicultured samples (JLcAp, JLhAp, JLpAp) and the control (JCON). Quantitatively, the compounds exhibited concentrations of 522.38, 599.85, 568.49, and 611.07 ng/100 g in JLcAp, JLhAp, JLpAp, and JCON, respectively. Esters predominated, followed by acids, alcohols, and aldehydes. The significantly higher total volatile concentration in the control sample could be attributed to the combined effect of alcohol and acids, suggesting inefficient bioconversion of these volatiles in the unrefmented sample, resulting in residues. This also implicated the most ester formation in the bicultured samples largely due to the use of these acids and alcohols for esterification by lactic and acetic acid bacteria activities. The results showed significant agreement with previous research by [PERSON] et al. [17] and [PERSON] et al. [30]. Maximum concentrations of esters, acids, alcohols, and aldehydes were evident in JLcAp (522.40 ng/100 g), JLhAp (599.84 ng/100 g), JLpAp (568.50 ng/100 g), and JCON (574.87 ng/100 g). Benzeneacetaldehyde emerged as the most abundant aldehyde, particularly in JLhAp (92.56 ng/100 g), exhibiting a decreasing trend in JLcAp and JLpAp, with significant differences (\(p<0.05\)), reducing in JCON to 1.36 ng/100 g. A contrasting pattern was observed for 2,4-dimethyl benzaldehyde, with concentrations of 0.52%, 2.11%, and 0.52% in JLcAp, JLhAp, and JLpAp, respectively, from their initial value of 4.25% (JCON). The synergistic interactions among bicultures led to the production of specific aldehydes, such as benzaldehyde, which are absent in JCON. Moreover, 2,4-dimethyl-benzaldehyde and benzeneacetaldehyde were synthesized by all bicultures, potentially contributing to desirable fruity sensory notes [46]. The observed bioconversion of aldehydes was attributed to the auto-oxidation of unsaturated fatty acids, as suggested by [PERSON] et al. [15]. In the unrefmented sample, JCON, seventeen volatile acid compounds were identified. However, the bicultured Junzao juibue pures exhibited a reduced concentration, with 7 to 10 acids identified. Isobutyric acid and butanoic acid were initially reported by [PERSON] et al. [47] in _Zizizplus jujuho_ cv. Junzao were exclusively detected during the red maturity stage. Dodecanoic, heptanoic, hydrocinnamic, n-decanoic, and octanoic acid consistently emerged in the bicultured and unrefmented samples. Among the nineteen acids profiled, 2-octenoic and 3-decenoic acids were remarkably absent in JCON and manifested after the lactic-acetic acid fermentation in all bicultures of JLcAp and JLhAp only. The decline in acid content in the unrefmented sample provided insights into potential alcohol and acid utilization during processes like esterification, contributing to the formation of flavoring compounds. A notable disparity was observed in esters, with 17 to 24 identified in the bicultured samples compared to 4 in JCON. On average, this represented a significant 42% increase in ester formation in the fermented samples, with concentrations of 220.86 ng/100 g (JLcAp), 210.71 ng/100 g (JLhAp), 271.22 ng/100 g (JLpAp), and 22.75 ng/100 g (JCON). The diversity in ester volatiles highlighted the distinctive contributions of specific strains in synergistic interactions, resulting in the formation of uncommon volatiles. This diversity may account for the heightened fruity, floral, and delightful characteristics of bicultured juibue pures compared to JCON.