## 2 Results and Discussion
### Volatilome of Different Palm Date Products
Subsequently, in fermented products such as alcohol and vinegar, many compounds are lost due to the fermentation process, which leads to a decrease in the volatiles characteristic of fruit by converting these into other chemical classes such as esters and volatile acids. In general, higher values of ethanol and acetic acid are observed due to the fermentation process in which AAB converts glucose into ethanol and then into acetic acid [21]. The high percentage of esters in this matrix derived from the condensation between acetic acid and alcohol compounds, previously increased in alcoholic fermentation. During the aging of fermented beverages, due to alcohol fermentation and the reaction of acids with alcohols, the last ones go against a gradual decrease, converting into esters like isoamyl acetate, 2-phenylethyl acetate, and diethyl succinate [22]. As acidification progresses, acetic acid bacteria metabolize other alcohols, converting them into their corresponding acids. This process leads to a decrease in 3-methyl-1-butanol, 2-methyl-1-butanol, and 1-hexanol, while octanoic, decanoic, and hexanoic acids increase, as shown in Figures 3 and 4. The heatmap in Figure 4 visually highlights the volatilome evolution at the different stages of production of palm date products. Based on Euclidean distances, the data are grouped into two hierarchical clusters: one containing fruit and juice and another with alcoholic and vinegar. Different colors indicate the significance of chemical compounds, with yellow representing a lower and red indicating higher abundance of volatile compounds. The relative amount of volatile compounds varies according to the fermentation process, showing a gradual  
Figure 3: Comparison of volatile normalized area response of different matrices analyzed by HS-SPME-GC-MS.  
increase from fruit (yellow) to juice and finally to vinegar. Acidification decreases ethyl esters due to hydrolysis, influenced by acidification duration and bacteria used [23]. Acetoin (3-hydroxy-2-butanone), considered one of the most aroma-active compounds, exists in some foods, especially in vinegas as a metabolite produced by _Lactobacillus_ and _Acetobacter_ during acetic acid fermentation [24]. Its presence can impart buttery, fruity, or caramel notes, adding depth to the sensory profile of the vinegar. However, an excess of acetoin may indicate incomplete fermentation or a suboptimal production process, negatively impacting the vinegar's quality. This compound was evaluated first because its presence is an indication of authenticity; second, because its concentrations give us indications about the characteristic and type of products. Date vinegar presents a significantly high concentration of acetoin (855 \(\pm\) 150 mg/L) that is an important aromatic compound produced during acid fermentation by bacteria such as _Lactobacillus_ and _Acetobacter_. However, unlike wine vinegar in which the determination of acetoin is used for authenticity and quality and its content should be between 100 mg/L and over 400 mg/L, no reference is reported in the literature about the acetoin amount in date vinegar [25; 26]. The production of acetoin is influenced by the combinations of bacterial strains used, which can vary among different date fermented beverages. Additionally, the oxidation of 2,3-butanediol by _Acetobacter_ contributes to the high acetoin content in date vinegar [27]. In support of this relationship, a negative correlation of \(-0.453\) was observed between 2,3-butanediol and acetoin in the analyzed samples. Although moderate in strength, this inverse association suggests a potential metabolic interconversion between the two compounds.