## 3 Results and Discussion
### Total Polyphenol, Anthocyanin, and \(\alpha\)-Amino Nitrogen and Protein Content  
Total polyphenols analysis showed no statistically significant differences between the investigated samples (Figure 5). Reported values were 4617 \(\pm\) 664 and 4301 \(\pm\) 494 mg GAE/L for C and S samples, respectively. The results were 44.6% and 34.7% higher than the median of the maximum values reported in literature for red wines (3192 mg GAE/L) [29]. This observation highlights differences in the nature and composition of the liqueuv, which, beside red wine, also contain other ingredients like red fruits juice, which could have increased the polyphenols value. In a previous study, the total phenolic compounds content of red fruit juices, ranged from 1234.27 mg GAE/L to 6361.89 mg GAE/L for red raspberry and elderberry, respectively [30]. The high internal variability observed in the cellar-aged liqueur sample could indeed be attributed to oxidative degradation affecting sample homogeneity. Oxidation is a common issue in wine and liqueur storage, leading to the degradation of phenolic compounds such as anthocyanins, which are responsible for colour and stability. A study on the stability of anthocyanins highlights that their degradation is influenced by factors such as pH, light, temperature, and oxygen exposure [31]. The presence of oxygen, in particular in the cellar-aged sample, could have led to a more pronounced oxidative degradation, affecting the colour and quality of the beverage. This degradation could have resulted in uneven distribution of these oxidated compounds, causing variability within the cellar-aged subsamples. Therefore, the observed variability in the cellar-aged liqueur sample is likely due to oxidative degradation processes affecting the homogeneity of anthocyanins and other phenolic compounds. The anthocyanin content of the liqueuv differed significantly (\(p<0.01\)) between the two treatments (Figure 5), with the undersea sample being the richer (61.3 \(\pm\) 3.4 mg/L), indicating a lower degradation of these chemical species in the undersea-aged sample compared to the cellar-aged sample, which had a  
Figure 5: Concentrations of total polyphenols, anthocyanins, free alpha-amino nitrogen, and total proteins in underwater-aged and cellar-aged liquors. Different letters indicate statistically significant differences (\(p\leq 0.05\)). lower value (56.5. \(\pm\) 2.0 mg/L). According to [PERSON], et al. [32] the typical concentrations of free anthocyanins in young red wines range from 500 mg/L to 2000 mg/L. However, another study reported that the anthocyanin concentration in red wines can range between 90 and 400 mg/L [33]. Additionally, other literature data report that the total anthocyanin content in berry juice ranged from 205.98 mg/L to 4188.63 mg/L, depending on the type of red fruits [30]. Although the measured anthocyanin content in our study is lower than these reported ranges, this discrepancy likely reflects the specific liqueur recipe and the composition of the raw materials, aligning more closely with the findings of [PERSON] et al. [33]. However, the quinones derived from the oxidation of anthocyanins and phenolic compounds present in the liqueurs could have immediately reacted both reversibly and irreversibly with the free amino acids and proteins in the wine, leading to their precipitation [34]. It is well established that the formation and activity of quinone-amino acid/protein conjugates can influence the colour, taste, and aroma of food products, particularly liqueurs [35]. Therefore, although the difference between the two samples remains negligible, the statistically significant higher content of free alpha amino nitrogen (i.e., amino acids and peptides resulting from the yeast fermentation), and total proteins in the undersea-aged sample, might represent an indirect clue supporting the better preservation of phenolic compounds in this sample compared to the control one (Figure 5).