## 3 Results and Discussion
### In Silico Analysis of Conformational Effects on Mx3 glc Predicted Color
Figure 2: Theoretical visible absorption spectra of mv3 glc conformers calculated with the dispersion-corrected hybrid functional B3 LYP. Modifying the torsion of the dihedral angle from 0\({}^{\circ}\) to 40\({}^{\circ}\) led to different mv3 glc conformers having similar predicted values of lightness and chroma (\(L^{*}\sim\) 50 and C\({}^{*}{}_{ab}\) = 50-54), similar in darkness and color intensity, respectively. However, they notably differ from each other regarding their predicted hue values (\(h_{ab}\) decreased from 1.5\({}^{\circ}\) to \(-8.1^{\circ}\)), indicating that the _in silico_ methodology applied reproduced important qualitative color variations (Figure 3). As the dihedral angle increases up to 50\({}^{\circ}\), simulated mv3 glc conformers show an increase in bluish tonalities. These predicted colorimetric effects based on the B3 LYP/6-31+G(d,p) theoretical level reflect the strong structure-color relationship of anthocyanin pigments. Accordingly, the colorimetric results provided an adequate color prediction for mv3 glc according to conformational variations. It is worth mentioning that these simulated conformations could result from structural changes or interactions between mv3 glc with other molecular species present in wine. This suggests that a particular conformation would result in a specific color in a food matrix that can be predicted by _in silico_ colorimetry. Higher torsions of the dihedral angles (\(\theta\) = 75\({}^{\circ}\), 80\({}^{\circ}\), and 90\({}^{\circ}\)) (Table 1) led to mv3 glc conformers with notably higher values of lightness and lower chroma values (\(L^{*}\)\(>\) 90 and C\({}^{*}{}_{ab}\) \(<\) 10). Thus, under these conformations, mv3 glc would appear almost colorless (Figure 3), as previously detected with the _in silico_ spectral effects. The color differences (\(\Delta E^{*}{}_{ab}\)) between the different mv3 glc conformations when the dihedral angles were increased (from 10\({}^{\circ}\) to 90\({}^{\circ}\)) compared to the initial conformation (0\({}^{\circ}\)) were calculated alongside the relative lightness, chroma, and hue differences (%\(\Delta L\), %\(\Delta C\), and %\(\Delta H\)) for each \(\Delta E^{*}{}_{ab}\) value (Table 2), which allows assessing the color attribute most influenced in the prediction. \(\Delta E^{*}{}_{ab}\) values varied from 4 to 67 units, confirming that conformational changes based on \(\theta\) torsion result in color variations of the mv3 glc flavylium cation, and in most cases, these changes can be considered visually perceptible. According to [PERSON] et al. (2016), \(\Delta E^{*}{}_{ab}\) values around 3-5 units are considered close to the visual threshold of clearly perceived color differences by average non-trained observers. Thus, the theoretical results showed that the greater \(\theta\) torsion, the more evident the chromatic effects are. By comparing the relative contributions of lightness (%\(\Delta L\)), chroma (%\(\Delta C\)), and hue (%\(\Delta H\)), it was confirmed that the \(\Delta E^{*}{}_{ab}\) calculated between the mv3 glc conformers corresponded to the predicted qualitative changes (%\(\Delta H\) = 99-84 from 10 to 60\({}^{\circ}\)). Figure 3: Location of the predicted color of mv3 glc conformers in the CIELAB (a*b*) diagram.