## 3 Results
Spectra are shown in the 3030–2800 cm\({}^{-1}\) (representative of lipids), and the 1780–1480 cm\({}^{-1}\) (representative of proteins) regions. Spectra are shifted along Y axis for a better comprehension. To better elucidate the composition of the lipid fraction, the following band area ratios were investigated: A\({}_{\rm CH}\)/A\({}_{\rm CH3}\) (calculated as the ratio between the areas of the peaks at 3010 cm\({}^{-1}\) and 2956 cm\({}^{-1}\)), which was representative of the unsaturation degree in lipid alkyl chains; and A\({}_{\rm CH2}\)/A\({}_{\rm CH3}\) (calculated as the ratio between the areas of the peaks at 2921 cm\({}^{-1}\) and 2956 cm\({}^{-1}\)), which was representative of the saturation degree in lipid alkyl chains. From the statistical analysis of these ratios, which is shown in Figure 5, the following considerations can be drawn: (i) with regard to the A\({}_{\rm CH}\)/A\({}_{\rm CH3}\), a higher degree of unsaturation was observed in **Y** than **O** CC samples (\(p<0.05\)); furthermore, within each group, statistically significant higher amounts were found in **CY** than **AY** samples and **CO** than **AO** ones (\(p<0.05\)); (ii) a similar trend was displayed by the A\({}_{\rm CH2}\)/A\({}_{\rm CH3}\) ratio, with longer saturated alkyl chains in **CY** compared to **CO** CC samples, and in **AY** compared to **CO** samples (\(p<0.05\)); within each group, higher values were found in **C** samples compared to **A** samples (\(p<0.05\)). Figure 4: Statistical analysis of the macromolecular composition of **A** and **C** regions of **Young** and **Old** CC samples: LIP/TBM (total amount of lipids); FA/LIP (relative amount of fatty acids to lipids); PRT/TBM (total amount of proteins), and LIP/PRT (relative amount of lipids to proteins). Asterisks indicate statistically significant differences between **A** and **C** regions within the same group (n.s., \(p>0.05\); **\(p<0.01\)**; **\(p<0.001\)**). Different lowercase letters over histograms were used to indicate significant differences between **Y** and **O** groups (\(p<0.05\)). With regard to proteins, the peak-fitting analysis allowed us to identify the following underlying peaks related to proteins' secondary structure [46; 47]: 1697 cm\({}^{-1}\), 1682 cm\({}^{-1}\), and 1627 cm\({}^{-1}\) (\(\beta\)-sheet structures); 1655 cm\({}^{-1}\) (\(\alpha\)-helix structures); and 1640 cm\({}^{-1}\) (random coil structures). The following band area ratios were taken into account: ALPHA (calculated as the ratio between the area of the peak at 1655 cm\({}^{-1}\) and the sum of the areas of all the peaks in the 1700-1480 cm\({}^{-1}\) interval); BETA (calculated as the ratio between the sum of the areas of the peaks at 1697 cm\({}^{-1}\), 1682 cm\({}^{-1}\), and 1627 cm\({}^{-1}\), and the sum of the areas of all the peaks in the 1700-1480 cm\({}^{-1}\) interval); RANDOM (calculated as the ratio between the area of the peak at 1640 cm\({}^{-1}\) and the sum of the areas of all the peaks in the 1700-1480 cm\({}^{-1}\) interval); and FOLDED/UNFOLDED (calculated as the ratio between the sum of the areas of the peaks at 1697 cm\({}^{-1}\), 1682 cm\({}^{-1}\), 1655 cm\({}^{-1}\), and 1627 cm\({}^{-1}\), corresponding to \(\beta\)-sheet and \(\alpha\)-helix structures, named FOLDED, and the area of the peak at 1640 cm\({}^{-1}\), corresponding to random coil structures, named UNFOLDED).