## 3 Results and Discussion
### Spectral Characteristics  
The NIR spectral characteristics of dried TMR samples exhibit distinct peaks, as shown in Figure 1.  
The samples, even if dried, maintained water absorption bands due to O-H groups, around 1400 nm and 1900 nm, producing sharper, more defined peaks, and offering enhanced resolution for organic compounds such as proteins, fats, fibres, and FAs.  
The C-H absorption bands associated with some FAs are detectable in the second and third harmonic overtones. As reported by [PERSON] et al. [46], FAs absorb within the C-H combination stretching region (2200-2500 nm).  
The harmonics of NIR refer to absorption phenomena within the NIR range (780-2500 nm), driven by molecular vibrations in functional groups containing bonds such as C-H, O-H, and N-H [47]. Proteins absorb primarily due to N-H and C-H bonds, with main absorption bands around 2050-2250 nm (amino groups) and 1600-1700 nm (secondary bands). Fats and FAs show absorption related to C-H groups, with key bands at  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & & **Calibration Set (168)** & \multicolumn{6}{c}{**Independent Set for Validation (72)**} \\ \hline
**\%** & **Mean** & **Range** & **S.D.** & **C.V.** & **Mean** & **Range** & **S.D.** & **C.V.** \\ \hline
14:0 & 0.47 & 0.52 & 0.10 & 20.64 & 0.50 & 0.48 & 0.10 & 20.80 \\
16:0 & 17.36 & 8.89 & 1.83 & 10.56 & 18.05 & 7.50 & 1.73 & 9.57 \\
16:1 & 0.46 & 0.70 & 0.12 & 25.22 & 0.46 & 0.67 & 0.10 & 21.09 \\
18:0 & 3.12 & 3.76 & 0.63 & 20.26 & 3.08 & 2.98 & 0.61 & 19.77 \\
18:1 cis-9 & 20.89 & 8.69 & 1.81 & 8.65 & 20.53 & 8.55 & 1.61 & 7.82 \\
18:1 cis-11 & 1.03 & 0.56 & 0.10 & 9.81 & 1.05 & 0.48 & 0.10 & 8.95 \\
18:2 n-6 & 42.54 & 21.57 & 3.62 & 8.04 & 43.25 & 17.88 & 3.73 & 8.62 \\
18:3 n-6 & 1.78 & 4.17 & 0.87 & 48.99 & 2.01 & 3.29 & 0.79 & 42.49 \\
18:3 n-3 & 9.77 & 13.98 & 3.59 & 36.77 & 8.64 & 13.77 & 3.96 & 45.84 \\ SFA & 21.81 & 7.91 & 1.99 & 9.11 & 22.21 & 7.81 & 1.81 & 8.13 \\ MUFA & 22.89 & 7.52 & 1.67 & 7.30 & 22.48 & 7.87 & 1.66 & 7.36 \\ PUFA & 55.19 & 12.16 & 2.28 & 4.14 & 54.89 & 9.91 & 1.98 & 3.61 \\ \hline \end{tabular}
\end{table}
Table 4: Descriptive statistics of fatty acids (% of total FAMEs) in Total Mixed Ratios (TMRs) from both the calibration (n = 168) and validation (n = 72) sets.  
1700-1800 nm (stretching of CH\({}_{2}\) and CH\({}_{3}\)) and 2300-2400 nm (specific to saturated/unsaturated fats). Fibres like cellulose and hemicellulose absorb in the 2100-2200 nm and 1700-1800 nm regions, which are associated with O-H and C-H bonds in complex carbohydrates [48].  
In the near-infrared spectrum, overtones and combination bands are associated with specific spectral regions and enable the detection of various compounds. The first overtone, typically observed between 1450 nm and 1900 nm, is dominated by C-H, N-H, and O-H vibrations and is particularly useful for identifying water, proteins, and fats. The second overtone, found in the range of 900 nm to 1300 nm, involves the same types of bonds but exhibits lower intensity. This region is commonly employed for the analysis of fats, carbohydrates, and proteins. The third overtone, located between 750 nm and 900 nm, is characterised by very low intensity, making its detection reliant on highly sensitive instruments. Consequently, it is less frequently used in practical applications. Combination bands, generally observed in the spectral range of 1900 nm to 2500 nm, are more intense than higher-order overtones and are particularly important for analysing complex chemical compositions such as proteins, starches, and FAs [24]. The plots of the variables contributing to the PLSR models for some compounds, for example, are provided in the Supplementary Materials (Figure S1).