### NIRS Prediction Equations (Calibration and External Validation)
#### 3.3.3 Fatty Acids Groups  
Regarding the models developed for the main groups of fatty acids, Test 1 was used for all groups and for both-intact and minced-presentation modes (Tables 4 and 5). Regarding the spectrum range, the full spectrum, from 1000 to 2500 nm, was used in intact models (Table 4), whereas different ranges were used in the minced presentation mode (Table 5).  
Generally, better coefficients of determination for cross-validation (1-VR) were observed in the minced presentation mode (Table 5) when compared to intact (Table 4) SFA, MUFA, and PUFA fatty acids groups. Values lower than 0.36 were observed for all fatty acids groups in intact samples, excluding PUFA n-3, which obtained a slightly higher result (0.41). In the minced presentation mode (Table 5), 1-VR coefficients were medium to high, reaching values of 0.61, 0.53, and 0.65 for SFA, MUFA, and PUFA, respectively, and values of 0.64 and 0.72 for n-6 and n-3 PUFA. These 1-VR values could have been influenced by those of their major individual fatty acids (C16:0 and C18:0 for SFA; C18:1 n-9 for MUFA and C18:2 n-6 and C18:3 n-3 for PUFA), according to data showed in Table 5. The average 1-VR values observed in the minced presentation mode were similar to those reported for sausages from Iberian breed pigs [17], but lower than those reported in the LTL muscle, also from Iberian breed pigs [28]. Better 1-VR values compared to our study were reported by [18] for the SFA, PUFA, and n-6 PUFA fatty acid groups, whereas they obtained lower accuracy for MUFA and PUFA n-3, in the same muscle but considering only Krskopolje and Turopolje breeds.  
Regarding RMSECV, values in the minced presentation mode ranged from 1.24 to 1.97 for SFA and MUFA (Table 5), respectively, which were slightly higher than those reported previously [17; 28]. Additionally, [18] found a lower RMSECV value for SFA, although the value observed for MUFA was higher.  
In the minced presentation mode, RPDcv values ranged from 1.45 (MUFA) to 1.75 (SFA) (Table 5), the latter being the only fatty acid group that exceeded the reliable limit described by [32]. The REcv value for SFA was quite high, at 10.43, thus pointing out the ability of the model for quantitative prediction in the minced presentation model (Table 5), whereas PUFA attained 1.69 for RPDcv and 8.43 for REcv, which are acceptable values. RPDcv values reported in the present study were in line for SFA and slightly higher for MUFA than those reported by [18]. Although these models could allow us to discriminate between high, medium, and low values for SFA, MUFA, and PUFA [30], further studies increasing the number of samples are required to increase the data set and thereby improve the accuracy of the prediction models obtained for SFA, MUFA, and PUFA. The moderate discriminating ability of the present models is probably due to the complexity of sample types when considering different breeds, with different production and feeding systems.  
When the calibration models were validated with an external set of samples, different patterns were noticed regarding the presentation mode of the samples. Surprisingly, in the intact presentation mode,there was an improvement in the determination coefficients (R\({}^{2}\)v) for MUFA and PUFA, a reduction in the RMSEV for both, and therefore an increase in the \(\text{RPD}_{\text{v}}\) and \(\text{RER}_{\text{v}}\) statistics (Table 4). The opposite trend was observed for SFA and MUFA in the minced presentation mode; however, PUFA obtained a higher R\({}^{2}\)v, a lower RMSEV, and a higher \(\text{RPD}_{\text{v}}\) and \(\text{RER}_{\text{v}}\)when compared to the calibration set (Table 5). In fact, the \(\text{RPD}_{\text{v}}\) for the latter was 1.79, showing a suitable predictive reliability, according to [32].