## 4 Discussion  
The development of robust and reproducible predictive models to discriminate between different commercial categories of the raw material of pre-sliced MAP Iberian _chorizo_, first requires obtaining representative spectra for each study sample. Thus, between 1000 and 2000 nm, the noise was not noticeable (Figure 2), showing the spectra an area with high signal/noise ratio, and therefore the region with the most amount of useful data. Above 2300 nm spectra displayed little useful information, so these wavelengths were discarded for the models developed in this study. More specifically, the main absorption dominated bands were observed around 1090 and 1270 nm, which would be associated with behavior to the C-H bonds, which is related to fatty acids and alpha and gamma tocopherols [22,23]. Therefore, the overlapping of spectra from _Black_ and _Red_ categories would support the similarity in the fatty acid profile (38.1 and 38.6 g per 100 g of fatty acid methyl esters (% FAMEs) of saturated fatty acids, 54.8 and 54.5% FAMEs of monounsaturated fatty acids and 7.2 and 6.8% FAMES of polyunsaturated fatty acids for _Black_ and _Red_ categories, respectively), and tocopherols content (14.4 and 13.9 \(\mu\)g/g of alpha tocopherol and 1.7 and 1.6 \(\mu\)g/g of gamma tocopherol for _Black_ and _Red_ categories, respectively) between Iberian _chorizo_ manufactured from meat and fat belonging to these two categories, as has been previously reported [8] and as has been also demonstrated in other Iberian dry-cured products [24,25]. This could be mainly explained by the same feeding regime of animals reared under the requirements of both _Black_ and _Red_ categories. [PERSON] et al. [26] also described bands located around 1210 nm corresponding to fatty acids when studying NIRS technology as rapid determination of the fatty acid profile in Spanish Iberian _salichichon_ and _chorizo_ dry-cured sausages. Later, [PERSON] et al. [27] also reported graphically that regions characteristic of CH2 absorption bands allowed some separations between samples of Iberian pig carcasses from animals with different feeding regime (acorns vs. compound feeds). Therefore, the ability to classify among the different categories may be ascribed to spectral differences, and more specifically, to these areas where the largest differences in absorbance intensity are found, i.e., the areas related to fatty acids (Figure 2), since the variables corresponding to these wavelengths proved to have an important weight in the development of the PLS-DA models (Figure S2). Spectra differences on account on animal feeding regime have been previously used for classification purposes. Thus, [PERSON] et al. [27] discriminated between carcasses of acorn-fed versus feed-fed Iberian pigs, whereas [PERSON] et al. [10] were able to classify Iberian pigs, carcass, meat and subcutaneous backfat according to animal feeding regime. The models developed by means of PLS-DA showed acceptable SE and SP values after external validation. Therefore, these results suggest that the combination of NIRS technology with PLS-DA would provide models to be used for Iberian dry-cured _chorizo_ under MAP classification according to the different quality labels of IQS. The same methodology has previously been used to classify fresh meat samples (psoas major muscle) into the same quality categories [10] and in pre-sliced MAP dry-cured loin [11]. Additionally, the PLS-DA chemometric algorithm in combination with spectroscopy techniques was also used for the discrimination between fresh versus frozen Iberian dry-cured loin [28]. In all studies, similar classificatory results to those obtained in the present research were found, concluding the high classificatory capacity of PLS-DA and enhancing its potential in official quality categories assignment support control. So, results of this work could be a preliminary breakthrough for use in cured, sliced and packaged sausage-type products.