# Investigation of Oil Extracted from Roasted and Unroasted Oats with Use of Chemometrics
## 3 Results and Discussion
### Statistical Modeling
#### 3.5.2 Reference Models  
MODEL 2: Time of Roasting and Spectral Data  
The discriminant model to assign samples to seven distinct homologous groups, i.e., 0, 10, 20, 30, 40, 50, and 60 min, was tried to be constructed, although unsuccessfully. Too many samples were assigned incorrectly. On the other hand, another model (MODEL 2) that correlates the roasting time with spectral data were successfully constructed. It is presented in Figure 8. MODEL 2 is a reference model in which time is the reference data. Both RMSEC and RMSEP are calculated to be 4.59 and 12.70, respectively. Resultant correlation coefficients are high, that is, 0.9771 and 0.8765 for calibration and prediction, respectively. The number of factors used to construct MODEL 2 was eight. Two spectral regions were used: 3636-3173 and 1790-1692 cm\({}^{-1}\). Actual versus calculated values are presented on the \(y\) (calculated) and \(x\) (actual) axis, respectively. Figure 7: MODEL 1 application. Oil samples were extracted from unroasted oats (triangles) versus the oil samples extracted from oat grains that were roasted for 60 min at 160 \({}^{\circ}\)C (squares). MODEL 3: Induction Time and Spectral Data  
The following model was designed to calibrate spectral data and oxidative induction time (OIT). MODEL 3 showed statistically significant values, with RMSEC and RMSEP values of 0.649 and 1.51, respectively. The correlation coefficient for calibration was 0.9635, while for prediction, it was 0.9022. MODEL 3 was constructed using seven factors. All data, the trend line, and the experimental point used for calibration and validation are presented in Figure 9. Circles stand for the calibration date set, while crosses stand for the validation set of data. Values calculated by the model are located on the \(y\)-axis, while actual, which means determined experimentally with the scientifically approved PDSC method, are on the \(x\)-axis. Spectral data for MODEL 3 were in almost the entire spectral region, 3699-435 cm\({}^{-1}\). Applying more narrow regions alone and in combination resulted in constructing models with worse statistical parameters, i.e., correlation coefficients and RMSEC and RMSEP. Acid values determined experimentally are presented in Figure 4. Although determined with an automatic titrator, it took significant time to complete. With IR spectroscopy,  
Figure 8: Time of roasting versus spectral data. Figure 9: Calculated (model predicted) versus actual (determined with PDSC OIT) values. it takes up to 3 min to register the spectrum and enter it into the model. It does not require any chemical reactant except cleaning liquids and water used for cleaning after measurement. The time required to register the spectral data necessary for MODEL 4 construction (model presented in Figure 10) was about 10 min. Registering the spectrum of one unknown sample to be evaluated needs less than 1 min. With the model already constructed, it takes less than 0.5 min to introduce spectral data of unknown samples into the model and obtain the acid value. The regions of spectral data used for calibration and validation of MODEL 4 were 3636-3145 cm\({}^{-1}\) and 1790-1692 cm\({}^{-1}\), respectively, with RMSEC = 1.69 and RMSEP = 2.64. The correlation coefficient for calibration is 0.9440, while for prediction, it is 0.9191. These values confirm the statistical strength of the model. If data from higher energy regions, i.e., 3636-3145 cm\({}^{-1}\), were rejected from the calibration and validation process, and data from only lower regions, i.e., 1789-1692 cm\({}^{-1}\), were used, then correlation coefficients were significantly lower, i.e., 0.8694 and 0.8897 for calibration and validation, respectively. Also, values of errors were higher, i.e., RMSEC = 2.51 and RMSEP = 2.71. It confirms that most chemical changes that decide on AV refer to bonds in these regions, where O-H and C=O bonds are present.