# Edible Films Based on Ovine Second Cheese Whey with Oregon Essential Oil
## 3 Results and Discussion
### Fourier Transform Infrared Spectroscopy (FTIR)  
FTIR spectra of films can be observed in Figures 2 and 3. Some bands corresponding to Amide I region (1600-1700 cm\({}^{-1}\)) showed changes in the wave number (WN) in SCW-added films compared with WPI films. This region is governed by the stretching vibration of the C=O and C-N groups and provides information about the secondary structure of proteins [36]. Bands observed at 1610-1634 cm\({}^{-1}\) and at 1675-1683 cm\({}^{-1}\) correspond to \(\beta\)-sheet structures; bands at 1641-1646 cm\({}^{-1}\) are attributed to random coil or unordered structure. The 1652 cm\({}^{-1}\) band has been assigned to \(\alpha\)-helix, and the 1660-1668 cm\({}^{-1}\) and 1692 cm\({}^{-1}\) bands to \(\beta\)-turn [37]. The mean values of each secondary structure were 56.9% \(\beta\)-sheet, 15.8% random coil, 10.6% \(\alpha\)-helix and 16.7% \(\beta\)-turn. The \(\beta\)-sheet structure proportion was found to be higher than the values reported by other authors [36; 38]. High levels of \(\beta\)-sheet structures are often observed in aggregate proteins, particularly those that have undergone extensive thermal denaturation [36] as in the case for samples to which SCW was added. In bands corresponding to the \(\beta\)-sheet structure of proteins, several differences were found: the band at 1625 cm\({}^{-1}\) in the WPI films shifted to a lower WN (1623 cm\({}^{-1}\)) in WPI-SCW films. Furthermore, a new band at 1628 cm\({}^{-1}\) was observed in the latter. Both bands have been assigned to the intramolecular \(\beta\)-sheet structure [37]. The band at 1643 cm\({}^{-1}\) in WPI films also showed a shift to a lower WN in SCW-added films, 1640 cm\({}^{-1}\), in which another new band was found at 1646 cm\({}^{-1}\). The appearance of a new band corresponding to random coils has been observed after emulsion formation in caseins dispersions [39]. The spectral region from 2850 to 2980 cm\({}^{-1}\) is assigned to the stretching vibrations of the C-H bonds from methyl groups [36; 40]. Two bands showed changes in their WN depending on the sample. The band at 2843 cm\({}^{-1}\) in the WPI films shifted to a higher WN (2850-2856 cm\({}^{-1}\)) in WPI-SCW films, with or without EO. By contrast, the band at 2932 cm\({}^{-1}\) in the WPI films shifted to a lower WN (2922-2925 cm\({}^{-1}\)) in films with SCW. These vibration frequencies have been assigned to the symmetrical and asymmetrical C-H stretching of -CH\({}_{2}\) from aliphatic chains, probably related to lipids [37; 40]. The intensity of the bands in this spectral region increased in SCW- and EO-added samples compared with WPI films, probably due to the high lipid content of the SCW. However, the increment \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Two-Way ANOVA** \\ \hline
**Antioxidant Activity** & \(F\) & _p Value_ \\ \hline DPPH & WPI/SCW & 1.02 & 0.376 \\ EO & 57.79 & **0.000** \\  & Interaction & 0.60 & 0.667 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Two-way ANOVA of the DPPH radical scavenging capacity of WS films. of the number of -CH\({}_{2}\) vibrations could also be due to the decrease in the interactions between lipids and proteins. Changes in the 2922 cm\({}^{-1}\) band have been related to emulsion stability [40]. The absorption peaks located in the spectral range between 3000 cm\({}^{-1}\) and 3600 cm\({}^{-1}\) and are related to free and bound O-H and N-H groups [36]. There were no differences in band wave numbers, although the intensity of the peaks in this region was lower in WPI-SCW films (lesser O-H vibrations) than in the WPI samples. This result may be derived from a higher degree of interactions by hydrogen bonding in the protein network, which involve a reduction in the availability of free -OH groups [36]. Figure 2: FTIR spectra of films with WPI and /or SCW described in the materials and methods section. Several absorption bands of glycerol were found in the spectral range between 800 and 1150 cm\({}^{-1}\).