## 3 Results and Discussion
### FTIR Spectroscopy  
The identification of the chemical structure of the prepared films was accomplished by recording their infrared (IR) spectra. Figure 4 illustrates the FTIR spectra for the wheat flour films composed of flour with varying coffee silverskin contents or aqueous extracts. \begin{table}
\begin{tabular}{l r r r r r r r} \hline  & **L*** & **a*** & **b*** & **c*** & **h** & **R\% (400 nm)** & **K/S** \\ \hline WFF & 81.56 & \(-\)1.28 & 11.39 & 11.46 & 96.43 & 36.72 & 0.55 \\ WFF-2.5 ss & 72.98 & 1.20 & 23.59 & 24.04 & 86.07 & 19.01 & 1.73 \\ WFF-5 ss & 63.22 & 4.64 & 20.56 & 21.72 & 78.87 & 13.01 & 2.91 \\ WFF-10 ss & 55.93 & 7.01 & 17.55 & 18.79 & 71.16 & 11.98 & 3.23 \\ WFF-15 ss & 51.91 & 8.61 & 16.71 & 17.59 & 62.73 & 11.75 & 3.31 \\ WFF-20 ss & 48.00 & 7.91 & 11.27 & 13.77 & 54.95 & 12.04 & 3.21 \\ WFF-1\%A & 80.73 & \(-\)1.27 & 13.15 & 13.21 & 95.53 & 34.72 & 0.61 \\ WFF-1\%B & 79.46 & \(-\)0.77 & 17.07 & 17.09 & 92.60 & 23.89 & 1.21 \\ WFF-2\%A & 77.17 & 0.05 & 18.69 & 18.69 & 89.85 & 21.88 & 1.39 \\ WFF-2\%B & 75.34 & 0.62 & 21.79 & 21.79 & 88.35 & 19.81 & 1.62 \\ \hline \end{tabular}
\end{table} 
Table 1: Color measurements of biocompatible wheat flour films (WFFs) with coffee silverskin particles and extracts. Figure 3: Color characteristics of the biocomposite materials studied. Figure 4: _Cont._  
The primary stretching mode of the -OH group is often associated with the spectral region between 3100 and 3700 cm\({}^{-1}\). This specific band is obtained from the polysaccharide molecules and specific amino acids present in proteins of wheat flour [33]. It was observed that this band, situated within the range of 3100-3700 cm\({}^{-1}\), exhibits an augmentation as the coffee silverskin particles or extract addition increased. The spectral region detected between 2800 and 3000 cm\({}^{-1}\) is frequently linked to the elongation of the C-H (CH\({}_{2}\)) group present in the protein of wheat flour [34]. These two sharp bands at 2920 and 2850 cm\({}^{-1}\) are attributed to C-H stretching vibration and have been previously reported in spectra of coffee silverskin [20], roasted Araibica and Robust coffee samples [35], and roasted coffee husks [36]. The occurrence of peaks in this particular area can also be attributed to the asymmetrical stretching of the C-H bonds within the methyl (\(-\)CH\({}_{3}\)) group present in the caffeine molecule and lipids [37; 38]. The band between 1700 and 1600 cm\({}^{-1}\) is highly associated with C=O and C=N functional groups present in proteins of wheat flour [34; 39]. These absorption peaks can be also linked to chlorogenic acids and caffeine [40]. The distinct peak around 1000 cm\({}^{-1}\) is associated with the characteristic absorption peak of polysaccharide molecules [41] and glycosidic bonds, which are related to galactomannans polysaccharide sugars, resulting from the stretching vibration of C-O in C-O-H bonds [42]. The FTIR/ATR spectrum of coffee silverskin in Figure 4 shows prominent bands at 3300 cm\({}^{-1}\) (OH and NH stretching vibrations), 2920-2850 cm\({}^{-1}\) (CH stretching in the methyl group of caffeine), 1640 cm\({}^{-1}\) (carbonyl stretching), and 1030 cm\({}^{-1}\) (CO stretching and CH rocking vibrations from polysaccharides like cellulose and hemicellulose) [29]. The addition of coffee silverskin extracts and particles to the FTIR spectra of wheat flour and glucose (WFF) membranes results in noticeable interactions with the matrix. The spectra containing coffee silverskin extracts show slight shifts and changes in absorption band intensities in the hydroxyl (3200-3500 cm\({}^{-1}\)) and amide I and II (1500-1700 cm\({}^{-1}\)) regions, indicating potential hydrogen bond formation or other secondary interactions with the matrix. Moreover, variations in the C-O-C and C-O stretching regions (1000-1300 cm\({}^{-1}\)) suggest interactions with polysaccharides.