## 3 Results
### Analysis of Muffin Samples by Fourier Transform Infrared Spectroscopy (FTIR)  
FTIR (Fourier transform infrared spectroscopy) analysis is a technique used to identify the chemical composition of a material based on the absorption of infrared radiation by the functional groups in the molecules. It is used to characterize ingredients and structural changes in dough, baked goods or other manufacturing processes. In the case of muffin dough, FTIR can provide information about the interactions between proteins, carbohydrates, lipids and other ingredients. The FTIR spectral information described for the ingredients and muffin samples highlights the presence of certain important functional groups, identified by the analysis of the corresponding spectral peaks. FTIR spectroscopy focuses on the specific absorption regions of these bonds, which confirm the presence of chemical groups characteristic of muffin samples [60]. Most of the spectra were observed in two regions (3900-2800 and 1700-1000 cm\({}^{-1}\)) confirming the presence or absence of specific functional groups. The FTIR spectra of the muffin samples, with visible peaks at frequencies of 3853, 3735, 3282, 2925, 1636, 1540, 1456, 1020, 1150, 1020, 995 and 926 cm\({}^{-1}\), are presented in Figure 9. Peaks at 3853 cm\({}^{-1}\) and 3735 cm\({}^{-1}\) correspond to stretching vibrations of O-H (hydroxyl) groups, indicating the presence of water or residual moisture in the samples, as well as possible interactions of proteins and carbohydrates with water. The peak at the 3282 cm\({}^{-1}\) frequency can be associated with the stretching vibrations of the N-H groups in flour proteins (especially gluten), as a result of the interaction with water (protein hydration). The 2925 cm\({}^{-1}\) peak corresponds to the asymmetric stretching vibrations of C-H bonds in aliphatic chains (CH\({}_{2}\), CH\({}_{3}\)). These groups are typical of fats (lipids) and triglycerides that are present in the dough through oil or other added fats [60]. The absorption peak at 1745 cm\({}^{-1}\) is characteristic of the stretching vibrations of the C=O (carbonyl) bond in esters, associated with fats and oils, especially triglycerides. This peak indicates the presence of fats used in the dough, such as vegetable oils. This peak is important because it confirms the presence of lipid compounds, which play an essential role in the formation of the texture and structure of the muffins, contributing to the tenderness and stability of the final product. However, this peak may also indicate the presence of pectin, since pectin is a polysaccharide that contains esterified groups in its structure. Pectin has galacturonic acid units, which can be esterified with methyl groups. In the case of methoxylated pectin, the C=O ester bond stretching vibration also appears around 1745 cm\({}^{-1}\). This absorption indicates the methoxylated ester groups in pectin, so the presence of pectin can be detected in the same frequency range. The peak at 1636 cm\({}^{-1}\) represents the stretching vibrations of C=O (carbonyl) bonds from amide (proteins) or absorbed water (H-O-H strain band). This peak indicates protein interaction with water [60]. The peak at 1540 cm\({}^{-1}\) is specific for the amide band II, indicating the presence of proteins. The torsional vibrations of the N-H bonds and the stretching vibrations of the C-N bonds are typical of protein structures such as gluten proteins in flour. The 1456 cm\({}^{-1}\) peak is associated with the torsional vibrations of C-H bonds in aliphatic CH\({}_{2}\) and CH\({}_{3}\) groups, typical of lipid components and long aliphatic chains in fats. The 1150 cm\({}^{-1}\) peak corresponds to stretching vibrations of C-O-C bonds in polysaccharide structures such as starch. This is also a region of the spectrum characteristic for the C-O-C stretching vibrations of the glycosidic bonds, which link the monosaccharides together within the polysaccharide structure of pectin.