# Physicochemical and Sensory Analysis of Apple Cream Fillings for Use in the Pastry Industry
## 3 Results & Discussion
The differences between samples are explained with the addition of water, where its presence dominates the spectrum, with strong O-H stretching and bending vibrations. FTIR spectrum of powder (PDWW), shows more pronounced peaks from carbohydrates and other organic compounds due to the lack of water. The spectrum of dried apple samples (DR.AP) is dominated by the natural components of the apple, such as cellulose, pectin, and sugars. The stretching frequency and the shape (broad or narrow) of the O-H peak in the FTIR spectrum show details concerning the amount and nature of water binding in the material. A strong broad O-H peak with a shift to lower wavenumbers as occurs for AP1, AP2 and PD compared to raw materials, i.e., PDDW and PR.AP. correspond to shorter hydrogen bond components indicating a significant amount of bound water [52]. Infrared spectra of raw and final materials during the water adsorption process show a broad band from 3290 to 3320 cm\({}^{-1}\) due to OH stretching which increases and decreases during the wetting/drying processes. The C-O stretching vibrations in starch are sensitive to the molecular environment. Specifically, the band at 1045 cm\({}^{-1}\) is associated with C-O stretches in the ordered, double-helical structures of amylopectin (crystalline regions), while the peak at 1022 cm\({}^{-1}\) is related to C-O stretches in the more amorphous regions of starch. This has led to the adoption of the band ratio at 1047:1022 cm\({}^{-1}\) as a measure of short-range ordered molecular structure [53]. In our study, the absorption band ratio of 1047/1022 cm\({}^{-1}\) falls from 1.07 for PDWW and 0.99 for DR.AP. in the dried state to 1.00 for AP1 and AP2 and to 0.98 for PD in the hydrated state. It seems that potato starch contained in PDWW, PD, AP1 and AP2 plays an important role showing that the hydrated materials are linked to C-O stretches in the more amorphous regions of the starch (due to the increase of absorbance in 1022 cm\({}^{-1}\)) and to less crystalline regions (due to a decrease of absorbance in 1047 cm\({}^{-1}\)) compared to dried powder materials (PDWW). According to the contact angle measurement using the Needle-In method the following images were taken. The hydrophobicity and hydrophilicity of a surface are measured using contact angle analysis, which evaluates the angle formed between a droplet of water and the surface it contacts. A water droplet is placed on the surface, and the angle between the surface and the tangent to the droplet's edge is measured using a goniometer or optical imaging. If the contact angle is greater than 90\({}^{\circ}\), the surface is hydrophobic, indicating water repellence. In contrast, if the angle is less than 90\({}^{\circ}\), the surface is hydrophilic, which indicates water affinity. Highly hydrophobic surfaces, such as those with superhydrophobicity, can have contact angles exceeding 150\({}^{\circ}\)[7]. According to Figure 5, AP1 exhibits moderate hydrophilicity, with contact angles between 42.27\({}^{\circ}\) and 56.18\({}^{\circ}\). This suggests that the surface of AP1 has a balanced mix of hydrophilic and hydrophobic properties, likely due to the presence of apple cubes and powdered ingredients. Apple cubes may introduce natural hydrophilic components (e.g., sugars, pectin), while powdered ingredients (e.g., potato starch, dextrose) may contribute to a slightly higher contact angle [4; 15; 19]. AP2 is highly hydrophilic, with contact angles consistently below 30\({}^{\circ}\). This indicates that the surface of AP2 strongly attracts water, likely due to the higher proportion of fine sugar (6.33% _w/w_ more than AP1) and the presence of apple cubes, which are rich in hydrophilic components like sugars, pectin, and cellulose and. The low contact angles suggest that AP2 has a more uniform and water-attracting surface compared to AP1 and PD. PD exhibits moderate hydrophilicity, with contact angles between 46.05\({}^{\circ}\) and 49.27\({}^{\circ}\).