## 3 Results and Discussion
### Thickness, Density, and Contact Angle Parameters of Films  
Table 2 shows the thickness, density, and contact angle parameters of the films produced from ozone-treated FFSs. The ozone treatment did not significantly affect the thickness (\(p\geq 0.05\)). The film samples had a thickness ranging from 0.31 to 0.38 mm. Due to the insignificant differences in the thickness of the films, the mechanical and colour properties could be determined without the effect of thickness [19].  
The density of the film samples was between 1.00 and 1.13 g/cm\({}^{3}\). The density of films from ozone-treated FFSs was lower than the control sample (\(p<0.05\)). However, similar density values were observed between the O-10 and O-30 samples (\(p\geq 0.05\)).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **pH** & **\(\boldsymbol{\zeta}\)-Potential (mV)** & **Average Diameter** \\  & & & **(nm)** \\ \hline Control & 5.71 \(\pm\) 0.01 c & \(-\)0.92 \(\pm\) 0.03 a & 684 \(\pm\) 19.8 ab \\ O-5 & 5.85 \(\pm\) 0.01 b & \(-\)1.24 \(\pm\) 0.04 b & 727.5 \(\pm\) 27.6 a \\ O-10 & 5.95 \(\pm\) 0.02 a & \(-\)0.99 \(\pm\) 0.01 a & 593.0 \(\pm\) 9.9 c \\ O-30 & 5.96 \(\pm\) 0.03 a & \(-\)0.88 \(\pm\) 0.03 a & 638.5 \(\pm\) 16.3 bc \\ \hline \hline \end{tabular} Data are the mean \(\pm\) standard deviation (\(n=3\)). Different letters within the same column show the significant differences between the samples (\(p<0.05\)). Control: non-ozonated FFS; O-5: ozone-treated FFS for 5 min; O-10: ozone-treated FFS for 10 min; O-30: ozone-treated FFS for 30 min.  
\end{table}
Table 1: pH, zeta potential, and average particle diameter parameters of the ozone-treated film-forming solutions (FFSs).  
The water resistance of biopolymer films is crucial for preserving food when coated items come into contact with water [41]. The contact angle (CA) is the angle between the tangent line touching the water drop at the point of contact and the baseline of the film surface ([PERSON] et al. [42]; [PERSON] et al. [43]). The contact angle (CA) parameter indicates a surface's hydrophobicity level. A high CA indicates surface hydrophobicity, while a low CA indicates surface hydrophilicity ([PERSON] et al. [44]). According to [PERSON] et al. [45], a material is called \"hydrophilic\" if the CA is smaller than 90\({}^{\circ}\) and \"hydrophobic\" if the CA is greater than 90\({}^{\circ}\). The CA values of the samples varied from 96.92 to 104.30\({}^{\circ}\); the increased ozonation time decreased this value. The CA values obtained were similar to those of gelatine-based edible films [46; 47]. According to the results of the CA analysis, all samples showed hydrophobic characteristics. Film affinity with water may or may not be desirable. Potential applications may require water insolubility to improve product integrity and water resistance [22].  
All film samples produced in this study were hydrophobic because the CA values of films were higher than 90\({}^{\circ}\). Although there was a significant difference between samples, the results revealed that the hydrophobicity of samples was decreased depending on the ozonation time. Similar to this study, a previous study reported that cassava starch ozonation reduced the biopolymer films' CA values [20].