## 2 Materials and Methods
### Characterization of Starch/MCC Films  
2.5.1. Thickness  
The film's thickness was measured with a digital thickness gauge. All tests showed the average results of six test specimens (n = 6).  
2.5.2. Chemical Composition and Interactions  
FTIR analysis was conducted to examine the chemical composition and interaction between starch and MCC in the composite films. This analysis utilized a Tensor 27 FTIR spectrometer (Bruker Optics, Ettlingen, Germany), with spectra recorded at room temperature within the spectral range of 4000-400 cm\({}^{-1}\).  
2.5.3. Morphology  
To examine the surface and cross-sectional morphology of the starch/MCC films, a field emission scanning electron microscope (FE-SEM, Carl Zeiss AURIGA(r), Thuringia, Germany) was employed. The film specimens were coated with gold using a sputter coater. SEM images of the samples were captured at an acceleration voltage of 3 kV.  
2.5.4. Mechanical Properties  
A texture analyzer (TA.XT-PLUS, Texture Technologies Corp., London, UK) fitted with a 5 kg load cell was used to measure the starch/MCC films' Young's modulus, tensile strength, and elongation at break. Film samples were attached to the center of the tensile grasp jaw, measuring 50 mm in length and 10 mm in width. The grasp jaw kept the sample's upper and lower parts, each measuring 10 mm, firmly in place, providing a gauge length of 30 mm for the tensile test. Tensile testing was carried out at a speed of 10 mm/min. Each measurement is the average of five test specimens' values (n = 5).  
2.5.5. Surface Wettability  
To evaluate the surface wettability of the starch/MCC films, the water contact angle was determined. A precise volume of 15 uL of distilled water was deposited onto the surface of each sample. Following a 60 s exposure at room temperature, the image of the water droplet on the sample surface was captured using a USB digital microscope (1600\(\times\)) and analyzed using ImageJ software version 1.53t ([PERSON], Washington, DC, USA). Three samples were analyzed per group. (n = 3).  
2.5.6. Moisture Content  
The moisture content of the starch/MCC films was analyzed utilizing a moisture analyzer (Sartorius MA 30, Sartorius Lab Instruments GmbH & Co. KG, Lower Saxony, Germany). Initially, the film was weighed to obtain its initial weight (W\({}_{\text{i}}\)). Subsequently, the film was subjected to drying at 105 \({}^{\circ}\)C until its weight remained constant (W\({}_{\text{d}}\)). The moisture content was then calculated using the following Equation (2). Each group comprised three samples (n = 3).  
\[\text{Moisture content (\%)}= \frac{\left(\text{W}_{\text{i}}\ -\ \text{W}_{\text{d}}\right)}{\text{W}_{\text{i}}}\times 100 \tag{2}\]  
2.5.7. Water Activity Index  
The water activity index (aw) was analyzed using a water activity meter (AquaLab equipment, ICT International, Armidale, Australia). To conduct the determinations, the samples were kept under controlled conditions at 50% \(\pm\) 5 relative humidity (RH) and a temperature of 25 \(\pm\) 1 \({}^{\circ}\)C. The sample was placed in a cup, which was then positioned within the water activity meter. The sample chamber lid was sealed over it, and it was left to reach vapor equilibrium. An infrared beam focused on a tiny mirror determined the precise dew point temperature of the sample, which was then translated into water activity. Each group comprised three samples (n = 3).