## 3 Results and Discussion
### Water Vapor and Gas Permeability  
The primary purpose of a food package is frequently to inhibit or reduce the movement of moisture from food to the surrounding environment, necessitating the lowest possible water vapor permeability (WVP) [46]. Conversely, there are instances where having a packaging film with inadequate water vapor barrier properties can be advantageous. This is because it permits the transfer of water vapor through the film, thereby averting water condensation, which could lead to microbial deterioration [47]. Table 3 shows the oxygen transmission rate (OTR), the water vapor transmission rate (WVTR), and the water vapor permeability (WVP) of all studied WFF biocomposite materials. The addition of coffee silverskin particles and water extracts in the WFF matrix led to a lower water vapor transmission rate (WVTR) and water permeability (WVP) up to 33.91% for films with CS particles, owing to its hydrophobic character, and up to 55.36% for films with CS extracts. These WVP values were slightly lower for starch-based films, such as babassu (3.52-5.52 \(\times\) 10\({}^{-10}\) g m\({}^{-1}\) s\({}^{-1}\) Pa\({}^{-1}\)) [48] and pinhao (3.11 \(\times\) 10\({}^{-10}\) g m\({}^{-1}\) s\({}^{-1}\) Pa\({}^{-1}\), 28 \(\pm\) 2% RH) [5], but marginally higher for rice (0.08 \(\times\) 10\({}^{-10}\) g m\({}^{-1}\) s\({}^{-1}\) Pa\({}^{-1}\), 75% RH) [49], semolino (0.09 \(\times\) 10\({}^{-10}\) g m\({}^{-1}\) s\({}^{-1}\) Pa\({}^{-1}\)) [50], and similar for chicken flour films (0.36 \(\times\) 10\({}^{-10}\) g m\({}^{-1}\) s\({}^{-1}\) Pa\({}^{-1}\)) [51]. WVP values of plasticized wheat flour filter film containing glycerol with carvacrol were slightly higher than ours (1.90 \(\times\) 10\({}^{-10}\) g/m-s-Pa), and wheat flour filter film with sorbitod showed lower values [32]. [PERSON] et al. [52] suggested that films produced using flour are anticipated to exhibit elevated water vapor permeability (WVP). The increased water vapor permeability (WVP) can be ascribed to the plentiful hydrophilic groups found in non-starchy substances such as proteins and fibers. The oxygen transmission rate (OTR) showed a decrease of up to 34.12% when coffee silverskin was added to the WFF matrix at the lowest concentration. Subsequently, in higher incorporations, the OTR increased and led to similar values as the control WFF. The OTR of the WFF-20 ss film was 72.1% higher than the control WFF film. Coffee silverskin extracts led to lower OTR values in the range between 14.51 and 28.07% with respect to the WFF control film. Wheat gluten-derived gel coatings and films demonstrate favorable oxygen barrier properties because of their heightened resilience against nonpolar substances, such as O\({}_{2}\), CO\({}_{2}\), and lipids [53]. The films produced in this work showed higher OTR values than biofilms based on amaranth flour [44]. The moisture of the samples played a very important role in the measurements of the above properties. The samples were very sensitive to moisture and were likely affected by this factor. The significant change in the values of the water vapor transmission rate (WVTR) and the oxygen transmission rate (OTR) with the addition of a small amount of coffee silverskin (CS) or extract can be explained by the interaction between the CS components and the film matrix. The role of polyphenols and other bioactive compounds in CS may be crucial in this case. Polyphenols have the ability to form secondary bonds such