Water vapor permeability and film solubility
Water vapor permeability is proportionality constant assumed to be independent of the water vapor pressure gradient applied across the films. However, hydrophillic (edible or nonedible) materials, such as protein films, derivative from this ideal behavior due to interactions of permeating water molecules with polar groups in the films structure (Hagenmaier and Shaw, 1990). Deviation from the ideal behavior can also be induced by temperature effects on materials (Myers et al., 1962). Since a main function of an edible films or coatings are often to impede moisture transfer between food and the surrounding atmosphere, or between two components of a heterogeneous food products, water vapor permeability should be low as possible. The WVP of rice starch composite films with different MCPF were examined at a vapor pressure difference of 0/60% across films. The effect of content of MCPF fillers on water vapor permeability (WVP) of the rice starch films is shown in Figure 2. The WVP of rice starch films decreased as the content of MCPF fillers increased. For example, the WVP of the films decreased from 67.2 g.mm/m2.day.kPa to 32.51 g.mm/m2.day.kPa when increasing the MCPF fillers content from 0 to 40% (Figure 2A). The improvement of the WVP of the films can be attributed to the formation of a rigid hydrogen-bonded network of cellulose in the composite that is governed by percolation mechanism (Pu et al., 2007). These considerations and the importance of the MCPF fillers aspect ratio are undoubtedly contributing factors to the mechanical and physical properties of the RS/MCPF biocomposite films reported in this study. Film solubility (FS) is advantageous in situations when the films will be consumed with a product that is heated prior to consumption and may also be an important factor that determines the biodegradability of films when used as a packaging wrap. Biocomposite film pieces produced from RS/MCPF maintain their integrity (i.e., did not dissolve or break apart) even after 24 h of incubation with a gentle motion. This indicates that the rice starch and MCPF had intermolecular networks that remained intact and only the monomers were soluble (Stuchell and Krochta, 1994). The FS of the rice starch films as a function of MCPF in the film forming solutions are shown in Figure 2B. The results demonstrated that the FS of rice starch films decreased with the addition of MCPF. These results could arise from the fact that higher content of MCPF induced a rice starch and MCPF interaction and resulted in a decrease in the FS.
ไอน้ำละลาย permeability และฟิล์มWater vapor permeability is proportionality constant assumed to be independent of the water vapor pressure gradient applied across the films. However, hydrophillic (edible or nonedible) materials, such as protein films, derivative from this ideal behavior due to interactions of permeating water molecules with polar groups in the films structure (Hagenmaier and Shaw, 1990). Deviation from the ideal behavior can also be induced by temperature effects on materials (Myers et al., 1962). Since a main function of an edible films or coatings are often to impede moisture transfer between food and the surrounding atmosphere, or between two components of a heterogeneous food products, water vapor permeability should be low as possible. The WVP of rice starch composite films with different MCPF were examined at a vapor pressure difference of 0/60% across films. The effect of content of MCPF fillers on water vapor permeability (WVP) of the rice starch films is shown in Figure 2. The WVP of rice starch films decreased as the content of MCPF fillers increased. For example, the WVP of the films decreased from 67.2 g.mm/m2.day.kPa to 32.51 g.mm/m2.day.kPa when increasing the MCPF fillers content from 0 to 40% (Figure 2A). The improvement of the WVP of the films can be attributed to the formation of a rigid hydrogen-bonded network of cellulose in the composite that is governed by percolation mechanism (Pu et al., 2007). These considerations and the importance of the MCPF fillers aspect ratio are undoubtedly contributing factors to the mechanical and physical properties of the RS/MCPF biocomposite films reported in this study. Film solubility (FS) is advantageous in situations when the films will be consumed with a product that is heated prior to consumption and may also be an important factor that determines the biodegradability of films when used as a packaging wrap. Biocomposite film pieces produced from RS/MCPF maintain their integrity (i.e., did not dissolve or break apart) even after 24 h of incubation with a gentle motion. This indicates that the rice starch and MCPF had intermolecular networks that remained intact and only the monomers were soluble (Stuchell and Krochta, 1994). The FS of the rice starch films as a function of MCPF in the film forming solutions are shown in Figure 2B. The results demonstrated that the FS of rice starch films decreased with the addition of MCPF. These results could arise from the fact that higher content of MCPF induced a rice starch and MCPF interaction and resulted in a decrease in the FS.
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