33.2. Physical properties of the films The composite films incorporating CEO and CWO were visually homogeneous with no brittle areas or bubbles, and could be easily peeled from the casting plates. To identify the highest concentration of either CEO or CWO that could be incorporated in to the CH matrix, increasing amounts (up to 50% w/w) were tested in the film-forming solution. As we expected, a stronger aroma was found when the concentration of essential oil increased. No lipid separation occurred in composite films even when the essential-oil content was high. Generally, the effects of additives on the properties of the films depended on the type of compounds and concentrations and their inherent hyrophilicity and hydrophobicity indices. The composite CH film thickness varied between the range of 22 and 27 m, and the incorporation of two essential oils(CEO and CWO) did not significantly (P > 0.05) affect the result-ing film thickness (data not shown). Control CH films generallywere very hydrophilic, and swelled when they absorbed water quickly. As shown in Table 1, CH films without any essential oil had significantly higher (P < 0.05) moisture uptake than did CH films incorporating either CEO or CWO. The moisture uptake of both CEO and CWO incorporated films decreased as the concentra-tion of essential oil increased from 10% to 20% w/w, although this reduction was not found to be significant (P > 0.05) in films incorporating either CEO or CWO. Moisture uptake decreased significantly(P < 0.05) to 41.1% and 38.8% for the films containing 30% w/w CEO and CWO, respectively. This was in accordance with our expectation that increasing the concentration of essential oils would decrease the films’ hydrophilicity. The lower moisture content of CWO-containing films compared to those containing CEO may be attributed to more hydrogen and covalent interactions between CH chains and CWO components, which reduced the availability of hydrogen groups to form hydrophilic bonds with water molecules.This would result in a decrease in the tendency of CH film to absorb water [40]. These findings were similar to those of other authors when they incorporated a hydrophobic agent such as -tocopherol or cinnamon essential oil into CH films [41,42].