Effect of the Addition of Carnauba Wax on Physicochemical Properties of Chitosan Films

Films and edible coatings of natural polymers have been proposed as an attractive alternative for conventional plastic packaging because of their excellent biodegradability and biocompatibility. However, natural polymers, like chitosan, are hydrophilic and present poor water barrier properties. The addition of wax or other hydrophobic substances decreases water permeability of natural polymers but can increases their opacity.The objective of this work was to produce biofilms based on chitosan and different concentrations of carnauba wax and analyze their optical and barrier properties. The films were obtained by dissolving chitosan in acetic acid. Carnauba wax was incorporated into film-forming solutions at0, 15, 30, 40 and 50% (w/w). The opacity increased with higher concentrations of wax, the film with 50% of wax showed the highest value with an increase of 10.5% compared to the control film. The water vapor permeability decreased from 2.73 g.mm/kPa.m2.h (0% of wax) to 0.77 g.mm/h.kPa.m2 (40% of wax). The solubility decreased to about 60% over the control films, and the contact angle increased from 53º to 83º, in film with 0 and 50% of wax, respectively.以天然高分子制备的薄膜及可食用涂层，凭借优异的生物降解性与生物相容性，已成为传统塑料包装极具吸引力的替代方案。然而，壳聚糖（chitosan）等天然高分子具有亲水性，阻水性能欠佳。添加蜡类或其他疏水物质可降低天然高分子的水蒸气透过率，但会提升其浊度。本研究旨在制备基于壳聚糖与不同浓度巴西棕榈蜡（carnauba wax）的生物膜，并对其光学性能与阻隔性能展开分析。薄膜通过将壳聚糖溶解于乙酸中制得，将巴西棕榈蜡以0、15、30、40及50%的质量比（w/w）添加至成膜液中。实验结果显示，随着蜡添加浓度升高，薄膜浊度逐步上升：添加50%蜡的薄膜浊度最高，较对照组提升10.5%。水蒸气透过率从0%蜡添加组的2.73 g·mm/kPa·m²·h降至40%蜡添加组的0.77 g·mm/h·kPa·m2。薄膜溶解度较对照组降低约60%，接触角则从0%蜡组的53º提升至50%蜡组的83º。