【作者】 陈霞；

【导师】 刘宏生； 肖杰；

【作者基本信息】 华南理工大学 ， 食品工程（专业学位）， 2020， 硕士

【摘要】 随着生活水平的提高,人们对食品的需求由数量转化为质量,这也给食品品质的提升和贮存保鲜技术提出了新的要求。开发环境友好、安全、性能可调控的生物基可食性活性膜已成为食品包装领域的研究热点。包装材料的高效水分子阻隔（阻湿性）功能是保证食品在货架期内保持品质的关键因素之一。理想的可食性包装膜内外两侧应对水蒸气分子具有选择性阻隔作用,不仅要防止包装外界水分渗透,还要保持内部食品保鲜所需的相对湿度。此外,开发可高效负载、控释天然功能性成分的活性包装已被认为是减少或防止运输和贮存过程中食品发生的氧化、褐变或微生物污染等质量安全问题的有力举措。本论文针对传统蛋白基可食性膜内外两侧无法选择性阻隔和吸附水蒸气分子及活性成分控释难等问题,采用具有功能互补特性的玉米醇溶蛋白（Zein）和明胶（Gelatin）为成膜基质,构建多层膜体系（Z-ZG-G）和复合膜体系（ZG）,开发了兼具单向阻湿性和长效控释功能的新型活性包装材料。系统研究了活性膜微观形貌结构与理化性能、及控释之间的构效关系,并将其应用于鲜切水果保鲜。主要研究结果如下:（1）基于Zein的阻水特性和明胶的亲水特性,以Zein为外层,Zein/Gelatin作为中间过渡层和明胶为内层的顺序,采用逐层流延的方法制备Z-ZG-G多层膜。当中间层ZG比例为1:2时,Z-ZG_1:2-G多层膜呈现出具有不同特征的三层结构,各层之间结合紧密但界面分隔清晰。该膜具有良好的透明度和机械性能,以及一定的抗紫外线作用。研究结果表明,水蒸气从Zein侧向明胶侧进行渗透得到的WVP值显著低于从明胶侧进行渗透的,表明多层膜两侧可对水蒸气进行选择性阻隔,进而实现单向阻湿的功能。构建了水蒸气渗透过程中结构响应（Zein疏水自聚集,明胶吸水溶胀）的物理模型,揭示多层膜单向阻湿特性的形成机制。（2）基于Zein的两亲特性和自组装行为,构建了Zein/Gelatin复合膜（ZG）,并对不同比例下ZG复合膜的微观结构及特性进行研究。当Zein含量较高时（ZG比例为3:1,2:1）,Zein和明胶产生宏观相分离,获得了具有明显相边界的分层结构;当明胶含量较高时（ZG比例为1:1,1:2,1:3）,发生微观相分离,可获得Zein球形聚集体分布在明胶连续性基质中的隔室化结构。当ZG比例为1:2时,ZG_1:2复合膜呈现致密的梯度结构,其中Zein聚集体粒径适中且倾向分布于明胶基质的空气侧。复合膜具有最低的水蒸气透过率,且其空气侧的水蒸气透过率值低于底面侧,可实现对水分子单向阻隔的功能。研究结果表明,通过调节ZG比例,可实现对相分离结构的精准调控。（3）基于膜基质与活性成分不同的亲和作用机制,利用ZG_1:2复合膜具有的隔室化结构实现分区共负载:分别将亲水性抗氧化剂茶多酚（TP）负载于明胶基质中,将疏水性抗菌剂牛至精油（OEO）负载于Zein聚集体中,开发了一种可控释不同类型活性成分的双功能复合膜材料。TP的引入可影响明胶规则网络结构的形成,使明胶连续性基质的表面形态较为粗糙,而OEO的包封导致Zein聚集体呈现出粗糙颗粒状的横截面形态。此外,TP、OEO分别和膜基质之间存在氢键和疏水相互作用。当进行共负载时,ZG_1:2复合膜具有更强的阻湿性和更高的TP和OEO保留率。动力学分析表明,Z_OG_TP膜中TP和OEO的释放机理为非Fick扩散,且接近于一级释放动力学。（4）基于分层结构对活性成分不同的滞留作用机制,利用Z-ZG_1:2-G多层膜体系,对茶多酚（TP）进行浓度梯度负载。在G内层负载较低浓度的TP可起到初始抗氧化作用,在ZG中间层负载高浓度的TP作为抗氧化剂储备层,进而开发了一种具有长效控释性的多层功能膜。TP在多层膜中表现出缓释性,其释放动力学与TP的浓度梯度和每个膜层的结构响应密切相关,且其在水溶液中的释放行为表现为:前期为扩散和一级动力学的组合机制（0–175 min）,中期为以浓度驱动的一级动力学机制（175-300 min）,后期为以扩散主导的动力学机制（>300min）。鲜切水果试验表明,载有TP的多层功能膜在控制水分流失、防止快速褐变和抑制微生物生长等方面显示出良好的保鲜效果。更多还原

【Abstract】 With the improvement of living standards in our country,people’s demand for food is transformed from quantity to quality,which also puts forward new requirements for the improvement of food quality and preservation technology.The development of biobased edible films with the advantages of environmental friendliness,safety and active functions has become a research hotspot in the field of food packaging.To ensure the quality of food during shelf life,one of the key factors is the efficient water barrier property of food packaging materials.Ideal edible packaging film should have permselective barrier property against water vapor on both sides.That is,while preventing the penetration of external moisture,the relative humidity required for food preservation inside the packaging is maintained.In addition,the development of active packaging that can efficiently load natural functional ingredients and control their release has been considered as a powerful measure to reduce or prevent the quality and safety issues such as oxidation,browning or microbial contamination of foods during transportation and storage.Addressing the problems that the traditional protein-based edible films do not have the selective barrier or and adsorption to water vapor molecules and the difficulty of controlled release of active compounds,this essay aims to take complementary advantages of zein and gelatin to construct multilayer film system(ZZG-G)and composite film system(ZG),and to further establish novel active packaging materials with one-way moisture barrier and long-term controlled release properties.We systematically study the effects of microstructure of active films on physicochemical properties and controlled release of active ingredients,and apply the film to the field of fresh-cut fruit preservation.The main contents are as followed:(1)Based on the Multilayer films with the stacking order of hydrophobic zein outer layer,hybrid zein/gelatin middle layer and the hydrophilic gelatin inner layer(Z-ZG-G)were fabricated by layer-by-layer solvent casting method.When the ZG ratio of the middle layer is 1:2,the Z-ZG1:2-G multilayer film exhibited tri-layers structure with different characteristics,which had well-defined borders but was tightly coupled.The film displayed good transparency and mechanical properties while keeping UV protection property.The results showed that when the moisture transferred from the zein side to gelatin side,the WVP value was significantly lower than that from the gelatin side,indicating that the multilayer film can achieving one-way moisture barrier property.The physical model of the structural response(Zein hydrophobic selfaggregation,gelatin swelled by water absorption)on both sides of the multilayer film during water vapor infiltration was constructed to reveal the formation mechanism of the one-way moisture barrier of the multilayer film.(2)Based on amphiphilic characteristics and self-assembly behavior of Zein,Zein/Gelatin composite films(ZG)were constructed,and the microstructure and characteristics of the composite films at different mass ratio of zein to gelatin were studied.When the Zein content was high,the macroscopic phase separation took place between Zein and Gelatin,and a layered structure with identified phase boundary was obtained.When the gelatin content was high(ZG ratio is 1: 1,1: 2,1: 3),microscopic phase separation occurs,and the compartmentalized structure that Zein spherical aggregates distributed in the gelatin continuous matrix can be obtained.The ZG1:2 composite film exhibited a dense gradient structure,in which Zein aggregate with moderate particle size tended to be distributed on the air side of the gelatin matrix.The ZG1:2 film also showed good comprehensive performance and the lowest WVP value,and the WVP value on the air side was lower than the bottom side,realizing one-way moisture barrier property.The results indicated that precise control of phase separation structure can be achieved by simply changing the ZG mass ratio.(3)Based on the different affinity between the film matrix and the active ingredients,the compartmentalized structure of the ZG1:2 composite film was utilized to achieve co-loading.The hydrophilic antioxidant tea polyphenol(TP)was loaded in gelatin matrix,and the hydrophobic antibacterial oregano essential oil(OEO)was loaded in Zein aggregates to develop bifunctional composite film with controlled release of various active ingredients.The incorporation of TP affected the formation of the regular network structure of gelatin,making the surface morphology of gelatin continuous matrix rough,while the encapsulation of OEO resulted in a graininess cross-section morphology of zein aggregates.FTIR results confirmed the hydrogen bond and hydrophobic interactions between TP,OEO and film matrix,respectively.The simultaneous loading led to stronger water barrier property with higher retention rate of TP and OEO in ZG1:2 film.Kinetic analysis suggested the release mechanisms of TP and OEO from ZOGTP film were non-Fick diffusion and were close to the firstorder release kinetic.(4)Based on the different retention mechanisms of the active ingredients in the layered structure,the optimized Z-ZG1:2-G multilayer film was used to load tea polyphenol(TP)with concentration gradient.The multilayer functional film with prolonged release property was fabricated,in which the inner G layer was loaded with a lower concentration of TP to play an initial antioxidant role,and the middle ZG layer as antioxidant reserve layer was loaded with a higher concentration of TP.TP released from the multilayer film in a prolonged manner and the release kinetic was closely related to the structure responses of each film layer.The release experiments of TP from multilayer film into distilled water suggested the combination mechanism of diffusion and first-order kinetics(0–175 min),followed by the concentration-driven first-order kinetic mechanism(175-300 min),and finally diffusion-dominated kinetic mechanism(> 300 min).When applied on freshly cut fruits,the TP loaded multilayer film exhibited preservation effects in terms of controlling weight loss,preventing rapid browning and inhibiting bacterial deterioration.更多还原