抗菌纳米复合包装膜的设计及控释机理研究

Controlled-release antimicrobial packaging represents future development in food preservation packaging. The packaging film has the limited ability in controlling release rate of antimicrobial if antimicrobial is added directly into the film, and the burst-release occurs easily. This project uses the design that the antimicrobial is first encapsulated in the pectin/chitosan polyelectrolyte nanoparticles and then the nanoparticles are incorporated into compatible film material.In this way, the antimicrobial could release gradually from packaging film due to double-controlling functions of the nanoparticles and the film, meanwhile,mechanical and barrier properties of the film are improved. The effects of pectin esterification and synthesis conditions on nanoparticle structure and morphology are first studied and the formation mechanism of nanoparticles is derived. The synthesis conditions of nanoparticles with regular morphology and good stability are screened out. Afterwards pectin/chitosan polyelectrolyte nanoparticles embedding antimicrobial are prepared and the encapsulation and controlled-release of antimicrobial are studied. The nanoparticles are then added into compatible polysaccharide film and the effect of nanoparticles on film properties are studied. The cumulative release rate of antimicrobial from film in different food stimulant are measured.It is able to calculate diffusion coefficients,describe the release kinetics of antimicrobial based on Fick mathematical mode,and present controlled-release mechanism. The biopolymer antimicrobial films are applied in food and their functions are evaluated. This study opens a new field for antimicrobial packaging study.

具有控释能力的抗菌包装技术代表着未来食品防腐包装工业的发展方向。 由于在包装膜中直接添加抗菌剂，膜调控抗菌剂释放速率的能力有限，易出现暴释现象，本项目拟采用低酯果胶/壳聚糖聚电解质纳米粒子包埋抗菌剂，再将抗菌纳米粒分散于具有相容性膜材料中的设计，利用纳米粒子和膜材料的双重调控作用，达到对抗菌剂的缓控释目的，同时增强膜的力学和阻隔性能。先研究果胶酯化度和合成条件对果胶/壳聚糖纳米粒子结构形貌的影响，推导其形成机理，筛选出形态规则、稳定性好的纳米体系，进而合成包埋不同抗菌剂的果胶/壳聚糖纳米粒子，探讨包埋和释放能力。再将抗菌纳米粒子加入多糖类膜材料，研究纳米粒对复合膜性能的影响，测定在不同食品模拟液中抗菌剂从膜中的累积释放量，采用基于Fick定律的扩散数学模型计算扩散系数，研究迁移机制，阐明控释机理，评价生物高分子抗菌膜在食品包装中应用的可能性。该研究为我国抗菌包装研究打开一个新的领域。

本项目采用纳米粒子包埋抗菌剂，再将抗菌纳米粒分散于具有相容性膜材料中制备抗菌包装膜。对抗菌纳米微粒体系进行设计并研究形成规律，考察了果胶与壳聚糖通过复凝聚法形成聚电解质复合物的机制，揭示了聚电解质所带电荷、配比及溶液pH值对纳米粒子形成的影响，果胶的羧酸和壳聚糖的氨基是通过静电相互作用形成复合物的。利用复合物对肽类抗菌剂乳酸链球菌素和油溶性抗菌剂肉桂醛进行包埋，确定了包埋不同抗菌剂的最佳工艺条件，证明了包埋对抗菌剂的抗菌稳定性起到很大的保护作用。研究了天然聚电解质包埋的抗菌粒子在不同温度和湿度下对抗菌剂的释放速率，表明抗菌剂经包埋后有助于缓慢释放，在加工贮藏过程中能持续长久地发挥作用。将抗菌粒子加入膜材料，研究了粒子对复合膜的机械性能、透明度、水蒸气透过率的影响，精油微胶囊降低了膜的抗张强度和透明度，增加了膜的断裂伸长率和水溶性，并且抗菌膜对金黄色葡萄球菌、大肠杆菌和黑霉菌都有较好的抑菌作用，可以应用于抗菌包装材料；采用Fick第二定律推导了山梨酸钾从明胶膜中释放的机理并建立了数学模型，表明了抗菌剂在膜中的扩散机理遵循Fickian模型。采用抗菌复合膜对罗非鱼肉进行冷藏保鲜，抗菌膜包覆的鱼肉TBA、菌落总数、pH值均处于较低的水平，说明抗菌复合膜能抑制鱼肉脂肪氧化腐败和微生物生长，延长鱼肉冷藏的货架期。同时加入挥发性抗菌精油微胶囊的包装能延长肉糜和水果贮藏的货架期。该研究为生物高分子抗菌膜在食品包装中应用的可能性提供了理论基础。