EGCG与明胶交联/缓释生物膜对冷藏罗非鱼片的保鲜作用机理研究

Our previous research results suggested that fish gelatin combined with Epigallocatechin Gallate (EGCG) coating significantly increased the storage life of fresh tilapia fillets. Based on the analysis physicochemical characteristics of EGCG and gelatin, “controlled-release system” was speculated by the cross-linking and formation of biofilm. EGCG was gradually released from the system and spread out to the surface and superficial layer of fillets. EGCG and gelatin have many advantages function, such as the antimicrobial, antioxidant and oxygen exclusion, and these function add together to achieve better synergy of preservation effect. To prove the preservation mechanism of controlled-release biofilm on fish fillet, gelatin serves as a carrier and biocompatibility crosslink with EGCG to prepare of composite biofilm system. Therefore, it is very important to research possible molecular cross-link of the biofilm system. Effect of controlled-release biofilm on freshness quality evaluation of tilapia fillets during cold storage will be studied. Synergy mechanism of controlled-release biofilm will be explored, with the evaluation parameters such as pH, total volatile basic nitrogen, TBARS value, K value, total bacterial colony counts, color, texture and flavor. Dynamic model of the shelf life will be established basing on freshness parameters of fillets, and the model will be used to predict the end of fish freshness. Hence, it has great theoretical and practical significance to study this program.

依据前期“表没食子儿茶素没食子酸酯（EGCG）/鱼皮明胶保鲜涂膜法显著提高生鲜罗非鱼片的保存期”的研究结果，以及对EGCG和明胶的物化特性和交联作用进行深入分析，我们推测EGCG与明胶交联获得的保鲜膜在鱼体表面可形成逐渐释放EGCG的“缓释体系”。EGCG具有的抑菌、抗氧化和明胶具有的隔氧性能经过叠加，将达到更好的保鲜协同增效作用。为了证明上述假设，本项目以明胶为载体与EGCG进行生物相容性交联制备复合保鲜生物膜，研究其可能的分子交联方式。以鱼片的新鲜度为评价指标，探讨该生物膜缓释体系对罗非鱼片冷藏过程中pH、挥发性盐基氮（TVB-N）、硫代巴比妥酸反应物（TBARS）值、K值、菌落总数、色泽、质构和风味等参数的影响，从本质上阐明该生物膜缓释体系的协同作用机制。并基于鱼片新鲜度变化参数建立鱼片货架期动力学模型，来预测鱼肉新鲜度值的终点，具有重要的理论和实际意义。

将EGCG和明胶交联成为一种新型的EGCG-明胶复合膜（以下简称复合膜, EGT）用于罗非鱼片的低温保鲜，探究其提高罗非鱼品质、改变菌群结构和延长货架期的效果及机制。结果表明，复合膜具有良好的抗氧化和抗菌活性。随着EGCG含量的增加（1%～5%），复合膜变性温度升高，凝胶强度升高，微观结构变得更加致密。红外光谱图和蛋白质凝胶电泳的结果表明，氢键是EGCG分子和明胶分子之间相互结合的主要作用力。EGCG在复合膜体系中的释放的过程显示，第13小时的释放速率最大，持续释放时间可达300小时。另外，复合膜处理（EGT）延缓了鱼片弹性、硬度和颜色的变化，降低了鱼片中TBARS和TVB-N值。与对照（CON）组相比，复合膜样品的K值（在18天时为74%）和生物胺含量均较低。感官评价结果显示，与CON组相比，EGT罗非鱼片的保质期延长了6天。罗非鱼片的微生物种类随着冷藏时间的增加而逐渐减少。EGT组的微生物数量和相对丰度比空白组低，EGT样品中每个分类水平的微生物群数量在第0天（门：13；类目：25；目：40；科：53；属：75，种：39）时较小，并且EGT降低了最终样品中气单胞菌和不动杆菌等优势腐败菌的相对丰度（21天）。因此，EGT改变了冷藏鱼片的菌群结构，抑制了鱼片腐败过程中微生物的生长和繁殖。因此，本研究具有重要的理论和实际意义。