【作者】 李学红；

【导师】 金征宇；

【作者基本信息】 江南大学 ， 粮食，油脂与植物蛋白， 2007， 博士

【摘要】 本论文选用挥发性和非挥发性两类食品抗菌剂,研究了环糊精（CD）在抗菌食品包装中的两种应用方式:一是先使环糊精与抗菌剂形成包合物,然后加入到食品包装材料中,通过抗菌剂从包合物中的缓慢释放以及在材料中的迁移,最后达到食品表面发挥抗菌作用;二是先将环糊精固载在纤维包装材料上,然后通过固载环糊精对食品抗菌剂的包埋与缓释来实现纤维材料的抗菌性能。异硫氰酸烯丙酯（AITC）对食品常见腐败菌和致病菌都有很强的杀灭作用,由于其具有强挥发性及刺激的气味,很难直接应用于包装材料上。本文利用环糊精或固载环糊精纤维对其进行包埋与释放,模拟了气态AITC释放形式的抗菌食品包装体系。首先,利用溶液共沉淀法制备环糊精-异硫氰酸烯丙酯包合物（CD-AITC,主客体摩尔比1:1）,通过均匀设计试验分析优化了包埋工艺。以环糊精包埋率为指标,MATHEMATICS4.0分析得到拟合方程y=9.44+4 x₁+22.74x₂+0.35 x₃-0.45 x₄ ,对各因素最佳取值后包埋率可达88.5%;以环糊精回收率为指标,利用MATHEMATICS4.0分析得到拟合方程y=17.87-2.5 x₁+42.87 x₂-0.15 x₃+0.074 x₄,对各因素最佳取值后环糊精回收率可达88.0%。同时,根据环糊精包合物的包埋与释放机理,建立了CD-AITC的准确定量分析方法,即利用无水环境下的有机溶剂洗涤法测定包合物表面吸附油、利用有机溶剂-水体系下的热浸提法测定包合物中的包合油,并以紫外分光光度法进行定量。实践证明,该方法具有需要样品量少、操作相对简便和准确度高的优点,RSD不大于1.26%,包合物含油量测定平均回收率为95.6%。通过红外光谱及热重分析,确认了CD-AITC包合物的形成。热重分析表明AITC经CD包埋后,挥发性大为降低,耐热性显著提高;释放实验表明,CD-AITC具有一定的缓释特性,其释放速率与环境相对湿度（RH%）和环糊精包埋率密切相关,随着RH%的增加其释放速率也相应变大,低包埋率时释放速度趋缓;α-及β-CD-AITC具有相似的释放规律,但由于空间结构的匹配性,α-CD-AITC的释放速率要缓慢得多。通过Avrami方程对包合物的释放过程进行拟和,得到50RH%、75RH%和98RH%三种相对湿度条件下α-及β-CD-AITC的释放速率常数k和释放机理参数n（均在0.5附近）,可以判断α-及β-CD-AITC中AITC的释放都是遵循限制扩散的动力学过程。其次,研究了聚丙烯酸法接枝环糊精到纤维素纤维上的新工艺。结果表明该法与常用柠檬酸接枝法相比能达到更理想的环糊精固载率;对反应温度的研究表明接枝反应分为两个阶段,聚丙烯酸的接枝主要发生在低温阶段,而环糊精的接枝固着主要发生在高温处理阶段,因此在不影响纤维品质的条件下高温处理有利于高环糊精固载纤维样品的获得。通过固载环糊精纤维对AITC的包埋试验发现,由于空间位阻作用纤维中环糊精固载率与AITC的包埋载量并不完全成正比,保持环糊精有效的包埋位点非常重要。试验结果显示,环糊精固载量应控制在7.5-9%之间较为合适,此范围的功能纤维样品对AITC的包埋量在600-750μL/100g之间,固载环糊精包埋率达95%以上。包埋AITC的功能纤维同样具有控制释放的特性,其释放规律与CD-AITC包合物相类似,并遵循限制扩散的动力学过程,而由聚丙烯酸网络层吸附的AITC基本不具控制释放的性能。由于空间位阻以及纤维对AITC的吸附等作用,固载环糊精纤维AITC的释放速度小于未固载环糊精包和物。作为常见的食品防腐剂,苯甲酸和尼泊金酯耐热性较差,直接加入包装材料中在热成型时会有较大损失,而且有时在包装材料中的迁移速度也不理想。通过环糊精包埋可显著提高其热稳定性,改变其迁移行为,使制备相应的抗菌包装材料成为可能。本论文利用溶液共沉淀法制备了苯甲酸和尼泊金乙酯与β-CD的固体包合物,采用均匀设计试验并用MATHEMATICS4.0软件对包合工艺进行分析优化。以环糊精包埋率为指标,苯甲酸包合过程的拟合方程为y=89.49-1.26x₁+21.34 x₂+81.15 x₃-4.42 x₄-17.57 x₂ x₃,各因素最佳取值后环糊精对苯甲酸的包埋率为83.5%,尼泊金乙酯包合过程的拟合方程为y=2.98-0.23x₁+23.81 x₂+81.14 x₃-2.83 x₄-1.78 x₅-16.86 x₂ x₃,各因素最佳取值后环糊精对尼泊金乙酯包埋率为83.1%%;以环糊精回收率为指标,苯甲酸包合过程的拟合方程为y=253.69-2.17x₁-6.14 x₂+15.24 x₃-8.5 x₄,各因素最佳取值后环糊精回收率为74.5%,尼泊金乙酯包合过程的拟合方程为y=2.24+0.37x₁+18.68 x₂+58.64 x₃-4.57 x₄+0.38 x₅-14.12 x₂ x₃,最佳取值后的环糊精回收率为81.5%。溶液中包合物相溶解度图显示苯甲酸和尼泊金乙酯可以与β-CD形成主客体摩尔比为1:1的包合物,其中尼泊金乙酯-CD包合常数K为551 L/moL,苯甲酸-CD包合常数K为270 L/moL,说明环糊精对尼泊金乙酯的包合能力要强于苯甲酸;环糊精包埋后苯甲酸和尼泊金乙酯的溶解度都得到提高。红外光谱和热重分析结果确认了两种β-环糊精固体包合物的形成。其中,热重分析曲线表明苯甲酸和尼泊金乙酯经β-环糊精包埋之后,热稳定性都得到很大提高。选用丙烯酸酯涂膜和聚乳酸膜作为包装材料基质,研究了尼泊金乙酯和苯甲酸的迁移行为。结果表明,两种抗菌剂在膜中的迁移速度很大程度上受食品模拟液性质的影响。在低醇类食品体系中,尼泊金乙酯和苯甲酸在聚乳酸膜中基本不发生迁移,只在高醇溶液中发生迁移;当抗菌剂以环糊精包合物形式加入膜中,由于包合物对膜的结构特性产生影响,致使其迁移能力得到很大提高,且迁移速度同时还受环糊精包合物控制释放机制的影响。在10%和50%乙醇溶液中包合物膜中抗菌剂迁移速度较快,而在60%甘油体系中则体现较明显的缓释效果,在正己烷中释放程度很低。该结果说明环糊精包合物聚乳酸膜在中低水分活度的食品中可以发挥长效抗菌作用。尼泊金乙酯和苯甲酸在丙烯酸膜中能发生迁移,迁移质量比在45-60%之间,而以环糊精包合物形式加入涂膜,其迁移质量比得到提高,且迁移速度同样受环糊精包合物控制释放的影响。研究表明,该类环糊精包合物丙烯酸涂膜不适合脂肪食品体系,而应用于中低水分活度的非脂食品中可以发挥长效抗菌作用。尼泊金乙酯和苯甲酸包合物在膜中的释放过程可利用Fickian公式来进行预测,通过对不同时间迁移质量比的测定,利用Mathcad软件计算得出相应的迁移系数D,可建立起相应的数学模型。将制得的β-CD-AITC包合物及其功能纤维应用于冷鲜肉的模拟包装,结果显示缓释的AITC对肉品中的腐败菌和致病菌都具有杀灭作用,由于释放出的为气态AITC,因此该类包装材料不需与食品直接接触,尤其适用于固态食品的防腐包装。将含有尼泊金乙酯环糊精包合物的聚乳酸膜应用于中式香肠的模拟包装,结果显示该包装膜具有很好的杀菌效果。以上试验说明,食品抗菌剂环糊精包合物及其功能材料应用于肉产品包装,可有效提高其安全性并延长货架期,具有很大的应用开发潜力。更多还原

【Abstract】 In the present study, two application patterns of CDs in antimicrobial food packaging were investigated using the volatile and non-volatile antimicrobials. One is to prepare the antimicrobials inclusion complex with CD and then incorporate the inclusion complex directly into polymers material. In this way the antimicrobial agents could migrate and release gradually from the packaging film to the food surface. The other way is to covalent immobilization of CDs onto polymers to obtain the antimicrobial functional material by the complexation of the fixed CDs with antimicrobial agents.Allyl isothiocyanate（AITC） has strong activity in inhibiting pathogens and food spoilage bacteria. But it is difficult for AITC to be directly applied in packaging materials due to the strong volatile and the strong odor.In the present study, packaging systems that release volatile antimicrobials was simulated by entrapping AITC with CDs or fixed CDs in fabrics. The results showed that the inclusion complex of AITC with CD （CD-AITC, Molar ratio of 1:1） could be prepared with co-precipitation method and the techniques parameters was optimized by the homogeneous design. As to the index of inclusion efficiency of CDs, a simulated equation y=17.87-2.5 x₁+42.87 x₂-0.15 x₃+0.074 x₄ was obtained by MATHEMATICS4.0 Analysis and the maximum was 88.5%; As to the recovery of CDs, a simulated equation y=9.44+4 x₁+22.74x₂+0.35 x₃-0.45 x4 was obtained MATHEMATICS4.0Analysis and the maximum was 89.11%. During the experiment, an accurate quantitative analysis method of CD-AITC was developed according to the entrap and Release mechanism of CDs. The surface AITC was determined by solvent（hexane）washing and the total AITC was determined using a solvent-water extraction method on the heat condition, followed by UV spectrophotometric analysis of the concentrated extract. It has proved that the methods have advantages of little sample needed, a relatively simple operation and high accuracy. The RSD was no more than 1.26% and the average recovery of AITC was 95.6%.The formation of CD-AITC inclusion complex was confirmed by infrared spectroscopy and thermal analysis. Thermogravimetric analysis showed that the entrapped AITC had much less volatile and significantly enhanced heat-stability. Release experiments show that CD-AITC have control release characteristics and the release rate was closely related with the relative humidity （RH%） and the inclusion efficiency of CDs, which increased with the increase of RH% and slowed down correspondingly with the low inclusion efficiency of CDs. Theα- andβ-CD-AITC have similar release property, but the release rateα-CD-AITC was more slow thanβ-CD-AITC due to the spatial structure matching. The release behavior of AITC fromα- andβ-CD-AITC complexes at different RH was simulated using the Avrami equation, and the release rate constant k and the parameter n representing the release mechanism were obtained All of the n values estimated were near 0.54, which indicated that the release of included AITC in the complexes belonged to the limited diffusion kinetics. The grafting of CDs onto cellulose fiber by polyacrylic acid is a new technology and its feasibility was investigated in this paper. The results showed that the polyacrylic acid method could achieve a more satisfactory graft rate of CD than that by citric acid. The studies on reaction temperature show grafting reaction is divided into two stages, the graft of polyacrylic acid occurred in low temperature stage and CD graft mainly in the hot stage. Therefore, high temperature conditions without prejudice to the fiber quality are conducive to the fix of CD. The complexation test found that the graft amount of CDs is not entirely proportional to the AITC load of fiber due to the steric hindrance, and it was important to maintain the effective entrapping site of CD. The experimental results showed that fixed CD should be controlled between 7.5-9% while the load AITC in functional fiber obtained was 600-750uL/100g samples and the inclusion efficiency of CDs beyond up to 95%. The release behavior of the functional fibre was similar to that of CD inclusion complex, and belonged to the limited diffusion kinetics. The absorbed AITC by polyacrylic acid Network Layer didn’t possess controlled release properties. Due to the steric hindrance and the AITC absorption of fiber, the AITC release rate of functional fiber is slower than unfixed CD-AITC.Since ethylparaben and benzoic acid both cannot tolerate the temperatures during polymer processing, the direct addition of the two preservatives into the packaging material would result in a great heat loss. Furthermore, their migration rate in packing materials sometimes is not satisfactory. The complexation of the two food preservative by CDs could significantly improve their thermal stability and migration behavior, and meanwhile the preparation of the corresponding antimicrobial packaging materials become possible. In this study, the solid inclusion complex of ethylparaben and benzoic acid with CD were prepared with co-precipitation method. The techniques parameters were optimized by the homogeneous design. As the index of inclusion efficiency of CDs, a simulated equation y=89.49-1.26x₁+21.34 x₂+81.15 x₃-4.42 x₄-17.57 x₂ x₃ was obtained for the benzoic acid complex and the maximum was 83.5%, a simulated equation y=2.98-0.23x₁+23.81 x₂+81.14 x₃-2.83 x₄-1.78 x₅-16.86 x₂ x₃ was obtained for the ethylparaben complex and the maximum was 83.1%, by MATHEMATICS 4.0 Analysis; As to the recovery of CDs, the simulated equation y=253.69-2.17x1-6.14 x₂+15.24 x₃-8.5 x₄ was obtained for the benzoic acid complex and y=2.24+0.37x₁+18.68 x₂+58.64 x₃-4.57 x₄+0.38 x₅-14.12 x₂ x₃ for the ethylparaben complex, the maximum values were 74.5% and 81.5%, respectively, by MATHEMATICS 4.0 Analysis. The phase solubility curve showed that both ethylparaben and benzoic acid could form inclusion complex with CD in molar ratio of 1 :1, with the complex constant K of 551 L/mol for ethylparaben and 270 L/mol for benzoic acid, which indicated that inclusion capacity of ethylparaben with CD was stronger than that of benzoic acid. The solubility of the two kind of food preservatives in water were improved by the CD complexation. The formation of the two kind of inclusion complex was also confirmed by infrared spectroscopy and thermal analysis. Thermogravimetric analysis showed that the entrapped guest had significantly enhanced heat stability.Specific migration studies were performed for both ethylparaben and benzoic using acrylate coating and polylactic acid membrane matrix filled with food simulant. The results showed that the migration behavors were influenced by the type of food stimulant. In the low-alcohol food system, both of ethylparaben and benzoic didn’t migrate in polylactate acid membrane, but did in high-alcohol solution. When inclusion complexes of antimicrobials were added into the membrane, the migration had been much improved due to their impact on the membrane structure properties, and more the migration rate was also affected by the control release mechanism of cyclodextrin. In 10% or 50% ethanol solution antibacterial agents moved faster from membrane, while in 60% glycerol system the release become slow obviously and release level is very low in hexane. It could be concluded that the antimicrobial membrane with CD complexes had longer-lasting effect in low-water-activity foods.Both of ethylparaben and benzoic acid could migrate in acrylate coating with the migration quality ratio of 45-60%, which were improved once antimicrobials complex with CDs were added. The migration speed also subjected to the control release of CDs. The study indicated that such acrylic coating was not suitable for fatty food system, however could play a role in long-term antibiotics in low water activity of non-fat foods. Fickian equation could model the migration behavior of ethylparaben, benzoic acid and their CD complexes in packaging membrane. Through determination of antimicrobials migrated to food simulant at different time, Mathcad software could calculate transfer coefficient D, and the corresponding migration model was established.The CD-AITC complex and its functional fibers were used in the simulated cold meat packaging system, and showed good inhibition activity to spoilage bacteria and pathogenic bacteria. The polylactic acid film was used in Chinese sausage packaging system and showed a good bactericidal effect. These test descripted above indicated that the inclusion complex of food antimicrobials with CD and their functional materials could be applied in meat packaging for the improvement of safety and extendence of the shelf-life.更多还原