【作者】 王芳；

【导师】 章建浩；

【作者基本信息】 南京农业大学 ， 农业推广硕士（专业学位）， 2016， 硕士

【摘要】 保鲜包装方式对咸鸭蛋的风味品质和保质期具有重要影响。目前市场上的咸鸭蛋普遍采用真空包装,不仅能耗高、机械化程度低,而且产生的包装废弃物对环境造成了严重的白色污染。因此探究咸鸭蛋新的保鲜包装方法对降低包装成本、提高生产效能、实现节能减排具有重要的意义。近年来,涂膜保鲜包装技术逐渐成为食品保鲜包装研究的热点。聚偏二氯乙烯(Polyvinylidenechloride,PVDC)作为涂膜保鲜包装的重要材料,相比于广泛应用的聚乙烯醇(PVA),其阻隔性能不随环境中湿度的变化而发生改变。但通过纳米材料改性来提高PVDC包装性能还未见研究。本论文拟采用经表面修饰的亲水性纳米SiO2粒子对聚偏二氯乙烯包装材料进行改性,并研究其涂膜保鲜包装特性及对咸鸭蛋的储藏保鲜效果,具体研究内容如下:1.表面活性剂对纳米SiO2水溶液分散体系的影响研究选用六种不同的表面活性剂,以重力沉降法结合平均粒径测定,研究不同表面活性剂对纳米SiO2水溶液的分散稳定性。初步筛选出十二烷基硫酸钠(SDS)对纳米SiO2水介质条件下的分散稳定性作用效果最强,以SDS为表面活性剂的纳米SiO2水溶液粒径较小且纳米粒子分布均匀。通过二次回归分析法进一步研究了不同pH条件及不同纳米SiO2/SDS配比对纳米SiO2表面修饰的影响。结果表明,酸性条件下表面活性剂SDS修饰纳米SiO2后可形成稳定的分散体系,其对应的最适pH范围在3.10-4.86之间;在SiO2/SDS配比为0.7时,纳米材料分散体系具有最小的粒径分布,为 207±14.2nm。2.纳米SiO2改性PVDC基涂膜材料结构及包装性能研究采用共混法在PVDC胶乳液的合成过程中加入SDS修饰的纳米SiO2粒子,通过流延成膜法制备不同纳米 Si02含量(0,0.03、0.05、0.1、0.12、0.15、0.2、0.3、0.5g/60mL水纳米SiO2,以SiO2/SDS为0.7:1)的PVDC/SiO2纳米复合膜。纳米改性复合膜的包装性能受纳米SiO2含量的影响,随着纳米SiO2含量的增加,PVDC/SiO2纳米复合膜液的粘度和成膜透光率显著降低,并且复合膜的水蒸气阻隔性能(成膜透湿率)显著提高(P<0.05),当纳米SiO2添加量为0.12%时,PVDC/SiO2纳米复合膜的透湿率与PVDC单膜相比下降了 22.5%。扫描电镜结果表明,当SiO2添加量为0.12%时,PVDC基涂膜材料有较好的平整性。涂膜效果感官评定表明当SiO2添加量在0.1%-0.12%时,PVDC乳液用于咸鸭蛋涂膜保鲜包装有较好的感官效果。3.纳米SiO2改性PVDC基复合涂膜材料对咸鸭蛋储藏保鲜效果的研究分别以PVDC/SiO2纳米改性复合膜材料、未改性的PVDC膜材料以及课题组前期研制的纳米SiO2/TiO2交联改性PVA基膜材料、纳米MMT改性PVA基膜材料涂膜咸鸭蛋,以未涂膜处理为对照组,置于28℃,相对湿度70%的条件下120天,检测储藏过程中咸鸭蛋的品质变化。结果表明:不同涂膜材料均能显著减少咸鸭蛋在储藏过程中的不良品质变化(失重率增加、挥发性盐基氮升高、菌落总数增加)(P<0.05)。纳米SiO2改性PVDC涂膜处理组相比于对照组失重率显著降低52.9%且对咸鸭蛋菌落总数、TVB-N和游离脂肪酸的累积以及蛋青蛋黄中pH的变化的抑制程度显著高于其它涂膜处理组(P<0.05),但储藏过程中TBARS的变化不显著(P>0.05)。在28℃,70%相对湿度条件下,PVDC/SiO2纳米改性复合膜可将咸鸭蛋的保质期延长至120 d。更多还原

【Abstract】 Fresh packaging has an important impact on the flavor quality and shelf life ofsalted duck eggs.The vacuum packaging is commonly used for preserving cooked salted duck eggs,of which higer energy consumption and lower mechanization,and could cause“white”pollution.Therefore,exploring new fresh packaging method for salted duck egg packaging are of great significance,which could reduce packaging costs,and improve production efficiency.In recent years,coating fresh-keeping technology has become a research hotspot.As an important coating fresh packaging material,polyvinylidene chloride shows the broad application prospects in the field of food,medicine,military,electronics.However,it has not been found to improve the packaging properties by modifying the nano materials.This paper proposes to study the packaging properties of PVDC-based nano-SiO2 composite materials,and as well as to explore the effect of nanocomposite on quality of salted eggs during storage,the detailed contents are as follows:1.Studies on the influence of surfactants on the dispersion system of nano silica aqueous solutionSelecting six different surfactants,we studied the dispersion stability of nano silica aqueous solution with different surfactants by using the gravitydepositionmethodcombined with the averageparticlesize determination.Preliminary screened out the effect of Sodium dodecyl sulfate(SDS)on the dispersion stability of nano SiO2 in water medium was the best,and the nano SiO2 aqueous solution with SDS as the surfactant had smaller particle size and uniform particle distribution.Then we studied the influence of different pH and different nano SiO2/SDS ratio on the surface modification of nano SiO2.The results showed that nano SiO2 modified by SDS could form a stable dispersion system under the acidic condition and the optimum range of pH was from 3.10 to 4.86.We also discovered that the nano material dispersion system had the minimum particle size distribution,when the ratio of SiO2/SDS was 0.7,and the minimum particle size was 207±14.2nm.2.Preparation and structural characterization of nano silica modified PVDC-based coating materialsSDS modified nano SiO2 particles were added to the PVDC emulsion by blending method,polyvinylidene chloride(PVDC)-based nanocomposite films with different amount of modified nano-SiO2 were fabricated by a solution-intercalation,film-casting method.Packaging properties of nanocomposite films was greatly influenced bynano-SiO2 content.With the increaseof nano-SiO2 content,the viscosity of nano composite films was significantly decreased and water vapor permeability and water resistance of films increased,but transparency property decreased.The mechanical properties of the composite film are also affected by the content of nano-SiO2.Results on scanning electron microscopy(SEM)revealed that PVDC-based coating material has good flatness when nano-SiO2 content is 0.12%.PVDC/SiO2composite films with 0.1%-0.12%nano-SiO2 addition was used to coating salted duck eggs based sensory evaluation.3.Effect of nano-SiO2 modified PVDC-based composites coating material on quality of salted duck eggs during preservation processSalted duck eggs that were coated withPVDC/SiO 2,unmodified PVDC material and SiO2/TiO2 modified PVA-based,namo-MMT modified PVA-based nanocomposite coating materialrespectively,were stored at 28℃,70%relative humidity for 120 days,quality changes were detected during the storage process.The treatment of different coating could significantly decrease the bad quality changes(increase of loss of weight,TVB-N,total bacteria counts)(P<0.05),and prolong the shelf life of the salted duck eggs.The inhibition of PVDC/SiO2nanocomposite to increase of loss of weight,total bacteria counts,TVB-N,free fatty acids,pH changes of egg yolk and albumen was significantly higher than other coating materials(P<0.05).However,the TBARS of salted duck eggs didn’t change significantlyduring preservation(P>0.05).The results of sensory evaluation indicated that PVDC/SiO2 composite coating materials could effectively preserve the quality of salted duck eggs.更多还原