【作者】 乔立文；

【导师】 杨严俊；

【作者基本信息】 江南大学 ， 食品科学， 2011， 硕士

【摘要】 鸡蛋营养价值高,具有很好的乳化性、凝胶性、起泡性等功能性质,但是鲜蛋不易储存运输,将其加工成液态蛋后,使用更加安全、方便,在食品企业中应用更加广泛。在全蛋液生产及应用过程中,经过温度、物理、机械剪切等处理后,全蛋液的功能性质会受到影响,但是由于全蛋液成分复杂,目前相关研究比较匮乏。本文以全蛋液为研究对象,通过研究理化条件、均质、热处理等加工过程对全蛋液功能性质的影响,确定其变化规律及机制,并研究了添加蔗糖与盐对于全蛋液耐热性及功能性质的影响,为减少加工过程对功能性质的影响提供理论指导,促进液蛋加工业的生产与发展。首先,研究pH值对于全蛋液功能性质的影响,pH值选择条件为6.5-9.0。结果表明全蛋液的溶解度、乳化液稳定性及凝胶硬度会随着pH值的增加而明显增加;乳化活力会随着pH值的增加而明显的降低;同时,起泡力与泡沫稳定性分别在pH7.0与7.5时最好,其他条件下较差。其次,研究高压均质处理对于全蛋液功能性质的影响,均质压力为5-40Mpa。结果表明高压均质处理会显著影响全蛋液的性质,均质处理后起泡力与乳化活力明显降低,而乳化稳定性、泡沫稳定性与凝胶硬度均明显增加,功能性质的变化与蛋白质结构及状态变化有关,因此,在生产全蛋液时,不同功能要求的产品应采用不同强度的均质处理。然后,研究58℃、61℃、64℃和67℃下加热2.5-10min对于全蛋液乳化性、起泡性、流变性质以及蛋白结构、变性程度等理化性质的影响。结果表明热处理导致不同蛋白质变性,进而影响全蛋液的性质;研究发现全蛋液在58-64℃时加热乳化活力变化不明显,而67℃时乳化活力随加热时间明显降低;适度的热处理(58℃、61℃)会改善蛋液的起泡力,继续升温则导致其明显降低,而泡沫稳定性在加热后明显增加;全蛋液性质的变化导致海绵蛋糕比容降低;全蛋液功能性质的变化与蛋白质结构改变有关,蛋白质在加热过程中不断展开与聚合,导致总的表面疏水性与巯基含量随加热温度与时间发生复杂变化,加热还导致全蛋液粘度增加,并且在67℃时全蛋液由牛顿流体变为假塑性流体,最后非变性聚丙烯酰胺凝胶电泳证明不同加热温度与时间会导致不同蛋白质变性。最后,研究了添加蔗糖与盐对于全蛋液耐热性的影响,添加量分别为4%-8%。结果表明添加蔗糖与盐可以提高全蛋液的耐热性,使其形成凝胶温度提高了3-7℃,而且全蛋液耐热性会随着盐添加量的增加而提高;添加盐可以使全蛋液在加热后具有良好的乳化活力与起泡力,而添加蔗糖可以改善全蛋液的乳化稳定性与泡沫稳定性;同时添加4%的蔗糖与盐则使全蛋液具有较好的乳化性与起泡性质,但是蔗糖与盐的添加会降低凝胶的硬度。更多还原

【Abstract】 Hen egg, in addition to its high nutritional quality, contributes functional properties to food such as emulsifying, foaming and gelling, however, fresh egg can not store for a long lime, and it is more convenient and safer when they were processed into liquid egg products, which make it widely used in food products. During the production and application of liquid whole egg (LWE), the proteins are subjected to several processing steps with thermal, physical and mechanical treatments that may damage egg protein functional properties, however, due to the material’s complicated composition and structure, its functional properties have not received the attention they deserved. The aim of this study was to investigate the influence of pH adjustment, homogenizing treatment, heat treatment and addition of sugar/salt on the functional and physicochemical properties of LWE, to understand the mechanism responsible for the functional property change in order to limit their harmful effects and promote the development of LWE production.First, the effects of pH adjustment (6.5-9.0) on functional property of LWE were investigated. Results showed that the solubility, emulsion stability and gel hardness significantly increased as pH increased, while the emulsifying activity of LWE decreased. It was also foud that the foaming ability and foaming stability was under the best when pH was 7.0 and 7.5 respectively.Secondly, we studied the influence of homogenizing treatment (5-40Mpa) on the properties of LWE. Results showed that homogenizing treatment significantly affected the functional properties of LWE, homogenizing at high pressure led to a decrease in foaming ability and emulsifying ability, but a increase in emulsion stability, foaming stability and gel hardness, however, it led to a slight change in solubility. Homogenizing treatments could distrubte the structure of egg proteins and polymer. Resultes suggested that the factory should use appropriate homogenizing treatment when producing liquid whole egg.Then,the paper dealed with the effect of heat treatment (58℃、61℃、64℃and 67℃,2.5-10min) on the physicochemical properties such as emulifying property, foaming property, rheology property and extent of protein denaturation of LWE. Results showed that heat treatments induced different proteins denature and influenced functional properties; it was found that the emulsifying activity of LWE changed slightly when the temperature was between 58-64℃and significantly decreased when the temperature was at 67℃,while heat treatments above 64℃significantly improved the emulsion stability. Foaming property changed more complex after heat treatment, moderate heat treatment (58-61℃) improved the foaming ability, which would decrease when the temperature increased. These changes induced the decrease of sponke cake volume; the changes in functional properties were related with the protein structure, heat treatment induced proteins unfold and aggregate, which resulted in the surface hydrophobicity and free sulfydryl content significantly changed after heat treatment. We also found that heat treatment increased the viscosity and changed the rheology property of LWE. Finally, Native-page electrophoresis proved that different heat treatments induce different proteins denaturation. Finally, we studied the effect of addition of sugar/salt (4%-8%) on the properties of LWE. Addition of sugar or salt resulted in the increase of heat resistance of LWE and the gelation temperature increased 3-7℃. LWE with salt had better emulifying activity and foaming ability after heat treatment, and LWE with sugar had better emulsion stability and foaming stability than others, meanwhile, LWE with sugar and salt(4%) had good emulifying property, foaming property, which indicates that there is a synergistic reaction between sugar and salt. It was also found that addition sugar or salt decreased the hardness of LWE gel .更多还原