【作者】 洪伦波；

【导师】 孟岳成；

【作者基本信息】 浙江工商大学 ， 食品科学， 2007， 硕士

【摘要】 本论文采用TPA（texture profile analysis）方法分析了结冷胶凝胶的质构特性；用动态流变学方法测定了结冷胶的凝胶温度、凝胶速率、储能模量（G′）和损耗模量（G″）的变化；利用激光共聚焦显微镜对FITC共价标记结冷胶进行了研究，探讨了结冷胶在酸性乳饮料中与酪蛋白胶束的结合状态。对结冷胶凝胶质构的研究表明：凝胶硬度随着结冷胶质量分数的增加而增大。0.02％的结冷胶凝胶强度随着钙离子浓度增加而增大，当钙离子到达0.015％～0.02％以后凝胶强度减小。相同的钙离子质量分数条件下，添加乳酸钙的凝胶强度高于氯化钙。pH降低会导致凝胶强度迅速下降；柠檬酸钠可以螯合钙离子使凝胶强度下降；低质量分数（0.0～12.5％）的蔗糖对于凝胶强度影响不明显。在结冷胶一卡拉胶—魔芋胶的复配胶体系中，结冷胶是胶体硬度、弹性和内聚性的主要影响因素。利用流变学的方法研究了结冷胶的凝胶温度和凝胶速率，发现二者均随着结冷胶的含量增加而升高，凝胶温度、凝胶速率与结冷胶浓度之间的关系符合下述方程：t_gel=0.43884exp(X_gellan／0.11441)+33.73519（R²=0.989）；g（t）=0.82615exp(X_gellan／0.04307)+4.60167（R²=0.999）。在钙离子浓度相同的条件下，添加乳酸钙样品的模量、凝胶温度和凝胶速率均高于氯化钙。在钙离子不过量条件下，凝胶温度与钙离子浓度之间关系均符合下列方程：1／T_gel=0.00035exp（-X_i／0.00494）+0.00324（R²=0.995，氯化钙源）；1／T_gel=0.00026exp（-X_r／0.00555）+0.00324（R²=0.993，乳酸钙源）。在结冷胶-卡拉胶-魔芋胶的复配体系中，结冷胶和钙离子的浓度是影响凝胶温度的主要因素，卡拉胶与魔芋胶的比率影响起始凝胶速率，卡拉胶：魔芋胶为3：1时起始凝胶速率最大。随着卡拉胶浓度的增加二次凝胶速率线性增大。利用FITC荧光标记和激光共聚焦显微镜对结冷胶的成胶研究表明：钙离子为0.04％，结冷胶含量0.005％时，凝胶结构虽然有大量的空白区域，但是已经存在连续的联结点，结冷胶0.01％时形成了致密的网络状结构。结冷胶和牛乳酪蛋白的结合形式与CMC（羧甲基纤维素钠）表现出明显的差异。在酸性乳饮料中可见酪蛋白胶束聚集在一起形成酪蛋白胶束团粒，CMC包裹在酪蛋白胶束周围（粒径为2.95-2.99μm）而对酪蛋白起到稳定作用；结冷胶则是吸附在酪蛋白胶束上（粒径为1.50-2.00μm），不能形成有效的保护层以阻止酪蛋白胶束团粒的聚集。更多还原

【Abstract】 The textural properties of gellan gum were investigated by TPA;gelling temperature, gelling rate and G’ were determined by usingdynamic rheological analysis; The interactions of gellan gum and CMCwith casein micelles in acidified milk drink were observed by laserconfocal microscope through covalently labeling FITC.The results of textural study show that hardness increased withincreasing gellan concentration. The hardness of 0.02%gellan increasedwith increasing calcium ions concentration until reached a criticallevel（0.015～0.02%）, after which further increase in calcium resulted in areduction of hardness. At the same concentration of calcium ion, theaddition of calcium lactate caused gels to be much higher hardness thanin the addition of calcium chloride. Hardness rapidly decreased with pHfalling down; sodium citrate can decrease the hardness; and lowconcentration（0.0～12.5%） of sucrose showed less effect on the hardnessof gellan. In the mixed gels of gellan-carageenan-konjac, gellan is themost effective factor to the hardness, springiness and cohesiveness.Gelling temperature and gelling rate were studied by rheological behaviour, and both of them increased with increasing gellanconcentration, and the equation shown below:t_gel=0.43884exp(X_gellan/0.11441)+33.73519 （R²=0.989）;g（t）=0.82615exp(X_gellan/0.04307)+4.60167 （R²=0.999）.At the sameconcentration of calcium ion, calcium lactate exhibited greater effects onthe G’, gelling temperature and gelling rate than calcium chloride. Underthe critical level of calcium ion concentration, our study indicatedexponential relationship between gelling temperature and calcium ionconcentration shown below:1/T_gel=0.00035exp（-X_i/0.00494）+0.00324（R²=0.995,calciumchloride）; 1/T_gel=0.00026exp（-X_r/0.00555）+0.00324（R²=0.993, calciumlactate）.In the mixed gels of gellan-carageenan-konjac, the concentrationsof gellan and calcium are the major factors which affected gellingtemperature and gelling rate. The ratio of carageenan to konjac affects thefirst stage of gelling rate which reached the highest when the ratio is 3:1.The second stage of gelling rate linear increased with increasingcarageenan concentration.Trough FITC labeling gellan gum and laser confocal microscopeobserving, our results shown that 0.005%gellan gum form continuousjuncture with 0.04%calcuim ion though there are widely void areasthroughout the gel, 0.01%gellan form homogeneous and compactnetwork. The interaction of casein micelles with gellan is different with CMC.In the acidified milk drink, few casein micelles agglomeratetogether to form a round particle, CMC coated the particle to stabilizecasein micelles with diameter 2.95-2.99μm,while gellan adsorbed ontocasein micelles with diameter 1.5-2.0μm.Gellan cannot form protectinglayer around the casein micelles particle to prevent the casein micelleparticles from agglomerating together.更多还原