钙盐和明胶对高酰基结冷胶的凝胶特性的影响

利用质构仪质构剖面分析法（TPA）研究了不同浓度的氯化钙、乳酸钙、葡萄糖酸钙对高酰基结冷胶凝胶特性的影响；明胶添加量对高酰基结冷胶凝胶特性的影响；以及三种钙盐和明胶对高酰基结冷胶凝胶特性的影响。结果表明，三种钙盐都可以提高高酰基结冷胶的凝胶强度。添加明胶可以提高高酰基结冷胶的凝胶强度、咀嚼性、弹性和内聚性。对比三种钙盐，添加乳酸钙的高酰基结冷胶-明胶复配胶凝胶特性最好。因此，适量的钙盐和明胶可以提高高酰基结冷胶的凝胶特性，为高酰基结冷胶在食品中的应用提供理论参考。     

高酰基结冷胶的溶胶和凝胶特性研究及结构初步分析

采用黏度计和质构仪对高酰基结冷胶的溶胶和凝胶性质进行研究。结果表明：高酰基结冷胶在质量浓度为 0.05～0.1g/100mL 时,表观黏度随质量浓度增加而增加,并呈现假塑性流体特性;在质量浓度为0.2～0.5g/100mL时形成凝胶,凝胶强度受胶体及 Ca2+ 质量浓度的影响明显,同时高酰基结冷胶比例增加,高低复配胶体的凝胶强度减小。并利用红外光谱扫描和核磁共振技术对高酰基结冷胶结构进行初步分析。     

低酰基结冷胶流变行为研究

研究了浓度、温度、剪切速率、pH和离子浓度对低酰基结冷胶流变行为的影响。结果表明,低酰基结冷胶为典型的切力变稀流体,其表观黏度和剪切速率的关系符合幂律方程。在同一剪切速率下,表观黏度随温度的升高而降低。在同一温度下,结冷胶溶液的表观黏度则随着剪切速率的增加而减小。低酰基结冷胶凝胶强度随着Ca2+和Na+浓度的增加出现先增大后减小的趋势,相对于Na+而言,Ca2+形成的凝胶强度更高,且用量更少。     

基于应力松弛原理的高酰基结冷胶凝胶特性研究

本文采用应力松弛模式研究了一价离子(K+和Na+)和二价离子(Ca2+和Mg2+)对高酰基结冷胶凝胶特性的影响。结果表明:高酰基结冷胶凝胶的应力松弛行为符合Peleg经验模型。离子浓度和离子种类对高酰基结冷胶凝胶应力松弛行为影响显著,平衡弹性模量(EA)随着离子浓度的增加呈马鞍形趋势变化,且其与凝胶硬度呈现较好的正相关(R=0.943~0.983),表明EA可以用来表征高酰基结冷胶凝胶的强度。相对于一价离子(K+、Na+)而言,二价离子(Ca2+、Mg2+)形成的凝胶强度更高,且用量更少。在相同离子浓度下,Na+形成的凝胶比K+形成的凝胶强,Ca2+形成的凝胶则比Mg2+形成的凝胶强。在16000 g下离心10 min,高酰基结冷胶凝胶保水性均在95%以上,与离子浓度基本无关,保水性能优异。高酰基结冷胶应力松弛机制是体系内部物理交联点的移动。     

高酰基结冷胶对乳清分离蛋白热诱导凝胶特性的影响

蛋白质-多糖凝胶具有良好的稳定性和机械强度,在稳定和传递生物活性物质、营养强化剂方面的应用前景广阔。该研究以乳清分离蛋白、高酰基结冷胶为原料制备热诱导混合凝胶,分析高酰基结冷胶对乳清分离蛋白-高酰基结冷胶混合凝胶的凝胶强度、保水性及显微结构等,揭示乳清蛋白-高酰基结冷胶凝胶形成机理。结果表明,高酰基结冷胶促使蛋白质巯基暴露从而使凝胶形成稳定结构,提高混合凝胶的凝胶强度和保水性,且随着高酰基结冷胶含量增加而显著增大,其质量浓度为4 g/L时,复合凝胶的凝胶强度最大,为26.97 g;保水性最好,为97.41%;透光率最低,为1.87%。温度扫描结果表明,增加高酰基结冷胶可以提高乳清分离蛋白的相转变温度,傅里叶红外光谱显示,乳清分离蛋白与高酰基结冷胶存在分子间作用力,扫描电子显微镜表明高酰基结冷胶诱导混合凝胶形成结构紧密的三维网络结构。该研究为拓展乳清分离蛋白和结冷胶的新型凝胶食品,提高传统食品的质量,改善食品的加工工艺提供基础理论数据。     

离子对结冷胶凝胶温度及强度的影响

主要研究了不同浓度的钙、镁、钾、钠离子对结冷胶凝胶温度及强度的影响;不同浓度的结冷胶与离子对凝胶强度的影响;当钙、镁、钾、钠离子含量一定时,不同浓度的结冷胶对凝胶温度及强度的影响;钙离子和钾、钠离子对结冷胶凝胶是否有协同作用。结果表明,随着离子浓度的增加,凝胶温度先升高后降低,凝胶强度先增大后减小,在离子含量很少或很多时,结冷胶的凝胶温度和强度都很低。凝胶强度和温度随着结冷胶浓度的增加而增加。钙离子和钾、钠离子在促进结冷胶凝胶上无协同作用。     

结冷胶LT100流变学特性的研究

研究了结冷胶LT100溶液的凝胶特性及其流变特性,着重研究了结冷胶LT100溶液在不同的浓度、温度、热处理温度、热处理时间、剪切速率、剪切时间、静置时间影响下的流变特性。结果表明:不同浓度的结冷胶LT100形成的凝胶强度有所不同。结冷胶LT100凝胶具有热可逆性、温度滞后性及明显的假塑性。     

影响结冷胶水溶液流变特性的因素

研究了质量分数、时间、温度、柠檬酸、pH值、Na^＋、Ca^2＋对结冷胶水溶液的粘度及形成凝胶后的凝胶强度的影响.结果表明：结冷胶的粘度随着溶液质量分数的增加呈非线性增大,室温下其粘度的稳定时间大于4 h.温度、pH值、柠檬酸对结冷胶水溶液粘度有相应的影响;柠檬酸、NaCl、CaCl2溶液对结冷胶的凝胶强度有较大影响.     

卡拉胶凝胶特性及其在巧克力牛奶中的应用

针对卡拉胶水凝胶的两个主要指标凝胶强度和胶体黏度,研究了卡拉胶含量、钾离子浓度和pH值三个主要因素对卡拉胶水凝胶特性的影响,结果表明:凝胶强度随胶体含量的增加线性增大后渐趋平稳、受钾离子的影响出现峰值、在pH值8.0和10处出现两个拐点;胶液黏度随卡拉胶含量增加迅速增大、随钾离子浓度提高而减小、中性时的黏度最大.通过正交实验确定了影响卡拉胶凝胶因素的主次顺序为卡拉胶浓度、钾离子浓度和溶液的pH值,最佳条件组合为卡拉胶浓度1.2%,钾离子浓度1.2%,pH值9.0;通过考察单独使用卡拉胶以及卡拉胶与魔芋胶、刺槐豆胶及结冷胶等几种食品胶在巧克力牛奶中形成凝胶时的结构状态,判定卡拉胶与刺槐豆胶的协同作用效果最佳.     

高酰基结冷胶特性及应用研究进展

目的:介绍新型微生物多糖-高酰基结冷胶的研究进展和前景.方法查阅近年来国内外的相关文献报道,并进行分析、整理和归纳.结果 胶体浓度、外加金属阳离子类型和含量、pH值、糖份都会对凝胶特性和流变性产生影响. 结论 高酰基结冷胶作为一种新型凝胶剂,只有在充分理解掌握其凝胶特性的基础上才能获得理想的效果.     

Influence of pH and added gums on the properties of konjac flour gels

The gel strength and texture of konjac gel and mixed gels of konjac and various gums were measured after gelation at various concentrations of alkali. A selection of different alkaline reagents was used. Regardless of alkali concentration, increasing konjac levels caused a decrease in pH but an increase in hardness and strength of konjac/gellan gum mixed gels. The highest gel strength and hardness were given by mixed konjac/gellan gum gels using sodium carbonate as the gelling medium. Under similar gelling conditions, the addition of gellan gum resulted in the greatest gel hardness. Of the gums examined, a possible synergistic effect on konjac/gellan gum mixed gel texture was observed.     

结冷胶凝胶特性及在食品工业中的应用

目的:介绍新型微生物多糖--结冷胶的凝胶特性及其在食品工业中的应用现状和前景.方法:查阅今年来国内外的相关文献报道,并进行分析、整理和归纳.结果:结冷胶组织相容性和复配性能良好,具有良好的透明性,凝胶性能卓越,具有独特的胶凝和融化温度,可形成多种凝胶质构,在极低的用量下形成的预(弱)凝胶可以发挥良好的悬浮、稳定作用.结论:结冷胶作为一种新型凝胶剂,其优异的性能将在食品工业中得到广泛应用.     

Characterization of gelation time and texture of gelatin and gelatin–polysaccharide mixed gels

The effects of cooling rate, holding temperature, pH and polysaccharide concentration on gelation characteristics of gelatin and gelatin–polysaccharide mixtures were investigated using a mechanical rheometer which monitored the evolution of G′ and G″. At low holding temperatures of 0 and 4 °C, elastic gelatin gels were formed whereas a higher holding temperature of 10 °C produced less elastic gels. At slow cooling rates of 1 and 2 °C/min, gelling was observed during the cooling phase in which the temperature was decreased from room temperature to the holding temperature. On the other hand, at higher cooling rates of 4 and 8 °C/min, no gelation was observed during the cooling phase. Good gelling behavior similar to that of commercial Strawberry Jell-O^® Gelatin Dessert was observed for mixtures of 1.5 and 15 g sucrose in 100 ml 0.01 M citrate buffer containing 0.0029–0.0066 g low-acyl gellan. Also, these mixed gels were stronger than Strawberry Jell-O^® Gelatin Desserts as evidenced by higher G′ and gel strength values. At a very low gellan content of 0.0029 g, increasing pH from 4.2 to 4.4 led to a decrease in the temperature at the onset of gelation, G′ at the end of cooling, holding and melting as well as an increase in gel strength. The gelation time was found to decrease to about 40 min for gelatin/sucrose dispersions in the presence of 0.0029 g gellan at pH 4.2 whereas the corresponding time at pH 4.4 was higher (79 min). In general, the gelation time of gelatin/sucrose dispersions decreased by a factor of 2 to 3 in the presence of low-acyl gellan. The addition of low-acyl gellan resulted in an increase in the gelation rate constant from 157.4 to 291 Pa. There was an optimum low-acyl gellan content for minimum gelation time, this optimum being pH dependent. Addition of guar gum also led to a decrease in gelation time to 73 min with a corresponding increase in the gelation rate constant to 211 Pa/min though these values were not sensitive to guar gum content in the range of 0.008–0.05 g. The melting temperature of gelatin/sucrose/gellan as well as gelatin/sucrose/guar mixtures did not differ significantly from that of pure gelatin or Strawberry Jell-O^® Gelatin Desserts. At pH 4.2, the melting rate constant was highest at a low-acyl gellan content of 0.0029 g whereas the rate constant was insensitive to low-acyl gellan content at pH 4.4. Addition of guar did not seem to affect the melting temperature or the melting rate constant.     

Gelling Temperatures of Gellan Solutions as Affected by Citrate Buffers

Effects of citrate buffers at pH 3.5 and 5.0 on gelling temperatures of gellan solutions with 0.4–1.8% gellan and 1.5–60 mM Ca²⁺were studied. Partial dissociation of the carboxyl groups in gellan polymer in pH 3.5 solutions resulted in weakened gels. The pH 3.5 buffer exhibited weak chelating ability for Ca²⁺. The gelling temperature of gellan solutions at pH 3.5 was quantitatively related to polymer and cation concentrations using a similar model to that for gellan water solutions. The pH 5.0 buffer exhibited strong chelating ability. Gelling temperatures at pH 5.0 were generally lower than those at pH 3.5, except at low calcium concentrations.     

薜荔籽果胶凝胶特性的研究

本实验采用LFRA质构仪测定不同影响因素对薜荔籽果胶凝胶强度的影响,初步探讨了薜荔籽果胶的凝胶特性和凝胶机理。实验结果表明,薜荔籽果胶在室温条件下,0.5%浓度的溶液就可形成凝胶;溶胶温度越高(50～100℃),其凝胶强度越大;薜荔籽果胶凝胶的pH值范围为3～6,最佳pH值为4;糖对薜荔籽果胶的凝胶强度影响较小,最佳糖添加量是20%;金属离子对其影响最大,影响效果依次为:Cu2 >Fe3 >Ca2 >Mg2 >K 。对薜荔籽果胶分子作用力的初步考察结果表明:疏水作用、氢键作用、静电作用在薜荔籽果胶形成凝胶的过程中均起到关键作用,疏水作用影响最大。     

银耳多糖与结冷胶复配体系的流变及凝胶特性

对不同质量浓度的银耳多糖溶液、结冷胶溶液（均为0.4、0.8、1.2、1.6、2.0 g/100 mL）及不同质量比（1.6∶0.4、1.2∶0.8、0.8∶1.2、0.4∶1.6）的银耳多糖/结冷胶复配体系的流变和凝胶特性进行研究,初步探讨其相互作用机理。结果表明,随着银耳多糖质量比的提高,复配体系的表观黏度和动态黏弹性增加,储能模量（G’）和损耗模量（G”）增加。复配体系的触变环随银耳多糖质量比例的增加而减小,说明银耳多糖可以改善复配体系的触变性。质构分析和持水性测试结果表明,结冷胶是银耳多糖/结冷胶复配凝胶强度和硬度的决定性因素,银耳多糖可以明显提高复配体系的弹性、黏性和持水性。基于傅里叶变换红外光谱和低温扫描电子显微镜分析,初步判断在复配体系中银耳多糖与结冷胶之间存在相互作用,形成了凝胶网络结构。     

EFECT OF pH BUFFERS ON MECHANICAL PROPERTIES OF GELLAN GELS

The strength and deformability of calcium cross-linked gellan gels as affected by pH 3.5 and 5.0 citrate and acetate buffers were measured by large compressive deformation test until failure. The trend of dependence of gel strength on polymer and calcium concentrations was similar to gels formed in distilled water without pH adjustment. A critical calcium concentration was observed for each gellan concentration. Gels formed at the critical calcium concentration exhibited the maximum strength. The chelating effect of pH 5.0 citrate buffer greatly increased the critical calcium concentration. The failure strain, representing the deformability, of gellan gels formed in buffers behaved differently from gels formed in distilled water. In the pH 3.5 buffer systems, gellan gels were brittle regardless of gellan and calcium concentrations. In the pH 5.0 buffer systems, gellan gels were brittle at high calcium concentrations and ductile at calcium concentrations less than 24 mM in citric buffer and less than 6 mM in acetate buffer.     

Effect of polymer ratio and calcium concentration on gelation properties of gellan/gelatin mixed gels

Gelation properties of gellan/gelatin mixed solutions were studied using dynamic viscoelastic testing at eight different ratios of gellan (1.6–0.2% w/v) to gelatin (0–1.4% w/v) and seven different calcium levels (0–30 mM). The gelation temperature and gelation rate of the mixed gels were significantly affected by the ratio of gellan to gelatin as well as concentration of calcium. Addition of calcium at low levels resulted in an increase in gelation temperature and gelation rate compared to gels with no added calcium. Further increases in calcium increased the gelation temperature, but caused a decrease in gelation rate of the mixed gels. In addition, the presence of gelatin generally had a negative influence on gelation rate, especially at high proportions and when the solution had a high gelling temperature, probably by physically hindering the growth and development of gellan crosslinks. It appeared that in the presence of calcium, gellan formed the continuous gel matrix, with gelatin present as a discontinuous phase. Gellan/gelatin mixtures can form gels over a wide temperature range by varying the ratio of the two polymers as well as the calcium concentration.     

低酰基结冷胶酸性凝胶的凝胶特性

以葡萄糖酸-δ-内酯(glucono-δ-lactone,GDL)作为酸诱导剂,制备低酰基结冷胶(low acyl gellan gum,LA)酸性凝胶,考察基体质量浓度、GDL/LA复配比例以及酸液浸泡对酸性凝胶凝胶特性的影响。研究结果表明,GDL酸化为缓慢酸化,GDL/LA复配比例越高、体系的pH值越低,酸化速率越快。基体质量浓度和GDL/LA复配比例对酸性凝胶结构影响显著,断裂应力和保水性随着GDL/LA复配比例的增大先升高后降低。基体质量浓度越高,断裂应力和不透明性越大。GDL/LA复配比例增大,断裂应变减小,不透明性增大。当酸液pH值为1时,酸液浸泡对GDL/LA复配比例为2∶1和4∶1的酸性凝胶强度无影响,但GDL/LA复配比例为1∶4、1∶2和1∶1时,凝胶强度随浸泡时间的增加而增强,酸液浸泡可以促使酸性凝胶进行结构重建。