γ-聚谷氨酸对罗非鱼皮酶促溶性胶原自聚集性的影响

研究γ-聚谷氨酸对罗非鱼皮酶促溶性胶原自聚集动力学和自聚集水凝胶的微观结构及性能的影响。结果表明,在不同含量γ-聚谷氨酸存在的条件下,胶原自聚集过程仍然包含成核阶段和生长阶段,但是γ-聚谷氨酸能够延长胶原的成核时间,并降低成核阶段的速率常数,而生长阶段的速率常数先增加后降低。胶原自聚集能够形成外观为白色的水凝胶,经扫描电镜观察其为三维纤维网络结构,但是γ-聚谷氨酸能够影响到胶原纤维的致密度,当γ-聚谷氨酸相对胶原的百分比增加到80%时,网络致密度表现增加趋势,当其进一步增加到100%时,致密度显著下降,相对应的凝胶强度也先增强后减弱。然而,γ-聚谷氨酸并未显著提高水凝胶的耐酶性和热稳定性,因此下一步研究将引入交联等技术进一步改善水凝胶的性能。     

聚集条件对罗非鱼皮Ⅰ型胶原自聚集动力学的影响

采用Boltzmann函数拟合结合两阶段动力学模型(成核阶段和生长阶段),研究了胶原浓度、温度、溶液p H和离子强度对罗非鱼皮Ⅰ型胶原自聚集动力学的影响。结果表明:胶原浓度、温度、溶液p H和离子强度能调控胶原自聚集动力学。当浓度达到或高于0.34 mg/m L时,胶原表现明显的自聚集,且浓度越高越有利于胶原晶核的形成,过量的胶原分子能阻碍胶原纤维的生长;聚集温度越接近胶原来源原料的生活温度或溶液p H偏碱性,胶原越易自聚集;Na Cl浓度也可影响胶原的自聚集动力学,适量浓度的Na Cl有利于胶原晶核的形成,但Na Cl浓度过高却对胶原纤维的生长有阻碍作用。      

聚集条件对罗非鱼皮Ⅰ型胶原自聚集动力学的影响

采用Boltzmann函数拟合结合两阶段动力学模型(成核阶段和生长阶段),研究了胶原浓度、温度、溶液p H和离子强度对罗非鱼皮Ⅰ型胶原自聚集动力学的影响。结果表明:胶原浓度、温度、溶液p H和离子强度能调控胶原自聚集动力学。当浓度达到或高于0.34 mg/m L时,胶原表现明显的自聚集,且浓度越高越有利于胶原晶核的形成,过量的胶原分子能阻碍胶原纤维的生长;聚集温度越接近胶原来源原料的生活温度或溶液p H偏碱性,胶原越易自聚集;Na Cl浓度也可影响胶原的自聚集动力学,适量浓度的Na Cl有利于胶原晶核的形成,但Na Cl浓度过高却对胶原纤维的生长有阻碍作用。     

黏多糖在眼科中的应用

目的综述黏多糖类药物在眼科的应用。方法查阅相关文献资料,分析透明质酸、肝素、硫酸软骨素及壳聚糖在眼科中的应用。结果黏多糖类药物具有大分子结构,水溶液有一定黏度,在眼科可作为药物媒介、眼科手术黏弹剂、保护角膜等。结论透明质酸、肝素、硫酸软骨素及壳聚糖在眼科均有应用价值。     

海藻酸钠与氯化钙对大米淀粉回生影响机理的热力学分析

为探究海藻酸钠与氯化钙对大米淀粉回生的影响机理,采用差示扫描量热仪研究海藻酸钠与氯化钙对大米淀粉回生热力学特性的影响,采用Avrami模型分析大米淀粉的回生动力学参数,并用热重分析法验证影响结果。结果表明：3?mmol/L氯化钙组、质量分数0.9%海藻酸钠组及其混合物分别使大米淀粉的糊化峰值温度提高1.0%、1.1%和2.2%,使糊化焓提高4.7%、14.0%和21.4%;储藏21?d后,氯化钙对大米淀粉的回生没有显著性影响（P＜0.05）,质量分数0.6%的海藻酸钠及其与氯化钙混合物分别使大米淀粉的回生焓降低23.7%和27.6%,使回生率降低33.9%和36%;氯化钙、海藻酸钠（0.9%）及其混合物使大米淀粉的成核方式由瞬间成核转变成连续成核,并分别使大米淀粉的结晶速率常数降低73.0%、90.1%和95.3%;海藻酸钠（0.6%）与氯化钙混合物使回生大米淀粉的水分损失率减少87.1%,验证海藻酸钠与氯化钙混合物对大米淀粉回生的抑制作用。     

氢化棉籽油等温结晶动力学的研究

用脉冲核磁共振(PNMR)法测定了两种氢化条件下氢化棉籽油的固体脂肪含量(SFC)。根据不同温度下固体脂肪含量随时间的变化绘制等温结晶曲线。等温结晶曲线有两种:双曲线和反曲线。当过冷却度高时,结晶曲线为双曲线;当过冷却度低时,结晶曲线为反曲线。用Avrami方程进行氢化棉籽油的等温结晶动力学分析,结果表明:过冷却度与晶体的成核和生长方式有显著相关性。当过冷却度高时,结晶常数较小,晶体成核和生长速率快;当过冷却度低时,结晶常数较大,晶体成核和生长速率慢。研究氢化棉籽油的结晶行为对人造奶油、起酥油和可可脂替代品基料油的选择有一定的指导意义。     

大菱鲆鱼肉透明质酸酶的酶学特性研究

以大菱鲆鱼肉为原料,经pH4.7的乙酸-乙酸钠缓冲液提取、硫酸铵分级沉淀、透析后获得鱼肉透明质酸粗酶液,并对其酶学性质进行研究。结果表明:鱼肉透明质酸粗酶的最适pH为4.0,最适反应温度为25℃,在(—3~30)℃具有较高的稳定性,浓度为0.15 mol/L的NaCl可使鱼肉透明质酸酶保持较高活性。金属离子Ca(~(2+))、Mg~(2+)、Zn~(2+)对鱼肉透明质酸酶活性具有促进作用,Cu~(2+)、Fe~(2+)、Fe3+对鱼肉透明质酸酶活性具有抑制作用,抑制剂EDTA、L-半胱氨酸和抗坏血酸在一定浓度范围内可较好地抑制鱼肉透明质酸酶活性。双倒数法绘制米氏动力学曲线确定米氏常数Km为0.132 mg/mL,鱼肉透明质酸酶对不同底物的水解能力依次为HA硫酸软骨素A硫酸软骨素C肝素钠。在4℃条件下贮藏32 d,鱼肉透明质酸酶活性损失率为56.48%。     

大菱鲆鱼皮透明质酸酶的提取及酶学特性研究

以大菱鲆鱼皮为原料,经pH 4.7乙酸-乙酸钠缓冲液提取、硫酸铵分级沉淀、透析后获得鱼皮透明质酸粗酶液,并对其酶学性质进行研究。结果表明,鱼皮透明质酸粗酶的最适pH为6.6,最适反应温度为20℃,在-3℃～45℃具有较高稳定性,浓度为0.15 mol/L的NaCl可使鱼皮透明质酸酶保持较高活性。50 mmol/L的金属离子Ca~(2+)、Mg~(2+)、Zn~(2+)、Cu~(2+)、Fe~(2+)、Fe~(3+),50 mmol/L的EDTA、L-半胱氨酸和抗坏血酸对鱼皮透明质酸酶均具有抑制作用。双倒数法绘制米氏动力学曲线确定米氏常数K_m为0.094 mg/mL,鱼皮透明质酸酶对不同底物的水解能力依次为:肝素钠透明质酸硫酸软骨素C硫酸软骨素A。在4℃和-18℃条件下贮藏32 d,鱼皮透明质酸酶活性损失分别为79.21%和56.78%。     

牛关节软骨中Ⅱ型胶原和硫酸软骨素的综合提取与表征

以新鲜牛关节软骨为原料,脱脂脱钙后采用乙酸与胃蛋白酶相结合的方法提取Ⅱ型胶原,然后采用稀碱与胰蛋白酶相结合的方法提取剩余残渣中的硫酸软骨素,并采用FT-IR、AFM和热重分析对所得Ⅱ型胶原和硫酸软骨素进行检测。结果表明,该方法提取得到的Ⅱ型胶原和硫酸软骨素均很好的保持了其天然结构,而且所得硫酸软骨素具有较高的纯度。     

草鱼和乌鳢鱼皮胶原体外自组装过程中的凝胶化行为比较研究

以草鱼和乌鳢鱼皮胶原为研究对象,分别采用浊度实验和流变学实验方法研究两种胶原的体外自组装行为和凝胶化行为。结果表明：两种胶原的组装浊度曲线和流变黏弹曲线均表现为典型的3 阶段模式,即成核段、组装段和平衡段。浊度实验测定的胶原组装成核时间为13.5 min（草鱼PSC）和3.5 min（乌鳢PSC）,平衡时间为72.6 min（草鱼PSC）和10.0 min（乌鳢PSC）;而流变学实验测定的胶原组装成核时间为6.7 min（草鱼PSC）和1.9 min（乌鳢PSC）,平衡时间为105 min（草鱼PSC）和58.0 min（乌鳢PSC）。流变学实验测定的成核段时间明显缩短而组装段时间显著延长。扫描电镜纤维直径分析结果表明：胶原纤维直径在浊度实验平衡时间之后仍在继续增长直至流变学测定的平衡时间,说明流变黏弹实验能更灵敏、更完整地反映胶原的体外自组装行为。与草鱼皮胶原相比,乌鳢胶原组装速率更快、形成的胶原凝胶强度更大,说明不同种类胶原体外自组装行为存在明显的差异性。     

Effect of concentration,pH and ionic strength on the kinetic self-assembly of acid-soluble collagen from walleye pollock (Theragra chalcogramma) skin

The effects of concentration, pH value and ionic strength on the kinetic self-assembly of acid-soluble collagen from walleye pollock (Theragra chalcogramma) skin were investigated. A two-phase kinetic process was provided which included the formation of nucleus center and nucleus growth, the first phase being the controlled step for collagen self-assembly. Collagen showed marked assembly behavior when concentration reaching and above 0.6 mg/mL, and higher concentration could accelerate collagen self-assembly. Rate constants of the first and second assembly phase both increased with pH to a maximum around pH 7.2 and then decreased, indicating that pH 7.2 was the optimum pH value for collagen self-assembly. The kinetics of collagen self-assembly could be modulated by NaCl concentration. The concentration of NaCl from 30 to 60 mM was more suitable to self-assemble for pollock skin collagen.     

PARAMETERS THAT DETERMINE TRIPALMITIN CRYSTALLIZATION IN SESAME OIL

The crystallization of tripalmitin (TP) in sesame oil (0.98, 1.80 and 2.62% w/v) was investigated under isothermal conditions using a cooling rate similar to the one achieved by industrial crystallizers (1 K/min) and utilizing a modification of the Avrami equation. It was concluded that z, the crystallization rate constant, and the associated energy of activation (Ea) values determined through Avrami's original equation yield erroneous results. Additional results indicated that the increase in supercooling at constant oil phase viscosity (e.g., 5.25–5.5 dynes/cm²) during crystallization, produced a higher degree of nucleation without an appreciable effect on TP crystal size. In contrast, as viscosity of the oil phase decreased at equal supercooling conditions (e.g., 22.0 - 22.5C) the main crystallization process evaluated through z and Ea was crystal growth. It was also concluded that the characteristic crystallization stages of induction time for nucleation, crystal nucleation and growth, and end of crystallization were evident in the viscosity profile of the solid fraction developed during TP crystallization. The predominance of any of these processes (i.e., nucleation or crystal growth) as a function of supercooling and viscosity of the oil phase determines, to a great extent, the rheological profile during crystallization and the final viscosity value of the crystal suspension.     

Crystallization kinetics of emulsified triglycerides

Nucleation and crystal growth process of triglycerides in water emulsions composed of trimyristin (c l4:0) admixed with 0, 40, and 80 ml litre^?1 trilaurin (c 12:0) (expressed v per total v emulsion) were followed with NMR (nuclear magnetic resonance) and DSC (differential scanning calorimetry). Mathematical analysis of the time dependence of the phase changes and thermal data distinguished two distinct ‘apparent’ kinetic phases. These phases were tentatively referred to as nucleation and crystal growth. With 40 and 80 ml litre^?1 trilaurin (NMR data at 293 K) nucleation and crystal growth phases of trimyristin were simulated with zero order and second order rate expressions, respectively. Relative to these mixtures, pure trimyristin nucleation was delayed in the initial phase, but crystal growth occurred with fast homogeneous nucleation and slower growth in the second phase. Statistical analyses indicated that homogeneous nucleation similarly occurred when 40 or 80 ml litre^?1 trilaurin was admixed with trimyristin. NMR resolution made it possible to follow the crystallization phenomena in different locations of the crystallization vessel effectively in situ and undisturbed. Statistical analyses in this case revealed a significant trilaurin-location interaction confirming that the rate of nucleation processes was affected both by the concentration of trilaurin and the heat transfer properties of the sample and vessel. The time-location interactions were not significant, confirming the hypothesis that in the absence of tilaurin, zero order nucleation did not occur in the first phase.     

Isothermal batch crystallization of alpha-lactose: A kinetic model combining mutarotation,nucleation and growth steps

A kinetic model combining first-order differential equations of the three consecutive steps of lactose crystallization, i.e., mutarotation, nucleation and crystal growth rate, was developed. Numerical solutions successfully fitted the variations of crystal mass growth rate as a function of lactose concentration during unseeded isothermal batch crystallization, at different initial lactose concentrations and temperatures. The model allowed the induction phase and the influence of seeding to be simulated by taking into account the dependency of crystal growth rate on total crystal surface area and, consequently, on nucleation rate. The proposed model highlights the large influence of the mutarotation step, even in unseeded crystallization kinetics. The effects of high lactose supersaturations that prevail at industrial scale during whey powder manufacturing and the effects of alkaline pH (9.5) on lactose crystallization kinetic were successfully predicted.     

阳离子淀粉/海藻酸钠二元纸张增强体系的初步研究

研究了阳离子淀粉（CS）与海藻酸钠（SA）二元增强体系对混合阔叶材KP浆所抄纸张的增强效果。结果表明：（1）单一加入阴离子助剂SA对纸张物理强度影响不大。（2）CS/SA二元增强体系对纸张物理强度提高的最大值均优于单一加入CS时对纸张增强效果的最大值。（3）CS/SA二元增强体系对纸张的耐折度影响最为明显。（4）浆料初始pH值约为7.0时,CS/SA二元体系对纸张物理强度的增强效果要优于酸性抄纸和碱性抄纸。     

Effect of galacto-oligosaccharide concentration on the kinetics of lactose crystallisation

Galacto-oligosaccharides (GOS) are said to have a retarding effect on the nucleation and growth of α-lactose monohydrate crystallisation. Studies regarding the kinetic parameters for crystal growth and nucleation were conducted utilising gravimetric analysis and laser light scattering to follow the lactose crystallisation. A statistically significant retarding effect of GOS on lactose crystal growth at concentrations between 0.8 and 3% (w/w) GOS of total solution was observed. A significant nucleation suppressing effect was confirmed further. Studies concerning the change in crystal morphology revealed that as GOS concentration was increased, a transition from the common tomahawk shape to a shape with shortened crystal faces away from the apex to a needle like appearance occurred, strongly suggesting a growth retardation effect on the (010) face. Crystals subjected to high pressure liquid chromatography (HPLC) analysis did confirm an incorporation or inclusion of GOS into the crystal lattice.     

Sonochemical desorption and destruction of 4-chlorobiphenyl from synthetic sediments

The application of ultrasound for the treatment of polychlorinated biphenyl (PCB) contaminated sediments was explored in this study with a model system of 4-chlorobiphenyl (4-CB) and synthetic sediments. In the presence of an ultrasonic probe, operating at 20 kHz with a power density of 460 W L(-1), more than 90% of 4-CB in aqueous homogeneous solution was destroyed after 20 min, with an apparent first-order rate constant, k, of 0.120 min(-1). In addition, experiments investigating the destruction of dissolved 4-CB in the presence of bare silica or alumina particles or dissolved humic acid (HA) had lower degradation rates than in aqueous homogeneous solutions. Increasing the bare particle concentration or dissolved HA concentration further lowered the degradation rate. However, in investigating the desorption and destruction of sorbed 4-CB from humic acid laden alumina particles, the effect of particles and released dissolved HA on the degradation rate are simply additive, and desorption of 4-CB does not appear to further complicate the system. A kinetic analysis of the system revealed that desorption of 4-CB from particles was not a limiting factor in this system.