鸡骨明胶的流变性研究

研究从鸡骨中提取的明胶的流变性质。结果表明：质量分数为0．5％的鸡骨明胶溶液为塑性流体，其流动需要克服一定的屈服应力，屈服应力的大小受温度影响，温度越高，屈服应力越小；当剪切应力大于屈服应力时，粘度基本不随剪切速率变化，表现出牛顿流体的流动特征；温度越高，鸡骨明胶溶液粘度越小，温度对其的影响符合Arrhenius模型，流动活化能为19．58kJ／mol；鸡骨明胶的粘度随质量分数的增加呈指数递增；鸡骨明胶的粘度受pH值影响，在等电点9附近，鸡骨明胶溶液的粘度最小，偏离pI则粘度增大；鸡骨明胶的粘弹性强烈受温度的影响，质量分数为3％的鸡骨明胶从粘性为主的溶胶体系变成以弹性为主的凝胶体系的转变温度(胶凝点)为23．6℃，而凝胶转变成溶液的转变温度(溶点)为33．6℃。适当质量分数及在室温条件下，鸡骨明胶主要表现为弹性体。     

鸡骨明胶的凝胶化研究

本研究采用差示扫描量热法(DSC)、红外光谱(FT-IR)、圆二色谱(CD)、荧光光谱、原子力显微镜(AMF)等手段研究鸡骨明胶溶液胶凝化过程.原子力显微镜观察到,随着明胶溶液中分子数目的增多,分子链逐渐聚集缔合形成网络结构.圆二色谱显示,明胶凝胶的交联点为类似胶原的三股螺旋结构.明胶溶液胶凝时,体系的荧光强度显著增大,红外光谱可见O-H和C=O伸缩振动增加.由此推断,明胶的凝胶化是明胶分子借助氢键力作用形成三股螺旋交联点的网络结构,同时疏水相互作用促进凝胶形成.     

假酸浆子胶质的胶凝特性

通过测定动态流变性质和凝胶强度,研究了假酸浆子胶质的胶凝特性.结果表明.假酸浆子胶质的胶凝分为凝胶网络快速形成和网络缓慢成长两个阶段.胶质具有胶凝性,能形成一种热可逆冷致凝胶,假酸浆子胶质溶液胶凝点低于其凝胶熔化点,且胶质溶液胶凝点及其凝胶熔化点均随浓度升高而升高;胶质浓度、pH、NaCl、CaCl2能影响胶质凝胶强度;假酸浆子胶质凝胶强度随着浓度增加而增强,在pH3时,假酸浆子胶质凝胶强度达到最大;NaCl可降低胶质凝胶强度,低浓度(<1.2g/L)的CaCl2可增强假酸浆子胶质凝胶强度,而高浓度(>1.2g/L)的CaCl2能降低胶质凝胶强度.     

迷迭香酸的添加对明胶凝胶体系的影响

将不同质量浓度的迷迭香酸(Ros A)加入到兔皮明胶中,通过荧光光谱、凝胶强度、流变学、聚丙烯酰胺凝胶电泳(SDS-polyacrylamide gel electrophoresis,SDS-PAGE)和圆二色谱(circular dichroism,CD)等测定方法研究Ros A的添加对明胶凝胶体系的影响。结果表明,Ros A能使兔皮明胶内源荧光静态猝灭,说明两者之间形成了复合物; Ros A可以提高明胶的凝胶强度、储能模量和损耗模量,但对明胶的胶凝和熔化温度影响不大;凝胶电泳结果表明,Ros A与明胶之间的相互作用主要是氢键等非共价键;圆二色谱表明,Ros A的加入使得明胶肽链结构部分展开,α螺旋含量减少,β折叠含量增加。     

NaCl存在下结冷胶以及结冷胶/明胶共混凝胶质构和熔点的研究

研究了不同浓度NaCl(1％～3％,w/v)、结冷胶(0.1 5％～0.35％,w/v)和明胶(1％～3％,w/v)对结冷胶和结冷胶明胶共混凝胶质构特性和熔点的影响.目的是得出结冷胶明胶复配胶凝胶特性,为复配胶在成味食品中的应用提供参考结果表明,共混凝胶硬度和熔点随NaCl浓度增加而增大,当NaCl浓度高于1.5％时,硬度和熔点均下降;结冷胶和明胶浓度对共混凝胶硬度影响较大;结冷胶形成的凝胶弹性差,与明胶复配使用,弹性显著提高,并且共混凝胶弹性随结冷胶浓度增大而降低,随明胶浓度增大而增大;结冷胶浓度决定了共混凝胶的熔点结冷胶和明胶复配可以弥补各自单独使用的不足,且复配胶兼具高熔点和入口即化的特性.     

魔芋胶、卡拉胶与黄原胶复配胶的特性及在肉丸中的应用

主要研究了魔芋胶、κ-卡拉胶与黄原胶复配胶的凝胶特性及在肉丸中的应用效果。通过实验证明,影响复配胶凝胶强度的因素和最佳条件是:魔芋胶、κ-卡拉胶与黄原胶的最佳配比为1.3∶1∶0.3;复配胶的总胶浓度为0.6%,且总胶浓度越高,凝胶强度越高;钾离子在较大程度上能影响复配胶的凝胶强度,氯化钾的浓度控制在0.12%,浓度过高会影响口感,浓度过低则会影响凝胶强度;磷酸盐的浓度与凝胶强度成反比;氯化钠的浓度在0.9%最效果最佳;热处理是复配胶形成凝胶的必需条件,复配胶液保持在恒温90℃,恒温加热时间为20min。并最终通过工艺优化得出最适肉丸的加工条件,总胶浓度为0.6%、淀粉添加量为10%,肉糜擂溃时间为15min,水浴加热成型温度为50℃,时间为15min,杀菌煮制温度90℃,时间为20min。     

大目金枪鱼皮明胶的理化性质及结构分析

以大目金枪鱼皮为原料制备明胶,对所得明胶的凝胶强度、胶凝温度、熔化温度、氨基酸组成、十二烷基硫酸钠-聚丙烯酰氨凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）、光谱学特性等理化性质及结构特性进行研究,并与猪皮明胶进行比较。结果表明,金枪鱼皮明胶的凝胶强度为403?g,胶凝温度和熔化温度分别为21.5?℃和28.8?℃,略低于猪皮明胶;氨基酸分析结果表明,金枪鱼皮明胶中亚氨基酸质量分数为19.09%,低于猪皮明胶的22.82%,可以解释金枪鱼皮明胶凝胶特性、胶凝温度和熔化温度低于猪皮明胶的原因。SDS-PAGE电泳结果显示,金枪鱼皮明胶的小分子组分质量分数仅为6.67%,说明预处理及热水提胶过程并没有破坏明胶中亚基的完整性。金枪鱼皮明胶的紫外光谱与红外光谱谱图均与猪皮明胶相似,进一步说明实验所制得的产物为高质量明胶。     

明胶—多糖共混凝胶的研制

以明胶、甘薯淀粉、海藻酸钠等为研究对象,以凝胶强度为指标,探讨了明胶-多糖凝胶形成条件。通过比较pH、蛋白质和多糖配比因素对凝胶性能的影响,对明胶-多糖体系凝胶形成的分子力作了初步探讨。结果表明:1)明胶/甘薯淀粉体系的凝胶形成条件为基质浓度9.0%,质量比1∶1,pH5,加热温度80℃,加热时间30 min,在此条件下形成凝胶的强度为2 038 g。2)明胶/海藻酸钠体系的凝胶形成条件为基质浓度3.0%,质量比1∶1,pH5,加热温度60℃,加热时间30 min,在此条件下形成凝胶的强度为611 g。     

海藻酸钙凝胶特性影响因素的探讨

实验研究了海藻酸钠浓度、pH、温度、溶涨时间、凝固剂、金属离子、乙醇以及海藻酸钠以其它食用胶的协同作用对海藻酸钙凝胶拉伸强度、弹性、脱水性等特性的影响。实验结果表明形成的海藻酸钙凝胶特性较好的条件是:海藻酸钠浓度为1.5％、pH为4—5,温度为50℃-60℃,溶胀时间为45min,采用乳酸钙、加入硫酸铝;另外,海藻酸钠与瓜尔豆胶、明胶、β-环状糊精、EDTA的协同增效作用有利于海藻酸钙凝胶的形成。     

微波辐射对几种增稠剂性质影响的研究

微波已经应用于食品加工中,但微波辐射对食品中增稠剂性质的影响,目前尚无人深入探讨。本文选取卡拉胶、明胶和黄原胶这三种常见的食品凝胶剂和增稠剂,将其按比例进行凝胶和增稠后,利用微波进行处理,然后利用质构仪和旋转粘度仪分别考察微波处理前后其凝胶性质和黏度的变化。结果表明:微波处理后,卡拉胶凝胶的硬度增大,且浓度越高,硬度增加的越显著,弹性显著降低;明胶凝胶与其类似,硬度增大,且浓度越高,增加的越显著,但弹性的变化不显著;黄原胶溶液的黏度也增大。这些实验结果可能都是因为:微波能够促进大分子的运动,加剧了分子间的缠绕,所形成的空间网状结构更加致密,从而使得凝胶的硬度增大,溶液的黏度增大。     

Effect of microbial transglutaminase on the functional properties of megrim (Lepidorhombus boscii) skin gelatin

This paper examines the effect of a microbial transglutaminase (TGase) on the gelling and viscoelastic properties of a gelatin from megrim (Lepidorhombus boscii) skins. Although TGase extended the setting time of fish gelatin, it was found that melting temperature, gel strength and viscosity in solution at 60 °C were considerably increased by the covalent cross‐linking action of the enzyme, as observed by SDS‐PAGE and SEM. Increasing concentrations of TGase increased the elasticity and cohesiveness of gelatin gels but reduced gel strength and hardness. Partial inactivation of the enzyme was achieved thermally without negatively affecting the properties of the gelatin; whether or not gelatin is thermoreversible depends essentially on the degree of enzyme inactivation. © 2001 Society of Chemical Industry     

Effects of Concentration,Bloom Degree,and pH on Gelatin Melting and Gelling Temperatures Using Small Amplitude Oscillatory Rheology

Concentration, gel strength (Bloom), and pH effects on both melting and gelling temperatures of gelatin were studied using small amplitude oscillatory rheology. Temperature sweeps were applied to gelatin gel samples for heating and cooling at fixed frequencies. Results showed that melting temperatures were higher than gelling temperatures, and both increased with increasing concentration at pH from 3 to 6 for all gel strength. For constant gelatin concentration and pH, as gel strength increased, melting temperatures decreased, whereas gelling temperatures increased. A mathematical model was obtained which correlates melting and gelling temperatures, respectively, with pH and concentration at fixed Bloom degrees. All gelatin gels showed storage modulus higher (2 to 10 kPa) than loss modulus (50 to 500 Pa).     

Effects of γ-polyglutamic acid on the gelling properties and non-covalent interactions of fish gelatin

The effects of γ-polyglutamic aid (γ-PGA) on the gelling properties and non-covalent interactions of fish gelatin were investigated. The gel strength and melting temperature of fish gelatin gradually increased, with increasing γ-PGA concentration, although there was no significant change when the γ-PGA concentration was greater than 0.04%. As the concentration of γ-PGA increased, the electrostatic interaction of fish gelatin increased and the hydrophobic interaction between gelatin molecules decreased. The fish gelatin system was comprised of γ-PGA concentrations of 0.04 and 0.06% showing a strong hydrogen bond. When the γ-PGA concentration increased from 0 to 0.04%, more phenolic hydroxyl groups in the tyrosine residue tended to form hydrogen bonds with the protein. However, an additional increase in γ-PGA concentration to 0.1% led to enhanced hydrogen bonding with water molecules. The results of this study showed that hydrogen bonds played an important role in improving the gelling properties of gelatin by γ-PGA.     

Comparison of gelling properties and flow behaviors of microbial transglutaminase (MTGase) and pectin modified fish gelatin

The gelling and structural properties of microbial transglutaminase (MTGase) and pectin modified fish gelatin were compared to investigate their performances on altering fish gelatin properties. Our results showed that within a certain concentration, both MTGase and pectin had positive effects on the gelation point, melting point, gel strength, textural, and swelling properties of fish gelatin. Particularly, low pectin content (0.5%, w/v) could give fish gelatin gels the highest values of gel strength, melting temperature, and hardness. Meantime, flow behavior results showed that both MTGase and pectin could increase fish gelatin viscosity without changing its fluid characteristic, but the latter gave fish gelatin higher viscosity. Both MTGase and pectin could increase the lightness of fish gelatin gels but decreases its transparency. More importantly, fluorescence and UV absorbance spectra, particle size distribution, and confocal microscopy results indicated that MTGase and pectin could change the structure of fish gelatin with the formation of large aggregates. Compared with MTGae modified fish gelatin, pectin could endow fish gelatin had similar gel strength, thermal and textural properties to pig skin gelatin.     

Rheological and functional properties of gelatin from the skin of Bigeye snapper (Priacanthus hamrur) fish: Influence of gelatin on the gel-forming ability of fish mince

The rheological and functional properties of gelatin from the skin of bigeye snapper (Priacanthus hamrur) fish were assessed. The protein content of dried gelatin was 94.6% and moisture content was 4.2%. The amino acid profile of gelatin revealed high proportion of glycine and imino acids. The bloom strength of solidified gelatin was 108 g. The average molecular weight of fish skin gelatin was 282 kDa as determined by gel filtration technique. The emulsion capacity (EC) of gelatin at a concentration of 0.05% (w/v) was 1.91 ml oil/mg protein and with increase in concentration, the EC values decreased. The gelling and melting temperatures of gelatin were 10 and 16.8 °C, respectively as obtained by small deformation measurements. The flow behavior of gelatin solution as a function of concentration and temperature revealed non-Newtonian behavior with pseudoplastic phenomenon. The Casson and Herschel–Bulkley models were suitable to study the flow behavior. The yield stress was maximum at 10 °C with the concentration of 30 mg/ml. Thermal gelation behavior of threadfin bream (Nemipterus japonicus) mince in presence of different concentration of gelatin was assessed. Gelatin at a concentration of 0.5% yielded higher storage modulus (G′) value than control. Frequency sweep of heat set gel with gelatin revealed strong network formation.     

酸/碱预处理对美洲鳗鲡（Anguilla rostrata）鱼骨明胶理化性质与凝胶特性的影响

以美洲鳗鲡（Anguilla rostrata）鱼骨为原料,采用酸或碱预处理结合热水浸提制备鱼骨明胶,并通过得率、凝胶强度测定、SDS-PAGE、紫外全波长扫描、红外光谱扫描、动态流变学测定以及扫描电镜等研究鱼骨明胶的理化性质和凝胶特性。结果表明:酸法预处理明胶（AG60）与碱法预处理明胶（BG60）得率分别为13.6%和6.88%,凝胶强度分别为101.95 g和78.74 g。AG60和BG60的羟脯氨酸含量为3.2 g/100 g和2.7 g/100 g。两种明胶均含有β和α₁、α₂链,其中AG60的α₁+α₂含量显著高于BG60。AG60与BG60均具有明胶的特征吸收峰,且无杂蛋白吸收峰。与BG60相比,AG60具有更高的凝胶温度与熔融温度,以及更短的胶凝时间。扫描电镜分析显示,AG60具有更致密、均一的凝胶网络结构。本研究表明,与碱法预处理相比,酸法预处理制备得到的鳗鱼骨明胶具有更高的得率与更好的凝胶特性。     

Extraction of Gelatin from Megrim (Lepidorhombus boscii) Skins with Several Organic Acids

ABSTRACT: Light-colored, dry collagen was obtained and, after dissolving in warm water, turned into soluble gelatin. The type of acid used influenced the gelatin viscoelastic and gelling properties. Acetic- and propionic-acid extracts produced the gelatins with the highest elastic modulus, viscous modulus, melting temperature, and gel strength, especially when skins were previously treated with dilute NaOH. After such treatment, lactic acid was also shown to be suitable for collagen or gelatin extraction. The lowest degree of turbidity was achieved by using citric acid, whereas propionic acid led to the most turbid gelatin. No improvements of rheological properties were observed when acid concentration for extraction was increased above 0.05 M.     

Storage of dried fish skins on quality characteristics of extracted gelatin

Drying was evaluated as preservation method for storage of Dover sole (Solea vulgaris) skins. Fish skins were air-dried by using ethanol, ethanol–glycerol mixture and marine salt, and stored at room temperature for 160 days. Gelatin extraction was carried out periodically during the storage time, and the quality of the resulting gelatin preparations was evaluated according to the molecular weight distribution, viscoelastic properties, gelling and melting temperatures and gel strength. All the drying methods used showed a similar effect on the gelatin quality characteristics evaluated. Although drying involved a slight decrease in viscoelastic properties as well as gelling and melting points, it was striking the great protein stability found throughout the storage period. Drying scarcely affected gel strength, which values did not show noticeable changes along the storage.     

Physicochemical,rheological, and molecular characterization of colloidal gelatin produced from Common carp by‐products using microwave and ultrasound‐assisted extraction

The effects of ultrasound‐assisted extraction (UAE) and microwave‐assisted extraction (MAE) methods on molecular and physicochemical characteristics of the resultant gelatin were examined. Before extraction procedure, we investigated the optimum pH for swelling of Common carp by‐products, which is an important pretreatment for gelatin production. The highest swelling yield was achieved at pH 13 among pH 1–14 with unit intervals. Results indicated that the UAE gelatin has a higher gel strength, viscosity, melting point, and gelling point. The power and time of sonication showed a reverse relation with these characteristics. In addition, as the time of microwave heating was raised, the gel strength, viscosity, melting point, and gelling point were decreased. The FT‐IR spectra showed similar peaks but the Amide B in UAE gelatin slightly vanished. The electrophoretic pattern also revealed the higher gel strength and viscosity of UAE gelatin due to the higher intensity of α and β chains compared to MAE gelatin. It can be concluded from all of the results of this study that the produced gelatin using these procedures can be a good source of gelatin in food and drug industries.