鱼鳞明胶与哺乳动物明胶性质的比较

研究了酶法制备的草鱼鱼鳞明胶的理化性质,并将其与哺乳动物明胶的性质作了比较。研究发现,草鱼鱼鳞明胶中富含甘氨酸、脯氨酸、羟脯氨酸和丙氨酸,而亚氨基酸、总疏水性氨基酸的含量以及平均疏水性值要小于哺乳动物明胶;分子质量分布主要以α组分和β组分为主,占明胶分子总量的88%;胶凝温度和熔化温度分别为20.8℃和26.9℃,低于哺乳动物明胶;特性黏度约为0.73;表面疏水性指数为259.59,有较好的乳化性和起泡性。此外发现,明胶的高凝胶强度和胶凝速度主要取决于明胶(α+β)组分的含量,而明胶胶凝和熔化温度则主要取决于亚氨基酸的含量,不同来源明胶的特性黏度η仅与其α组分(α1+α2)的含量存在线性相关。     

鸡骨明胶的胶凝特性

通过测定动态流变性质和凝胶强度研究鸡骨明胶的胶凝特性.研究表明,鸡骨明胶的胶凝分为凝胶网络的快速形成阶段和网络的缓慢成长两个阶段.相对分子质量越大,胶凝温度越低;明胶浓度越高、pH值越接近等电点、胶凝温度和熔化温度越高,胶凝时间越短,同时形成的凝胶网络的弹性和凝胶强度大;随着陈化时间的延长或温度降低,凝胶网络弹性和凝胶强度增大,且逐渐稳定;适当浓度的尿素和SDS可以阻止凝胶网络的形成;明胶胶凝网络结构的形成主要借助分子间氢键相互作用,同时静电斥力和疏水相互作用也影响凝胶网络的形成.     

60Co-γ不同剂量辐照对明胶特性的影响

研究经0~52.7kGy 60Co-γ射线照射后的明胶黏度、胶凝特性、蛋白组分、分子量与吸收剂量的关系,结果表明,明胶的特性黏度、相对黏度、凝胶强度、熔化温度和分子量随剂量的增加呈下降趋势. 明胶的大分子物质含量随剂量的增加而减少,Mn和Mw范围为7839~10861, 32444~36506. 分子量分布逐渐加宽,范围为3.36~4.45. 同时,辐照后明胶膜的胶凝点上升,范围39.8~42.7℃. 明胶颗粒的致密性好,表面平滑. 实验结果说明,在有限水和无限氧气存在下,小分子量明胶的辐射反应为分解反应.     

大目金枪鱼皮明胶与κ-卡拉胶复配胶凝胶特性探究

将大目金枪鱼皮明胶和κ-卡拉胶按不同配比混合制成复配胶,测定了复配胶的凝胶强度、流变学性质、凝胶持水性、质构、红外光谱和电镜。结果表明:复配胶的凝胶强度、粘度、储能模量和耗能模量均随着κ-卡拉胶比例的增大而增大。复配胶的凝胶持水率在明胶/κ-卡拉胶比例为7:3时为75.9%,远低于单组分明胶凝胶的97.1%,但继续增大κ-卡拉胶的比例会出现显著增大的趋势,质构特性与持水率有相同的变化趋势。红外光谱分析结果表明κ-卡拉胶与明胶之间的交互作用随着κ-卡拉胶比例的增大而减小,说明复配胶中形成了以κ-卡拉胶为主体的结构。电子扫描结果显示复配胶中出现褶皱与聚集,进一步说明κ-卡拉胶与明胶以不同比例混合后通过氢键发生了不同程度的交互作用。实际生产中,可通过改变明胶/κ-卡拉胶的配比来调节复配凝胶的特性,适应不同产品的需要。     

亚麻籽胶的胶凝性质

采用流变学法测定了亚麻籽胶溶液的胶凝点、熔化点，并采用质构仪、扫描电镜和原子力显微镜等手段研究了影响亚麻籽胶凝胶强度的因素，结果表明亚麻籽胶具有胶凝性，它能形成一种热可逆的冷致凝胶，亚麻籽胶溶液的胶凝点低于其凝胶的熔化点，且亚麻籽胶溶液的胶凝点及其凝胶的熔化点均随冷却的起始温度的升高而升高。亚麻籽胶浓度、溶解温度、pH、NaCl、CaCl2及复合磷酸盐能影响亚麻籽胶的凝胶强度，亚麻籽胶的凝胶强度随着浓度的增加及溶解温度的升高而增强；在pH6～9的范围内，亚麻籽胶的凝胶强度达到最大；NaCl和复合磷酸盐可以降低亚麻籽胶的凝胶强度，低浓度（〈0．3％）的CaCl2可以增强亚麻籽胶的凝胶强度，而高质量分数（〉0．3％）的CaCl2能降低亚麻籽胶的凝胶强度。     

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。     

兔皮明胶提取工艺优化

以兔皮为原料,研究稀盐酸短时诱导兔皮制备明胶的工艺。以明胶提取率和凝胶强度为评价指标,对兔皮明胶制备工艺中的盐酸质量分数、盐酸处理时间、提胶pH值、提胶温度4 个因素进行了优化,在此基础上通过正交试验确定最佳工艺为盐酸质量分数1%、盐酸处理时间10 min、提胶温度65 ℃、提胶pH 4。在此工艺条件下明胶提取率高达（86.85±1.71）%,凝胶强度为（481.43±16.89）g。明胶基本性质符合GB 6783-2013《食品添加剂：明胶》要求。     

κ-卡拉胶胶凝特性研究

以胶凝理论为基础,就卡拉胶质量分数、钾离子质量分数、ｐＨ值对胶凝特性的影响进行了定量分析与研究,并通过对实验数据的回归处理,总结出了κ－卡拉胶质量分数和钾离子质量分数与胶凝温度、凝胶强度之间的数学关系式,还探讨了ｐＨ值对κ－卡拉胶胶凝特性的影响．结果显示,随ｐＨ值降低,卡拉胶的凝胶强度快速下降．     

喷雾干燥入口温度对大目金枪鱼皮明胶乳化特性的影响

研究不同喷雾干燥入口温度（130、160、190 ℃）对大目金枪鱼皮明胶乳化特性的影响。通过乳析指数和乳液微观结构评价乳化效果,通过表面疏水性和凝胶强度评价不同乳液界面与连续相的差异,通过明胶分子质量分布和红外光谱初步分析喷雾干燥入口温度影响明胶乳化特性的机制。结果表明,随着喷雾干燥入口温度的升高,明胶的高分子质量亚基被过度破坏,降低了三螺旋结构的完整性,从而导致更多的亲水性氨基酸被暴露,进而降低了凝胶强度（851.29～676.65 g）和表面疏水性（218.81～82.96）,表面疏水性的降低不利于明胶在油-水界面的吸附及网络结构的形成,明胶凝胶强度的降低表明乳液连续相中网络结构变得松散,最终表现为明胶乳液的液滴粒径和乳析指数增大,乳液稳定性降低。由此可见,当前研究的喷雾干燥入口温度（130、160、190 ℃）与乳液稳定性呈负相关,利用喷雾干燥制备乳化型鱼皮明胶,入口温度不宜过高,130 ℃时效果更佳。     

鱼鳞明胶的提胶工艺

根据单因素试验结果,利用正交试验,考察了提胶温度、pH值和时间对鱼鳞明胶品质的影响。并得到提胶条件为:提胶温度为55℃,pH值为6,时间为5h。在该条件下明胶的提取率达到58%,6.67%的明胶溶液在60℃时的黏度为8.16mPa·s,7℃下保温18h后凝胶强度为1 202.65g,约290Bloom,凝胶温度和熔化温度分别为20.8℃,26.9℃,等电点约为pH 7,可达到高品质明胶的要求。     

Rheological properties of channel catfish (Ictalurus punctaus) gelatine from fish skins preserved by different methods

Gelatins were extracted from channel catfish skins preserved by different methods using 50 mmol/l acetic acid. Molecular weight distribution, gel strength and viscoelastic properties of gelatin samples were studied. Compared to gelatins from fresh and frozen skins, gelatin from dried channel catfish skin exhibited higher gel strength. This can be explained by the large α-chains content of gelatin from the dried skins. The gelling point and melting point of dried channel catfish skin gelatin solution were similar to those of fresh skin gelatin solution, but distinctly different from those of frozen skin gelatin. After maturation at low temperature, melting points of gelatins increased. But the melting point of frozen skin gelatin was still the highest among the three gelatin samples studied.     

Rheological Properties of Fish Gelatins

ABSTRACT: The rheological properties of fish gelatins (cod, megrim, tuna, and tilapia) and conventional gelatin (bovine and porcine) were compared. The different fish gelatins had from low to high viscosity values. They also had from low to high gel strength values. However, they had lower melting and gelling temperatures than gels from conventional gelatins. Cold-water fish gelatins were more different from conventional gelatins than warm water fish gelatins reflecting the different amino acid composition, as cold-water fish gelatins are low in imino acids. Binary blends of cod and other fish or conventional gelatins seemed to be completely compatible.     

Characteristic tryptic peptides and gelling properties of porcine skin gelatin affected by thermal action

Thermal action in extraction process had effects on characteristic tryptic peptides identification and gelling properties of porcine gelatin. SDS-PAGE, HPLC-LTQ/Orbitrap high-resolution mass spectrometry, texture analyser and rheometer were used to evaluate collagen depolymerisation degree, characteristic tryptic peptides and gelling properties of gelatins prepared in various thermal actions. Results showed that with increasing temperature and time, depolymerisation degree enlarged, while gel strength, gelling and melting temperature decreased. Mass spectra showed that 47 and 49 common characteristic tryptic peptides were identified in gelatins extracted at 50 °C and 100 °C with various times, respectively. Moreover, 34 common characteristic tryptic peptides were identified in all gelatin samples. Further comparison between this work and our previous investigations yielded 20 common characteristic tryptic peptides, which stably exist in various thermal actions. These common characteristic tryptic peptides may be very helpful for the accurate authentication of porcine gelatin.     

Rheological and physico‐chemical properties of gelatin extracted from the skin of a few species of freshwater carp

The physico‐chemical and rheological properties of gelatin from the skins of three different freshwater carp species, namely Catla catla, (catla) Cirrhinus mrigala (mrigal) and Labeo rohita (rohu), have been assessed and compared with that of gelatin from porcine skin. The average solids yield from the three species of carp varied in the range of 11.8–14.1%. The amino acid profile showed that the porcine gelatin had a higher proportion of imino acids and glycine than carp skins gelatin. The average molecular weight of carp skins gelatin as determined using a gel filtration technique was 233 kDa, while that of porcine skin gelatin was 282 kDa. The gelling temperature of carp skins gelatin was in the range of 6–15.7 °C, and the melting temperature was 17.9–23.7 °C as determined using a controlled stress rheometer. A higher gelling and melting temperature was observed for porcine skin gelatin.     

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).     

Seasonal differences in the properties of gelatins extracted from skin of silver carp (Hypophthalmichthys molitrix)

The gelatins were extracted from skins of silver carp (Hypophthalmichthys molitrix) caught in winter and summer, respectively. The physicochemical (molecular weight distribution and melting point) and rheological characteristics (viscosity property), as well as functional properties (emulsifying capacity and stability) of the gelatin from winter silver carp skin were compared with those of the summer equivalent. The results showed the properties of the summer gelatin were superior to those of the winter one, showing higher viscosity, emulsion stability, melting point and lower concentration for gelling. The summer gelatin has slightly denser strands of the gel microstructure which was observed by scanning electron microscopy (SEM). Different properties of gelatins from skin of silver carp may be attributed to the big discrepancy of the environmental temperature in the two seasons.     

Chemical compositions and functional properties of gelatin from pre-cooked tuna fin

Gelatin was extracted from pre-cooked tuna caudal fin with the yield of 1.99%. Tuna fin gelatin (TFG) contained high protein content (89.54%) with hydroxyproline content of 14.12 mg g⁻¹. TFG comprised a lower content of high-molecular-weight cross-links and hydroxyproline content than porcine skin gelatin (PSG). However, proline content in TFG was twofold higher than that of PSG. The highest bloom strength and turbidity of TFG were observed at pH 6, while the lowest solubility was noticeable at the same pH. The bloom strength of TFG gel was lower than that of PSG gel at all pHs. TFG exhibited the lower emulsifying activity but greater emulsifying stability than PSG (P < 0.05). TFG showed poor foaming properties than PSG. The tensile strength, elongation at break, water vapour permeability of film from PSG was greater than those of TFG (P < 0.05). The study revealed that gelatin of good quality can be prepared from tuna processing discards.