环氧基有机硅改性明胶及其稳定性的研究

研究了两种含环氧基的硅烷偶联剂2-(3,4-环氧环己基)乙基三甲氧基硅烷(E-6)和3-(2,3-环氧丙氧基)丙基三甲氧基硅烷(E-3)分别在反应介质CH3COONa—CH3COOH酸性缓冲溶液(pH值5.50)和Na2HPO3—NaH2PO3碱性缓冲溶液(pH值7.80)中对明胶的改性反应,采用红外光谱和差式扫描量热法(DSC)对改性产物进行了表征,并测定了改性明胶的吸水率与耐酶解能力。结果表明,两种环氧基硅烷偶联剂改性后明胶的热稳定性提高,尤其是碱性条件下E-3改性明胶的热变性温度提高最为显著,由未改性明胶的58.2℃提高到了89.6℃;无论是酸性还是碱性条件下,E-3改性明胶的吸水率都明显降低;碱性条件下E-3改性明胶酶解率由未改性明胶的90%下降至50%,抗酶解能力最强。可见,在实验条件范围中碱性条件下E-3改性明胶的稳定性最优。     

聚氨酯改性明胶的合成与表征

通过单因素试验对聚氨酯改性明胶反应体系中异氰酸酯基(-NCO)质量分数的分析,优化了聚氨酯改性明胶的最佳条件:聚氨酯预聚体与明胶的质量比为7:6.改性温度为75℃,改性时间为3h.使用红外光谱和综合热分析仪分别对聚氨酯预聚体、明胶、聚氨酯改性明胶进行了结构表征和热稳定性分析.结果表明,聚氨酯已经接枝到明胶分子链上,而且...     

水性聚氨酯改性明胶浆料的制备及其上浆性能

针对在高比例涤棉纱线上浆过程中,改性明胶浆料浆纱耐磨性、浆膜的断裂伸长率不够理想等缺点,通过制备带有醛基的功能性水性聚氨酯,与改性明胶进行共聚改性,制得水性聚氨酯改性明胶浆料。使用核磁氢谱以及红外光谱对浆料进行结构表征,对改性明胶浆料SX-3和水性聚氨酯改性明胶浆料进行浆料性能测试和上浆试验,并对浆纱进行SEM表征。结果表明:水性聚氨酯改性明胶浆料的浆膜断裂伸长率明显提高,浆纱耐磨性明显增加,用于高比例涤棉纱的上浆性能优于改性前的明胶浆料。认为:用水性聚氨酯改性明胶是提高明胶浆料对高比例涤棉纱浆纱性能的有效途径,能够满足高比例涤棉纱的浆纱需求。     

基于原位缩聚的氨基树脂鞣剂的鞣性研究

以明胶作为皮胶原模拟物,利用原位生成的三聚氰胺-甲醛树脂对其改性,并通过红外(FT-IR)、总碳含量(TOC)、总氮含量(TNb)、等电点(PI)和热重分析(TG)等分别对改性前后明胶的结构和性能进行了表征。结果显示:改性后明胶的氨基含量增加;总碳、氮含量分别提高了29.5%和65.7%;等电点由原来的4.8上升到5.3;改性前后明胶5%和10%的热失重温度分别由75.8℃和123.4℃提高到186.4℃和223.3℃,上述研究表明:明胶和三聚氰胺-甲醛树脂之间发生了化学键合反应。将该方法应用于软化皮坯的鞣制,采用差示扫描量热分析(DSC)技术,考察鞣制前后皮胶原的热变性温度,结果显示:与仅添加甲醛的空白样相比,经三聚氰胺树脂原位反应改性后,皮胶原的热变性温度提高了20.3℃,基于原位缩聚的三聚氰胺树脂鞣剂表现出良好的鞣性。     

纳米TiO2改性明胶在合成革后整理中的应用

采用原位有机-无机杂化技术将纳米TiO2引入明胶体系,制备了纳米TiO2的改性蛋白材料,通过扫描电镜(SEM)发现,原位生成的TiO2颗粒直径都在100 nm左右,相对未经改性的明胶具有良好的耐热稳定性.将改性明胶应用于合成革的后整理中,且与传统酪素涂饰的成革在透湿性、表面接触角和抗菌性能等方面的比较研究,结果表明:加入改性明胶涂饰后的成革的透湿性与酪素涂饰后的成革相当;并且由于改性明胶亲水基团的增加,表面接触角与酪素的相当,降低了表面张力,改善了再涂性;经改性明胶涂饰后的合成革还具有良好的抗菌性,这是酪素所不具备的.充分说明改性明胶可以取代酪素在合成革后整理中的应用.另外,改性明胶价格低廉、易于制备,这对促进行业技术进步,提高企业经济效益都有积极的意义.     

胶原蛋白改性亚麻纱线结构及性能研究

研究胶原蛋白改性亚麻纱线的结构及性能。先采用高碘酸钠对亚麻纱线进行选择性氧化生成双醛基,然后经亚硫酸氢钠磺化处理得到磺化亚麻纱线,再利用明胶蛋白溶液对磺化亚麻纱线进行接枝改性处理。采用红外光谱、X-射线衍射、SEM等方法对改性亚麻纱线的结构进行表征与分析。测试了改性亚麻纱线的断裂强力、断裂伸长率和回潮率等性能指标。结果表明:磺化亚麻纱线和明胶蛋白在亚麻纤维的非结晶区以化学键结合;不同的明胶溶液浓度对磺化亚麻纱线的接枝率有一定的影响,明胶蛋白接枝率在0～10%(质量分数)范围内时,亚麻纱线断裂强力基本不变,回潮率随着接枝率的增大略有增加,断裂伸长率随着接枝率的增大有较明显的提高。     

转谷氨酰胺酶改性对明胶耐酶解性的影响

以转谷氨酰胺酶改性明胶的耐酶解性为关注点,通过单因素试验和均匀设计试验研究转谷氨酰胺酶浓度、改性pH值、改性温度和改性时间等因素对改性明胶耐酶解性的影响。通过均匀试验得到的最优改性条件为:转谷氨酰胺酶质量浓度为0.20 g/L,改性pH 6.0,改性温度44℃,改性时间35 min。与未改性明胶相比较,改性明胶的耐酶解能力提高了14.44%。本研究结果表明转谷氨酰胺酶改性可以显著提高明胶的耐酶解能力。     

氧化绿原酸改性鳕鱼皮明胶功能特性的研究

该试验研究经不同浓度氧化绿原酸(2.5%、5.0%、10.0%和20.0%)改性后鳕鱼皮明胶的抗氧化能力和乳化性。测定氧化绿原酸改性的鳕鱼皮明胶游离氨基的含量、表面疏水性、浊度、抗氧化活性以及硫代巴比妥酸值。结果表明,经氧化绿原酸改性的明胶抗氧化活性提高,但游离氨基含量和表面疏水性降低。5.0%氧化绿原酸改性明胶的浊度最高,较高浓度的氧化绿原酸会影响明胶的乳化性能。氧化绿原酸能够增强供氢能力,并作为金属螯合剂增强明胶的抗氧化活性。此外,氧化绿原酸改性的明胶能够增加乳状液的氧化稳定性。     

明胶与合成高分子复合膜的研究进展

明胶是一种绿色的天然高分子,来源广泛,价格低廉,具有良好的成膜性、生物相容性、生物降解性等。明胶用作膜材料时,具有广泛的用途。但纯明胶膜存在着质脆、力学性能差、对水敏感、潮湿环境下易霉变等缺陷,通常需要对其进行改性处理。将明胶与合成高分子复合制备明胶基复合膜,往往赋予其良好的性能和特性,从而使明胶复合膜具有广阔的应用前景。简单综述了明胶与一些合成高分子(聚乙烯醇、聚乳酸等)共混复合制备明胶基复合膜的研究进展。     

苎麻织物活性染料深浓染色工艺方法研究

采用浓碱与自制的阳离子明胶蛋白助剂联合处理苎麻织物,探讨浓碱预处理条件(碱用量、处理时间)对改性效果和活性染料染色效果的影响,并研究阳离子蛋白助剂改性条件(助剂用量、氢氧化钠用量、改性时间、改性温度)对苎麻织物活性染料染色的上染百分率、固色效率、染色深度的影响,确定了最佳苎麻预处理条件及浸渍改性条件。结果表明,经浓碱预处理后,再经阳离子明胶蛋白助剂改性的苎麻织物染色性能显著改善,活性染料利用率明显提高。     

Functional properties of gelatin from cuttlefish (Sepia pharaonis) skin as affected by bleaching using hydrogen peroxide

Functional properties of gelatin from dorsal and ventral skin of cuttlefish with and without bleaching by H₂O₂ at different concentrations (2% and 5% (w/v)) for 24 and 48 h were studied. Gelatin from skin bleached with 5% H₂O₂ for 48 h showed the highest yield (49.65% and 72.88% for dorsal and ventral skin, respectively). Bleaching not only improved the colour of gelatin gel by increasing the L^∗-value and decreasing a^∗-value but also enhanced the bloom strength, and the emulsifying and foaming properties of the resulting gelatin. Gelatin from bleached skin contained protein with a molecular weight of 97 kDa and had an increased carbonyl content. Fourier transform infrared spectroscopic study showed higher intermolecular interactions and denaturation of gelatin from bleached skin than that of the control. These results indicated that hydrogen peroxide most likely induced the oxidation of gelatin, resulting in the formation of gelatin cross-links, giving improved functional properties.     

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by oxidised phenolic compounds

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by different oxidised phenolic compounds including caffeic acid, ferulic acid and tannic acid at different concentrations were investigated. Oxidised phenolic compounds were covalently attached to gelatin as indicated by the decrease in amino groups. Fourier transform infrared spectroscopic studies indicated the presence of an aromatic ring and a hydroxyl group in gelatin after modification. Modified gelatin had the increased antioxidative activity but the decreased surface hydrophobicity. Gelatin modified with 5% oxidised tannic acid had no change in emulsifying properties. Emulsion stability and oxidative stability of menhaden oil-in-water emulsion stabilised by 0.5% and 1.0% gelatin without and with modification by 5% oxidised tannic acid were studied. Both gelatins at a higher concentration (1.0%) yielded an emulsion with a smaller particle size. Modified gelatin inhibited the formation of TBARS in the emulsion more effectively than the control gelatin throughout the 12 days of storage.     

Characteristics and functional properties of gelatin from seabass skin as influenced by defatting

Gelatins from nondefatted and defatted seabass skins were characterised and evaluated for their functional properties in comparison with commercial fish skin gelatin. All gelatins contained α₁‐ and α₂‐chains as the predominant components and showed a high imino acid content (199–201 residues/1000 residues). All gelatins had a relative solubility greater than 90% in the wide pH ranges (1–10). Foaming properties of all gelatins increased with increasing concentrations (1–3%, w/v). Gelatin from defatted skin had higher foam expansion and stability than that extracted from nondefatted skin. Emulsion containing gelatin from defatted skin had smaller oil droplet size (d₃₂, d₄₃), compared with that having gelatin from nondefatted skin (P < 0.05). After 10 days of storage at room temperature (28–30 °C), emulsion stabilised by gelatin from defatted skin showed the higher stability as indicated by the lower increases in d₃₂ and d₄₃, and lower flocculation factor and coalescence index. Coincidentally, emulsion stabilised by gelatin from defatted skin had higher zeta potential than that containing gelatin from nondefatted skin. Thus, defatting of seabass skin directly affected characteristics and functional properties of resulting gelatin.     

Emulsifying Property and Antioxidative Activity of Cuttlefish Skin Gelatin Modified with Oxidized Linoleic Acid and Oxidized Tannic Acid

Cuttlefish skin gelatins modified with oxidized linoleic acid (OLA) and oxidized tannic acid (OTA) were characterized and determined for emulsifying properties and antioxidative activity. Modification of gelatin with 5% OTA increased the total phenolic content and 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity and ferric reducing antioxidant power of gelatin–OTA. Incorporation of OLA into gelatin (OLA-to-free amino group molar ratio of 10:1) increased surface hydrophobicity of gelatin from 17.39 to 32.38 and reduce surface tension at air/water interface of gelatin solution from 53 to 32 mN/m. Gelatin–OLA had the increase in emulsion activity index, compared with gelatin without modification and was capable of producing a fine emulsion (d ₃₂?=?0.79 μm, d ₄₃?=?0.82 μm). Modification of gelatin–OLA complex with OTA at different concentrations (2.5%, 5%, and 10%) increased antioxidative activity but decrease emulsifying properties. However, gelatin–OLA modified with 5% OTA had higher emulsifying properties than the commercial gelatin (bovine gelatin). The presence of an alkyl group and a hydroxyl group in gelatin after modification with OLA and OTA, respectively, was revealed by Fourier transform infrared study. Coincidental decrease in free amino group was also noticeable in modified gelatin. Menhaden oil-in-water emulsion stabilized by gelatin modified with OLA and 5% OTA was more resistant to lipid oxidation and phase separation as evidenced by the lower thiobarbituric acid reactive substances value and smaller oil droplet size, compared with that stabilized by commercial bovine gelatin. Thus, the modification of gelatin by both OLA and OTA was able to improve antioxidative and emulsifying properties of cuttlefish skin gelatin.     

Radical scavenging properties of protein hydrolysates from Jumbo flying squid (Dosidicus eschrichitii Steenstrup) skin gelatin

Gelatin extracted from Jumbo flying squid skin was hydrolyzed with serials of protease. The scavenging effects of gelatin hydrolysates on superoxide and hydroxyl radical were assessed by chemiluminescence analysis. Properase E and pepsin have shown efficient hydrolysis of squid skin gelatin to obtain high radical scavenging activity peptides. The conditions chosen for enzymic hydrolysis of squid skin gelatin with properase E were pH 9.0, 45 °C, 3 h reaction time, and enzyme‐to‐substrate ratio of 1:50. Hydrolysates combining properase E and pepsin showed the best radical scavenging activity. For fragmented hydrolysates by ultrafiltration, fractions UF‐2 (M_w < 2000 Da) had high yield and radical scavenging activity. Copyright © 2006 Society of Chemical Industry     

Thermomechanical study of the phase behaviour of agarose/gelatin mixtures in the presence of glucose syrup as co-solute

In an effort to draw attention to the subject of structure/function relationships in high-solid biopolymer mixtures, this investigation produces binary composites of agarose with gelatin and systematically increases the amount of glucose syrup, which is the co-solute in this system. Experimental work was carried out using small-deformation dynamic oscillation on shear and modulated differential scanning calorimetry. Agarose/gelatin mixtures in an aqueous low-solid environment form non-interactive bicontinuous networks. Addition of glucose syrup to the polymeric blend prevents the formation of stable double helices in the environment. Gelatin, on the other hand, better withstands the co-solute-induced change in solvent quality. At subzero temperatures, materials go through the rubber-to-glass transition whose DSC glass transition temperature (T_g) is governed by the total level of solids in the system. Estimation of the mechanical T_g acquires physical significance by utilising the theory of free volume, as modelled by the Williams, Landel and Ferry (WLF) equation. The single value of T_g estimated by this approach argues in accordance with experimental observations for the predominance of the gelatin network in the high-solid mixture.     

Release kinetics of antioxidant compounds from Hibiscus sabdariffa L. encapsulated in gelatin beads and coated with sodium alginate

Gelatin beads containing a concentrated extract of Roselle (Hibiscus sabdariffa L.) calyx rich in polyphenolic compounds were coated with sodium alginate and ionotropically gelled using CaCl₂. Single‐coated beads and double‐coated beads were obtained by this technique, and the release pattern of the loaded extract was evaluated. As a result, release pattern of these compounds fits properly to a first–order Weibull distribution equation. The release rate constant decreased linearly with the number of alginate coats and with the increase in immersion time in CaCl₂ and the Lag period increased significantly with the number of alginate coats. The release of H. sabdariffa's polyphenols can be well controlled manipulating the number of alginate coats and the immersion time in a CaCl₂ solution, allowing not only to control the gastrointestinal segment where they could be released but also to control the release rate with the certainty that the initial concentration will be completely released showing a highly significant antioxidant activity as well.     

Indigenous proteases in the skin of unicorn leatherjacket (Alutherus monoceros) and their influence on characteristic and functional properties of gelatin

Indigenous proteases in the skin of unicorn leatherjacket (Alutherus monoceros) were characterised using autolytic study. Maximised autolysis was found at pH 7 and 50 °C. Autolysis was markedly inhibited by 0.04 mM soybean trypsin inhibitor (SBTI), suggesting that heat activated serine protease was predominant in the skin. The impact of indigenous proteases on the properties of gelatin extracted from unicorn leatherjacket skin was investigated. Gelatin was extracted from unicorn leatherjacket skin using distilled water at 50 °C for 12 h in the presence and absence of 0.04 mM SBTI. In the presence of SBTI, the degradation was markedly inhibited, but a lower gelatin extraction yield was obtained (P < 0.05). Extracted gelatins contained α₁ and α₂ chains as the predominant components with some degradation peptides. FTIR spectra indicated a greater loss of molecular order of the triple helix and a higher degradation was found in gelatin extracted in the absence of 0.04 mM SBTI. The net charge of gelatin samples extracted with and without 0.04 mM SBTI became zero at pHs of 8.45 and 7.31, respectively, as determined by ζ-potential titration. Higher gel strength (320.68 ± 3.02 g) was obtained in gelatin extracted with SBTI, compared with that of gelatin extracted without SBTI (288.63 ± 1.44 g). High emulsifying activity index but lower emulsifying stability index was observed in the former. Therefore, heat-activated serine protease was involved in the degradation of gelatin molecules, thereby affecting the yield, proteinaceous components and properties of gelatin from unicorn leatherjacket skin.     

Changes in salted yoghurt during storage

The study was conducted to determine the gross chemical composition and concentrations of free fatty acids (FFAs) and volatile compounds of salted yoghurt made from indigenous goat's milk. The effects of some chemical properties on sensory attributes of salted yoghurt were also studied. Changes in FFAs (P < 0.01) and volatile compounds were statistically significant (P < 0.05) during storage. The most abundant FFAs were 9‐octadecenoic (C_18:1), hexadecanoic (C₁₆), tetradecanoic (C₁₄) and decanoic (C₁₀) acids, respectively. Ethanol and ethyl acetate were principal volatile compounds through the end of storage period. The storage period affected the intensity of flavour attributes and overall flavour score of salted yoghurt (P < 0.05). According to factor analysis result, chemical compounds including volatiles, FFAs up to C₁₄, tyrosine and titratable acidity, and flavour attributes explained 86.50% and 55.33% of total variance, respectively.     

Enhancement of Emulsifying Properties of Cuttlefish Skin Gelatin by Modification with N-hydroxysuccinimide Esters of Fatty Acids

Cuttlefish (Sepia pharaonis) skin gelatin modified with N-hydroxysuccinimide esters of various fatty acids including capric acid (C10:0), lauric acid (C12:0), and myristic acid (C14:0) at different molar ratios was characterized and determined for emulsifying property. Fatty acid esters were incorporated into gelatin as indicated by the decrease in free amino group content. Gelatin modified with fatty acid ester had the increased surface hydrophobicity and emulsifying property with coincidental decrease in surface tension. Gelatin modified with fatty acid ester of C14:0 showed the highest surface activity, especially with the high degree of modification. Emulsion stabilized by gelatin modified with fatty acid ester of C14:0 had a smaller mean particle diameter with higher stability, compared with that stabilized by the control gelatin (without modification). Emulsion stabilized by modified gelatin remained stable at various pH (3–8) and salt concentrations (NaCl 0–500 mM). Emulsion was also stable after being heated at 50–90 °C for 30 min.