Structural Characteristics of Tilapia (Oreochromis mossambicus) Bone Gelatin: Effects of Different Liming Methods

Fish bone is a good source of gelatin. In this study, gelatins were prepared from tilapia bone after the bone was pretreated with alkali protease, desalted immediately by 0.6 mol L^?1 HCl, and hydrolyzed by papain or limed by Ca(OH)₂. Gelatins extracted from papain-treated tilapia bone exhibited space structures similar to those of alkali-treated tilapia bone. Despite this similarity, many differences were observed between these gelatin samples. Compared with alkali-treated gelatin, papain-treated gelatins showed higher values for imino residue content, molecular weight proportion, bloom strength, and viscosity. The bloom strengths of the second and third papain-treated gelatins were 163 and 94 bloom, respectively, which were lower than the bloom strength of the first papain-treated gelatin (189 bloom). The viscosities of the three papain-treated gelatin samples were 4.18, 2.81, and 0.51 mPa.s^?1. The first papain-treated gelatin achieved the highest gelling (16 °C) and melting points (23.9 °C). The yields of the first (5.40%) and second (6.71%) papain-treated gelatins were higher than those of the alkali-treated gelatins (3.33 and 5.76%, respectively). However, the yield of the third papain-treated gelatin (2.27%) was lower than that of the third alkali-treated gelatin (5.42%). More importantly, papain hydrolysis can prevent destruction by Ca(OH)₂ in the bone structure and effectively reduce the denaturation temperature of tilapia bone collagen. Moreover, papain hydrolysis can dramatically reduce the time required for liming (0.8% of traditional liming process spent). Papain hydrolysis is a clean production method that can replace traditional liming.     

Functional Properties of Grass Carp (Ctenopharyngodon Idella), Nile Perch (Lates Niloticus) and Nile Tilapia (Oreochromis Niloticus) Skin Hydrolysates

The influence of using an endo-peptidase (alcalase) on the functional properties of hydrolysis products from Nile perch, Grass carp, and Nile tilapia skin was studied. Reaction conditions were controlled at pH 8.25, 60°C, and the enzyme was added on the basis of standard activity units at an enzyme to substrate ratio of 1.7 g/100 g protein. The reaction was allowed to proceed for 85 min and enzyme was inactivated by heat. The soluble protein fractions were recovered and lyophilized. All freeze-dried fish skin hydrolysates powders had a light yellow color and contained up to 90% protein. Nitrogen solubility varied from 95.93 to 98.72% and was not significantly different at 5% probability level. The water and oil holding capacities of the skin hydrolysates were good in the range of 2.8 to 3.2 mL/g and 3.4 to 3.8 mL/g, respectively. Emulsification capacity varied from 11.3 to 21 mL/0.5 g with Nile perch skin hydrolysate having the highest score while Nile tilapia skin hydrolysate was the lowest. Grass carp skin hydrolysate was not able to form stable foam, unlike the Nile perch and Nile tilapia skin hydrolysate. Alcalase treated freshwater fish skin exhibited satisfactory functional properties hence may play an important role as an ingredient in the food and pharmaceutical industry.     

罗非鱼肉蛋白酶解液的抗氧化活性

采用胰蛋白酶、复合蛋白酶、风味蛋白酶、木瓜蛋白酶、菠萝蛋白酶、罗非鱼胃蛋白酶和罗非鱼肠蛋白酶分别酶解罗非鱼肉蛋白,研究并比较不同酶对罗非鱼肉蛋白的酶解效果及产物的抗氧化特性。结果表明:7种酶的酶解液都显示了一定的抗氧化性,其中木瓜蛋白酶酶解液水解度(DH)最高,为20.85%,对DPPH自由基、O2-.清除率均最佳,分别为75.74%、34.35%;罗非鱼胃蛋白酶酶解液的DH为17.03%,对.OH清除率和还原力均最高,分别为60.51%、0.653。整体的抗氧化性能显示:罗非鱼胃蛋白酶和木瓜蛋白酶酶解罗非鱼肉蛋白得到的酶解液的抗氧化活性优于其他酶。     

Properties of Bio-nanocomposite Films from Tilapia Skin Gelatin as Affected by Different Nanoclays and Homogenising Conditions

Fish gelatin films incorporated with hydrophilic and hydrophobic montmorillonite (mmt) nanoclays with the aid of homogenisation using different pressure levels (1,000 to 4,000 lb/in²) and passes (two and four) were characterised. Young’s Modulus, tensile strength and elongation at break of films decreased with increasing pressure levels and number of passes. High pressure homogenisation generally lowered the mechanical properties of nanocomposite films. Additionally, water vapour barrier property became poorer, when high pressure homogenisation was implemented. Films incorporated with hydrophobic nanoclay (Cloisite 20A) exhibited the lower water vapour permeability (WVP) than those with hydrophilic nanoclay (Cloisite Na⁺). Colour parameters (L*, a*, b* and ?E*) of nanocomposite films were affected to some degrees by homogenisation conditions. Transparency of films increased when homogenisation pressure and number of passes increased. As revealed by wide angle X-ray diffraction (WAXD) analysis, nanocomposite films prepared using homogenisation had exfoliated nanostructure, whilst those prepared without homogenisation exhibited intercalated nanostructure. Thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses indicated that thermal stability of nanocomposite films varied with homogenisation condition, being higher in these films than in those without nanoclay. Thus, homogenisation condition and hydrophobicity of nanoclay directly affected the properties of nanocomposite films from fish skin gelatin.     

Properties of Alaska Pollock Skin Gelatin: A Comparison with Tilapia and Pork Skin Gelatins

ABSTRACT:  The objective of this work was to compare the physiochemical and rheological properties of Alaska pollock skin gelatin (AG) to those obtained for tilapia and pork skin gelatins. Results were also obtained for some mixed gels containing AG and pork skin gelatin, or AG and tilapia gelatin. AG contained about 7% hydroxyproline (Hyp), which was lower than that of tilapia (∼11%) or pork skin gelatin (∼13%). Most of the protein fractions in AG were α chain, β chain, and other oligomers. The gel strength of AG was 98 gram-force at 10 °C, and increased at a greater rate than other gelatins with decreasing temperature. The gel melting point of AG was the lowest with the oil-drop method, while the viscosity of AG was the highest of the samples studied. The rheological properties of gelatins were determined using small amplitude oscillatory shear testing. G' was nearly independent of frequency for most of the gelatin gels, but AG gels showed a slight dependence on G' and a minimum in G". G' was found to be a power law function of concentration for all gelatins used: G'= k × Cⁿ. In rheological measurements, AG also showed the lowest gel melting temperature and sharpest melting region. Increasing gelatin concentration resulted in a higher melting temperature and a broader melting region for all gelatin gels. For both the AG-pork and AG-tilapia mixed gels, the gel melting temperatures decreased and melting regions narrowed as the AG fraction was increased.     

Yield,viscosity, and gel strength of wami tilapia (Oreochromis urolepis hornorum) skin gelatin: Optimization of the extraction process

A factorial design and response surface methodology were used to optimize the extraction process of tilapia skin gelatin (Oreochromis urolepis hornorum). The concentrations of NaOH (0.15%–0.35%) and H₂SO₄ (0.15%–0.35%), the extraction temperature (40°C–60°C), and the extraction time (3–15 h) were independent variables. Response variables were yield (%), viscosity (mPa·s), and gel strength (g). The NaOH (%) and H₂SO₄ (%) concentrations had significant influences (p<0.05) on viscosity and gel strength, while the extraction temperature (°C) and the extraction time (h) showed significant influences (p<0.05) on all dependent variables. Increasing the temperature and extraction time provided higher yields with a reduction in the gelatin viscosity and gel strength. Tilapia fish skin can be used as a source for production of gelatin.     

罗非鱼皮明胶的制备及性质研究

以干燥的罗非鱼鱼皮为原料,经脱色溶胀后热水熬胶来制备明胶,通过正交实验法对罗非鱼鱼皮明胶的提取工艺进行优化,并分别对明胶黏度、吸水性、保水性、等电点和氨基酸组成进行了测定。结果表明,鱼皮明胶最佳提取工艺为氢氧化钠浓度2．0％,浸泡24h,盐酸的浓度为0．5％,浸泡4h时,熬胶温度在80℃,时间为8h,提取率为47．54％。     

Recovery and Properties of Muscle Proteins Extracted from Tilapia (Oreochromis niloticus) Light Muscle by pH Shift Processing

ABSTRACT: Functional proteins can be extracted from fish muscle using acid- or alkali-aided solubilization and recovered with isoelectric precipitation. It was of interest to evaluate acid- and alkali-aided solubilization/precipitation on muscle material from the warm-water fish tilapia. Higher levels of proteins were extracted with high compared with low pH ( P < 0.05) because of higher protein solubility at high pH. Protein extraction was not influenced by the specific low or high pH tested or homogenization time. Similar protein types were extracted for the low and high pH solubilization, while proteolysis was observed at low pH. Viscosity was significantly higher at pH 2.3 to 2.9 compared with pH 10.8 to 11.4 ( P < 0.05) and varied greatly at low pH indicating a more unstable system. Two different low (pH 2.5 and 2.9) and high (pH 11 and 11.2) solubilization pH values were selected and protein recovery investigated in the pH range 5.1 to 5.7. The alkali-extracted proteins had more solubility at pH 5.1 to 5.7 ( P < 0.05) and thus less protein ( P < 0.05) was precipitated compared with the acid-aided process. More protein was recovered as pH increased from 5.1 to 5.7 ( P < 0.05). More protein types were found in the supernatant after precipitation for the alkali-aided treatment, and soluble proteins were similar to those of untreated tilapia muscle homogenate. Viscosities of the acid- and alkali-extracted proteins at pH 5.1 to 5.7 were significantly higher than the viscosity of native proteins at that pH ( P < 0.05). While this study demonstrated significant differences in protein extractability and precipitation of the 2 processes, no statistical difference ( P > 0.05) was found for overall protein recovery (61% to 68% for alkali-aided process and 56% to 61% for acid-aided process) of the 2 processes.     

Extracting Conditions for Megrim (Lepidorhombus boscii) Skin Collagen Affect Functional Properties of the Resulting Gelatin

Various procedures for extracting collagen and/or gelatin from megrim skins were compared on the basis of gelatin functional properties. It was possible to prepare a dry powder of soluble collagen with good viscoelastic and gelling properties, which can be converted into gelatin by dissolving at temperatures above 45 °C. Physical properties of gelatins are influenced more by extracting conditions than by imino acid composition. A high-quality, readily-dissolved gelatin was obtained from megrim skins using a pretreatment of the skins with NaCl and dilute NaOH, then swelling with 0.05 M acetic acid followed by an extraction step in water at 45 °C.     

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...     

提取温度对罗非鱼皮明胶理化性质的影响

本研究以罗非鱼皮为原料,研究在不同温度(30、40、50、60、70、80、90℃)下提取的明胶所表现的得率、凝冻强度、聚丙烯酰胺凝胶电泳分析、傅里叶红外光谱分析、热变性温度、流变性性能等理化特征。结果表明,提取温度对鱼皮明胶的紫外吸收无明显影响;随着提取温度的升高,鱼皮明胶的得率逐渐增大,在提取温度为60~80℃时差异不显著(p>0.05),在90℃达到最大值(62.60%±0.84%);聚丙烯酰胺凝胶电泳图谱显示,较低温度(30、40、50℃)下提取的鱼皮明胶由α₁、α₂、β 3条肽链组成,提取温度升高后电泳条带强度降低;提取温度为50℃时,罗非鱼皮明胶的凝冻强度最大,高达(884.33±26.76)g;FTIR光谱显示,不同温度下提取的鱼皮明胶在酰胺区都具有特征吸收峰,在光谱中显示出微小的差异;不同温度下提取的鱼皮明胶的热变性温度分别为(101.05±2.97)、(104.35±3.54)、(107.59±0.37)、(97.80±4.21)、(95.35±2.60)、(92.52±3.15)、(89.66±1.23)℃;提取温度通过改变明胶的分子量大小影响明胶溶液内部贮藏能量的多少,进而对明胶溶液的流变性能产生影响。     

氯化钠添加量对鱼皮明胶凝胶性能和结构的影响

以罗非鱼鱼皮为原料制备鱼皮明胶,通过单轴压缩实验、差示扫描量热实验(DSC)和红外光谱法(FT-IR)探讨了不同氯化钠添加量(0、0.5%、1.0%、1.5%、2.0%、3.0%,w/v)对不同浓度鱼胶凝胶样品(2%、4%、6.67%,w/v)的真实应力、杨氏模量、热焓值和结构的影响。结果表明,随着鱼胶浓度增加其真实应力和杨氏模量显著增加,表明鱼胶的凝胶强度和硬度显著增加,添加氯化钠后,鱼胶体系的凝胶强度和硬度随氯化钠添加量的增加呈现显著下降趋势,当氯化钠添加量达到3%时,鱼胶凝胶强度和硬度的值最小。差式扫描量热量热分析结果表明,随着氯化钠浓度的增加,热焓值下降,鱼胶的凝胶网络交联程度变弱。傅里叶变换红外光谱分析结果表明,随着氯化钠添加量增加,酰胺Ⅰ带吸收峰逐渐向低波数方向移动,氢键形成受到抑制,鱼胶凝胶强度降降低。研究表明氯化钠的存在破坏了鱼胶凝胶样品的空间结构,降低了鱼胶的凝胶性能。     

彩鲷和普通罗非鱼不同部位营养及质构特性的研究

通过对彩鲷和普通罗非鱼背部、腹部和尾部肌肉的基本营养成分、氨基酸、营养价值及质构特性的研究,评价两种鱼不同部位的营养与质构特性.研究结果表明,两种罗非鱼背部的蛋白质、必需氨基酸含量、化学评分、必需氨基酸指数和氨基酸评分均最高,这表明背部肌肉的营养价值最高,最适合作为人体补充营养的部位;彩鲷背部和尾部肌肉蛋白质的含量和必...     

Physicochemical and Rheological Properties of White-Cheek Shark (Carcharhinus dussumieri) Skin Gelatin

Physicochemical and rheological properties of white-cheek shark (Carcharhinus dussumieri) skin gelatin were determined as a function of either an alkaline-acid or an acid pretreatment. With alkaline-acid pretreatment, the purity of white-cheek shark skin gelatin was increased, with a significantly lower extraction yield, a higher retention of high molecular weight components, and greater preservation of the triple helical structure. Moreover, gelatin from alkaline-acid treated skins showed denser spherical structure, significantly (p < 0.05) different textural properties, better thermostability (T_g = 21°C, T_m = 27.5°C), higher values of both G′ and G″, higher gel strength (330 g), more imino acids (20.3%), and lighter colored gels compared with acid treated white-cheek shark skin gelatin.     

低热量甜味剂对鳕鱼皮明胶理化及功能性质的影响

以鳕鱼皮明胶为原料,研究木糖醇、三氯蔗糖、甜菊糖和蔗糖对鱼皮明胶物理、流变、功能特性及拉曼光谱的影响。结果表明,甜味剂/蔗糖可以提高凝胶样品的凝胶强度、硬度、热变性温度及焓变值。流变和功能特性研究结果表明,甜味剂/蔗糖可使凝胶样品具有更高的储能模量、耗能模量,起泡性和持水性。拉曼光谱结果显示,混合体系的蛋白二级结构中,无规则卷曲转化为α-螺旋,使得体系结构更稳定。低热量甜味剂可作为蔗糖替代物应用于食品工业。     

Effects of Pretreatment on Properties of Gelatin from Perch (Lates Niloticus) Skin

Fish gelatins obtained from perch fish skin pretreated with various solutions containing acetic acid, sodium hydroxide (NaOH) and sodium chloride (NaCl) were successfully characterized for their nanostructure pattern using field emission scanning electron microscopy. Each pretreatment transformed collagen to gelatin with fibril, zigzag cracks, straight rods, and cross-linked rods nanostructure patterns. Pretreatment solutions also affect the gel yield, gel strength, amino acid profile, and functional groups in perch gelatin as analyzed by Fourier transform infrared spectroscopy. Samples pretreated with NaCl, NaOH, and acetic acid solution showed the highest gel yield (22.84%) and gel strength (179.84 g). Fourier transform infrared spectra for perch gelatins also revealed weak C–N amide II and III bond stretches as well as weak C=O bond stretch.     

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.     

几种生物大分子对罗非鱼皮Ⅰ型胶原自聚集性的影响

研究海藻酸钠、硫酸软骨素、透明质酸和壳聚糖对罗非鱼皮Ⅰ型胶原自聚集动力学和聚集后微观结构的影响。结果表明:在海藻酸钠、硫酸软骨素、透明质酸和壳聚糖存在的情况下,胶原自聚集过程仍然包含两个阶段:成核阶段和生长阶段,但是各物质对两阶段的动力学参数影响不同。海藻酸钠、透明质酸和壳聚糖均能够降低生长阶段的速率常数,然而对成核阶段的影响各有差异。海藻酸钠对成核阶段的速率常数没有显著影响,但是随着含量的增加能够延长成核时间;壳聚糖能够提高成核阶段的速率常数,同时缩短成核时间;透明质酸对成核阶段的速率常数和成核时间却没有显著影响。而硫酸软骨素对成核阶段和生长阶段均没有显著影响。扫描电子显微镜结果表明海藻酸钠、硫酸软骨素、透明质酸易使胶原纤维横向聚集形成纤维束,影响其直径大小的顺序为硫酸软骨素海藻酸钠透明质酸,而壳聚糖却未表现类似作用。     

Effect of Extraction Temperature on Functional Properties and Antioxidative Activities of Gelatin from Shark Skin

Physico-chemical properties, functional properties, and antioxidative acitivities of gelatin from the skins of brownbanded bamboo shark (BBS; Chiloscyllium punctatum) and blacktip shark (BTS; Carcharhinus limbatus), as affected by extraction temperature, were investigated. ??-Amino acid group content and surface hydrophobicity of both gelatins from both species increased as the extraction temperature increased (P?<?0.05). Both gelatins had a high solubility (more than 80%) in a wide pH range (1?C10). Both gelatins extracted at 60?°C exhibited the highest emulsion activity index (EAI), emulsion stability index (ESI) and foam expansion (FE). The lowest foam stability (FS) was obtained when gelatin was extracted at 75?°C (P?<?0.05). The BBS gelatin had lower EAI, ESI, and FE than did BTS gelatin. Nevertheless, a higher FS was found in the former (P?<?0.05). Antioxidative activities of both gelatins increased with coincidental increase in ??-amino group content as the extraction temperature increased (P?<?0.05). The BTS gelatin generally exhibited the higher antioxidative activities, compared with the BBS gelatin (P?<?0.05). Gelatin extracted at 60?°C showed the highest interfacial properties, while those extracted at higher temperature (75?°C) had enhanced antioxidative activities. Extraction temperature may therefore be regulated to maximize applications.     

乙酸溶胀-挤压提取对罗非鱼真皮胶原蛋白理化性质的影响

以磷酸预处理辅助实现罗非鱼皮真皮与表皮的分离,采用低温乙酸溶胀法提取真皮中的胶原蛋白,并对所得胶原蛋白样品进行理化性质分析。结果表明,在4℃环境中,以0.006 mol/L磷酸、50 g/L料液处理鱼皮3 h,可获得最佳真皮、表皮分离效果。所得真皮在4℃环境中,以0.035 mol/L乙酸溶液(料液质量浓度为100 g/L)溶胀处理6 h,挤压后可得羟脯氨酸质量分数为7.9%的真皮胶原蛋白样品,提取得率达27.6%(干基)。凝胶电泳结果分析表明,所得样品主要含有α1、α2和β链,由紫外光谱分析结果可知其最大吸收在230 nm波长附近,符合典型Ⅰ型胶原蛋白特征;衰减全反射傅里叶变换红外光谱分析结果显示其三螺旋结构得到较好地保留。样品热变性温度及热收缩温度分别为29.2℃和55.0℃。研究结果为鱼皮资源的高效开发利用以及高品质胶原蛋白的制备提供了理论参考。