Yield and Gel Strength of Gelatin Extracted from Smoked Salmon (Salmo salar) Skins

The gelatin yield and gel strength of gelatin extracted from the skins of smoked salmon were determined. The skins had a crude protein content of 43.5 ± 1.2% and an estimated collagen content of 23.6 ± 1.0%. Following an alkali extraction process under varying extraction conditions, the protein content varied from 2.78% to 32.1%, and the gelatin yield ranged from 2.23% to 22.4% of the initial skin weight. The gelatin purity (gelatin/protein) ranged from 55.4% to 100%, with the highest Hyp/protein sample arbitrarily designated as being 100% pure, i.e., an assumption of pure gelatin. Statistical analysis showed that HCl concentration, pretreatment temperature, and extraction temperature significantly affected the protein yield and gelatin yield. The wide range of gel strengths indicates that the gelatin might have been hydrolyzed to different extents during the different extraction and cooling processes. Statistical analysis did not show that any of the factors studied affected the gel strength. However, the data indicated that low NaOH concentrations and HCl concentrations might not prevent hydrolysis during the extraction process. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) showed that the gelatins contained α- and β-chains and that the gelatins composed of higher concentrations of larger molecular weight polypeptide chains had higher gel strengths.     

Effects of Protein Concentration,Plasticiser, and pH on the Properties of Protein Films from Whitemouth Croaker (Micropogonias furnieri) Residues

ABSTRACT

Proteins have been used extensively because of their relative abundance, nutritional qualities, and film-forming ability with a good structural integrity and mechanical properties. This study investigated the effects of protein isolate and glycerol concentration and pH on the properties of protein films obtained from Whitemouth croaker (Micropogonias furnieri) residues. The films were evaluated for mechanical properties, thickness, water solubility, water vapor permeability (WVP), and morphological properties. The lowest water solubility of the films occurred at low pHs and low glycerol concentrations. The films had high elongation and higher tensile strength when prepared with higher concentrations of protein isolate, lower concentrations of glycerol, and at lower pHs. The WVP and thickness of the films had a low correlation coefficient. The films were rough and had irregular surfaces. These results indicated that protein isolates from fish of low commercial value can be used as a component of new polymeric films for packaging. However, more studies are needed to assess their barrier action against oxygen, thermal behaviors, and their performance in different types of packaging.     

Characteristic and Functional Properties of Gelatin from the Bones of Alaska Pollock (Theragra chalcogramma) and Yellowfin Sole (Limanda aspera) with Papain-Aided Process

Fish gelatin was extracted from the bone of Alaska pollock (Theragra chalcogramma) and yellowfin sole (Limanda aspera) using papain-aided process and the characteristic and functional properties were analyzed. The bones of Alaska pollock and yellowfin sole yielded 9.07% and 7.15% gelatin, respectively. Protein was the main component (84.67–91.76 g/100 g) in both gelatins. There was no significant difference in whiteness between the two gelatins. The absorption peak of Alaska pollock bone gelatin (ABG) and yellowfin sole bone gelatin (YBG) in ultraviolet-visible (UV-vis) spectra was 209 nm and 211 nm, respectively. Scanning electron microscope (SEM) and Fourier transform infrared (FTIR) investigations indicated the existence of helical arrangements and uniform network structures in the two gelatins. The gel strength of ABG (105.64 g) was significantly lower than that of YBG (187.39 g), possibly due to the presence of shorter chains as indicated by the degradation of α-, β-, and γ-chains. ABG also had lower emulsibility and foamability than YBG, which was associated with relatively lower hydrophobic amino acids. Therefore, yellowfin sole would be a better potential marine source of gelatin obtained from fish processing by-products.     

Rheological,Physico-chemical,and Surface-Active Properties of Gelatin Extracted from Bigeye Tuna (Thunnus obesus) Skin Waste

ABSTRACT

In the present investigation, bigeye tuna (Thunnus obesus) skin waste was utilized for the extraction of gelatin. Physico-chemical, rheological, and surface-active properties of the obtained gelatin were assessed. Proximate compositional analysis of tuna skin gelatin recorded high protein content of 88.6% and low levels of fat and ash contents. The isoelectric point (IEP) of tuna skin gelatin was around 6.24. Amino acid profiling recorded a glycine [31.7%] higher proportion, followed by imino acids (hydroxyproline + proline) [18.4%], and alanine [12.2%]. The electrophoretic pattern of purified gelatin exhibited three major bands (β, α1, and α2) with wider molecular weight distribution in the range of 200–120 kDa. The Fourier Transform Infrared (FT-IR) spectra of gelatin also confirmed the bands corresponding to α helix, β sheet, and random coil structures. The rheological studies of tuna skin gelatin revealed Newtonian and shear thickening properties. The method of extraction and assessment of its characteristic properties could be useful in the field of formulation of functional foods, nutraceutical, and biomedical applications.     

Characterization and Functional Properties of Gelatin Extracted from Chinese Giant Salamander (Andrias Davidianus) Skin

The characteristics and functional properties of gelatin obtained from Chinese giant salamander (Andrias davidianus) skin were investigated. After alkaline and acetic acid pre-treatment, yield of the gelatin by hot water extraction (60°, 8 h) was 17.63 g/100 g (wet basis), and the gelatin contained 89.46 g/100 g protein, 0.3 g/100 g fat, and 0.41 g/100 g ash (dry basis). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results of the gelatin showed clear band pattern for collagen subunits,β- and α-chains. The gelatin contained 18.85% imino acids, 28.62% hydrophobic amino acids, and 19.68% essential amino acids, which is slightly lower than porcine skin gelatin (PSG). The gelatin exhibited thermo-reversible properties, with gel strength of 192.50 ± 11.47 g, rupture distance of 10.17 ± 0.20 mm, gelling temperature of 4.98°, and melting temperature of 18.04°, Emulsifying activity index (EAI) of the gelatin diminished with increasing concentrations from 10 to 40 mg/mL (p < .05), whereas the emulsifying stability index (ESI) improved significantly (p < .05). Higher concentrations (30 and 40 mg/mL) could significantly enhance the gelatin’s foam expansion (FE) and foam stability (FS) (p < .05). Water absorption ability and oil absorption ability of the gelatin were 7.1 g water/g gelatin and 9.8 g oil/g gelatin, respectively. These results imply that the gelatin with good interfacial properties could potentially be used as a novel ingredient in food emulsion systems.

Abbreviations: CGSS, Chinese giant salamander skin; CSG, Chinese giant salamander skin gelatin; PSG, porcine skin gelatin; EAI, emulsion activity index; ESI, emulsion stability index; FE, foam expansion; FS, foam stability; WAC, water absorption capacity; OAC, oil absorption capacity.     

Dynamic Viscoelastic Properties of Tilapia (Oreochromis niloticus) Skin Gelatin

ABSTRACT

The viscoelastic properties of gelatin extracted from tilapia skin (protein yield: 21.2%) were evaluated using dynamic rheology tests. The flow curves of tilapia gelatin sols (1.0–6.6% w/w, 40°C; 0.5%, 2–40°C) complied with the Herschel-Bulkley model (R² = 0.92–0.99), indicating the presence of yield stress, while the gelling and melting temperature of gelatin dispersions (1.0–6.6%) fit well with the Eldridge-Ferry model (R² = 0.97). Tilapia skin gelatin displayed good thermo-stability and strong gel-forming properties, showing great potential as an alternative for mammal-based gelatin applied in various food products.     

Extraction Optimization and Characterization of Gelatin from Half-Smooth Tongue Sole (Cynoglossus semilaevis Gunther) Skin

Half-smooth tongue sole is a popular warm-water fish, and its skin may be an available resource for gelatin extraction. Response surface method was used to optimize the extraction of gelatin from the fish skin. The most suitable conditions for maximum gelatin yield (24.2%) were pretreatment with 1.9 g/L NaOH, followed by hot water extraction at 63.54ºC for 4.81 h. The obtained gelatin had a high imino acid content (185 residues/1,000 residues), with a high content of crude protein and low levels of ash, fat, and moisture. The predominant sodium dodecyl sulfate–polyacrylamide gel electrophoresis bands revealed that the gelatin contained low-molecular-weight peptides, α-, β-, and γ chains. As compared with bovine gelatin, the fish skin gelatin solution had lower values of strength and clarity and higher levels of L* and viscosity. Additionally, Fourier-transform infrared spectra showed that gel from the gelatin had four amide bands (amide A, amide I, amide II, and amide III) similar to commercial gelatin. The results suggest that half-smooth tongue sole skin could be a promising source of gelatin in view of the comparability between its gelatin and commercial gelatin in physicochemical properties.     

鱼皮明胶在食品加工业中的应用

【目的】明胶是由胶原蛋白部分降解得到的天然多肽聚合物,具有良好的乳化性、成膜性、发泡性和凝胶性以及生物相容性和生物可降解性,在食品加工业中有着广泛应用。哺乳动物明胶占明胶市场的主要份额,但由于存在宗教因素和健康方面的担忧,哺乳动物明胶在食品加工业中的应用受到限制和质疑。鱼皮明胶与哺乳动物明胶具有相似的功能性质,且由于鱼皮明胶来源独特并能满足有特殊文化和需求人群的要求,已逐渐成为食品加工业中的重点研究对象。为了综合介绍鱼皮明胶在食品中的应用,【方法】本文综述了鱼皮明胶作为乳化剂、发泡剂、澄清剂、增稠剂和胶凝剂以及可食用包装、可食用涂层、乳液、微胶囊、纳米纤维和水凝胶制备材料在食品加工业中的研究进展。【结果】鱼皮明胶的功能特性使其在食品加工业中可作为食品添加剂、食品包装材料和活性物包裹材料并显示出优于哺乳动物明胶的生物安全性和加工特性。【结论】由此可见,鱼皮明胶在食品加工业中具有良好的应用前景并有望成为哺乳动物明胶的良好替代品。【意义】本综述可为今后进一步提高鱼皮明胶的功能性质和扩大鱼皮明胶在食品中的应用提供一定指导。     

Suitability of Antimicrobial Grouper Bone Gelatin Films as Edible Coatings for Vacuum-Packaged Fish Steaks

ABSTRACT

Grouper bone gelatin films were prepared along with chitosan (GC), clove (GL), and pepper (GP) essential oils and examined for their mechanical, barrier, and antimicrobial properties. GC films had a high tensile strength (TS) of 28 MPa, and GL and GP films had a high elongation at break (EAB) of 162 and 166%, respectively. Water solubility and water vapor transmission rate (WVTR) were low in GL films. All the films exhibited inhibitory activities against Staphylococcus aureus, Aeromonas hydrophila, and Listeria monocytogenes. Vacuum-packed fish steaks coated with GC and GL film extended the shelf life from 4 days to 8 days at 4ºC.     

Characteristics and Physicochemical Properties of Gelatin Extracted from Scales of Seabass (Lates calcarifer) and Grey Mullet (Mugil cephalus) in Vietnam

In this study, gelatin was obtained from the scales of seabass (Lates calcarifer) and grey mullet (Mugil cephalus) collected in Vietnam by using Alcalase® 2.4 L FG for pretreatment and electrochemically activated water with pH 2.0–2.5 for extraction. The characteristics and physicochemical properties of gelatin were investigated. The results indicated that the gelatin had a high protein content (88.6–90.0%) with ash (1.43–1.55%) and no fat. The gelatin was identified as type A due to its pH value. The yields of gelatin were 14.1–15.2%. The gel strength and melting point were 270.3 g and 26.7°C, respectively, for gelatin from seabass scales and 249.1 g and 25.9°C, respectively, for samples from grey mullet scales. In contrast, the viscosities of gelatin were found to be 6.97 cP for seabass and 8.73 cP for grey mullet. Both gelatins contained α-chain and β-chain as the major components. Circular dichroism spectra indicated that the triple helical structure in collagen was almost transformed to the random coil structure in gelatin. The proportion of imino acids was high (197–205 residues/1,000 residues). So, gelatin from seabass and grey mullet scales could be used as a potential replacement for mammalian gelatin.     

Gelatin Films Containing Hydrolysates from Whitecheek Shark (Carcharhinus dussumieri) Meat

The effect of adding different concentrations of freeze-dried (FD-WCPH) and spray-dried (SD-WCPH) whitecheek shark (Carcharhinus dussumieri) protein hydrolysate to the physical properties (solubility in water, contact angle, water vapor permeability, and opacity), mechanical properties (tensile strength, elongation at break, and elastic modulus) and color of gelatin films has been studied. The results showed that FD-WCPH and SD-WCPH led to an increase in water solubility and water vapor permeability and a decrease in contact angle and opacity of gelatin films (P < 0.05). Fish protein hydrolysate concentration showed a linear relation with elongation at break and an inverse relation with the tensile strength and elastic modulus of the films (P < 0.05).     

Development,Characterization, and Antimicrobial Activity of Gelatin/Chitosan/ZnO Nanoparticle Composite Films

ABSTRACT

In order to enhance antimicrobial activity of the film, zinc oxide (ZnO) nanoparticles were incorporated in gelatin/chitosan composite film, and the physical-mechanical properties were investigated. The film-forming solution of gelatin/chitosan/ZnO films showed increased gel strength (GS), elastic modulus (G’), and viscous modulus (G’’) compared to that of the Control. Fish gelatin/chitosan/ZnO films showed lower water vapor permeability (WVP), higher glass transition temperatures (T_g), and antibacterial activities against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Vibrio parahemolyticus. Fourier transform infrared spectra (FTIR) and microstructure studies indicated gelatin, chitosan, and ZnO interactions determined the properties of the composite film.     

Comparative Effects of Fish and Cow Gelatins and Locust Bean Gum on Chemical,Textural, and Sensory Properties of Yogurt

ABSTRACT

Yogurt is a traditional dairy product widely consumed all over the world. Syneresis, which is a result of lower water holding capacity, is a big concern and an important quality parameter. In this study, the efficiency of locust bean gum and different gelatins (fish skin, fish scale, and bovine skin) in preventing syneresis was investigated. Samples were stored at 4°C for 2 weeks, a typical shelf life of yogurt, and analyzed periodically for quality parameters. Syneresis, viscosity, and water holding capacity of the control and gum added samples were almost identical, while gelatin added samples were generally significantly improved (p < 0.05).     

Development of Optimized Edible Packaging Based on White-cheek Shark (Carcharhinus dussumieri) Skin Gelatin Biopolymer: Mechanical,Water Vapor Permeability,and Structural Properties

White-cheek shark skin gelatin (WSG) edible films were optimized with respect to their barrier, mechanical, and structural properties using response surface methodology (RSM), with the introduction of gelatin concentrations (1–4% w/v based on film forming solution) and glycerol contents (15–35% w/w based on gelatin weight) as the independent variables. WSG films with moderate levels of glycerol had higher tensile strength (TS), elastic modulus (EM), and elongation at break (E@b) depending more significantly on gelatin content. Adding higher levels of glycerol, film roughness was observed to decrease exponentially but water vapor permeability (WVP) increased linearly. Structural analysis using Fourier transform infrared spectroscopy (FTIR) showed more aggregated protein structures at higher gelatin content, which could be strongly related to the notable increase of contact angle. According to the model, the optimum conditions for the WSG film formula were found to be 3.3% WSG and 19.3% glycerol, giving a predicted maximum E@b, TS, EM, roughness, and contact angle of 183%, 4.4 MPa, 92 MPa, 4.93 nm, and 101°, respectively, with a predicted minimum WVP of 11.8 g.mm/day.m².kPa.     

响应面法优化斑点叉尾鮰鱼皮明胶-壳聚糖可食膜的制备工艺

以斑点叉尾鮰(Ietalurus punetaus)鱼皮明胶、壳聚糖、甘油为原料制备可食膜,采用响应面法对可食膜的制备工艺进行优化。在单因素试验的基础上,使用Design-Expert软件对鱼皮明胶添加量、热处理温度与甘油添加量进行三因素响应面试验设计,以抗拉伸强度为响应值优化可食膜性能,并验证响应面预测值与实测值的一致性。结果表明,复合可食膜最佳制备工艺为:鮰鱼皮明胶添加量60%、热处理温度70℃、甘油添加量为10%时,制备得到的明胶-壳聚糖可食膜抗拉伸强度达最大值24.20 MPa,验证结果为23.44 MPa,二者相对误差为3.2%,实测值与响应面预测值拟合良好,说明通过响应面试验设计优化是有效的。     

罗非鱼皮营养成分分析及鱼皮明胶提取工艺的探讨

以罗非鱼皮为原料，对其营养成分进行分析，并通过正交试验方法探讨罗非鱼皮明胶的提取工艺，同时对明胶的理化及微生物指标进行分析。结果表明，罗非鱼皮中粗蛋白含量高达33．14％，其中胶原蛋白含量为27．8％，占其粗蛋白的83．9％；鱼皮提取明胶的适宜工艺条件为在2．5％（W／V）NaOH溶液中浸泡3．5h，然后在0．02％（V／V）HCl浸泡约3h，熬胶温度为55℃，提取得率为26．5％；所得鱼皮明胶的凝胶强度达468g，粗蛋白含量为82．46％，菌落总数为1．3×10^5CFU·g^-1，大肠菌群结果报告为阴性。     

Characteristics of Gelatin Extracted from the Swim Bladder of Yellowfin Tuna (Thunnus albacores) as Affected by Alkaline Pretreatments

ABSTRACT

Gelatins extracted from the swim bladder of yellowfin tuna (Thunnus albacores) using various alkaline pretreatments were characterized. Alkaline mixtures (Na₂CO₃:NaOH) at different ratios (9:1, 8:2, 7:3, and 6:4) with a concentration of 4% (w/v) were used. The corresponding gelatins termed “G1,” “G2,” “G3,” and “G4” had yields of 9.78, 14.91, 35.96, and 13.60% (dry weight basis), respectively. All gelatins had α-chains as the major components. Fourier transform infrared spectra of obtained gelatins revealed the significant loss of molecular order of the triple-helix. G3 having the highest imino acid content and exhibited the highest gel strength (p < 0.05), compared with others. The microstructure of G3 gel was finer with smaller voids, compared with others. With increasing proportion of NaOH, the L*-value of gelatin gel increased with coincidental decrease in ΔE*-value. Gelling and melting temperatures of swim bladder gelatin were 12.3–15.1 and 21.3–22.3°C, respectively.     

鱼皮明胶蛋白膜的制备及其热稳定性

利用鲨鱼皮明胶制备蛋白可食膜,测定了成膜液蛋白浓度、甘油含量对明胶蛋白膜理化性质的影响,以及环境湿度对膜热稳定性的影响.结果发现,利用鲨鱼皮明胶可以制备成无色透明的蛋白可食膜,成膜液蛋白浓度对明胶蛋白膜的断裂延伸率(EAB)、水蒸气透过率(WVP)以及透明度值有一定的影响,对拉伸强度(TS)没有发生显著影响,但甘油含量从10％增加到70％时蛋白膜的TS逐渐降低.利用DSC对膜的热稳定性进行分析,结果表明当水分活度(Aw) ＜0.33时,明胶蛋白膜在常温下可以处于玻璃态,机械性质能够保持稳定.然而,当Aw超过0.44后,膜的玻璃化转变温度(Tg)起始点低于25℃,膜的EAB上升,TS出现显著下降.当Aw达到0.92时,膜甚至开始溶解变成溶胶.因此,利用鲨鱼皮制备的明胶蛋白膜只适合在Aw小于0.44的干燥环境中应用.     

脱钙罗非鱼鱼鳞明胶提取工艺优化及其理化性质

文章以罗非鱼（Oreochromisnilotica）鱼鳞为原料,经乙二胺四乙酸二钠（EDTA—Na,）脱钙处理后采用酸法提取明胶。根据中心组合试验设计（centercombination of experimental design,CCD）原理展开试验,考察提取时间（h,X,）、提取温度（℃,X2）、浸酸时问（h,X1）和柠檬酸质量浓度（g·L-1,X）对明胶得率（％,y）的影响,并对所得明胶的理化性质与牛骨明胶进行比较。响应面分析结果表明,提取温度、提取时间和浸酸时问与明胶得率之间具有显著相关性;优化的提取条件为提取温度65℃、提取时间3．6h、柠檬酸质量浓度200g·L-1、浸酸时间11．3h。在此条件下的明胶得率为28．4％,与预测值30．1％相近。制得的鱼鳞明胶粗蛋白含量为89．9％,氨基酸组成中每1000总氨基酸残基中甘氨酸为352个,亚氨基酸（脯氨酸和羟脯氨酸）173个;凝胶强度高达245Bloom（g）,熔点为27．0℃,而比浓对数粘度及成胶质量浓度分别为0．030L·g-1。和8．0g·L-1。     

The Effects of Grass Carp Skin Gelatin and Whey Protein Interactions on Rheological and Textural Properties and Nanostructure

The physical properties and nanostructure of fish skin gelatin with and without whey protein isolate (WPI) were investigated. The addition of low concentrations of WPI (1 and 3%, w/v) into fish gelatin decreased the gel strength and textural properties. The addition of 5% WPI did not significantly influence textural properties but increased the melting and gelling temperatures of fish skin gelatin and improved the appearance of gelatin gels. X-ray diffraction indicated that a higher degree of crystallinity with an ordered structure or ordered structure snippets occurred with increasing WPI concentrations in line with the slight decrease in the loss factor (tan δ) with time sweeps. Fish gelatin had a spherical nanostructure, and a homogeneous nanostructure was observed in gelatin with 3% WPI. The addition of 5% WPI led to large aggregates in gelatin gels. The results indicated that whey protein could affect the nanostructure of fish skin gelatin gels and thus change their gelation properties and texture in food and pharmaceutical applications.