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.     

Comparative study on characteristics of gelatin from the skins of brownbanded bamboo shark and blacktip shark as affected by extraction conditions

Gelatins from the skins of brownbanded bamboo shark (BBS; Chiloscyllium punctatum) and blacktip shark (BTS; Carcharhinus limbatus) were extracted using the distilled water at different temperatures (45, 60 and 75 °C) and times (6 and 12 h). Yields of gelatin from the skins of BBS and BTS were 19.06–22.81% and 21.17–24.76% (based on wet weight), respectively. Gelatins from both species extracted at 45 °C for 6 h exhibited the highest bloom strength (206–214 g), which was higher than that of commercial bovine bone gelatin (197 g) (p < 0.05). Gelatin gels from BBS skin could set at room temperature (25–26 °C) within 24 min. However, gelatin gels from BTS skin was not able to set within 3 h at the same temperature. Scanning electron microscopic study showed that gelatin gel from BBS skin presented the thicker strand than those from BTS skin and bovine bone. Cross-linked components (β- and γ-chains) and α-chains were more degraded with increasing extraction temperatures, especially at 75 °C. Gelatin from BTS skin was more susceptible to hydrolysis than that from BBS skin. Fourier transform infrared (FTIR) study revealed that the major absorption bands of gelatin from the skins of both sharks shifted to a higher wavenumber, compared with their corresponding acid soluble collagen (ASC). Therefore, gelatins from the skin of BBS has a potential to replace mammalian for gelatin, due to its similarity in bloom strength and setting behavior to the commercial bovine bone gelatin.     

Improvement of the antioxidant properties of squid skin gelatin films by the addition of hydrolysates from squid gelatin

Gelatin hydrolysates (HG1 and HG2) were obtained from giant squid (Dosidicus gigas) gelatins (G1 and G2) by hydrolysis with Alcalase. Antioxidant properties of both gelatins were highly increased by hydrolysis, especially ABTS radical scavenging capacity, whereas no significant differences were found between HG1 and HG2. The amino acid composition of HG1 and HG2 closely resembled the amino acid composition of the parent proteins, gelatins G1 and G2. Both, HG1 and HG2 were composed by peptides below 30 kDa, although no clear protein bands were observed in HG2. Edible gelatin films with increasing percentages of HG1 (0–10%) were made from G1, giving rise to increasing values of FRAP and ABTS, as well as changes in mechanical properties (decrease puncture force and increase puncture deformation) and water vapour permeability (increase). HG1 gelatin hydrolysate showed lower antioxidant capacity in the gelatin films than in the free form at the same amount added into the filmogenic solution, probably due to interactions with protein matrix.     

Characteristics of gelatin from the skin of unicorn leatherjacket (Aluterus monoceros) as influenced by acid pretreatment and extraction time

Gelatins from the skin of unicorn leatherjacket (Aluterus monoceros) pretreated with different acids (0.2 M acetic acid or 0.2 M phosphoric acid) and extracted with distilled water at 45 °C for various times (4 and 8 h) were characterized. Yields of 5.23–9.18 or 6.12–11.54% (wet weight basis) were obtained for gelatins extracted from the skin pretreated with 0.2 M acetic acid or 0.2 M phosphoric acid, respectively. Extracted gelatins contained α₁ and α₂ chains as the predominant components and some degradation peptides. The absorption bands of gelatins in FTIR spectra were mainly situated in the amide band region (amide I, amide II and amide ???) and showed the significant loss of molecular order of triple helix. Gelatin samples had a relative solubility greater than 90% in the wide pH ranges (1–10). The gel strength of gelatin from skin pretreated with phosphoric acid (GPA) was higher than that of gelatin from skin pretreated with acetic acid (GAA). Both GPA and GAA had the lower gel strength than that of commercial bovine gelatin (P < 0.05). Net charge of GAA and GPA became zero at pHs of 6.64–7.15 and 6.78–7.26, respectively, as determined by zeta potential titration. Emulsifying and foaming properties of GAA and GPA increased with increasing concentrations (1–3%, w/v). Those properties were governed by pretreatments and extraction time. Thus gelatin can be successfully extracted from unicorn leatherjacket skin using the appropriate acid pretreatment and extraction time.     

Sea bream bones and scales as a source of gelatin and ACE inhibitory peptides

Sea bream scales and bones were used as sources of gelatin. Scales gave a higher gelatin yield than bones pretreated with HCl or Alcalase. Demineralization with EDTA was effective especially in the case of scale gelatin that showed the lowest ash content. The pretreatment of bones with HCl led to an increase in the removal of minerals. The gel strength and viscoelastic properties of sea bream scale gelatins were higher than those of bone gelatins, and only slight differences were found between gelatin extracted from bones pretreated with HCl or Alcalase, although the amino acid profile was similar in the three gelatins. The gel strength of scale gelatins was higher than that of a commercial bovine gelatin used for comparative purpose (Bloom 200–220). When the scales gelatin was hydrolyzed with Esperase, a high ACE-inhibitory activity was found in the peptide fraction below 3 kDa, and the amount of this peptide fraction required to inhibit 50% of the ACE activity (IC₅₀) was around 60 μg/mL.     

Characterization of tilapia (Oreochromis niloticus) skin gelatin extracted with alkaline and different acid pretreatments

Tilapia production is growing worldwide and to better utilize wastes from the processing industry, one important application is production of high quality fish gelatin to meet the needs of markets that are not amenable to beef or porcine gelatin. The extraction process from tilapia skin gelatin was optimized through the use of a combination of alkali (0.3 M NaOH) with different types and concentrations of acids before thermal hydrolysis. The effects of acid pretreatments on the protein yields and the physicochemical properties of tilapia gelatin were investigated. Acid concentrations (0.01–0.20 M) influenced gelatin protein recovery: 10.52%–22.40% for citric acid, 1.92%–21.55% for acetic acid, and 4.47%–24.35% for HCl. It was possible to increase gelatin yield for each of the tested acids by adjusting the acid concentration. Gelatin viscosity and the molecular weight distribution of gelatin proteins were related to the acid concentration used. Gelatin prepared using too low a concentration (e.g. 0.01 M acetic acid or HCl) or too high a concentration (e.g. >0.05 M HCl or citric acid) yielded an extract with a smaller ratio of large molecule components, such as β-chains, and exhibited lower viscosity. The film forming properties of gelatins extracted from three acid-optimized pretreatments showed no significant difference in transparency, tensile strength and elongation at break; though the gelatin film made from 0.03 M citric acid pretreated gelatin had somewhat better water barrier property than those made with HCl or acetic acid.     

Properties of Gelatin Film from Horse Mackerel (Trachurus japonicus) Scale

Optimal conditions for extracting gelatin and preparing gelatin film from horse mackerel scale, such as extraction temperature and time, as well as the protein concentration of film‐forming solutions were investigated. Yields of extracted gelatin at 70 °C, 80 °C, and 90 °C for 15 min to 3 h were 1.08% to 3.45%, depending on the extraction conditions. Among the various extraction times and temperatures, the film from gelatin extracted at 70 °C for 1 h showed the highest tensile strength and elongation at break. Horse mackerel scale gelatin film showed the greatly low water vapor permeability (WVP) compared with mammalian or fish gelatin films, maybe due to its containing a slightly higher level of hydrophobic amino acids (total 653 residues per 1000 residues) than that of mammalian, cold‐water fish and warm‐water fish gelatins. Gelatin films from different preparation conditions showed excellent UV barrier properties at wavelength of 200 nm, although the films were transparent at visible wavelength. As a consequence, it can be suggested that gelatin film from horse mackerel scale extracted at 70 °C for 1 h can be applied to food packaging material due to its lowest WVP value and excellent UV barrier properties.     

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.     

Structural and mechanical properties of fish gelatin as a function of extraction conditions

The effect of 18 different extraction conditions on yield, weight average molecular weight, dynamic storage modulus, gelling and melting temperature, and helix recovery was studied. Gelatins were extracted from saithe (Pollachius virens) skins with an average yield of 8.9 ± 0.8% (average ± S.D.; n = 54), on a wet weight basis. High weight average molecular weight gelatins extracted at room temperature exhibit higher resulting dynamic storage modulus, higher gelling and melting temperatures and more helix formation compared to highly hydrolyzed gelatins extracted under harsher conditions. The storage modulus was increased 5 times compared to commercial cold water fish gelatin. The highest gelling and melting temperatures observed for 5% (w/v) fish gelatin were 8 °C and 16 °C, respectively. The present study suggests that the dynamic storage modulus, gelling and melting temperatures and helix content are related and increase with increasing weight average molecular weight up to about 250 kg/mol. The dynamic storage modulus correlates with the helix concentration according to the previously published correlation between dynamic storage modulus and helix concentration, which has been defined as the master curve for gelatin.     

Re-extraction,Recovery, and Characteristics of Skin Gelatin from Farmed Giant Catfish

This study was aimed to investigate the re-extraction process for gelatin recovery from the skin of farmed giant catfish. The first extraction was done by incubating the acid-treated fish skin at 45 °C for 12 h. The remnant was re-extracted at temperatures of 60–90 °C for 1–12 h. The gelatin yield of the first extraction was 10.14%, while the re-extraction at high temperature provided higher recovery (19.5%). Low band intensity of α₁ and α₂ chains of gelatin was observed when it was re-extracted at high temperature for a longer time. The absorption bands of amide I and II from both extracted gelatins were similar. Low-transition temperature with high transition enthalpy of gelatin extracted at 90 °C was observed. The obtained results suggested that the re-extraction process could be applied as a supplemental step for other sources to obtain high recovery with the desired properties.     

Extraction and Physicochemical Characterization of Greater Lizardfish (Saurida tumbil) Skin and Bone Gelatin

ABSTRACT:  Type A gelatins were extracted from skins and bones of lizardfish and analyzed to determine their functional and chemical properties. Lizardfish skin gelatin had ash content of 2.2 ± 0.3% while bone gelatin had ash content of 12.2 ± 0.2%. Gel strength was 159.1 ± 14 and 135 ± 7.9 g, respectively, for skin and bone gelatins compared to 224.3 ± 7.7 g for porcine gelatin. Gelatin from skin exhibited higher viscosity and lower setting time than bone. Skin gelatin had higher imino acid content than bone gelatin. The total imino acid content was 21.71% and 19.83% for skin and bone, respectively. Both skin and bone gelatins contained more α chains than β and γ components. Both bone and skin gelatins also contained low molecular weight (< α) peptides. The differences in functional properties between the skin and bone gelatins appeared to be related to differences in amino acid composition and molecular weight distribution of the gelatins.     

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.     

Preparation and functional properties of fish gelatin–chitosan blend edible films

With the goal of improving the physico-chemical performance of fish gelatin-based films, composite films were prepared with increasing concentrations of chitosan (Ch) (100G:0Ch, 80G:20Ch, 70G:30Ch, 60G:40Ch and 0G:100Ch, gelatin:Ch), and some of their main physical and functional properties were characterised. The results indicated that the addition of Ch caused significant increase (p < 0.05) in the tensile strength (TS) and elastic modulus, leading to stronger films as compared with gelatin film, but significantly (p < 0.05) decreased the elongation at break. Ch drastically reduced the water vapour permeability (WVP) and solubility of gelatin films, as this decline for the blend film with a 60:40 ratio has been of about 50% (p < 0.05). The light barrier measurements present low values of transparency at 600 nm of the gelatin–chitosan films, indicating that films are very transparent while they have excellent barrier properties against UV light. The structural properties investigated by FTIR and DSC showed a clear interaction between fish gelatin and Ch, forming a new material with enhanced mechanical properties.     

Characteristics and chemical composition of skins gelatin from cobia (Rachycentron canadum)

Gelatin was obtained from cobia (Rachycentron canadum) skins, which is an important commercial species for marine fish aquaculture, and it was compared with gelatin from croaker (Micropogonias furnieri) skins, using the same extraction methodology (alkaline/acid pre-treatments). Cobia skins gelatin showed values of protein yield, gelatin yield, gel strength, melting point, gelling point and viscosity higher than the values found from croaker skins gelatin. The values of turbidity and Hue angle for cobia and croaker gelatins were 403 and 74 NTU, and 84.8° and 87.3°, respectively. Spectra in the infrared region had the major absorption band in the amide region for both gelatins, but it showed some differences in the spectra. The proline and hydroxyproline contents from cobia skins gelatin (205 residues/1000 residues) was higher than from croaker skins gelatin (188 residues/1000 residues). SDS-PAGE of both gelatins showed a similar molecular weight distribution to that of standard collagen type I. Therefore, cobia skins could be used as a potential marine source of gelatin obtainment for application in diversified industrial fields.     

不同提取温度对白鲢鱼皮明胶理化性质的影响

本实验以白鲢鱼皮为原料提取鱼皮明胶,考察不同提取温度（30、50、70、90、100 ℃）对鱼皮明胶得率和理化性质的影响。结果表明：不同温度条件下提取的鱼皮明胶的紫外吸收峰均在波长218 nm左右;明胶提取率在提取温度为90 ℃时最大,为（86.91±0.98）%;50 ℃条件下提取的鱼皮明胶的凝胶强度最大,为（896.75±117.03）g;聚丙烯酰胺凝胶电泳图谱显示,30、50 ℃条件下提取的鱼皮明胶由α1、α2、β 3 条肽链组成,70、90、100 ℃条件下提取的鱼皮明胶由于明胶分子的热降解,电泳条带不明显;30、50、70、90、100 ℃条件下提取的鱼皮明胶的热变性温度分别为（97.88±2.65）、（108.66±0.43）、（106.48±3.33）、（100.27±2.37）、（99.56±0.37）℃;提取温度越高,明胶的G’’和G’值越小、流变性能越差。     

Changes in functional properties of shark (Isurus oxyrinchus) cartilage gelatin produced by different drying methods

Fish gelatins extracted from shark ( Isurus oxyrinchus ) cartilage were dried by three different methods: freeze drying, hot-air drying and spray drying; and their functional properties were investigated. Freeze-dried gelatin was found to have the strongest gel strength, while gelatins made at high temperatures formed weaker gels. The 135-kPa gel strength of freeze-dried gelatin was relatively high. While foam formation ability of the freeze-dried gelatin was the highest, its foam stability was the lowest. In addition, spray-dried gelatin had the best emulsion capacities. Dynamic viscoelastic properties of shark cartilage gelatins prepared by these drying methods were closely correlated with their gel strength. Elasticity modulus ( G '; Pa) and loss modulus ( G "; Pa) of the freeze-dried gelatin had higher values than those prepared by hot-air drying and spray drying; viscoelastic properties of the freeze-dried gelatin were maintained longer than those of other drying methods.     

马哈鱼鱼皮明胶提取温度和甘油质量浓度对其成膜特性的影响

明胶提取温度和甘油质量浓度是影响明胶膜性质的基本因素。本研究以马哈鱼（Oncorhynchus keta） 鱼皮为原料,采用不同温度（40、50、60、70、80、90 ℃）提取明胶,考察不同甘油质量浓度（1.1、1.2、 1.5 g/100 mL）下明胶膜的厚度、机械性能、光学性质、微观结构和红外特性。研究发现,40、50、60 ℃明胶 膜的厚度高于70、80、90 ℃明胶膜的厚度（P＜0.05）。50、60 ℃膜的拉伸强度（tensile strength,TS）高于 70、80、90 ℃膜的（P＜0.05）;添加1.5 g/100 mL甘油,膜的断裂伸长率随提取温度升高而上升（P＜0.05）; 50、70、80 ℃膜的TS随甘油质量浓度升高而下降（P＜0.05）。色差分析表明,膜的a*值随提取温度升高而上升 （P＜0.05）。水蒸气透过率随提取温度和甘油质量浓度的升高而升高（P＜0.05）。明胶膜于200、280 nm波长处 的透光率为0.00%,350～800 nm范围内的透光率为46.53%～74.57%,60 ℃膜的透光率低于40、50 ℃膜的透光率 （P＜0.05）。衰减全反射傅里叶变换红外光谱分析表明膜的图谱呈现典型酰胺A、B、Ⅰ、Ⅱ、Ⅲ带,酰胺A带随 提取温度的升高向低波数移动,且振幅随甘油质量浓度升高而增加。扫描电子显微镜结果显示,膜的截面和表面未 呈现明显断裂或空隙。以上结果表明,温度对马哈鱼鱼皮明胶膜的机械性能、透水性、颜色、透光率影响显著,甘 油质量浓度仅对前二者影响显著,可通过优化提取温度与甘油质量浓度改善马哈鱼鱼皮明胶膜性质。     

Effects of essential oil on the water binding capacity,physico-mechanical properties,antioxidant and antibacterial activity of gelatin films

Gelatin films were prepared from gelatin solutions (10% w/v) containing Zataria multiflora essential oil (ZMO, 2, 4, 6 and 8% w/w of gelatin). Scanning electron microscopy observations indicate that ZMO droplets were well dispersed in the film matrix. Water solubility, water swelling, water uptake, water vapor permeability, tensile strength, elongation at break and Young's modulus for gelatin films were 27 ± 0.8%, 391 ± 11%, 135 ± 5%, 0.22 ± 0.014 g mm/m² kPa h, 4.4 ± 0.4 MPa, 125 ± 7% and 8.8 ± 0.4 MPa, respectively. Incorporation of ZMO into gelatin films caused a significant decrease in swelling and water uptake and increase in solubility and water vapor permeability, a significant decrease in tensile strength, increase in elongation at break, decrease in Young's modulus of the films, dose-dependently. Gelatin/ZMO showed UV–visible light absorbance/transmission ranging from 280 to 480 nm with maximum absorbance at 420 nm. Gelatin films exhibited very low antioxidant activity while, gelatin/ZMO films exhibited excellent antioxidant properties. The gelatin/ZMO films also exhibited excellent antibacterial properties against both Gram-positive and Gram-negative bacteria. Our results suggested that the gelatin/ZMO films could be used as an active film due to its excellent antioxidant and antimicrobial properties for food packaging applications.     

Preparation and characterisation of gelatins from the skins of sin croaker (Johnius dussumieri) and shortfin scad (Decapterus macrosoma)

Gelatins were prepared from the skins of the tropical fish, sin croaker (Johnius dussumeiri) and shortfin scad (Decapterus macrosoma). Visual appearance, colour, pH, bloom strength, viscoelasticity, melting point and amino acid profiles of the fish gelatins were evaluated. Shortfin scad gelatin had higher melting and gelling temperatures than those of sin croaker gelatin. The bloom strengths of gelatins from sin croaker and from shortfin scad were 125 and 177 g, respectively, compared to 240 g for commercial bovine gelatin. The pH values were significantly different between the solutions of the two fish gelatins. The elastic modulus (G′) of the fish gelatin gels increased by more than 10-fold and the viscous modulus (G″) of fish gelatin solution increased sixfold after holding at 5 °C for 2 h. These viscoelastic properties of bovine gelatin only increased by less than twice.     

Characteristics of gelatin from the skins of bigeye snapper, Priacanthus tayenus and Priacanthus macracanthus

Gelatins extracted from the skins containing fine scales of two species of bigeye snapper, Priacanthus tayenus (GT) and Priacanthus macracanthus (GM), were characterised. Both gelatins had the protein as the major component with high content of imino acids (proline & hydroxyproline) (186.29–187.42 mg/g). GT and GM contained calcium at levels of 6.53 and 2.92 g/kg, respectively. Both gelatins contained α1 and α2 chains as the predominant components and some degradation peptides. The absorption bands of both gelatins in Fourier transform infrared (FTIR) spectra were mainly situated in the amide band region (amide I and amide II). GT and GM had a relative solubility greater than 90% in the wide pH ranges (1–10). The bloom strength of GM (254.10 g) was higher than that of GT (227.73 g) (P < 0.05), but was slightly lower than that of commercial bovine gelatin (293.22 g) (P < 0.05). Finer gel structure with smaller strands and voids was observed in GM gel, in comparison with that observed in GT counterpart.