Fish Gelatin Gels Research Articles

Improvement of Gel Properties of Fish Gelatin Using Gellan

Abstract The impact of gellan (GL) at different levels (5–20 % of total solid) on the properties of fish gelatin (FG) gels was studied. Gel strength and hardness of FG/GL mixed gel increased, while springiness and cohesiveness decreased as the levels of GL were increased (p < 0.05). Gelling and melting temperatures also increased with increasing levels of GL incorporated (p < 0.05). L*- and b*-values of FG/GL mixed gel decreased, whereas ∆E*-value increased with increasing GL levels (p < 0.05). Microstructure studies revealed that denser structure with very small voids in gel network was observed upon GL addition. The addition of GL at a low level (5 %) had no adverse effect on sensory property, and no effect on syneresis of FG/GL mixed gels. Therefore, the addition of 5 % GL can be used to improve gelling property of FG via increasing gelling points without affecting sensory property of the resulting gel.

Physical and sensory properties of gelatin from seabass (Lates calcarifer) as affected by agar and κ-carrageenan.

Due to the poor gelling property of fish gelatin, compared to its mammalian counterpart, improvement of this property using the selected hydrocolloids can be a promising means. In this work, it was found that agar or κ-carrageenan can be incorporated to fish gelatin to improve gelling, textural and sensory properties of gelatin from skin of seabass (Lates calcarifer). Both agar and κ-carrageenan could increase gelling and melting temperatures of seabass gelatin. The incorporation of hydrocolloids (agar and κ-carrageenan) could also improve the quality of fish gelatin gel, which in turn can widen the applications of fish gelatin in the food and other industries.

Property of Fish Gelatin gel as Affected by the Incorporation of Gellan and Calcium Chloride

Properties of fish gelatin (FG) gel as affected by gellan (GL) at different levels (2.5–7.5% FG substitution) in combination with calcium chloride (CaCl2) at various concentrations (3–9 mM) were studied. Gel strength and hardness of FG/GL mixed gel increased as the levels of GL increased (P < 0.05). Increasing CaCl2 concentration also resulted in the increases in both gel strength and hardness of mixed gel when GL at the same level was incorporated (P < 0.05). Conversely, the increasing GL and CaCl2 levels caused a decrease in springiness but an increase in syneresis of mixed gels (P < 0.05). Gelling and melting temperatures were increased in the mixed gel as levels of GL and CaCl2 increased. L*- and b*-values of mixed gels decreased, whereas ∆E*-value increased with increasing GL and CaCl2 levels (P < 0.05). Microstructure studies revealed that denser structure with smaller voids in gel network was observed in the mixed gel in the presence of CaCl2 at higher levels. However, mixed gels incorporated with GL above 5%, regardless of CaCl2 levels, yielded the lower likeness score than FG gel (control) (P < 0.05). The addition of GL at low level (2.5%) with CaCl2 (up to 6 mM) had no adverse effect on sensory property of mixed gels but could improve gelling property of FG via increasing gel strength and gelling point.

Effect of Aloe vera ( Aloe barbadensis Miller) gel on the physical and functional properties of fish gelatin films as active packaging

Abstract Present study was conducted to investigate the feasibility of the combination of fish gelatin and Aloe gel in producing composite films and to determine the effect of Aloe gel concentrations (1, 3, 5, 7 and 9% wt/wt) on the physical properties and antioxidant activity of the composite films. The moisture content of the composite films was proportional to the concentration of Aloe gel. Also, the water solubility and tensile strength of the films decreased with increasing Aloe gel concentration. However, Aloe gel did not cause any significant effect ( p ≥ 0.05) on thickness, water vapour permeability (WVP) and colour of the composite films. The gelatin/ Aloe composite films exhibited smooth surface microstructures similar to non-composite gelatin film when observed under scanning electron microscope (SEM). The gelatin/ Aloe composite films also showed concentration dependant ABTS and DPPH radical scavenging activities.

Comparison of rheological behaviors and nanostructure of bighead carp scales gelatin modified by different modification methods.

In this study, microbial transglutaminase (MTGase) and pectin were compared to modify bighead carp (Hypophthalmichthys nobilis) scale gelatin. The functional properties of modified fish scales gelatin (FSG) were largely improved, including melting temperature and rheological behavior. While, modification methods decreased the triple-helix content and destroyed the single left-hand helix chain of modified FSG as investigated by X-ray diffraction. MTGase could induce the denser and finer gels network, but had none significant effect on nanostructural properties of fish gelatin. Pectin inserted itself into the fish gelatin gels network and caused aggregations, forming crystalline peaks and various nanostructures. In particular, compared with pectin modified FSG, MTGase produced FSG with lower storage modulus and apparent viscosity, but higher gel points and melting points.

Gelation and thermal characteristics of microwave extracted fish gelatin-natural gum composite gels.

In this study, the gelation and thermal characteristics of microwave extracted fish scale gelatin blended with natural gums such as gum arabic (AG), xanthan gum (XG), guar gum (GG), and tragacanth gum (TG) was evaluated. The nature of interaction and behavior of gelatin in presence of various gums was confirmed by particle size analysis, viscosity profile, FT-IR analysis and turbidity measurements. DSC data revealed that addition of AG, TG and GG remarkably improved the thermal stability of fish gelatin gel. The composite gels of TG, AG, and XG exhibited higher hardness and bloom strength values as compared to pure fish gelatin implying its textural synergy. Based on qualitative descriptive analysis, TG was found to be superior in improving the stability of fish gelatin gel, closely followed by AG. The results suggest that addition of these gums can reduce syneresis and retard melting of gelatin gels at ambient temperature, which are otherwise soft and thermally unstable.

Rheological and sensory properties of fish gelatin gels as influenced by agar from Gracilaria tenuistipitata

SummaryAgar extracted from Gracilaria tenuistipitata and commercial agars were incorporated into fish gelatin at various levels (0, 5, 10, 15 and 20% gelatin substitution). G. tenuistipitata agar (GA) had lower failure stress (~16 kPa) than commercial agar (CA) (~20 kPa). However, the former showed higher failure strain (~30%) with lower melting temperature (65.9 °C). The critical linear stress and failure stress of agar/gelatin mixed gels increased with increasing agar levels (P &lt; 0.05). At 15 and 20% of agar used, the mixed gels containing CA exhibited higher failure stress than those with added GA (P &lt; 0.05). Two melting points of agar/gelatin mixed gels were observed, corresponding to the melting temperatures of gelatin and agar gels. Nevertheless, the incorporation of agar lowered the likeness score of gelatin gel. Thus, both GA and CA had the impact on rheological property and the selected sensory characteristics of fish gelatin, depending on the level of substitution.

Extraction and Characterization of Halal Gelatin from Fish Skin

Gelatin was extracted from fish skin of (mosa, EMG) flathead grey mullet, (hamor, EHG) greasy grouper and (bolti, EBG) Nile tilapia by a series of pretreatment with sodium hydroxide and citric acid. The results showed significant higher (p<0.05) gelatin yield from hamor skin (12.7 %) compared to other type of fish skins. The viscosity of hamor gelatin gel (7.73 cP) and bloom value (123.7g) were significantly higher (p<0.05) than gelatin gels from mosa and bolti. On the other hand, Gelatin extracted from mosa and bolti had similar gelatin yield, viscosity, gel strength and pH value. All extracted fish gelatin gels showed significant (p<0.05) higher viscosity value than halal bovine gelatin gel (HBG). The extracted gelatin has the potential use as halal gelatin to replace non-halal gelatin from porcine and nonhalal bovine.

Ultraviolet‐B Radiation Induced Cross‐linking Improves Physical Properties of Cold‐ and Warm‐Water Fish Gelatin Gels and Films

Cold- and warm-water fish gelatin granules were exposed to ultraviolet-B radiation for doses up to 29.7 J/cm(2). Solutions and films were prepared from the granules. Gel electrophoresis and refractive index were used to examine changes in molecular weight of the samples. Also, the gel strength and rheological properties of the solutions as well as the tensile and water vapor barrier properties of the films were characterized. SDS-PAGE and refractive index results indicated cross-linking of gelatin chains after exposure to radiation. Interestingly, UV-B treated samples displayed higher gel strengths, with cold- and warm-water fish gelatin having gel strength increases from 1.39 to 2.11 N and from 7.15 to 8.34 N, respectively. In addition, both gelatin samples exhibited an increase in viscosity for higher UV doses. For gelatin films, the cold-water fish gelatin samples made from irradiated granules showed greater tensile strength. In comparison, the warm-water gelatin films made from irradiated granules had lower tensile strength, but better water vapor barrier properties. This might be due to the UV induced cross-linking in warm-water gelatin that disrupted helical structures.

Effects of Extraction Conditions on the Sensory and Instrumental Characteristics of Fish Gelatin Gels

Fish skin gelatin has recently been of interest as a product that eliminates religious concerns (Jewish and Muslim) and could be an alternative value-added product from fish waste. Recent research has shown that extraction conditions affect gelatin quality. In this study, gelatin from Asian silver carp skin and extracted under different conditions have been studied sensory properties using descriptive analysis and time intensity testing to determine how extraction conditions affect gelatin sensory properties. Three pairs of gelatin samples were selected based on their gel strength, viscosity, and melting temperature. The impacts of different extraction conditions on instrumental methods were examined. Some functionality measurements were also done to determine how sensory measurements correlate with instrumental measurements. The gel strength varied between 60 ± 10 g and 590 ± 30 g while the viscosity varied between 1.9 ± 0.0 cP and 7.4 ± 0.2 cP. The hardness, melting and gelling temperature of the samples were well correlated with the gel strength (r > 0.90). The results indicated that the strongest correlation among all the sensory attributes was between firmness and melting temperature, which was a negative correlation (-0.75) suggesting that the firmer the gel samples the slower they melt. The viscosity was found to be very discriminative between samples in terms of sensory properties. The functional measurements were found to be strongly correlated within themselves while the sensory measurements were less so, which might be due to the greater variability when using sensory panelists or sensory parameters simply might not be related. The firmness, melting rate, and aftertaste were those sensory attributes most successfully discriminated by the panelists.

Maturation effects in fish gelatin and HPMC composite gels

This study assessed the effectiveness of using hydroxylpropylmethylcellulose (HPMC) to enhance mechanical strength and thermal stability in fish skin gelatin (FG). The significant increase in absorbance ( A 400) observed after HPMC had been added to FG and then matured indicated successful formation of a composite gel. Increased gel strength and storage modulus ( G′) indicated the enhanced gelation ability of the matured composite gel, while increased melting temperature ( T m) and enthalpy (Δ H) indicated its improved thermal stability. Maturation-related rheological property improvements were more noticeable at 4 °C than 10 °C, but no apparent differences in T m improvement were observed between 4 °C and 10 °C maturation. Nevertheless, the composite gel exhibited reversible cold and thermal gelation properties.

Characterization of fish gelatin from surimi processing wastes: Thermal analysis and effect of transglutaminase on gel properties

Fish gelatin extraction from wastes of fish Herring species ( Tenualosa ilisha) was carried out by a series of pretreatment with 0.2 M Ca(OH) 2 followed by 0.1 M citric acid and final water extraction at 50 °C for 3 h. The resulting fish gelatin preparation was evaluated for its dynamic viscoelastic properties, gelling and melting temperatures and gel strength. The gelling and melting temperatures of gelatin samples (at 6.67%, w/v) were obtained from differential scanning calorimetry and rheological studies. The melting temperature of extracted fish gelatin (EFG) obtained ranged from 16.2 to 16.7 °C compared to that of commercial fish gelatin gel (CFG), from 23.7 to 25.6 °C and halal bovine gelatin (HBG), from 26.5 to 28.7 °C. On the other hand, gelling temperatures of EFG, CFG and HBG ranged from 5.1 to 5.2 °C, 11.9 to 17.46 °C, and 12.6 to 19.33 °C, respectively. EFG gave gels with a considerably lower G′ values than CFG and HBG. The bloom strength of EFG gels at 6.67% (w/v) was 69.03 g which was much lower than HBG (336.2 g) and CFG (435.9 g). Enzyme transglutaminase was added in the amounts of 0.5, 1.0, 3.0 and 5.0 mg/g gelatin to modify the gel properties of the extracted fish gelatin. The modified EFG gels obtained had higher gel strengths of 101.1 g and 90.56 g with added transglutaminase of 1.0 and 3.0 mg/g, respectively. However with addition of 5.0 mg/g enzyme the gel strength increased only up to 75.06 g. SDS-PAGE of extracted gelatin gel showed protein band intensities for α1-chains and 53 kDa but in gels added with higher concentration of transglutaminase, these protein band intensities seemed to disappear.

Proteolytic degradation of cold-water fish gelatin solutions and gels

The stability of cold-water fish gelatin (FG), both in solution and in the gel phase, has been studied as function of both temperature and exposure towards novel proteases of marine origin. A 1% (w/v) FG solution was readily degraded by such proteases above 20 °C, which was expected since FG at this temperature is a random coil molecule lacking the protective triple helical structure found in collagen. The dynamic storage modulus for a 10% (w/v) FG gel increased monotonically at 4 °C. Ramping the temperature to 6, 8 or 10 °C led to a drastic reduction in G′, but an apparent partial recovery of the network (increasing G′) was observed with time at all temperatures. In the presence of proteases, a lower storage modulus was observed. At constant 4 °C, an apparent maximum value was reached after curing for 2 h followed by a decrease in G′ indicating protease activity. Ramping of temperature in the presence of proteases led to an even more drastic reduction in G′ and no recovery of structure was observed with time. In this case, the overall rheological behaviour is a complex function of both thermal influence as well as proteolytic activity. In an endeavour to quantify the effect of the presence of proteolytic enzymes on the gelatin network, rheological investigation were undertaken where the dynamic storage moduli were recorded on different 10% (w/v) FG samples that had been acid hydrolysed to yield different average molecular weights. A significant reduction in storage modulus for average molecular weights below 50 kDa was found. This critical molecular weight most probably reflects the on-set of a regime where shorter chain lengths prevent percolation due to an increase in the loose end and sol fraction as well as a reduction in the average length of the pyrrolidine-rich regions reducing the number of possible junction zones.

Characterizations of fish gelatin films added with gellan and κ-carrageenan

Fish gelatin is known to be inferior to mammalian gelatins. Gellan and κ-carrageenan were added to improve properties of the fish gelatin films. Initially, polysaccharides were added to make fish gelatin gels, and tested for the melting point. Mechanical, barrier, color and microstructure properties, as well as Fourier transform infrared (FTIR) and thermal analysis (DSC) of the modified fish gelatin films were evaluated. The addition of gellan and κ-carrageenan increased the melting point of fish gelatin gels, gellan being more effective. Polysaccharides modified fish gelatin films by increasing tensile strength and barrier against water vapor, but made films slightly darker. Scanning electron microscopy (SEM) microstructure analysis revealed that gellan eliminated cracks present in the film matrix resulting in a more uniform structure. FTIR and DSC analyses showed that both polysaccharides effectively interacted with fish gelatin, and moreover, gellan being more effective. Overall, addition of gellan up to 2 g/100 g of gelatin performed better in enhancing fish gelatin films properties.

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.

Modification of the properties of gelatin from skins of Baltic cod ( Gadus morhua) with transglutaminase

The aim of the investigations was to optimize the procedure of gelatin extraction from the skins of Baltic cod ( Gadus morhua) and to modify the properties of fish gelatin, using transglutaminase, to form gels at room temperature. A temperature of 45 °C and 30 min of extraction was established as optimal conditions for preparing gelatin from cod skins. Fish gelatin in 5% solutions formed gels at room temperature in the presence of transglutaminase (0.15–0.7 mg of enzyme protein/ml), depending on the reaction time. Transglutaminase was also active in crosslinking of fish gelatin at 4–5 °C. The deformation of gels obtained from 5% gelatin solutions after a 24-h incubation with transglutaminase, at concentration 0.25 mg/ml, measured at 6–8 °C, was the same as or slightly lower than in control samples (without enzyme). Fish gelatin gels, enzymatically crosslinked, did not melt after 30 min of heating in a boiling water bath.

Reagent-free crosslinking of aqueous gelatin: manufacture and characteristics of gelatin gels irradiated with gamma-ray and electron beam

In order to obtain a gelatin hydrogel crosslinked by a reagent-free method, gamma-ray and electron beam radiation was applied to porcine, bovine and fish gelatin gels and the products were characterized by measuring the gel fraction, the swelling ratio and the enzymatic degradability. On increasing the radiation dose, the gel fraction increased and both the swelling ratio and the enzymatic degradability decreased. The transition temperature from gel to sol of the hydrogel containing more than 5% mammal gelatins increased up to more than 90°C when gamma-ray or electron beam were irradiated by more than 10 kGy. The results show that the degree of crosslinking of irradiated gelatin hydrogels increases with increasing irradiation dose and with decreasing concentration. It is suggested that the radiation crosslinking occurs around the physical crosslinking point or multiple helix structure of gelatin gel.