Fish gelatin: properties, challenges, and prospects as an alternative to mammalian gelatins

Phase Diagram of Aqueous Two-Phase System (ATPS) Composed of Polyethylene Glycol (PEG) and Gelatin

Phase diagram of aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and gelatin is of paramount importance for the application of such system in microencapsulation of bioactive compounds. Phase separation of PEG/gelatin aqueous solution was investigated in the present work and the phase diagram of resultant ATPS was reported for the first time. The results show that phase separation will happen if the solid content of PEG/gelatin aqueous solution is higher than a critical value, resulting in an ATPS. The resultant ATPS consists of a low-density phase enriched in PEG and a dense phase enriched in gelatin. The phase compositions of the resultant ATPS were determined accurately using the method developed. The phase diagrams obtained show that higher solid content is required for the phase separation of PEG10,000/gelatin aqueous solution when compared with that of PEG20,000/gelatin one. And PEG is found to be more hydrophilic when compared with gelatin.

ACE inhibitory activity of pangasius catfish (Pangasius sutchi) skin and bone gelatin hydrolysate

Skin and bone gelatins of pangasius catfish (Pangasius sutchi) were hydrolyzed with alcalase to isolate Angiotensin Converting Enzyme (ACE) inhibitory peptides. Samples with the highest degree of hydrolysis (DH) were separated into different fractions with molecular weight cut-off (MWCO) sizes of 10, 3 and 1 kDa, respectively and assayed for ACE inhibitory activity. Skin and bone gelatins had highest DH of 64.87 and 68.48 % after 2 and 1 h incubation, respectively. Results from this study indicated that by decreasing the molecular weight of fractions, ACE inhibitory activity was increased. Therefore, F3 permeates (MWCO < 1 kDa) of skin (IC50 = 3.2 μg/ml) and bone (IC50 = 1.3 μg/ml) gelatins possessed higher ACE inhibitory activity compared to their untreated gelatins and corresponding hydrolyzed fractions. In this study, the major amino acids were Glycine followed by Proline with an increased amount of hydrophobic amino acid content in F3 permeates of skin (4.01 %) and bone (5.79 %) gelatin. Digestion stability against gastrointestinal proteases did not show any remarkable change on ACE inhibition potency of these permeates. It was concluded that alcalase hydrolysis of P. sutchi by-products could be utilized as a part of functional food or ingredients of a formulated drug in order to control high blood pressure.

A comparative study on the physical, chemical and functional properties of carp skin and mammalian gelatins

Carp species forms the bulk of the aquaculture production in India and studies have shown that the filleting waste of these species, particularly skin can be a good source of gelatin. This study is a comparison of the gelatins from these unexploited sources with that of mammalian gelatins to get a better understanding of their physicochemical and functional properties with respect to mammalian gelatins. The study showed that mammalian gelatins had significantly superior physical properties viz., higher viscosity, melting & setting temperature and faster setting time. The odour scores were significantly higher (P < 0.05) for bovine and porcine skin gelatins (3.1-3.12), indicating that they had a distinguishable odour and hence can be considered as inferior to fish skin gelatins in organoleptic qualities. The gel strengths of rohu and common carp skin gelatins were significantly lower than mammalian gelatins. Among the carp skin gelatins, grass carp skin gelatin was found to have better compatibility with gelatin from bovine and porcine skins.

Towards producing novel fish gelatin films by combination treatments of ultraviolet radiation and sugars (ribose and lactose) as cross-linking agents

Developing novel fish gelatin films with better mechanical properties than mammalian gelatin is a challenging but promising endeavor. Studies were undertaken to produce fish gelatin films by combining treatments with different sugars (ribose and lactose) followed 'by' 'and' ultraviolet (UV) radiation, as possible cross-linking agents. Increase in tensile strength and percent elongation at break was recorded, which was more significant in films without sugars that were exposed to UV radiation. Films with added ribose showed decreased solubility after UV treatment and exhibited higher swelling percentage than films with added lactose, which readily dissolved in water. FTIR spectra of all the films showed identical patterns, which indicated no major changes to have occurred in the functional groups as a result of interaction between gelatin, sugars and UV irradiation. The results of this study could be explored for commercial use, depending on industrial needs for either production of edible films or for food packaging purposes.

Peptides derived from atlantic salmon skin gelatin as dipeptidyl-peptidase IV inhibitors

The dipeptidyl-peptidase IV (DPP-IV)-inhibitory activity of peptides derived from Atlantic salmon skin gelatin hydrolyzed by alcalase (ALA), bromelain (BRO), and Flavourzyme (FLA) was determined. The FLA hydrolysate with the enzyme/substrate ratio of 6% showed the greatest DPP-IV-inhibitory activity. The hydrolysate was fractionated by ultrafiltration with 1 and 2.5 kDa cutoff membranes, and the <1 kDa fraction had the highest DPP-IV-inhibitory activity with an IC(50) value of 1.35 mg/mL. The F-1 fraction further isolated by HPLC showed the IC(50) value against DPP-IV of 57.3 μg/mL, and the peptide sequences were identified as Gly-Pro-Ala-Glu (372.4 Da) and Gly-Pro-Gly-Ala (300.4 Da). The synthetic peptides showed dose-dependent inhibition effects on DPP-IV with IC(50) values of 49.6 and 41.9 μM, respectively. The results suggest that the peptides derived from Atlantic salmon skin gelatin would be beneficial ingredients for functional foods or pharmaceuticals against type 2 diabetes.

Enhanced bonding strength of a novel tissue adhesive consisting of cholesteryl group-modified gelatin and disuccinimidyl tartarate

The bonding strength and biocompatibility of a novel tissue adhesive consisting of cholesteryl group-modified gelatin and disuccinimidyl tartarate was evaluated. The approach was based on hydrophobically-modified gelatin to enhance the penetration of an adhesive into tissue. Disuccinimidyl tartarate was used to cross-link the cholesteryl group-modified gelatin. The cholesteryl group-modified gelatin was prepared by partially converting the gelatin amino groups with cholesteryl chloroformate. The bonding strength was evaluated by mixing cholesteryl group-modified gelatin and unmodified gelatin with the fixed amino groups/active ester groups of disuccinimidyl tartarate. The bonding strength of the resulting tissue adhesive was 1.7 times greater than the commercial aldehyde-based adhesive. The level of inflammation transcription factor, nuclear factor-kappa B, of the new tissue adhesive was significantly lower compared to the aldehyde-based adhesive after subcutaneous implantation. These results indicate that hydrophobic groups, such as cholesteryl, enhance tissue penetration as well as increase the bonding strength of tissue adhesive without a negative effect on the biocompatibility.

Dietary supplementation with fish gelatine modifies nutrient intake and leads to sex-dependent responses in TAG and C-reactive protein levels of insulin-resistant subjects

Previous studies have shown that fish protein, as well as marine n-3 PUFA, may have beneficial effects on cardiovascular risk profile. The objectives of this study were to investigate the combined effects of fish gelatine (FG) and n-3 PUFA supplementation on (1) energy intake and body weight, (2) lipid profile and (3) inflammatory and CVD markers in free-living insulin-resistant males and females. Subjects were asked to consume, in a crossover study design with two experimental periods of 8 weeks each, an n-3 PUFA supplement and n-3 PUFA supplement plus FG (n-3 PUFA + FG). n-3 PUFA + FG led to an increase in protein intake and a decrease in carbohydrate intake compared with n-3 PUFA (P < 0·02) in males and females. Sex–treatment interactions were observed for TAG (P = 0·03) and highly sensitive C-reactive protein (hsCRP) (P = 0·001) levels. In females, n-3 PUFA reduced plasma TAG by 8 % and n-3 PUFA + FG by 23 %, whereas in males, n-3 PUFA reduced plasma TAG by 25 % and n-3 PUFA + FG by 11 %. n-3 PUFA increased serum hsCRP by 13 % and n-3 PUFA + FG strongly reduced hsCRP by 40 % in males, whereas in females, n-3 PUFA reduced serum hsCRP by 6 % and n-3 PUFA + FG increased hsCRP by 20 %. In conclusion, supplementation with FG may enhance the lipid-lowering effect of marine n-3 PUFA in females and beneficially counteract the effect of n-3 PUFA on serum hsCRP in males. Further studies are needed to identify the sex-dependent mechanisms responsible for the divergent effects of FG on TAG and hsCRP levels in females and males, respectively.

State diagram of salmon (Salmo salar) gelatin films

BACKGROUND

A state diagram presents different physical states of a biomaterial as a function of solid content and temperature. Despite their technological interest, little information is available on protein systems such as gelatin/water mixtures. The objective of this work was to develop state diagrams of salmon gelatin (SG) and bovine gelatin (BG) in order to determine maximal freeze concentration parameters (T'(g) , T'(m) and X(s') ) and to relate possible differences to their biochemical characteristics.

RESULTS

Biochemical characterisation of SG showed lower molecular weight and iminoacid concentration compared with BG. Likewise, the glass transition temperature (T(g) ) was lower for SG at X(s) > 0.8, which was associated with its lower molecular weight. Unexpectedly, the depression of freezing temperature (T(f) ) was greater for SG at X(s) > 0.1, which was associated with its higher ash content. Isothermal annealing produced effective values of T'(g) ≈ - 52 °C, T'(m) ≈ - 46 °C and X'(s) ≈ 0.6 for both gelatins. Interestingly, the enthalpy change associated with T'(m) (ΔH T m) was significantly higher for SG than for BG after annealing, indicating a higher proportion of ice present at about - 50 °C.

CONCLUSION

Maximal freeze concentration parameters were similar between the two gelatins, though differences in biochemical properties were evident. The results show that there are likely different ways of interaction of SG and BG with water.

Research on the Extraction of Collagen from Scales of Tilapia

The scales is a kind of precious resource with high nutritional value. The collagen protein from scales have a widely usage prospection in the areas of health food, cosmetics and so on, and they are worthy of further studied. In this paper, the method of extracting collagen protein from the scales of Tilapia was studied by pepsin hydrolysis. First, the calcium was demineralized from the scales with using of 0.5 mol/L EDTA solution, then, the scales hydrolyzed by pepsin was made to extract the collagen, and the content of L – hydroxyproline was taken as an index to measure the extraction percentage. On this basis, the collagen extract conditions was discussed from the Tilapia scales by the pepsin. It was showed that the pepsin hydrolysis conditions were the enzyme dosage 3%, citric acid 12g/L, hydrolysis time 20h, so the rate of collagen extraction is higher.

Effect of microbial transglutaminase on gel properties and film characteristics of gelatin from lizardfish (Saurida spp.) scales

The addition of microbial transglutaminase (MTGase) generally increased the gel strength of lizardfish (Saurida spp.) scale gelatin gels (P≤0.05) with an increase in gel strength with the addition of MTGase up to 0.5% (w/v). The texture profile analysis compression tests of lizardfish scale gelatin gel with and without MTGase were studied to determine their effects on gel characteristics. MTGase added to the gels decreased the band intensity of the β- and α-components with increasing concentrations of enzyme. Gel microstructures with various concentration of MTGase showed denser strands in the gels with enzyme compared with the looser stands in non-enzyme-treated gel samples. Films cast from lizardfish scale gelatin with and without 0.5% MTGase and bovine gelatin films were transparent and flexible. The lizardfish gelatin films were all slightly yellowish while the bovine gelatin films were clearer. The L value of bovine gelatin films had the highest value (P≤0.05) whereas lizardfish scale gelatin films with and without enzyme were not significantly different (P>0.05) for L, a, and b values and ΔE. The film's mechanical properties included tensile strength (TS) and elongation at break (E) were not significantly different (P > 0.05) for E and the films of lizardfish scale gelatin showed higher TS than the films without enzyme added (P ≤ 0.05). The water vapor permeability of films from lizardfish scale gelatin with and without 0.5% MTGase and bovine gelatin films were 21.0 ± 0.17, 26.3 ± 0.79, and 25.8 ± 0.09 g·mm/m(2)·d·kPa, respectively, while the oxygen transmission rate of all 3 types of films were less than 50 cc O(2)/m(2)·d.

Preparation of fish gelatin and fish gelatin/poly(L-lactide) nanofibers by electrospinning

Ultrafine fibers were successfully fabricated from Channel catfish skin-extracted gelatin via electrospinning (ES). Important ES parameters, such as concentration of aqueous acid and fish gelatin solutions, and electric field intensity were examined to investigate the effects on the morphology of the gelatin nanofibers. Due to the poor mechanical properties of the fish gelatin membranes, composite nanofibers made of fish gelatin and poly(L-lactide)(PLLA) were produced with a novel solution. The introduction of PLLA remarkably improved the mechanical properties of the gelatin membranes. With a combination of good biocompatibility and mechanical properties, fish gelatin/PLLA blending non-woven mats are considered to be very promising in tissue regeneration area.

Fish gelatin

Gelatin is a multifunctional ingredient used in foods, pharmaceuticals, cosmetics, and photographic films as a gelling agent, stabilizer, thickener, emulsifier, and film former. As a thermoreversible hydrocolloid with a narrower gap between its melting and gelling temperatures, both of which are below human body temperature, gelatin provides unique advantages over carbohydrate-based gelling agents. Gelatin is mostly produced from pig skin, and cattle hides and bones. Some alternative raw materials have recently gained attention from both researchers and the industry not just because they overcome religious concerns shared by Jews and Muslims but also because they provide, in some cases, technological advantages over mammalian gelatins. Fish skins from a number of fish species are among the other sources that have been comprehensively studied as sources for gelatin production. Fish skins have a significant potential for the production of high-quality gelatin with different melting and gelling temperatures over a much wider range than mammalian gelatins, yet still have a sufficiently high gel strength and viscosity. Gelatin quality is industrially determined by gel strength, viscosity, melting or gelling temperatures, the water content, and microbiological safety. For gelatin manufacturers, yield from a particular raw material is also important. Recent experimental studies have shown that these quality parameters vary greatly depending on the biochemical characteristics of the raw materials, the manufacturing processes applied, and the experimental settings used for quality control tests. In this review, the gelatin quality achieved from different fish species is reviewed along with the experimental procedures used to determine gelatin quality. In addition, the chemical structure of collagen and gelatin, the collagen-gelatin conversion, the gelation process, and the gelatin market are discussed.