The effect of chicken skin gelatin and whey protein interactions on rheological and thermal properties

Effect of low-frequency ultrasound-assisted acid extraction on gel properties and structural characterization of sheep's hoof gelatin

In this study, we investigated the effects of various low-frequency ultrasound-assisted extraction processes, including ultrasound-assisted acid-soaked water bath extraction (UAW), ultrasound-assisted water bath extraction after acid soaking (AUW), acid-soaked water bath extraction followed by ultrasonics (AWU), and acid-soaked water bath extraction without ultrasound (CON), on the structural properties, thermal stability, gel properties, and microstructure of sheep's hoof gelatin. The results revealed that the primary components of sheep's hoof gelatin consisted of α1-chain, α2-chain (100-135 kDa), and β-chain. In addition, it was observed that among the three sonication groups, sheep's hoof gelatin extracted in the AUW group exhibited the highest yield (27.16 ± 0.41 %), the best gel strength (378.55 ± 7.34 g), and higher viscosity at the same shear rate. The gelling temperature (25.38 ± 0.45 °C) and melting temperature (32.28 ± 0.52 °C) of sheep's hoof gelatin in the AUW group were significantly higher than those in the other groups (p > 0.05). Moreover, our experiments revealed that the sequence of low-frequency ultrasonic pretreatment processes was a crucial factor influencing the gel properties and structural characteristics of sheep's hoof gelatin. Specifically, the acid treatment followed by the ultrasound-assisted approach in the AUW group yielded high-quality and high-yield sheep's hoof gelatin.

Mechanically Tough and Conductive Hydrogels Based on Gelatin and Z-Gln-Gly Generated by Microbial Transglutaminase

Gelatin-based hydrogels with excellent mechanical properties and conductivities are desirable, but their fabrication is challenging. In this work, an innovative approach for the preparation of gelatin-based conductive hydrogels is presented that improves the mechanical and conductive properties of hydrogels by integrating Z-Gln-Gly into gelatin polymers via enzymatic crosslinking. In these hydrogels (Gel-TG-ZQG), dynamic π-π stacking interactions are created by the introduction of carbobenzoxy groups, which can increase the elasticity and toughness of the hydrogel and improve the conductivity sensitivity by forming effective electronic pathways. Moreover, the mechanical properties and conductivity of the obtained hydrogel can be controlled by tuning the molar ratio of Z-Gln-Gly to the primary amino groups in gelatin. The hydrogel with the optimal mechanical properties (Gel-TG-ZQG (0.25)) exhibits a high storage modulus, compressive strength, tensile strength, and elongation at break of 7.8 MPa at 10 °C, 0.15 MPa at 80% strain, 0.343 MPa, and 218.30%, respectively. The obtained Gel-TG-ZQG (0.25) strain sensor exhibits a short response/recovery time (260.37 ms/130.02 ms) and high sensitivity (0.138 kPa-1) in small pressure ranges (0-2.3 kPa). The Gel-TG-ZQG (0.25) hydrogel-based sensors can detect full-range human activities, such as swallowing, fist clenching, knee bending and finger pressing, with high sensitivity and stability, yielding highly reproducible and repeatable sensor responses. Additionally, the Gel-TG-ZQG hydrogels are noncytotoxic. All the results demonstrate that the Gel-TG-ZQG hydrogel has potential as a biosensor for wearable devices and health-monitoring systems.

Physicochemical Properties of Mixed Gelatin Gels with Soy and Whey Proteins

The physicochemical properties of the mixed gelatin gels with soy and whey proteins were investigated to develop the gel base with a soft texture and abundant essential amino acids for the elderly. Gelatin-only gel (control) was prepared at 6% (w/v), and mixed gelatin gels were formulated by replacing gelatin with soy protein isolate and whey protein concentrate at different mixing ratios [gelatin (G):soy protein isolate (S):whey protein concentrate (W)]. Results showed that replacing gelatin with the globular proteins in gelatin gels increased the pH value and processing yield (p < 0.05). Moreover, the mixed gelatin gels, particularly the G2:S1:W3 treatment, showed significantly higher essential amino acids than the gelatin-only control. The partial replacement of gelatin with the globular proteins could decrease the hardness of gelatin gel (p < 0.05), but there was no difference in hardness between the G2:G3:W1, G2:S2:W2, and G2:S1:W3 treatments (p > 0.05). The results of protein pattern, x-ray diffraction, and microstructure had no clear evidence for specific protein-protein interaction in the mixed gelatin gels. Therefore, this study indicates that mixed gelatin gels with the globular proteins at specific mixing ratios could be a practical approach to providing a soft texture and high-level essential amino acids to the elderly.

Complex Modification Orders Alleviate the Gelling Weakening Behavior of High Microbial Transglutaminase (MTGase)-Catalyzed Fish Gelatin: Gelling and Structural Analysis

In this paper, the effects of different modification orders of microbial transglutaminase (MTGase) and contents of pectin (0.1-0.5%, w/v) on the gelling and structural properties of fish gelatin (FG) and the modification mechanism were studied. The results showed that the addition of pectin could overcome the phenomenon of high-MTGase-induced lower gelling strength of gelatin gels. At a low pectin content, the modification sequences had non-significant influence on the gelling properties of modified FG, but at a higher pectin content (0.5%, w/v), P0.5%-FG-TG had higher gel strength (751.99 ± 10.9 g) and hardness (14.91 ± 0.33 N) values than those of TG-FG-P0.5% (687.67 ± 20.98 g, 12.18 ± 0.45 N). Rheology analysis showed that the addition of pectin normally improved the gelation points and melting points of FG. The structural results showed that the fluorescence intensity of FG was decreased with the increase in pectin concentration. Fourier transform infrared spectroscopy analysis indicated that the MTGase and pectin complex modifications could influence the secondary structure of FG, but the influenced mechanisms were different. FG was firstly modified by MTGase, and then pectin (P-FG-TG) had the higher gelling and stability properties.

From Grape By-Products to Enriched Yogurt Containing Pomace Extract Loaded in Nanotechnological Nutriosomes Tailored for Promoting Gastro-Intestinal Wellness

Grape pomace is the main by-product generated during the winemaking process; since it is still rich in bioactive molecules, especially phenolic compounds with high antioxidant power, its transformation in beneficial and health-promoting foods is an innovative challenge to extend the grape life cycle. Hence, in this work, the phytochemicals still contained in the grape pomace were recovered by an enhanced ultrasound assisted extraction. The extract was incorporated in liposomes prepared with soy lecithin and in nutriosomes obtained combining soy lecithin and Nutriose FM06^®, which were further enriched with gelatin (gelatin-liposomes and gelatin-nutriosomes) to increase the samples' stability in modulated pH values, as they were designed for yogurt fortification. The vesicles were sized ~100 nm, homogeneously dispersed (polydispersity index < 0.2) and maintained their characteristics when dispersed in fluids at different pH values (6.75, 1.20 and 7.00), simulating salivary, gastric and intestinal environments. The extract loaded vesicles were biocompatible and effectively protected Caco-2 cells against oxidative stress caused by hydrogen peroxide, to a better extent than the free extract in dispersion. The structural integrity of gelatin-nutriosomes, after dilution with milk whey was confirmed, and the addition of vesicles to the yogurt did not modify its appearance. The results pointed out the promising suitability of vesicles loading the phytocomplex obtained from the grape by-product to enrich the yogurt, offering a new and easy strategy for healthy and nutritional food development.

Impacts of Industrial Modification on the Structure and Gel Features of Soy Protein Isolate and its Composite Gel with Myofibrillar Protein

Native soy protein isolate (N-SPI) has a low denaturation point and low solubility, limiting its industrial application. The influence of different industrial modification methods (heat (H), alkaline (A), glycosylation (G), and oxidation (O)) on the structure of SPI, the properties of the gel, and the gel properties of soy protein isolate (SPI) in myofibril protein (MP) was evaluated. The study found that four industrial modifications did not influence the subunit composition of SPI. However, the four industrial modifications altered SPI's secondary structure and disulfide bond conformation content. A-SPI exhibits the highest surface hydrophobicity and I_850/830 ratio but the lowest thermal stability. G-SPI exhibits the highest disulfide bond content and the best gel properties. Compared with MP gel, the addition of H-SPI, A-SPI, G-SPI, and O-SPI components significantly improved the properties of the gel. Additionally, MP-ASPI gel exhibits the best properties and microstructure. Overall, the four industrial modification effects may impact SPI's structure and gel properties in different ways. A-SPI could be a potential functionality-enhanced soy protein ingredient in comminuted meat products. The present study results will provide a theoretical basis for the industrialized production of SPI.

Physico-Chemical Changes Induced by Gamma Irradiation on Some Structural Protein Extracts

In this study, the effect of gamma irradiation (10 kGy) on proteins extracted from animal hide, scales, and wool was evidenced by calorimetric (μDSC) and spectroscopic (IR, circular dichroism, and EPR) methods. Keratin was obtained from sheep wool, collagen and bovine gelatin from bovine hide, and fish gelatin from fish scales. The μDSC experiments evidenced that gamma irradiation influences the thermal stability of these proteins differently. The thermal stability of keratin decreases, while a resistance to thermal denaturation was noticed for collagen and gelatins after gamma irradiation. The analysis of the IR spectra demonstrated that gamma irradiation determines changes in the vibrational modes of the amide groups that are associated with protein denaturation, most meaningfully in the case of keratin. As evidenced by circular dichroism for all proteins considered, exposure to gamma radiation produces changes in the secondary structure that are more significant than those produced by UV irradiation. Riboflavin has different effects on the secondary structure of the investigated proteins, a stabilizing effect for keratin and fish gelatin and a destabilizing effect for bovine gelatin, observed in both irradiated and non-irradiated samples. The EPR spectroscopy evidences the presence, in the gamma-irradiated samples, of free radicals centered on oxygen, and the increase in their EPR signals over time due to the presence of riboflavin.

The non-covalent interactions between whey protein and various food functional ingredients

In daily diet, Whey protein (WP) is often coexisted with various Food functional ingredients (FFI) such as proteins, polyphenols, polysaccharides and vitamins, which inevitably affect or interact with each other. Generally speaking, they may be interact by two different mechanisms: non-covalent and covalent interactions, of which the former is more common. We reviewed the non-covalent interactions between WP and various FFI, explained the effect of each WP-FFI interaction, and provided possible applications of WP-FFI complex in the food industry. The biological activity, physical and chemical stability of FFI, and the structure and functionalities of WP were enhanced through the non-covalent interactions. The development of non-covalent interactions between WP and FFI provides opportunities for the design of new ingredients and biopolymer complex, which can be applied in different fields. Future research will further focus on the influence of external or environmental factors in the food system and processing methods on interactions.

Comparative Study of Heat- and Enzyme-Induced Emulsion Gels Formed by Gelatin and Whey Protein Isolate: Physical Properties and Formation Mechanism

Emulsion gels have received increasing attention due to their unique physicochemical properties. In this paper, gelatin and whey protein isolate (WPI) were used to construct emulsion-filled gels by heat-induced or enzyme-induced methods, and their rheology, texture properties and microstructure were explored and compared. The effect of the preparation methods, emulsion droplet characteristics and gel matrix concentration on the elastic modulus and hardness of the gels were firstly investigated, then the key control factors were picked out by calculating the Pearson correlation index, and the design principle was constructed by combining these factors flexibly for emulsion gels with adjustable texture. The results show that the emulsion gels formed by different preparation methods have completely distinct microstructures and emulsion distributions, as well as the macroscopic properties of the gels, specifically the enzyme-induced gels exhibited greater elastic modulus and hardness, while heat-induced gels were softer and more delicate. In addition, the droplet sizes of filled emulsions and matrix concentration mainly affected the rheological properties and hardness of the gels. This study successfully established the design principles of emulsion gels with tunable texture structure, which provided a reference for targeted gels preparation according to the texture properties required by specific application scenarios.

Rheological properties and interactions of fish gelatin-κ-carrageenan polyelectrolyte hydrogels: The effects of salt

This study mainly explored the effects of low-concentration salts (0.1, 0.5 mM NaCl and Na₂ SO₄ ) on the gel, rheological and structural properties of fish gelatin (FG)-κ-carrageenan (κC) polyelectrolyte hydrogels. The results showed that κC could increase the gel strength, hardness, and chewiness of the FG-κC polyelectrolyte hydrogels, while the addition of salts had a negative effect. The rheological behaviors showed that the addition of salts reduced the apparent viscosity, gel, and melting points of the FG-κC polyelectrolyte hydrogels. Compared with NaCl, Na₂ SO₄ -treated FG-κC had lower gel strength, hardness, viscosity, gelation, and melting points, while the addition of salts increased the fluorescence intensity by unfolding FG molecules. The secondary structure analysis results showed that the addition of NaCl and Na₂ SO₄ decreased α-helix and β-sheet contents of FG-κC by destroying the hydrogen bond of FG-κC.

Research progress on polysaccharide/protein hydrogels: Preparation method, functional property and application as delivery systems for bioactive ingredients

Some bioactive ingredients in foods are unstable and easily degraded during processing, storage, transportation and digestion. To enhance the stability and bioavailability, some food hydrogels have been developed to encapsulate these unstable compounds. In this paper, the preparation methods, formation mechanisms, physicochemical and functional properties of some protein hydrogels, polysaccharide hydrogels and protein-polysaccharide composite hydrogels were comprehensively summarized. Since the hydrogels have the ability to control the release and enhance the bioavailability of bioactive ingredients, the encapsulation and release mechanisms of polyphenols, flavonoids, carotenoids, vitamins and probiotics by hydrogels were further discussed. This review will provide a comprehensive reference for the deep application of polysaccharide/protein hydrogels in food industry.

The Influence of Enzymatic Hydrolysis of Whey Proteins on the Properties of Gelatin-Whey Composite Hydrogels

Amino-acids, peptides, and protein hydrolysates, together with their coordinating compounds, have various applications as fertilizers, nutritional supplements, additives, fillers, or active principles to produce hydrogels with therapeutic properties. Hydrogel-based patches can be adapted for drug, protein, or peptide delivery, and tissue healing and regeneration. These materials have the advantage of copying the contour of the wound surface, ensuring oxygenation, hydration, and at the same time protecting the surface from bacterial invasion. The aim of this paper is to describe the production of a new type of hydrogel based on whey protein isolates (WPI), whey protein hydrolysates (WPH), and gelatin. The hydrogels were obtained by utilizing a microwave-assisted method using gelatin, glycerol, WPI or WPH, copper sulfate, and water. WPH was obtained by enzymatic hydrolysis of whey protein isolates in the presence of bromelain. The hydrogel films obtained have been characterized by FT-IR and UV-VIS spectroscopy. The swelling degree and swelling kinetics have also been determined.

Enhanced heat stability and antioxidant activity of myofibrillar protein-dextran conjugate by the covalent adduction of polyphenols

In the present study, three types of polyphenols, namely, (-)-epigallocatechin-3-gallate (EGCG), catechin (C), and gallic acid (GA), were grafted to myofibrillar protein (MP)-dextran (DX) conjugate through a free radical-mediated adduction method. The analysis of secondary structure showed that conjugation of polyphenols induced a decrease in contents of α-helix structures. The surface hydrophobicity of MP-DX conjugate was increased after polyphenols were covalently adducted, while that of the free amino, thiol groups, and tyrosine residues were decreased, especially with the addition of EGCG (p < 0.05). Analysis of rheological properties showed that covalently linking of polyphenols decreased the thermal gelling capacity by inhibiting myosin-head aggregation and myosin tails interaction. Moreover, polyphenol adduction was able to remarkably improve the thermal stability and antioxidant activity of MP-DX conjugate. The findings regarding enhanced functionalities evidence potential of applying the ternary adduct as a novel antioxidant.

Molecular forces governing protein-protein interaction: Structure-function relationship of complexes protein in the food industry

The application of protein-protein interaction (PPI) has been widely used in various industries, such as food, nutraceutical, and pharmaceutical. A deeper understanding of PPI is needed, and the molecular forces governing proteins and their interaction must be explained. The design of new structures with improved functional properties, e.g., solubility, emulsion, and gelation, has been fueled by the development of structural and colloidal building blocks. In this review, the molecular forces of protein structures are discussed, followed by the relationship between molecular force and structure, ways of a bind of proteins together in solution or at the interface, and functional properties. A more detailed look is thus taken at the relationship between the various influencing factors on molecular forces involved in PPI. These factors include protein properties, such as types, concentration, and mixing ratio, and solvent conditions, such as ionic strength and pH. This review also summarizes methods tha1t are capable of identifying molecular forces in protein and PPI, as well as characterizing protein structure.

Advancement of food-derived mixed protein systems: Interactions, aggregations, and functional properties

Recently, interests in binary protein systems have been developed considerably ascribed to the sustainability, environment-friendly, rich in nutrition, low cost, and tunable mechanical properties of these systems. However, the molecular coalition is challenged by the complex mechanisms of interaction, aggregation, gelation, and emulsifying of the mixed system in which another protein is introduced. To overcome these fundamental difficulties and better modulate the structural and functional properties of binary systems, efforts have been steered to gain basic information regarding the underlying dynamics, theories, and physicochemical characteristics of mixed systems. Therefore, the present review provides an overview of the current studies on the behaviors of proteins in such systems and highlights shortcomings and future challenges when applied in scientific fields.

Design of Bioinspired Emulsified Composite European Eel Gelatin and Protein Isolate-Based Food Packaging Film: Thermal, Microstructural, Mechanical, and Biological Features

The study focused on the elaboration and the characterization of blend biofilms based on European eel skin gelatin (ESG) and protein isolate (EPI) and the assessment of European oil (EO) incorporation effect on their properties. Data displayed that the incorporation of EPI and EO to the gelatin formulation decreased the lightness and yellowness of composite and emulsified films, respectively, compared to ESG film. Moreover, ESG films exhibited improved mechanical properties than EPI films. FTIR analysis, all incorporated films with EO at the ratio 1:4 (oil/polymer) revealed similar characteristic bands as in free-oil films. Further, the SEM images of 100% ESG and 100% EPI films showed a smooth and homogenous structure, whereas the cross-section of blend film (at a ratio 50:50) displayed a rougher microstructure. In addition, emulsified film ESG100 revealed a smooth and homogeneous microstructure compared to that prepared using EPI/ESG 50/50 ratio. Furthermore, EPI or EO addition into the ESG matrix enhanced the blend films antioxidant activities.

Rheological, physical, and mechanical properties of chicken skin gelatin films incorporated with potato starch

The aim of this study was to investigate the rheological, physical, and mechanical properties of chicken skin gelatin film forming solutions (FFSs) and films incorporated with potato starch. Chicken skin gelatin-based FFSs with various potato starch concentrations (0, 2, 4, 6, 8, and 10%, w/w) were prepared via casting technique. The dynamic viscoelastic properties of FFS were measured, and film characterization in terms of physical and mechanical properties was conducted. Potato starch incorporation with chicken skin gelatin-based FFS resulted in improvement of viscous behavior (G″ > G'). As potato starch concentration increased, the tensile strength, elongation at break, and elastic modulus values of chicken skin gelatin-based films also increased (p < 0.05). Additionally, increasing the concentration of potato starch caused incremental changes in water vapor permeability and melting temperatures (T m), but a reduction in water solubility (p < 0.05). In addition, the surface smoothness and internal structure of composite films improved via potato starch incorporation. The incorporation of potato starch was also found to provide good barrier properties against ultraviolet and visible light, but did not significantly influence the transparency values of composite films. Overall, chicken skin gelatin film with 6% potato starch concentration incorporation was the most promising composite film, since it was found to exhibit optimal performance in terms of physical properties.

Gelation of food protein-protein mixtures

Gelation of proteins is one of the principal means to give desirable texture to food products. Gelation of individual proteins in aqueous solution has been investigated intensively in the past, but in most food products the system contains mixtures of different types of proteins. Therefore one needs to consider interaction between different proteins both before and during gelation. Most food proteins can be classified as globular proteins, but casein and gelatin are also important food proteins. In this review the focus is on gelation induced by heating or cooling, which is the most commonly used method. After briefly discussing general features of protein aggregation and gelation, the literature on gelation of mixtures of different types of globular proteins is reviewed as well as that of mixtures of globular proteins with gelatin or with casein. The effect on the gel stiffness and the microstructure of the gelled mixtures will be discussed in terms of different scenarios that can be envisaged: independent aggregation and gelation, co-aggregation and phase separation.

Development of Antibacterial Nanocomposite: Whey Protein-Gelatin-Nanoclay Films with Orange Peel Extract and Tripolyphosphate as Potential Food Packaging

Antibacterial and biodegradable whey protein isolate (WPI-) gelatin nanocomposites were prepared using natural orange peel extract (OPE) in percentage of 7, 14, and 21% (v/v solution) and Cloisite 30B (5% w/w dry whey protein) made by a casting method. Mechanical, physical, and antibacterial properties of prepared films were measured as a function of OPE concentration. Higher concentrations of OPE led to higher antibacterial activity, tensile strength, and water solubility, but lower moisture content and transparency. The films microstructures were studied by field emission scanning electron microscopy (FESEM) and ATR-FTIR. Overall, the film containing 21%(v/v) OPE resulted in the best antibacterial, mechanical, and physical performance. Addition of tripolyphosphate (TPP) as a crosslinker to this sample led to the significant increase in transparency. Cloisite 30B, OPE, and TPP can therefore be used to improve the properties of WPI films as a promising natural food packaging.

Physiochemical and functional properties of gelatin obtained from tuna, frog and chicken skins

Growing demand for gelatin has increased interest in using alternative raw materials. In this study, different animal skins; namely frog, tuna and chicken skins; were utilized in gelatin extraction by previously optimized extraction procedures. Quality characteristics and functional properties of the resultant gelatins were comparatively investigated. Frog skin gelatin had the highest protein content with 77.8% while the highest hydroxyproline content was found in chicken skin gelatin with 6.4%. Frog skin gelatin showed a significantly higher melting point (42.7 °C) compared to tuna and chicken gelatins. Bloom value was also significantly higher in frog skin gelatin compared to that of chicken and tuna skin gelatins. Results showed that processing waste like skins of different animals may present opportunities in gelatin production as high quality alternatives. This study may help the industry by providing one hand comparable data over potentially significant sources.

Gelation kinetics and characterization of enzymatically enhanced fish scale gelatin-pectin coacervate

BACKGROUND

Protein-polysaccharide complex coacervations have been considered extensively for the development of functional foods. The main problem of the complex coacervates is that they are highly unstable under different conditions and that cross-linking is necessary to stabilize them. In this study, the effects of pectin at different concentrations on the gel and structural properties of fish scale gelatin (FSG)-high methoxyl citrus pectin (HMP) coacervate enhanced by microbial transglutaminase (MTGase) were studied.

RESULTS

The gelation rates and gel strength of the MTGase-enhanced FSG-HMP coacervate gels decreased with increasing HMP concentration. However, the enhanced coacervate gels exhibited better thermal behavior and mechanical properties compared with the original gels. Also, TG-P₈ exhibited the highest melting point (27.15 ± 0.12 °C), gelation point (15.65 ± 0.01 °C) and stress (15.36 ± 0.48 kPa) as HMP was 8 g kg^-1 . Particle size distribution, fluorescence emission and UV absorbance spectra indicated that MTGase and HMP could make FSG form large aggregates. Moreover, confocal laser scanning microscopy of treated coacervate gels showed a continuous protein phase at low HMP concentrations.

CONCLUSION

FSG and HMP could form soluble coacervate, and MTGase could improve the thermal and mechanical properties of coacervate gels. © 2017 Society of Chemical Industry.

The effect of conformational transition of gelatin-polysaccharide polyelectrolyte complex on its functional properties

The blends of gelatin and shear-thinning hydrocolloids (guar gum, kappa-carrageenan and xanthan gum) were examined to determine the effect of the conformational change on the functional properties of the solutions. The polyelectrolyte complexes of 0.5% gelatin/0.5% polysaccharide in 70 mM KCl or 70 mM NaCl were investigated by the laboratory rheometer and conductivity meter in the temperature range 25 - 45 °C. The rheological data were fitted by the power-law and Herschel-Bulkley model to obtain the flow parameters. The functional properties of the samples were substantially affected by the conformational change of the polysaccharide, as well as by the type of the hydrocolloid and salt solution. There was an evident change of viscosity and conductivity of the solutions upon heating, corresponding to the helix-coil transition of the polysaccharide at temperature about 35 °C. The type of the salt solvent had an effect on the gelation properties of the samples. Gelatin/kappa-carrageenan blend in NaCl provided a gel of high consistency at ambient temperature (20 - 25 °C), whereas the blend in KCl did not gel in the studied temperature range. The potential stability of the blends was determined by zeta-potential analysis. The low values of ζ-potential indicate that the gelatin/polysaccharide blends are electrically unstable systems which tend to coagulate. The mixtures of gelatin/polysaccharide electrostatic complexes may have a great potential in many food applications.

Effect of egg albumen protein addition on physicochemical properties and nanostructure of gelatin from fish skin

The physicochemical properties and nanostructure of mixtures of egg albumen protein (EAP) and gelatin from under-utilised grass carp (Ctenopharyngodon idella) skins were studied. The gelatin with 1% EAP had an acceptable gel strength. The addition of 5% EAP significantly increased the melting and gelling temperatures of gelatin gels. Additionally, the colour turned white and the crystallinity was higher in gelatin gels with gradient concentrations of EAP (1, 3, and 5%). Gelatin with 5% EAP had the highest G' values while gelatin with 1% EAP had the lowest G' values. Atomic force microscopy showed the heterogeneous nanostructure of fish gelatin, and a simple coacervate with a homogeneous distribution was only observed with the addition of 1% EAP, indicating interaction between gelatin and EAP. These results showed that EAP effect fish gelatin's physicochemical and nanostructure properties and has potential applications in foods and pharmaceuticals.