Changes in textural and rheological properties of gels from tilapia muscle proteins induced by high pressure and setting

Preservation processes of liquid nitrogen spray freezing technology on Sebastes schlegelii in two stages of freezing and frozen storage: Focusing on changes in water status, protein characterization, texture properties and volatile compounds

This study explored the preservation process of liquid nitrogen spray freezing (LNSF) technology for Sebastes schlegelii during freezing and frozen storage. The findings demonstrated that Sebastes schlegelii achieved optimal storage quality at -100 °C LNSF technology and -40 °C frozen storage conditions. The -100 °C LNSF group exhibited water holding capacity and water migration patterns closest to the control group, maintaining firm fish texture and myogenic fiber integrity by decresing ice crystal formation by 39.40 %. Furthermore, it suppressed the synthesis of fishy odors and irritants substances, such as heptanal, nonanal and sulfur ethers. The -40 °C frozen storage maintained stable texture, significantly decreasing lipid oxidation and the degradation and aggregation of myofibrillar proteins (MP). This process also preserved protein spatial structure and muscle integrity while minimizing flavor changes. The results indicated that LNSF technology has significant potential to enhance the quality of Sebastes schlegelii.

Ovalbumin/sodium alginate Pickering emulsion: Structural characteristics and its contribution to enhancing the gel properties of Hairtail (Trichiurus haumela) surimi

In this study, ovalbumin (OV) and sodium alginate (SA), two macromolecular complexes, were coagulated into the emulsifier (OV/SA), which stabilized soybean oil by electrostatic interaction, hydrophobic interactions, and hydrogen bonding. The structure of OV/SA and properties of OV/SA Pickering emulsion were investigated. Additionally, the effect of emulsions on the gel and protein properties of hairtail surimi was studied. The results revealed that with the increasing concentration of OV/SA, the particle size and zeta potential value (negative value) of the emulsion initially decreased and then increased, while the rheological properties gradually improved. Compared with the surimi gel directly supplemented with soybean oil, the addition of emulsion enhanced gel strength, whiteness, water holding capacity, and hydrophobic interactions, resulting in a more stable gel network structure. In summary, incorporating emulsion into surimi at the same lipid content not only maintained its gel properties but also improved its color and compensated for lipid loss.

Insight into the effect of large yellow croaker roe phospholipids on the physical properties of surimi gel and their interaction mechanism with myofibrillar protein

BACKGROUND

The present study aimed to investigate the effects of large yellow croaker roe phospholipids (LYCRPLs) on the physical properties of surimi gels and to clarify their interaction mechanism with myofibrillar proteins (MPs) in terms of chemical forces and the spatial conformation.

RESULTS

LYCRPLs could improve the gel strength, textural properties, rheological properties and water-holding capacity of surimi gels. Moreover, the interaction mechanism between LYCRPLs with MPs was revealed through intermolecular forces, Fourier transform infrared spectroscopy and ultraviolet visible absorption spectroscopy. The findings demonstrated that LYCRPLs enhanced the surface hydrophobicity and particle size of MPs, facilitating expansion and cross-linking of MPs.

CONCLUSION

These results provide a theoretical basis for improving the characteristics of surimi gels and thus facilitate the application of LYCRPLs in the aquatic food industry. © 2023 Society of Chemical Industry.

Improving the texture attributes of squid meat (sthenoteuthis oualaniensis) with slight oxidative and phosphate curing treatments

This study aimed to improve the pasty texture of squid meat by oxidative and phosphate curing (OPC) treatment, and elucidate the underlying mechanism. The shear force, springiness, weight gain, water-holding capacity (WHC), color and sensory evaluation of squid meat samples treated with a mild OPC approach (OPC_2, 10 mM H2O2 solution with complex phosphate solution) were significantly improved. However, the samples subjected to over-oxidized (20 and 30 mM H2O2 solution with complex phosphate solution) treatment did not obtain favorable outcomes. Microstructure analysis revealed that muscle fibers aggregated after moderate OPC treatments, leading to an increased spacing between muscle fiber bundles. This gap facilitated a more uniform distribution and restriction of water, according to low-field nuclear magnetic resonance (LF-NMR) results. The results from in vitro simulated oxidation of myofibrillar proteins (MPs) demonstrated that increased H2O2 led to formation of carbonyl groups and decreased sulfhydryl groups, and even secondary structure changes, according to fourier transform infrared spectroscopy (FT-IR). Particle size, zeta potential and sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE) results showed that oxidation caused protein aggregation into larger molecules. This study presents a novel approach to improve pasty texture of squid meat.

Effects of 2,2'-Azobis(2-methylpropionamidine) Dihydrochloride Stress on the Gel Properties of Duck Myofibrillar Protein Isolate

The aim of this study was to investigate the biochemical properties and gel-forming capacity of duck myofibrillar proteins under the effects of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH)-mediated oxidation. Duck myofibrillar proteins were extracted and treated with different concentrations of AAPH solutions (0, 1, 3, 5, 10 mmol/L) and then analysed for carbonyl content, dynamic rheology, protein profiles and gel-forming properties (colour, water holding capacity, gel strength and microstructure). The results showed that with increasing AAPH concentration, the carbonyl content of the proteins exhibited an increasing trend (p < 0.05); SDS-PAGE pattern changes indicated that moderate oxidation (3 mmol/L AAPH) induced myosin aggregation via covalent bonds including disulfide, enhanced protein-protein interactions, and thus affected the gel strength of the DMPs' heat-induced gels. However, high oxidation (5 and 10 mmol/L AAPH) led to the partial degradation of the myosin heavy chain (MHC) isoforms, as evidenced by lower storage modulus and irregular microstructures, which significantly reduced gelation ability. These results suggest that the internal relationship between alkylperoxyl radical-induced oxidation should be taken into account in the processing of duck meat, as mild protein oxidation is conducive to improving gel quality.

Synergistic effects of pH shift and heat treatment on solubility, physicochemical and structural properties, and lysinoalanine formation in silkworm pupa protein isolates

The application of silkworm pupa protein isolates (SPPI) in food industry was limited because SPPI's solubility is poor and it contains a potential harmful component of lysinoalanine (LAL) which formed during protein extraction. In this study, combined treatments of pH shift and heating were performed to improve the solubility of SPPI and to reduce the content of LAL. The experimental results showed that the promoting effect on SPPI's solubility by alkaline pH shift + heat treatment was greater than that by acidic pH shift + heat. And an 8.62 times increase of solubility was observed after pH 12.5 + 80 ℃ treatment compared to the control SPPI sample which was extracted at pH 9.0 without pH shift treatment. Very strong positive correlation was found between alkali dosage and SPPI solubility (Pearson's correlation coefficient r = 0.938). SPPI with pH 12.5 shift treatment showed the highest thermal stability. Alkaline pH shift combined with heat treatment altered the micromorphology of SPPI and destroyed the disulfide bonds between macromolecular subunits (72 and 95 kDa), resulting in reduced particle size and increased zeta potential and free sulfhydryl content of the isolates. The fluorescence spectra analysis showed red shifts phenomena with pH increasing and fluorescence intensity increase with temperature increasing, implying the alterations in the tertiary structure of protein. Compared to the control SPPI sample, the amount of LAL reduced by 47.40 %, 50.36 % and 52.39 % using pH 12.5 + 70 ℃, pH 12.5 + 80 ℃ and pH 12.5 + 90 ℃ treatment, respectively. These findings provide fundamental information for the development and application of SPPI in food industry.

Effect of High Pressure Homogenization-Modified Soy 11S Globulin on the Gel and Rheological Properties of Pork Myofibrillar Protein

The changes in texture and rheological characteristics, water holding capacity, and microstructure of pork myofibrillar protein with high-pressure homogenization-modified (0-150 MPa) soy 11S globulin were studied. The cooking yield, whiteness values, texture properties, shear stress, initial apparent viscosity, storage modulus (G'), and loss modulus (G″) of pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were significantly increased (p < 0.05) compared with the sample of 0 MPa, and centrifugal yield was significantly decreased, except for the sample of 150 MPa. Therein, the sample of 100 MPa had the largest values. Meanwhile, the water and proteins bonded more tightly because the initial relaxation times of T_2b, T₂₁ and T₂₂ from pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were shorter (p < 0.05). Overall, the water-holding capacity, gel texture and structure, and rheological properties of pork myofibrillar protein could improve when adding soy 11S globulin treated with 100 MPa.

Characterization of four thermogelled egg yolk varieties based on moisture and protein content

There are obvious differences between egg yolks of different varieties. Additionally, boiled eggs, which are widely liked and consumed globally, are nutrient rich. However, they absorb water in the esophagus during swallowing, and this result in an uncomfortable sensation. Here, we determined the moisture content and distribution as well as the protein contents and properties of 4 varieties of thermogelled egg yolks. Among the varieties, Green Shelled thermogelled egg yolk showed the highest protein content and solubility. Additionally, the ionic, hydrogen, and disulfide bonds corresponding to Rhode Island Red thermogelled egg yolk samples were the weakest, while the hydrophobic interaction force corresponding to the Hetian Dahei (HD) egg yolk samples was the weakest. Further, the distribution of the moisture contents of the 4 varieties was significantly different (P < 0.05). HD egg yolk showed the highest moisture content, and its bound and immobile moisture contents were significantly higher than those of the other 3 varieties. Egg yolk moisture content also affected free amino acid content, which was the highest for HD egg yolk. Therefore, owing to its high moisture content, HD egg yolk was conducive for chewing and swallowing and given its high free amino acid content, it also had a more suitable taste and flavor. The results of this study provide a theoretical basis for the application of egg yolks in food processing.

Gelation Process Optimization of Shrimp Surimi Induced by Dense Phase Carbon Dioxide and Quality Evaluation of Gel

Dense phase carbon dioxide (DPCD) is a new non-thermal method to induce surimi gel. However, the gel quality is affected by many factors, such as DPCD treatment time, temperature, and pressure, which makes it complicated to determine its operating parameters. Box-Behnken and backward linear regression were used to optimize the conditions (temperature, pressure, and treatment time) of DPCD-induced shrimp surimi gel formation, and a model between shrimp surimi gel strength and treatment conditions was developed and validated in the present study. Meanwhile, the heat-induced method was used as a control to analyze the effect of DPCD on the quality of shrimp surimi gel in the present study. The results showed that DPCD treatment affected the strength of shrimp surimi gel significantly, and the pressure of DPCD had the greatest influence on the gel strength of shrimp surimi, followed by time and temperature. When the processing pressure was 30 MPa, the temperature was 55 °C, and the treatment time was 60 min, the gel strength of the shrimp surimi was as high as 197.35 N·mm, which was not significantly different from the simulated value of 198.28 N mm (p > 0.05). The results of the gel quality properties showed that, compared with the heat-induced method, DPCD reduced the nutrient and quality loss of the shrimp surimi gel, and increased the gel strength and gel water-holding capacity. The results of low-field nuclear magnet resonance showed that DPCD increased the binding capacity of shrimp surimi to bound water and immobilized water, and reduced their losses. Gel microstructure further demonstrated that DPCD could improve shrimp surimi gelation properties, characterized by a finer and uniformly dense gel network structure. In summary, DPCD is a potential method for inducing shrimp surimi to form a suitable gel. The prediction model established in this study between DPCD treatment temperature, pressure, time, and gel strength can provide a reference for the production of shrimp surimi by DPCD.

Modification of myofibrillar protein gelation under oxidative stress using combined inulin and glutathione

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Inulin and glutathione (GSH) are combined to treat myofibrillar proteins (MP).

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GSH significantly suppresses oxidation-induced carbonylation and protein insolubility.

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Inulin, GSH and their combination improve the gelling properties of oxidized MP.

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Treatment with inulin + GSH shows the best oxidative stability and textural characteristics.

The effects of inulin (1.5%), glutathione (GSH, 0.05%), and their combination (1.5% inulin + 0.05% GSH) on the conformational structure and gel performance of pork myofibrillar protein (MP) under oxidation condition were examined. The addition of GSH significantly prevented oxidation-induced carbonylation, reduction of α-helix content, and protein aggregation. As a result, treatment with GSH significantly reduced the particle size of oxidized MP by 35%, increased the solubility by 17.3%, and improved the gelling properties. The presence of inulin also obviously enhanced the gelling behavior of MP under oxidation condition, although it could hardly inhibit the modification of MP structure caused by oxidation. Treatment with inulin + GSH exhibited the highest cooking yield (84.2%) and the best textural characteristics, with a denser and more uniform network structure comprising evenly distributed small pores. The findings of this study provide a useful method for processing meat protein gel products with better oxidative stability and textural properties.

Effects of different curing methods on edible quality and myofibrillar protein characteristics of pork

This study aimed to investigate the effects of standing curing (SC), tumbling curing (TC), vacuum tumbling curing (VTC) and ultrasonic-assisted curing (UAC) on the edible quality of black pork and property of myofibrillar proteins (MPs) extracted from black pork. The results showed that all curing methods could improve the marinating absorptivity and the gel water retention of black pork, the solubility and surface hydrophobicity of myofibrillar proteins, and reduce the cooking loss and shear force of black pork, the hydrogen bond content of myofibrillar proteins and the gel whiteness compared with the control group (SC). The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the concentration of protein bands by VTC treatment was decreased obviously. In addition, the result of the scanning electron microscope (SEM) presented that tumbling and ultrasound treatment would destroy the structure of muscle fibers and make them loose and disordered.

Effects of high-pressure processing on the functional properties of pork batters containing Artemisia sphaerocephala krasch gum

Here, the effect of high-pressure conditions (0.1-400 MPa) on the water-loss, texture, gel strength, color, dynamic rheological property, and water migration of pork batters containing 0.1% (W/W) Artemisia sphaerocephala krasch gum (PB-AG) is studied. Results indicated that the cooking yield, water-holding capacity, texture, gel strength, L^* values, and G' values increased with the increase in pressure (0.1-300 MPa) (p < 0.05). Dynamic rheological results (G') revealed that the thermal gelling ability of the PB-AG gel gradually increased with pressure (0.1-300 MPa). The minimum of T₂₂ content was observed and the proportion of immobilized water decreased at 300 MPa by low-filed nuclear magnetic resonance. However, excessive high-pressure processing treatments (400 MPa) resulted in lower gel strength, WHC, texture, and G'. The scanning electron microscopy results shown that a denser network structure with small cavities was observed at 300 MPa. Therefore, moderate pressure treatment (≤300 MPa) may improve gelation properties of PB-AG gel, while excessive pressure treatment (400 MPa) may weaken the gelation properties. PRACTICAL APPLICATION: High-pressure processing combining Artemisia sphaerocephala krasch gum could enhance the gelation properties of pork batters. To do so, establishing knowledge on gelation properties of pork batters with Artemisia sphaerocephala krasch gum at different pressure levels treatment would be of paramount importance, because this contributes furnishing engineering data pertinent to the technical progress for the processing of emulsion-type meat with high quality.

Investigation on the Molecular and Physicochemical Changes of Protein and Starch of Wheat Flour during Heating

The behaviors of starch and protein in wheat flour during heating were investigated, and the molecular changes of starch and protein and their effects on the textural characteristics were assessed. The results showed that with the increased temperature, soluble protein aggregated to insoluble high-molecular-weight protein polymers when the heating temperature exceeded 70 °C, and the aggregation of protein was mainly caused by covalent bonds of disulfide (SS) bonds. Hydrophobic interaction was the main noncovalent bond that participated in the formation of protein aggregates. The major change in the secondary structure during heating was a pronounced transition towards β-sheet-like structures. Considerable disruption of ordered structures of starch occurred at 70 °C, and starch was fully gelatinized at 80 °C. Typical starch pasting profiles of cooked flour were observed when the temperature was below 70 °C, and heat treatment decreased the pasting viscosity of the cooked flour from control to 80 °C, whereas the viscosity of the wheat flour increased in heating treatment at 90, 95 and 100 °C. The intense protein-starch interaction during heating affected the textural characteristic of flour gelation, which showed higher strength at 90, 95 and 100 °C. This study may provide a basis for improving wheat flour processing conditions and could lead to the production of new wheat products.

Stability improvement of reduced-fat reduced-salt meat batter through modulation of secondary and tertiary protein structures by means of high pressure processing

This study investigated the effect of high-pressure processing (HPP) at 100 to 400 MPa for 2 min on the stability of reduced-fat reduced-salt (RFRS) meat batter. Total expressible fluid (TEF) of RFRS batter reached its minimum value at 200 MPa. The results of Raman spectra revealed that α-helix reached its random coils increased as the pressure level was increased, and pressure up to 200 MPa remarkably increased protein unfolding but 400 MPa increased aggregation. Finally, Raman spectra and magnetic resonance imaging (MRI) revealed that 200 MPa significantly increased tryptophan, tyrosine doublet, CH₃ and/or CH stretching and proton intensities related to water and fats; but decreased β structures, SS stretching (475) and (g-g-t or t-g-t, 540), as compared with the control. RFRS batter treated at 200 MPa is beneficial for the meat industry from the technological point of view and for consumers from the health point of view, as the improved emulsion stability contributed by the modified secondary and tertiary structures.

Effects of high pressure and thermal combinations on gel properties and water distribution of pork batters

The effects of high pressure (100-500 MPa) and heated (80 °C, 25 min) combinations on gel properties, rheological characteristic and water distribution of pork batters were investigated. Compared to the only-heat, the cooking yield, a* value, hardness, cohesiveness, and chewiness of cooked pork batters treated less than 300 MPa were significantly increased (P < 0.05), meanwhile, the b* value was significantly decreased (P < 0.05). Opposite, the color and cooking yield were not significant different (P > 0.05) when over 300 MPa, except the L* value. At 300 MPa, the cooking yield, hardness, chewiness, and G' value at 80 °C of pork batter were the highest. The initial relaxation time of T₂₁ was decreased significantly (P < 0.05), and the peak ration of P₂₁ was increased significantly (P < 0.05) when treated at 200 and 300 MPa, that indicated the water was bound tightly and the ratio of immobilized water was increased. Overall, 300 MPa treatment and thermal combinations could improve the gel properties of pork batters.

Effect of hydroxyl radical induced oxidation on the physicochemical and gelling properties of shrimp myofibrillar protein and its mechanism

Protein oxidation is considered as an important factor affecting the texture quality of surimi. In this work, the myofibrillar protein (MP) from shrimp (Penaeus vannamei) was subjected to a hydroxyl radical generating system at various concentrations of H₂O₂, to simulate the oxidative environment during surimi processing. After the hydroxyl radical oxidation, it was found that the carbonyl content, surface hydrophobicity, and MP aggregation increased. Meanwhile, the a-helix decreased, but β-sheet increased after oxidation. The moderate oxidation led to a dense network microstructure, increased water holding capacity (WHC) and decreased water mobility, which ultimately enhanced textural (hardness and springiness increased by 0.51- and 0.06-fold, respectively) and rheological properties of MP gel (MPG). However, excessive oxidation could reduce the mechanical properties of MPG. The microstructure, WHC and water distribution played a key role in the mechanical properties of MPG. This study can provide a theoretical basis for processing of shrimp surimi products.

Effect of high pressure and setting condition on physico-chemical, structural and functional characteristics of transglutaminase mediated fish gels

Application of High pressure and low temperature setting condition on microbial transglutaminase (MTGase) mediated gelation was studied against conventional cooking in pink perch mince. A high pressure of 250 MPa was given to pink perch mince samples added with and without MTGase enzyme, for a holding time of 12 min and a setting condition of 25 °C for 30 min was given prior and after the treatments. Nine random experiments (T1 to T9) were made against high pressure and cooking and analysed its textural and functional properties. Addition of MTGase and setting conditions had significant effect on the textural properties of the both samples especially in inducing the gel strength. Reduction in total and reactive sulfhydryl groups observed was due to the formation of disulfide linkages, which was found more in T6 to T9. Setting condition had significant effect on protein hydrophobicity in both pressure and heat induced gels. No significant variation in the Ca^2+-ATPase enzyme activity was observed among treatments. SEM images revealed more closed and dense fibrous network in samples with enzyme (T6 to T9), due to more protein polymerisation. So MTGase enzyme along with pressure treatment enhanced the conformational stability and produce stronger networks through the formation of non sulfide bonds between proteins and setting reinforced these networks. Hence the synergistic effect of high pressure and MTGase can enhance the textural and functional properties of fish gels, when compared with the conventional cooking.

The sol-gel-sol transformation behavior of egg white proteins induced by alkali

In the current study, we found an interesting phenomenon that fresh egg white (EW) undergo the sol-gel-sol transition with alkali treatment. The transformation behavior at different alkalinity (1.5%, 2.0%, and 2.5%) was investigated. As the gel formed, the hardness, lightness, surface hydrophobicity and the total number of identified peptides increased, and then, remarkable reduction when the gel collapsed. Rheological behavior indicated that the viscosity varied with shear rate. Fourier transform infrared spectroscopy (FTIR) showed that β-sheets gradually decreased as the α-helices increased during gel-sol transformation. The quantification of EW peptides analysis revealed that there was no dramatic correlation between the number of identified peptides and alkalinity. It was concluded that the sol-gel-sol transition was strongly dependent on alkali levels, moreover, high concentration promoted gel formation as well as liquefaction. The EW transformation behavior induced by alkali had a significant effect on protein aggregation and denaturation, and further changed physicochemical properties.

Effect of hydroxyl radicals on biochemical and functional characteristics of myofibrillar protein from large yellow croaker (Pseudosciaena crocea)

The oxidative modification effect of hydroxyl radicals generated by an H₂ O₂ oxidative solution on the biochemical and functional characteristics of myofibrillar protein (MP) from large yellow croaker (Pseudosciaena crocea) was investigated. The results showed that MP of large yellow croakers was vulnerable to hydroxyl radicals. Incubation of MP with increased concentration of H₂ O₂ led to the gradual formation of carbonyl derivatives, disulphide bonds and dityrosine, and loss of available lysine, sulphydryl, and free ammonia. Surface hydrophobicity increased, while tryptophan residues decreased, indicating a conformational transition of MP. SDS-PAGE demonstrated that both disulphide and nondisulphide bonds were involved in MP aggregation. The MP functionalities were also affected by hydroxyl radicals, including reduced solubility, gelling, and emulsifying properties. Mild oxidation (0.1 mM H₂ O₂ ) slightly improved MP gel strength and water-holding capacity, while excessive oxidation caused a reduction in gel properties. The results suggested that the MP oxidation should be controlled. PRACTICAL APPLICATIONS: Protein oxidation mediated by hydroxyl radicals is one of the most crucial reasons affecting the quality of large yellow croaker during processing and storage. Additionally, it is well known that the quality of protein in fish systems directly determines the quality stability and nutritional value of the fish products. Hence, the study explored how the hydroxyl radicals influenced the physicochemical and functional properties of fish MP. The changes in amino acid residues (carbonyl, available lysine, sulphydryl, free ammonia, tryptophan residues, etc.) of MP and its gelling and emulsifying properties after oxidation not only benefit the awareness of quality deterioration and quality control of large yellow croaker, but also provide a basis for the understanding of protein oxidation on the nutritional value of aquatic products and human health.

Gelation of barramundi (Lates calcarifer) minced muscle as affected by pressure and thermal treatments at low salt concentration

BACKGROUND

Barramundi minced muscle with salt 10 g kg^-1 and 20 g kg^-1 added is gelled by different combinations of pressurisation (300, 400 and 500 MPa at 4 °C for 10 min), cooking (0.1 MPa, 90 °C for 30 min) and setting (0.1 MPa, 50 °C for 2 h) to improve mechanical properties of barramundi gels and reduce salt added to barramundi gels.

RESULTS

At the low salt concentration of 10 g kg^-1 , pressurisation prior to cooking (P-C) treatment induced barramundi gels with comparable mechanical properties and water-holding capacity to those of conventional heat induced (HI) gels with 20 g kg^-1 added salt. At salt concentration of 20 g kg^-1 , pressurisation prior to setting (P-S) and P-C gels exhibited higher mechanical properties and water-holding capacity as compared to HI gels. Scanning electron microscopy images showed a smooth and dense microstructure of P-C and P-S gels whereas the microstructure of HI gels is rough and less compact.

CONCLUSIONS

P-C treatment can reduce salt concentration added to barramundi gels to 10 g kg^-1 . P-S and P-C treatment can result in higher mechanical and functional properties of barramundi gels at conventional salt concentration (20 g kg^-1 ) as compared to HI gels. © 2017 Society of Chemical Industry.