Effect of κ-carrageenan on the quality of crayfish surimi gels

The demand for crayfish surimi products has grown recently due to its high protein content. This study examined the effects of varying κ-carrageenan (CAR) and crayfish surimi (CSM) concentrations on the gelling properties of CAR-CSM composite gel and its intrinsic formation process. Our findings demonstrated that with the increasing concentration of carrageenan, the quality of CAR-CSM exhibited rising trend followed by subsequently fall. Based on the textural qualities, the highest quality CAR-CSM was achieved at 0.3% carrageenan addition. With the exception of chewiness, and the cooking loss of the gel system was 1.62%, whiteness was 82.35%, and the percentage of β-sheets increased to 57.18%. Further increase in CAR (0.4-0.5%) addition resulted in internal build-up of LCAR-CSM, conversion of intermolecular forces into disulfide bonds and gel breakage. This study exudes timely recommendations for extending the CAR application for the continuous development of crayfish surimi and its derivatives and its overall economic worth.

Effects of different temperatures on the physicochemical characteristics, microstructure and protein structure of preserved egg yolk

To clarify the mechanism of lower temperatures promoted the solidification of preserved egg yolk, the effects of temperature (4 °C, 10 °C and 25 °C) on the physicochemical properties, microstructure and protein structure of preserved egg yolk were studied. Results showed that the exterior egg yolk (EEY) exhibited higher pH, hardness and free sulfhydryl content at low-temperature pickling. The microstructure showed that the EEY gradually formed a denser gel network structure at lower temperatures. Electrophoresis results and Fourier transform infrared spectroscopy (FTIR) indicated that there were different degrees of protein degradation and cross-linking of proteins in the IEY (the interior egg yolk) and EEY and the decrease of β-sheets in the secondary structure was accompanied by an increase of β-turns during the formation of egg yolk gels. These results indicated that egg yolk solidification was faster and denser gel structure at 4 °C and 10 °C.

Regulation of different copper salts on alkali-induced egg white gels: Physicochemical characteristics, microstructure and protein conformation

The effects of different copper salts (CuSO4, CuCl2, Cu(CH3COO)2) on the physicochemical characteristics, microstructure and protein conformation of alkali-induced egg white (EW) gels were investigated. With increasing concentration, three copper salts promoted the aggregation of EW proteins while decreasing the β-sheet content. The three-dimensional gel network was promoted to form, and the water-holding capacity (WHC), texture and solubility of gels were improved by three copper salts at low concentrations. While at high concentrations, the gel deteriorated. The main forces maintaining the alkali-induced EW gels added with copper salts were mainly ionic and disulfide bonds. And the protein component was not affected by ion concentration. Due to the difference in charge density, the three anions had different effects on the stability of proteins, and finally showed different gel characteristics (gel strength, WHC, solubility): CuSO4 > CuCl2 > Cu(CH3COO)2. Therefore, copper salts (especially CuSO4) can be used to improve EW protein aggregation.

Quantitative proteomics provides insights into the mechanism of the differences in heat-induced gel properties for egg white proteins with different interior quality during ageing in laying hens

The purpose of this study was to investigate the mechanism for the differences in heat-induced gel properties of egg white proteins with different interior quality during ageing in laying hens. Quantitative proteomic analysis revealed that the abundance of ovotransferrin, avidin, mucin 5B, and clusterin increased with decreasing Haugh units (HU), leading to the transition from disorder to order in the secondary and tertiary structure of egg white proteins, with the burial of hydrophobic groups and a reduction in the negative charge on the protein surface, rendering the egg white protein solution aggregated. These changes would accelerate the rate of aggregation of egg white proteins during heating, resulting in the loss of orientation of the molecular chains, forming coarse and porous gel structures and poor gel properties. This research provides a new idea for improving the gelling properties of egg whites from lower interior quality during ageing in laying hens.

Addition of NaCl or Sucrose on the Protein Content, and Functional and Physicochemical Properties of Egg Whites Liquid under Heat Treatment

In this study, differences in the protein content and functional and physicochemical properties of four varieties of egg white (EW) were studied by adding 4-10% sucrose or NaCl and then heating them at 70 °C for 3 min. According to a high-performance liquid chromatography (HPLC) analysis, the percentages of ovalbumin, lysozyme and ovotransferrin rose with an increase in the NaCl or sucrose concentration; however, the percentages of ovomucin and ovomucoid decreased. Furthermore, the foaming properties, gel properties, particle size, α-helixes, β-sheets, sulfhydryl groups and disulfide bond content also increased, whereas the content of β-turns and random coils decreased. In addition, the total soluble protein content and functional and physicochemical properties of black bone (BB) chicken and Gu-shi (GS) EWs were higher than those of Hy-Line brown (HY-LINE) and Harbin White (HW) Ews (p < 0.05). Subsequently, transmission electron microscopy (TEM) confirmed the changes in the EW protein structure in the four varieties of Ews. As the aggregations increased, the functional and physicochemical properties decreased. The protein content and functional and physicochemical properties of Ews after heating were correlated with the concentration of NaCl and sucrose and the EW varieties.

Preparation and Properties of Egg White Dual Cross-Linked Hydrogel with Potential Application for Bone Tissue Engineering

In this study, an egg white dual cross-linked hydrogel was developed based on the principle that the external stimulus can denature proteins and cause them to aggregate, forming hydrogel. The sodium hydroxide was used to induce gelation of the egg white protein, subsequently introducing calcium ions to cross-link with protein chains, thereby producing a dual cross-linked hydrogel. The characteristics of the dual cross-linked hydrogels-including the secondary structure, stability, microstructure, swelling performance, texture properties, and biosafety-were investigated to determine the effects of calcium ion on the egg white hydrogel (EWG) and evaluate the potential application in the field of tissue engineering. Results showed that calcium ions could change the β-sheet content of the protein in EWG after soaking it in different concentrations of CaCl₂ solution, leading to changes in the hydrogen bonds and the secondary structure of polypeptide chains. It was confirmed that calcium ions promoted the secondary cross-linking of the protein chain, which facilitated polypeptide folding and aggregation, resulting in enhanced stability of the egg white dual cross-linked hydrogel. Furthermore, the swelling capacity of the EWG decreased with increasing concentration of calcium ions, and the texture properties including hardness, cohesiveness and springiness of the hydrogels were improved. In addition, the calcium cross-linked EWG hydrogels exhibited biocompatibility and cell-surface adhesion in vitro. Hence, this work develops a versatile strategy to fabricate dual cross-linked protein hydrogel with biosafety and cell-surface adhesion, and both the strategy and calcium-egg white cross-linked hydrogels have potential for use in bone tissue engineering.

Use of Incinerated Eggshells to Produce Pidan

Preserved eggs (pidans) are used in traditional Chinese cuisines. However, the alkaline conditions and metal ions generated during its preparation have caused some concerns. This study developed an innovative process for pidan processing using incinerated eggshell powder, an abundant by-product that can generate a highly alkaline solution and provide calcium ions (Ca2+). Either 0.5, 3, or 5% of the eggshell powder solution was used for basic pickling. Different combinations of ZnSO4 (0.175%), MgCl2 (0.08%), and CuSO4 (0.16%) were added. Duck eggs were pickled for 25 days at 25–27 °C, followed by 14 days of ripening. The pidan processed in 5% eggshell powder containing 0.175% ZnSO4 demonstrated the closest physiochemical and sensory characteristics to commercial pidans. Thus, the results offer a new technique to manufacture pidans and reduce the harmful impact of metal ions on human health and the environment.

Relationship of co-gelation and co-aggregation on egg white ovalbumin-lysozyme heteroprotein complex: Formation and thermodynamics

This study aimed to establish binary protein system on egg white ovalbumin (OVA) -lysozyme (LYS), and investigated the relationship between co-aggregation and co-gelation. We focused on the formation of OVA-LYS complex, the typical thermo-dynamically favored coacervation process, in terms of gelling properties, microstructure and thermodynamics. Benefited from synergistic effects during co-gelation, the thermally induced gels of OVA-LYS complex formed at extremely low protein concentration (18 mg/mL) and showed higher storage modulus with increasing LYS concentration. Moreover, the rising particle size, reduced zeta potential, unordered secondary structure and strengthened protein chain were observed with the addition of LYS. Remarkably, the divalent ions enhanced thermodynamic stability of OVA-LYS complex, although the growth of aggregates units were prevented by ions at room temperature. ITC and molecular docking analyses revealed the binding affinity stoichiometry and combination phase, which were closely related to the decrease of minimum energy resulted from the formation of hydrogen bond.

Ions-regulated aggregation kinetics for egg white protein: A promising formulation with controlled gelation and rheological properties

This study aims to evaluate the structure of ions-regulated gelation of egg white protein (EWP) via aggregation kinetics model, which was built by monitoring turbidity. Results showed that compared with NaCl and KCl, the addition of Na2SO4 increased free sulfhydryl content, surface hydrophobicity and particle size of EWP significantly, while weakened the order of secondary structure. Hence, strengthened gel network structure was observed with higher porosity, which improved the texture profiles and rheological properties of EWP gels. Based on these phenomena above, the relationship between aggregation behavior and gelling properties with ions was further investigated by aggregation kinetics model and principal component analysis. Because of the enhancement of protein interactions, the aggregation growth rate with Na2SO4 was much faster than the samples with NaCl, which reflected over-aggregation due to the accelerated nucleation process and resulted in firmed gel network structure.

Synergistic gelation in the hybrid gel of scallop (Patinopecten yessoensis) male gonad hydrolysates and xanthan gum

This study evaluated the gel and microstructure properties of scallop (Patinopecten yessoensis) male gonads hydrolysates (SMGHs) combined with xanthan gum (XG). SMGHs/XG hydrogel matrix properties and structures were elucidated via different analysis tools such as rheometry, LF-NMR, FTIR, AFM, and Cryo-SEM. The addition of XG significantly improved the rheological properties of SMGHs, as indicated by 3.1-fold G' and 1.3-fold melting temperature with increasing the XG dose to 5.6 mg/ml. The corresponding decrease in the T₂₃ relaxation time from 450.3 to 365.6 ms also signified the strong binding between SMGHs and XG. SMGHs/XG also had a higher proton density (T₁ and T₂ weighted images) due to the higher bound and free water content of the hybrid gel systems, respectively. Additionally, the blueshift in the amide I and II bands in SMGHs/XG further indicated stronger electrostatic interactions between SMGHs and XG. Such scenarios resulted in a well-distributed and compact network with a rougher surface of SMGHs/XG in comparison to pure SMGHs and XG, as assessed by AFM and SEM. These results suggest that SMGHs/XG gel could be a potential hybrid gel applied in the food industry. PRACTICAL APPLICATION: Scallop (Patinopecten yessoensis) male gonads are edible, but are usually discarded during processing of scallop adductor. Because of its rich nutrition and gelation properties, scallop male gonads have a potential role in developing marine source-protein as a functional food base. The SMGHs/XG binary gel would be potentially applied in delivery system in food and biological fields. Further study is undergoing to apply SMGHs/XG binary gel to embed bioactive compounds, such as curcumin and β-carotene.

Changes in physicochemical properties, gel structure and in vitro digestion of marinated egg white gel during braising

In this paper, changes in physicochemical properties, gel structure and in vitro digestion of marinated egg with spice or tea during braising were investigated. Results indicated that the moisture content and surface hydrophobicity of marinated egg white showed an overall decreased trend. The springiness of marinated egg white showed an increased trend, and the hardness in the late stage showed an increased trend. Microstructure showed that compact gel structures formed many holes during the braising. Intermolecular forces showed that ionic bonds and disulfide bonds played a dominant role in the marinated egg white. Secondary structure showed that the β-turn showed a decreased trend, contrary to that of random coils and α-helices. Appropriate braising increased the digestibility of marinated egg white, but excessively long-time braising could reduce it. Both spice and tea braising could improve the gel strength of protein, and the tea braising was also slightly better than spice braising.

Effects of temperature on quality of preserved eggs during storage

The effects of storage temperature (4°C, 25°C, and 35°C) on sensory quality, physicochemical properties, texture, molecular forces, flavor, and microbial indexes of preserved eggs were studied. The results showed that the sensory quality, weight loss rate, pH, and color of preserved eggs were significantly different at different storage temperatures (P < 0.05). Compared with high temperature and normal temperature storage, low temperature storage reduced weight loss rate by 55.15 and 64.1%, respectively, improved the sensory score (P < 0.05), inhibited the reduction of pH and the increase of total volatile base nitrogen (P < 0.05), and decreased the change of color (P < 0.05). During storage, there was no difference in the springiness of preserved egg white stored at different temperatures (P > 0.05). Hardness and chewiness at 3 different temperatures increased first and then decreased, and low temperature significantly inhibited the progress of these changes to a certain extent (P < 0.05). The content of ionic bond in egg white first decreased and then increased, and content of disulfide bond increased first and then decreased. Content of ionic bond in yolk decreased all the time, and high temperature could promote this change. Whatever the temperature was, the content of free amino acids in preserved egg white and yolk increased first and then decreased, and the total content of amino acids stored at different temperatures was significantly different (P < 0.05). The content of free fatty acids in yolk decreased. At the end of storage, no microorganisms were detected in 3 temperatures during the storage period of 84 D. The results showed that low temperature storage is more conducive for preservation of preserved eggs.