Effects of high pressure processing on gelation properties and molecular forces of myosin containing deacetylated konjac glucomannan

Gelling properties of silver carp surimi incorporated with konjac glucomannan: Effects of deacetylation degree

Effects of konjac glucomannan (KGM) with different deacetylation degrees on silver carp surimi gel properties were studied. As deacetylation degree increased, viscosity, solubility, and water absorption capability of KGM decreased gradually while particle size increased. The gel strength of surimi gel increased with the KGM deacetylation degree up to 50.72% and then significantly decreased. The maximum gel strength was 3.26 times higher than that of surimi gel with native KGM. The relaxation time of immobilized water decreased from 108.22 to 104.70 ms and then increased up to 110.92 ms with the deacetylation degree, while the proportion of the immobilized water increased from 92.74 to 98.59% and then decreased to 97.46%. Water distribution became less uniform as the deacetylation degree exceeded 50.72%. Surimi gel with KGM of a higher deacetylation degree formed a denser microstructure along with a higher dimensional fraction value. However, the microstructure was disrupted and the dimensional fraction value decreased as the deacetylation degree exceeded 50.72%. Chemical interactions including hydrogen bonds, hydrophobic interactions, and cross-linking extent increased with the KGM deacetylation degree up to 50.72% and then gradually decreased. The results suggest that KGM with a deacetylation degree of 50.72% is the most suitable for surimi products.

Effects of the Mixture of Xylooligosaccharides and Egg White Protein on the Physicochemical Properties, Conformation, and Gel-Forming Ability of Culter alburnus Myofibrillar Protein during Multiple Freeze-Thaw Cycles

This study focuses on the effect of the mixture (XO/EW) of xylooligosaccharides (XO) and egg white protein (EW) on the physicochemical properties, conformation, and gel-forming ability of Culter alburnus myofibrillar proteins (MP) during multiple freeze–thaw (FT) cycles. In our methodology, MP samples added with EW, XO, or XO/EW mixture (1%, v/v) are prepared, and after multiple FT cycles, the XO or XO/EW-treated samples show significant (p < 0.05) inhibition on the decrease of sulfhydryl content and the increase of carbonyl content of MP. Compared with EW, XO or XO/EW could delay the increase of surface hydrophobicity and the decline of secondary and tertiary structural properties of MP, indicating that XO or XO/EW could more effectively increase the stability of MP conformation. Meanwhile, XO/EW could more effectively reduce the decrease of gel strength and gel water holding capacity, and the increase in the T₂ relaxation time of MP gel, confirming that XO/EW could substantially improve the MP gel-forming ability. Analysis of intermolecular interaction force proves that, compared with EW, XO/EW could reduce the content decrease of ionic and hydrogen bonds in MP gel. Overall, XO/EW could improve the stability of MP functional properties over multiple FT cycles. This study provides a new perspective for the potential commercial application of EW as a low-calorie cryoprotectant in aquatic products.

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.

Effects of High Hydrostatic Pressure on the Conformational Structure and Gel Properties of Myofibrillar Protein and Meat Quality: A Review

In meat processing, changes in the myofibrillar protein (MP) structure can affect the quality of meat products. High hydrostatic pressure (HHP) has been widely utilized to change the conformational structure (secondary, tertiary and quaternary structure) of MP so as to improve the quality of meat products. However, a systematic summary of the relationship between the conformational structure (secondary and tertiary structure) changes in MP, gel properties and product quality under HHP is lacking. Hence, this review provides a comprehensive summary of the changes in the conformational structure and gel properties of MP under HHP and discusses the mechanism based on previous studies and recent progress. The relationship between the spatial structure of MP and meat texture under HHP is also explored. Finally, we discuss considerations regarding ways to make HHP an effective strategy in future meat manufacturing.

Insight into the Effect of Ice Addition on the Gel Properties of Nemipterus virgatus Surimi Gel Combined with Water Migration

The effect of the amount of ice added (20–60%) on the gel properties and water migration of Nemipterus virgatus surimi gel obtained with two-stage heat treatment was studied. The gel strength and water-holding capability (WHC) of the surimi gel with 30% ice added were significantly higher than those of other treatment groups (p < 0.05). The addition of 30% ice was conducive to the increase of protein β-sheet proportion during heat treatment, exposing more reactive sulfhydryl groups. These promoted the combination of protein-protein through disulfide bonds and hydrophobic-hydrophobic interactions, forming an ordered three-dimensional gel network structure. Meanwhile, the increase in hydrogen bonds promoted the protein-water interaction. Low-field nuclear magnetic resonance analysis showed that more bound water was locked in the gel system, reducing the migration of immobile water to free water and finally showing better gel properties. When the amount of ice added was insufficient (20%), the gel structure lacked the support of immobile water, resulting in deterioration of gel strength. However, excessive addition of ice (>30%) was not conducive to the combination of protein-protein and protein-water, forming a large and rough gel structure, resulting in the migration of immobile water to free water and ultimately exhibited weak gel properties.

Effect of deacetylated konjac glucomannan on heat-induced structural changes and flavor binding ability of fish myosin

This work investigated the effects of deacetylated konjac glucomannan (DKGM) on heat-induced structural changes and flavor binding in bighead carp myosin. DKGM could cross-link with fish myosin to form a thermostable complex and improve the gel strength of myosin. The incorporation of DKGM increased the surface hydrophobicity and total sulfhydryl content of heat-induced myosin. Increasing DKGM concentrations resulted in a decrease in the absolute zeta potential and a continuous increase in particle size. DKGM addition significantly reduced the α-helical content of myosin with a concomitant increase in β-sheet, β-turn, and random coil content. The binding abilities of myosin to flavors were significantly enhanced by increasing amounts of DKGM, attributing to the accelerative unfolding of myosin secondary structures and the exposure of additional hydrophobic and thiol binding sites. Increased numbers of available hydroxyl groups after DKGM treatment could also cause an increase of flavor adsorption by hydrogen bonding.

Structural characteristics and emulsifying properties of myofibrillar protein-dextran conjugates induced by ultrasound Maillard reaction

In this study, we investigated the effect of the ultrasound-assisted Maillard reaction on the structural and emulsifying properties of myofibrillar protein (MP) and dextran (DX) conjugates with different molecular weights (40, 70 and 150 kDa). Compared with classical heating, mild and moderate ultrasound-assisted methods (100-200 W) could accelerate the later stage of the Maillard reaction, which increased the degree of graft (DG) and the content of advanced Maillard reaction products (MPRs). Structural analysis revealed conjugates obtained by Maillard reaction induced the loss of ordered secondary structures (α-helix, β-sheets) and red-shift of maximum emission wavelength of intrinsic fluorescence spectrum. The conjugate containing 40 kDa DX exhibited higher extent of Maillard reaction compared to those containing 70 kDa and 150 kDa DX under various treating methods. Moreover, the ultrasound-assisted Maillard reaction could effectively improve the emulsifying behaviors. 100 W ultrasound-induced conjugates grafted by 70 kDa DX produced the smallest emulsion size with optimum storage stability. Confocal laser scanning microscopy and analytical centrifugal analyzer further confirmed MP grafted by 70 kDa DX with the assistance of 100 W ultrasound field could produce the smallest and most homogeneous MP-base emulsion with no flocculation. Our study demonstrated that mild ultrasound treatment resulted in well-controlled Maillard reaction, and the related glycoconjugate grafted with 70 kDa DX showed the greatest improvements in emulsifying ability and stability. These findings provided a theoretical foundation for the development of emulsion-based foods with excellent characteristics.

Quality characteristics of fortified silver carp surimi with soluble dietary fiber: Effect of apple pectin and konjac glucomannan

The study focused on assessing quality parameters of the surimi incorporated with soluble dietary fibers apple pectin and konjac glucomannan at different levels. The results showed that apple pectin at 0.025% and konjac glucomannan at a 2% level exhibited improved gel-forming ability significantly (p < 0.05). SDS- PAGE revealed high molecular weight protein crosslinks in apple pectin treated surimi gels and disappearance of myosin bands in konjac glucomannan treated surimi gels. The water holding capacity of surimi was the highest when 0.075 g/100 g of apple pectin was added. Konjac glucomannan treated gels exhibited superior whiteness values. The analysis of soluble protein revealed that hydrophobic bonds increased in both the treatments. The hardness values of pectin gels enhanced as the level increased. Other TPA parameters are shown an inconsistent trend. It can be demonstrated that the incorporation of apple pectin and konjac glucomannan at a level of 0.025 and 2.0% may be a novel strategy to improve the gel strength of the surimi.

Structural, gelation properties and microstructure of rice glutelin/sugar beet pectin composite gels: Effects of ionic strengths

In this study, the rice glutelin (RG)/sugar beet pectin (SBP) composite gels were prepared by laccase induced cross-linking and subsequent heat treatment, and the effects of different calcium ion concentrations (0-400 mM) on the gelation, structural properties and microstructure of the RG/SBP composite gels were investigated. The results showed that the addition of 200 mM calcium ion could improve the rheological, textural properties and water holding capacity of the RG/SBP composite gels. The addition of SBP and calcium ions enhanced the hydrophobic interaction between RG molecules, thereby increased the gel properties of RG. The changes in Raman spectroscopy reflected the positive effect of the addition of SBP and calcium ions on the formation of a denser and more homogeneous protein gel, as evidenced by the results of scanning electron microscopy. Overall, SBP and calcium ions could be applied to the plant protein gel systems as gel-strengthening agents.

Effect of two-step microwave heating on the gelation properties of golden threadfin bream (Nemipterus virgatus) myosin

The effects of different microwave heating (MH) methods on gelation properties of golden threadfin bream myosin and related mechanism were investigated in this study. Compared with conventional heating and one-step MH methods, myosin gel developed by 100 W coupled with 300 W MH method (MH100 + MH300) had stronger gel strength (p < 0.05) with more immobilized water (p < 0.05). Raman analysis suggested that this two-step method promoted the suitable unfolding of myosin before aggregation formation, and contributed to stabilizing the ordered secondary structure. Confocal laser scanning microscopy images revealed that 100 W microwave followed by 300 W MH produced a compact networked structure with small cavities and a thick cross-linked gel wall. Furthermore, from a perspective of molecular forces, the improvement of gelation properties by the MH100 + MH300 method were mainly involved in the enhancement of regular hydrophobic interaction and stabilization of weak protein-water hydrogenbonds.

In Vitro Susceptibility of Oxidized Myosin by μ-Calpain or Caspase-3 and the Determination of the Oxidation Sites of Myosin Heavy Chains

The effect of susceptibility to in vitro oxidation on the degradation of myosin isolated from beef muscles via μ-calpain or caspase-3 was examined, and the measurement of the oxidation sites of myosin heavy chains was performed. Myosin was incubated with hydroxyl free radical-generating systems, which were composed of 0.01 M FeCl₃, 0.1 M ascorbic acid, and 0, 25, 50, and 100 μM H₂O₂ at 37 °C for 20 min. The oxidized myosin then reacted with μ-calpain or caspase-3 at 37 °C for 30 min, respectively. The results showed that protein oxidation systems in vitro resulted in different levels of myosin oxidation, leading to significant changes in the secondary structure of myosin (P < 0.05). The sodium dodecyl dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting results showed that in vitro oxidation promoted myosin degradation via μ-calpain or caspase-3. Proteomics research suggested that the number of myosin oxidation sites increased constantly with the increase of oxidation levels. Oxidation sites of myosin were mainly cysteine, methionine, arginine, histidine, tyrosine, lysine, and asparagine. These results indicated that oxidation using H₂O₂ in the range of 0-100 μM could increase the degradation of myosin via μ-calpain and caspase-3 due to increased exposure of the oxidation sites of myosin.

Effects of oxidative modification on the functional, conformational and gelling properties of myofibrillar proteins from Culter alburnus

Protein oxidation is a critical process in the deterioration and spoilage of fish and related commodities during processing and storage. In this study, the hydroxyl radical generation system (HRGS) was used to simulate the effect of oxidation on the functional, conformational and gelling properties of topmouth culter (Culter alburnus) myofibrillar proteins (MP). Additionally, the effects of oxidation on the gel-forming abilities of MP were also systematically analyzed from the perspective of intermolecular interaction forces. Oxidation was shown to decrease the total sulfhydryl content, increase the surface hydrophobicity, and induce conformational changes in MP. Rheological analysis showed that oxidation reduced the gel strength. Water holding capacity (WHC) and low-field nuclear magnetic resonance (LF-NMR) analyses showed that low oxidation could enhance water binding of protein matrix, while high-degree oxidation could substantially reduce the gelling properties of MP. The selective solubility of MP gel proved that oxidation could reduce the content of ionic and hydrogen bonds and increase hydrophobic interactions. All the results indicate that oxidation could alter the intermolecular interactions between protein-protein and protein-water molecules, due to irregular unfolding and inhibition of the cross-linking of amino acid side chains, leading to reduction in the quality and function of fish and related products.

Effect of ultrasound thawing, vacuum thawing, and microwave thawing on gelling properties of protein from porcine longissimus dorsi

Effect of new thawing methods (ultrasound thawing (UT), vacuum thawing, (VT), microwave thawing (MT)) on gelling properties of myofibrillar protein (MP) from porcine longissimus dorsi was investigated, compared with traditional thawing methods (water immersion thawing, (WT)) and fresh meat (FM). The results showed that a decrease in MP gelling properties of all thawing samples was observed. The increase in roughness of MP gel from all thawing samples explained that the flatter, smoother, and denser surface morphology of that from FM samples was destroyed based on the observation by atomic force microscopy. There was significant difference (P < 0.05) in all gel indicators (particle size, turbidity, whiteness, water-holding capacity (WHC), moisture distribution, rheological characteristics, surface morphology) of MP from MT samples and there was insignificant difference (P > 0.05) in turbidity, whiteness, WHC of MP from VT samples compared with that from FM samples. There was insignificant difference (P > 0.05) in gel properties between UT and VT. The effect of UT and VT (new thawing methods) on MP gelling properties was significantly lower (P < 0.05) than that of WT (traditional thawing methods), and the effect of that from MT was obviously compared with other thawing methods.

Two-dimensional infrared spectral explorations into bilayer and monolayer self-assemblies of amphiphilic polypeptides

Poly(2-(3-((2-hydroxyethyl)amino)-3-oxopropyl)ethyleneamido) (PHAOE) is an amphiphilic polypeptide. The self-assembly is significant, but the ultrafast dynamic analyses of the peptide self-assembly are exiguous and worth further exploring. In this investigation, the temporal dynamic characteristics of the aggregates and unaggregated PHAOEs are mined by the two-dimensional infrared (2D IR) spectroscopy. The homogeneous and inhomogeneous diffusion processes of the carbonyl stretching modes of the unaggregated PHAOEs are slower than those of the self-assemblies. The inhomogeneous spectral diffusion proportion of the biopolymer PHAOE in methanol is greater than that in dimethyl sulfoxide (DMSO). The solvation shells surround the aggregates and unaggregated PHAOEs in the protic solvent methanol, but there are not any solvation shells around the aggregates or unaggregated PHAOEs in the dipolar solvent DMSO. The massive hydrogen-bonded monolayer self-assembly has merely an aggregate of PHAOEs and no solvation shell in DMSO. But the hydrogen-bonded bilayer self-assembly has a self-assembled methanol shell and an interior aggregate of PHAOEs in methanol. The self-assemblies of PHAOEs motivate the methanols to self-assemble. The large delocalized amide structure results in the fast spectral diffusion of the carbonyl stretching mode.Communicated by Ramaswamy H. Sarma.

Ultrasonic Degradation of Konjac Glucomannan and the Effect of Freezing Combined with Alkali Treatment on Their Rheological Profiles

The effect of freezing combined with alkali treatment on physicochemical property of konjac glucomannan (KGM) with different molecular weight was investigated in this work. The properties and structure of degraded KGM was characterized by means of intrinsic viscosity measurement, atomic force microscope (AFM) and Fourier transformation infrared (FT-IR). The results suggested that the intrinsic viscosity of KGM solution gradually decreased during the ultrasonic treatment. The AFM observation indicated that KGM with lower viscosity average molecular weight had smaller height and lateral diameter of molecules. The main repeating units of the KGM chain could not be destroyed no matter how long the KGM was sonicated. Rheometrical studies revealed that with increasing alkali concentration from 0% to 0.36%, both viscosities and shear stress of deacetylated konjac glucomannan (Da-KGM) system were increased and moduli G' were substantially higher in either freezing or unfreezing samples. Da-KGM system performed a solid-like behavior (G' > G'') along the frequency range after freezing treatment. With increasing sonication time, both viscosity and shear stress of unfreezing samples were decreased while had an inverse effect for freezing treated samples. The modulus G' and G'' declined for unfreezing samples but rise significantly for freezing treated samples with increase of sonication time.