Modification of low-salt myofibrillar protein using combined ultrasound pre-treatment and konjac glucomannan for improving gelling properties: Intermolecular interaction and filling effect

Effect of psyllium husk powder on the gelation behavior, microstructure, and intermolecular interactions in myofibrillar protein gels from Andrias davidianus

The interaction between proteins and soluble dietary fibers plays a vital role in the development of animal-derived foods. Herein, the effects of different contents (0-3.0%) of round-bracted psyllium husk powder (PHP) on the gelation behavior, microstructure, and intermolecular interactions of Andrias davidianus myofibrillar protein (MP) were investigated. Rheological and chemical forces suggested that PHP (1.5%-2.0%) enhanced the functional properties of MP at low ionic strength, thereby increasing the viscoelasticity of mixed gels. SDS-PAGE revealed that PHP reinforced the cross-linking and aggregation of protein molecules. Circular dichroism spectroscopy, low-field nuclear magnetic resonance, and scanning electron microscopy demonstrated that PHP induced the transformation of α-helix (decreased by 14.85%) to an ordered β-sheet structure (increased by 81.58%), which was more favorable for the formation of dense network structure and improved (10.53%) the water retention of MP gels. This study provided new insights for PHP to effectively meliorate the heat-induced gelling properties of MP.

Insight into the effects of ultrasound-assisted intermittent tumbling on the gelation properties of myofibrillar proteins: Conformational modifications, intermolecular interactions, rheological properties and microstructure

The aim of the present study was to evaluate the effects of ultrasound-assisted intermittent tumbling (UT) at 300 W, 20 kHz and 40 min on the conformation, intermolecular interactions and aggregation of myofibrillar proteins (MPs) and its induced gelation properties at various tumbling times (4 and 6 h). Raman results showed that all tumbling treatments led the helical structure of MPs to unfold. In comparison to the single intermittent tumbling treatment (ST), UT treatment exerted more pronounced effects on strengthening the intermolecular hydrogen bonds and facilitating the formation of an ordered β-sheet structure. When the tumbling time was the same, UT treatment caused higher surface hydrophobicity, fluorescence intensity and disulfide bond content in the MPs, inducing the occurrence of hydrophobic interaction and disulfide cross-linking between MPs molecules, thus forming the MPs aggregates. Additionally, results from the solubility, particle size, atomic force microscopy and SDS-PAGE further indicated that, relative to the ST treatment, UT treatment was more potent in promoting the polymerization of myosin heavy chain. The MPs aggregates in the UT group were more uniform than those in the ST group. During the gelation process, the pre-formed MPs aggregates in the UT treatment increased the thermal stability of myosin, rendering it more resistant to heat-induced unfolding of the myosin rod region. Furthermore, they improved the protein tail-tail interaction, resulting in the formation of a well-structured gel network with higher gel strength and cooking yield compared to the ST treatment.

Potential mechanisms and effects of ultrasound treatment combined with pre- and post-addition of κ-carrageenan on the gelling properties and rheological behavior of myofibrillar proteins under low-salt condition

This study investigated the effect of ultrasound (US) combined with pre- and post-addition of κ-carrageenan (KC) on the gelling properties, structural characteristics and rheological behavior of myofibrillar proteins (MP) under low-salt conditions. The results showed that US combined with either pre- or post-addition of KC rendered higher gel strength and water holding capacity (WHC) of MP gels than those treated with US alone and added with KC alone (P < 0.05). US combined with pre-addition of KC facilitated the binding between MP and KC, which enhanced the gel strength and WHC of the mixed MP gels and significantly improved the rheological behavior of MP. This was also confirmed by the highest surface hydrophobicity, disulfide bonds and β-sheet content of the MP gels with US combined with pre-addition of KC. Moreover, microstructural results reflected a denser structure for the pre-addition of KC in combination with US. However, US combined with post-addition of KC resulted in limited MP unfolding and relatively weak hydrophobic interactions in the composite gels, which were less effective in improving the gel properties of the MP gels. This study provides potential strategies for enhancing the gelling properties of low-salt meat products via application of US and KC.

An unfolding/aggregation kinetic instructed rational design towards improving graft degree of glycation for myofibrillar protein

Glycation is an effective strategy for the application of myofibrillar protein (MP) in beverage formulas by improving water solubility. In conventional glycation, the efficiency was limited as MP-saccharides conjugates mostly produced at low temperature due to thermosensitivity. This study was aimed to explore unfolding/aggregation kinetics of MP, including aggregate behavior, structural characteristics, and micromorphology, which guided the selection of temperature for glycation. It was shown that 40 °C/47.5 °C were critical temperature for MP unfolding/aggregation, respectively. Accordingly, an innovative technology of glycation (cyclic continuous glycation, CCG) was established by combining such temperatures. The results confirmed that cyclic continuous heating (CCH) inhibited excessive exposure of sulfhydryl and hydrophobic groups impeding protein aggregation. Importantly, it was revealed that rational designed CCG promoted covalent binding of MP to glucose by regulating unfolding-aggregation balance, exhibiting higher glycation degree. Overall, CCG-modified MP is expected to motivate the application of meat proteins in food formulations.

Salt reduction in myofibrillar protein gel via inhomogeneous distribution of sodium-containing encapsulated fish oil coacervate: Mucopenetration ability of sodium carboxymethyl cellulose

The potential application of fish oil microcapsules as salt reduction strategies in low-salt myofibrillar protein (MP) gel was investigated by employing soy protein isolates/carboxymethyl cellulose sodium (SPI-CMC) coacervates enriched with 25 mM sodium chloride and exploring their rheological characteristics, taste perception, and microstructure. The results revealed that the SPI-CMC coacervate phase exhibited the highest sodium content under 25 mM sodium level, albeit with uneven distribution. Notably, the hydrophilic and adhesive properties of CMC to sodium facilitated the in vitro release of sodium during oral digestion, as evidenced by the excellent wettability and mucopenetration ability of CMC. Remarkably, the fish oil microcapsules incorporating SPI-CMC as the wall material, prepared at pH 3.5 with a core-to-wall ratio of 1:1, demonstrated the highest encapsulation efficiency, which was supported by the strong hydrogen bonding. Interestingly, the presence of SPI-CMC coacervates and fish oil microcapsules enhanced the interaction between MPs and strengthened the low-salt MP gel network. Coupled with electronic tongue analysis, the incorporation of fish oil microcapsules slightly exacerbated the non-uniformity of sodium distribution. This ultimately contributed to an enhanced perception of saltiness, richness, and aftertaste in low-salt protein gels. Overall, the incorporation of fish oil microcapsules emerged as an effective salt reduction strategy in low-salt MP gel.

Design of colloid structure to realize gel salt reduction: a review

Excessive consumption of salt is associated with increased incidence of cardiovascular diseases, hypertension, diabetes, and other health issues. However, it is challenging to find appropriate strategies that balance sensory qualities while achieving sodium reduction as salt plays a crucial role in providing desired appearance, texture, and taste. The impact of hydrocolloid properties (addition and type) on saltiness perception were reviewed. Additionally, considering the interactions between food components, both covalent and noncovalent, we propose designing specialized colloidal structures capable of binding sodium ions to enhance salt-taste perception. The effects of hydrocolloids on the physicochemical, structural, and sensory qualities of gel foods are then discussed. Finally, by addressing current issues with low-salt foods and consumer demands, we provide a future outlook for low-salt food development. The selection of suitable hydrocolloids and precise control of the addition are crucial considerations for achieving salt reduction. The interaction between hydrocolloids and other food components can be utilized to design specialized colloidal structures, thereby accomplishing gel-based salt reduction and enhancing properties. This review serves as a theoretical reference for developing healthy, nutritious, and flavorful low-salt foods that can aid in the prevention and mitigation of diseases associated with excessive salt consumption.

Elucidating the mechanisms of ultrasound treatment combined with κ-carrageenan addition enhancing the gelling properties of heat-induced myofibrillar protein gel

This work investigated the effect of ultrasound (US) treatment synergized with κ-carrageenan (KC) on the gel properties, structural characteristics and microstructures of myofibrillar protein (MP) gel. The results demonstrated that simply adding KC enhanced the gel strength and water holding capacity (WHC) of MP gels. Moreover, the gel strength and WHC of MP gels were increased by 56.67 % and 76.19 % via 20 min US treatment synergized with KC, which was mainly attributed to the changes in sulfhydryl content, surface hydrophobicity, and fluorescence intensity of MP gels. Based on the results of molecular docking and secondary structure, it can be hypothesized that the synergistic effect resulted in the rearrangement of the proteins, which altered the interaction site between MP gels and KC, accompanied by stronger binding. Furthermore, the microstructural results indicated that moderate US treatment (20 min) facilitated the production of a more compact and denser MP gels matrix with uniformly sized and distributed pores. However, excessive US treatment (40 and 50 min) caused the MP gels to form looser and disordered gel structure, which reduced the gel strength and WHC. This study suggested that combining of US and KC was a potential tactic to enhance the gelling properties of heat-induced MP gels.

Inhibition of water-diluted precipitate formation from egg whites by ultrasonic pretreatment: Insights from quantitative proteomics analysis

The formation of the egg white precipitate (EWP) during dilution poses challenges in food processing. In this paper, the effects of 90 W and 360 W ultrasonic intensities on the inhibition of EWP formation were investigated. The findings revealed that 360 W sonication effectively disrupted protein aggregates, decreasing the dry matter of EWP by 5.24 %, particle size by 57.86 %, and viscosity by 82.28 %. Furthermore, the ultrasonic pretreatment unfolded protein structures and increased the content of β-sheet structures. Combined with quantitative proteomics and intermolecular forces analysis, the mechanism by which ultrasonic pretreatment inhibited water-diluted EWP formation by altering protein interactions was proposed: ultrasonic pretreatment disrupted electrostatic interactions centered on lysozyme, as well as hydrogen-bonding interactions between ovomucin and water. In conclusion, our research provides valuable insights into the application of ultrasonic pretreatment as a means to control and improve the quality of egg white-based products.