Effects of ultrasound frequency mode on myofibrillar protein structure and emulsifying properties

The utilization of an ultrasonic mung bean protein-starch conjugate as a fat substitute in whipping cream

BACKGROUND

Amidst the rising trend of healthy eating, there is a surge in demand for low-fat food options. Within the realm of fat substitutes, modified proteins have shown the most effective ability to replace fat due to their nutritional attributes and functional properties. This study focused on the development of a fat substitute for low-fat whipping cream using the conjugate of ultrasonic mung bean protein and mung bean starch.

RESULTS

Our findings revealed that the emulsifying properties and solubility of the conjugates were significantly superior to those of mung bean protein alone (P < 0.05). This enhancement was attributed to a smaller particle size, depolymerization of protein molecules and increased total sulfhydryl content, especially the conjugate formed by 60 min ultrasonic mung bean protein and mung bean starch (UMBP60+MS). Incorporating UMBP60+MS as a fat substitute at a 10% ratio in the formulation of low-fat whipping cream resulted in a product with enhanced apparent viscosity, superior environmental stability, and commendable sensory characteristics. Moreover, the fat digestion rate was significantly reduced by 13.5% with the 10% substitution. This 10% substitution also endowed the whipping cream with the most desirable β'-type crystal morphology and the most stable three-dimensional network structure. An intimate encapsulation of fat globules by the conjugate was observed using cryogenic scanning electron microscopy.

CONCLUSION

The UMBP60+MS conjugate emerged as an effective fat substitute in whipping cream, providing significant contributions to addressing health concerns in the food industry. © 2024 Society of Chemical Industry.

Investigating the cryoprotective mechanism of phosphorylated nano-chitin in shrimp (Litopenaeus vannamei) during frozen storage

This study aims to explore the cryoprotective effects of phosphorylated surface deacetylated chitin nanofibers (PS-ChNFs) on shrimp. Compared to the control- and those treated with surface deacetylated chitin nanofibers (S-ChNFs) or sodium tripolyphosphate (STPP), the PS-ChNFs-treated group showed lower thawing losses and cooking losses, alongside higher myofibrillar protein concentrations and Ca2+-ATPase activity in frozen shrimp. Additional, PS-ChNFs-treated significantly delayed protein aggregation and the deterioration of the secondary structure in shrimp during frozen storage (p < 0.05). Furthermore, microscopy analysis revealed PS-ChNFs effectively inhibited ice crystal growth and slowed the damage to muscle tissue structures. Molecular simulations suggested that the cryoprotective effect of PS-ChNFs were primarily achieved through the "water substitution" and "glassy state" hypotheses, wherein PS-ChNFs formed hydrogen bonds with water and reduced the number of water molecules around myosin. These findings indicate that PS-ChNFs hold significant potential as cryoprotectants for freeze-stored aquatic products.

Lactic acid fermentation improves rehydration and emulsifying properties of spray-dried egg yolk powder

In this study, we investigated the protein structures, powder characteristics, as well as rehydration and emulsifying properties of spray-dried egg yolk powder after short-time lactic acid fermentation (3.5 h). Results indicate that fermentation improved the rehydration and emulsifying properties of yolk powder. Limosilactobacillus reuteri-fermented yolk powder exhibited better wettability due to the porous structure of particles and higher hydrophilicity. Lacticaseibacillus rhamnosus-fermented yolk powder had an enhanced coefficient of stability due to its smaller particles and higher surface charge. The higher water solubility of fermented yolk powder samples is mainly attributed to their lower hydrophobicity and higher zeta potential. The enhanced emulsifying activity of fermented yolk powder samples is primarily related to their increased β-turn structure and better solubility. Furthermore, fermentation treatment altered powder moisture content and bulk densities, while not affecting its flow behavior and thermal stability. This study provides an effective approach to improving the quality of yolk powder.

Effect of ultrasonic pretreatment on the emulsion rheological properties and interface protein structure of epigallocatechin-3-gallate and rice bran protein complex

The effect of ultrasonic pretreatment on the emulsion rheological properties and the structural characteristics of interface-adsorbed protein (IAP) and interface-unabsorbed protein (IUP) of rice bran protein and epigallocatechin-3-gallate complex (RBP-EGCG) were studied. Compared to RBP-EGCG without ultrasonic pretreatment, appropriate ultrasonic pretreatment (ultrasonic power was 425 W) enhanced the IAP trypsin sensitivity (from 3.20 to 3.73), increased the IUP surface hydrophobicity (from 12.59 to 20.87), and decreased the ζ-potential (from -24.93 mV to -36.88 mV) and particle size (from 567.30 nm to 273.13 nm) of IUP, thereby increasing the viscosity and viscoelasticity of emulsion. Compared to appropriate ultrasonic pretreatment, high-power ultrasonic pretreatment (ultrasonic power was 500 W) attenuated the IAP trypsin sensitivity, and increased the ζ-potential and particle size of IUP, thereby decreasing the viscosity and viscoelasticity of emulsion. Overall, ultrasonic pretreatment changed the EGCG-RBP emulsion viscoelasticity by regulating spatial structural characteristics and flexibility of interface protein.

Effect of ultrasound on the functional properties and structural changes of chicken liver insoluble proteins isolated by isoelectric solubilization/precipitation

The studies investigated the effects of different ultrasonic powers (180, 360 and 540 W) on the functional properties and structural changes of chicken liver insoluble proteins (CLIPs) isolated by isoelectric solubilization/precipitation (ISP) (with alkaline solubilization at pH 11.0 and pH 12.0 respectively, and acid precipitation at pH 5.5). Results indicated that ultrasonic significantly increased the solubility of ISP-isolated CLIPs, and narrowed the particle size distribution of D3,2 and D4,3 (P < 0.05). The highest solubility was observed at pH 11.0 and 360 W ultrasound treatment, reaching 77.26 %. The ultrasonic with 360 W exhibited higher shear stress and apparent viscosity. Spectroscopy revealed that compared to without ultrasonic treatment, there was an increase in β-sheet and random curling content accompanied by a decrease in β-turn and α-helix structure when ultrasonication. Ultrasound altered the tyrosine hydrophobic residues to be exposed to the surface of the ISP-isolated CLIPs, thus improving the hydrophilicity. Overall, ultrasound combined with ISP treatment effectively improved the functional properties of CLIPs, and it might be a potential, safe and efficient method for improving the processing properties and broadening the application of insoluble animal-derived proteins.

Effect of ultrasound combined with plasma protein treatment on the structure, physicochemical and rheological properties of myofibrillar protein

This study aimed to investigate the effect of ultrasound combined with plasma protein (UPP) treatment on the structure, physicochemical and rheological properties of myofibrillar protein (MP). The results indicated that the UPP group caused changes in the secondary structure, increased fluorescence intensity and enhanced surface hydrophobicity of MP. Then, UPP significantly decreased the content of free and total sulfhydryl group, and high molecular weight protein contents were observed in MP. These findings implied moderate cross-linking and aggregation between plasma protein and MP in this ultrasound treatment. Furthermore, the physical characteristics, stability and rheological properties of MP were improved in UPP, as evidenced by increased storage modulus and decreased loss angle tangent. Therefore, this study suggested that the combined treatment not only had the potential to enhance the product quality in the process of ground meat, but also improved the utilization rate and added value of plasma proteins.

Role of ultrasound and pectin in regulating the foaming properties and baking applications of liquid egg white

The capacity of liquid egg white (LEW) to generate foam has become crucial in food processing. This study investigated the impact of ultrasound (US) and pectin in regulating the foaming properties and baking applications of LEW. Results showed that US treatment combined with pectin significantly (P < 0.05) improved foam ability (FA) from 142 ± 3.464 % to 236 ± 2.65 % and foam stability (FS) from 33.32 ± 2.63 % to 60.4 ± 1.82 %. The lowest surface tension achieved was 44.691 mN/m for EW600 + 1 % P. High-intensity US and pectin also enhanced the ξ-potential, solubility, and surface hydrophobicity. Dynamic rheological analysis indicated increased in apparent viscosity and viscoelasticity. Furthermore, increasing US power led to significant turbidity enhancements, rising from 41.22 ± 0.093 % to 96.30 ± 0.026 % (P < 0.05). Importantly, angel cakes made from US-treated LEW with pectin showed a higher specific volume, with EW600 + 1 % P reaching 3.2297 ± 0.017 mL/g compared to 2.9258 ± 0.022 mL/g for the control (P < 0.05). These findings suggest that US and pectin enhance foaming rates and baking performance, addressing reduced FS in egg whites (EW) and angel cakes when different US treatments were applied alone.

Mitigation of mechanical damage and protein deterioration in giant river prawn (Macrobrachium rosenbergii) by multi-frequency ultrasound-assisted immersion freezing

In order to investigate the effects of multi-frequency ultrasound-assisted immersion freezing (MUIF) on the meat quality of Macrobrachium rosenbergii, tail meat was subjected to different MUIF treatments respectively, namely 20 + 40 kHz (MUIF-20 + 40), 20 + 60 kHz (MUIF-20 + 60), 40 + 60 kHz (MUIF-40 + 60) and 20 + 40 + 60 kHz (MUIF-20 + 40 + 60), and the immersion freezing (IF) as control. Results showed that average diameter of ice crystals was 28 μm in IF, and that was only 8 μm in MUIF-20 + 40 + 60. When compared to IF, MUIF alleviated oxidative deterioration of lipids and proteins, but only at higher ultrasound frequency (MUIF-40 + 60; MUIF-20 + 40 + 60). Carbonyl content of MUIF-20 + 40 + 60 was only 40% of that in IF. Similarly, protein denaturation was inhibited in MUIF (except for MUIF-20 + 40). Transmission electron microscopy showed greater distortion of the ultrastructural components in IF, MUIF-40 + 60, and MUIF-20 + 40 + 60, suggested by bended Z-line. In conclusion, MUIF can be an effective strategy to mitigate mechanical damage and protein deterioration in the meat of Macrobrachium rosenbergii.

Fabrication and characterization of edible Pickering emulsion stabilized by donkey myofibrillar protein

This study aims to investigate the properties of edible Pickering emulsions (PEs) stabilized by donkey myofibrillar protein (DMP). The DMP was characterized by an atomic force microscope and interfacial tensiometer. The PEs stabilized by DMP were characterized by a confocal laser scanning microscope, rheometer, and lumisizer stability analyzer. The results showed that the DMP particles were spherical nanoparticles with an average size of 143.97 nm. The DMP could reduce the oil-water interfacial tension very well. The emulsifying activity index was below 14.06 m2/g, and the emulsion stability index was up to 93.76% when the DMP concentration was above 10 mg/mL. Increasing the concentration of DMP (5 mg/mL to 25 mg/mL) could decrease the emulsion droplet sizes and fluidity of the PEs and increase the viscoelasticity of the PEs. The increase in the oil-water ratio (1:9 to 5:5) resulted in a larger average emulsion droplet size, reduced fluidity, and enhanced viscoelasticity. The increase in DMP concentration (from 5 mg/mL to 25 mg/mL) and oil-water ratio (from 1:9 to 4:6) improved the physical stability of the PEs. These results may expand the application of DMP and provide new insight into developing edible PEs suitable for the formulation of functional foods.

Effect of starch categories and mass ratio of TA/starch on the emulsifying performance and stability of emulsions stabilized by tannic acid-starch complexes

This study compounded natural corn starch (CS), mung bean starch (MBS) and potato starch (PS) with tannic acid (TA) to stabilize O/W Pickering emulsion. The effect of TA/starch mass ratio (0-0.25) and three starch categories on particle properties, emulsifying properties, lipid oxidation, freeze-thaw stability, emulsion powder and digestive properties were comprehensibly investigated. In detail, the TA/starch complexes size increased gradually (91.14 nm-200.87 nm) and the hydrophobicity first increased and then decreased (TA/CS > TA/MBS > TA/PS) with increasing TA/starch mass ratio. In addition, the emulsifying ability of TA/starch complexes also increased first and then decreased with increasing mass ratio, especially TA/CS system was the best, which was the same as the hydrophobicity conclusion (θow = 80.46°). Moreover, four starch-based emulsion application characteristics were further evaluated to reveal interface structure. Compared to CS and PS system, TA/MBS emulsion had stronger ability to resist the oil oxidation (TBA = 2.54 μg/mL), destruction of ice crystal (whiter emulsion powder) and digestive enzymes (FFAs = 75.33 %). It mainly attributed to the crosslinking network structure and the highest surface load of TA/MBS complexes. This study would provide new ideas for the design and application of emulsifying properties and emulsion stability.

Effects of ultrasonic treatment on the structure and functional characteristics of myofibrillar proteins from black soldier fly

In the process of utilizing black soldier fly larvae (BSFL) lipids to develop biodiesel, many by-products will be produced, especially the underutilized protein components. These proteins can be recycled through appropriate treatment and technology, such as the preparation of feed, biofertilizers or other kinds of bio-products, so as to achieve the efficient use of resources and reduce the generation of waste. Myofibrillar protein (MP), as the most important component of protein, is highly susceptible to environmental influences, leading to oxidation and deterioration, which ultimately affects the overall performance of the protein and product quality. For it to be high-quality and fully exploited, in this study, black soldier fly myofibrillar protein (BMP) was extracted and primarily subjected to ultrasonic treatment to investigate the impact of varying ultrasonic powers (300, 500, 700, 900 W) on the structure and functional properties of BMP. The results indicated that as ultrasonic power increased, the sulfhydryl content and turbidity of BMP decreased, leading to a notable improvement in the stability of the protein emulsion system. SEM images corroborated the changes in the microstructure of BMP. Moreover, the enhancement of ultrasound power induced modifications in the intrinsic fluorescence spectra and FTIR spectra of BMP. Additionally, ultrasonic treatment resulted in an increase in carbonyl content and emulsifying activity of BMP, with both peaking at 500 W. It was noteworthy that BMP treated with ultrasound exhibited stronger digestibility compared to the untreated. In summary, 500 W was determined as the optimal ultrasound parameter for this study. Overall, ultrasound modification of insect MPs emerges as a dependable technique capable of altering the structure and functionality of BMP.

Investigating the impact of ultrasound on the structural, physicochemical, and emulsifying characteristics of Dioscorin: Insights from experimental data and molecular dynamics simulation

This study investigated the impact of ultrasound treatment on dioscorin, the primary storage protein found in yam tubers. Three key factors, namely ultrasound power, duration, and frequency, were focused on. The research revealed that ultrasound-induced cavitation effects disrupted non-covalent bonds, resulting in a reduction in α-helix and β-sheet contents, decreased thermal stability, and a decrease in the apparent hydrodynamic diameter (Dh) of dioscorin. Additionally, previously hidden amino acid groups within the molecule became exposed on its surface, resulting in increased surface hydrophobicity (Ho) and zeta-potential. Under specific ultrasound conditions (200 W, 25 kHz, 30 min), Dh decreased while Ho increased, facilitating the adsorption of dioscorin molecules onto the oil-water interface. Molecular dynamics (MD) simulations showed that at lower frequencies and pressures, the structural flexibility of dioscorin's main chain atoms increased, leading to more significant fluctuations between amino acid residues. This transformation improved dioscorin's emulsifying properties and its oil-water interface affinity.

The Effect of Ultrasound Treatment on the Structural and Functional Properties of Tenebrio molitor Myofibrillar Protein

The objective of this study was to explore the impacts of various ultrasonic powers (0, 300, 500, 700, and 900 W) on the structure and functional attributes of the myofibrillar protein (MP) of Tenebrio molitor. As the ultrasonic intensity escalated, the extraction efficiency and yield of the MP rose, while the particle size and turbidity decreased correspondingly. The reduction in sulfhydryl group content and the increase in carbonyl group content both suggested that ultrasonic treatment promoted the oxidation of the MP to a certain extent, which was conducive to the formation of a denser and more stable gel network structure. This was also affirmed by SEM images. Additionally, the findings of intrinsic fluorescence and FTIR indicated that high-intensity ultrasound significantly altered the secondary structure of the protein. The unfolding of the MP exposed more amino acid residues, the α-helix decreased, and the β-helix improved, thereby resulting in a looser and more flexible conformation. Along with the structural alteration, the surface hydrophobicity and emulsification properties were also significantly enhanced. Besides that, SDS-PAGE demonstrated that the MP of T. molitor was primarily composed of myosin heavy chain (MHC), actin, myosin light chain (MLC), paramyosin, and tropomyosin. The aforementioned results confirmed that ultrasonic treatment could, to a certain extent, enhance the structure and function of mealworm MP, thereby providing a theoretical reference for the utilization of edible insect proteins in the future, deep-processing proteins produced by T. molitor, and the development of new technologies.

Study on stabilized mechanism of high internal phase Pickering emulsions based on commercial yeast proteins: Modulating the characteristics of Pickering particle via sonication

The primary significance of this work is that the commercial yeast proteins particles were successfully used to characterize the high internal phase Pickering emulsions (HIPPEs). The different sonication time (0,3,7,11,15 min) was used to modulate the structure and interface characteristics of yeast proteins (YPs) that as Pickering particles. Immediately afterward, the influence of YPs particles prepared at different sonication time on the rheological behavior and coalescence mechanism of HIPPEs was investigated. The results indicate that the YPs sonicated for 7 min exhibited a more relaxed molecular structures and conformation, the smallest particle size, the highest H0 and optimal amphiphilicity (the three-phase contact (θ) was 88.91°). The transition from extended to compact conformations of YPs occurred when the sonication time exceeded 7 min, resulting in an augmentation of size of YPs particles, a reduction in surface hydrophobicity (H0), and an elevation in hydrophilicity. The HIPPEs stabilized by YPs particles sonicated for 7 min exhibited the highest adsorption interface protein percentage and a more homogeneous three-dimensional (3D) protein network, resulting in the smallest droplet size and the highest storage (G'). The HIPPEs sample that stabilized by YPs particles sonicated for 15 min showed the lowest adsorption protein percentage. This caused a reduction in the thickness of its interface protein layer and an enlargement in the droplet diameter (D [3,2]). It was prone to droplet coalescence according to the equation used to evaluate the coalescence probability of droplets (Eq (2)). And the non-adsorbed YPs particles form larger aggregation structures in the continuous phase and act as "structural agents" in 3D protein network. Therefore, mechanistically, the interface protein layer formed by YPs particles sonicated 7 min contributed more to HIPPEs stability. Whereas the "structural agents" contributed more to HIPPEs stability when the sonication time exceeded 7 min. The present results shed important new light on the application of commercial YPs in the functional food fields, acting as an available and effective alternative protein.

Combined effects of high-intensity ultrasound treatment and hydrogen peroxide addition on the thermal stabilities of myofibrillar protein emulsions at low ionic strengths

In this study, the effects of high-intensity ultrasound (HIU) treatment combined with hydrogen peroxide (H2O2) addition on the thermal stability of myofibrillar protein (MP)-stabilized emulsions in low-salt conditions were investigated. Results showed that compared to using either HIU or H2O2 treatment alone, HIU treatment combined with H2O2 was most effective in enhancing the physical stability of emulsions. Moreover, the emulsion stabilized by MPs co-treated with HIU and H2O2 exhibited the most uniform distribution, highest absolute zeta potential, and optimal rheological properties upon heating. This combination effect during heating was caused by the inhibition of disulfide bond cross-linking of myosin heads by H2O2 and the dissociation of filamentous myosin structures using the HIU treatment. In addition, the results of oxidative stability analysis indicated that the addition of H2O2 increased the content of oxidation products; however, the overall influence on the oxidative stability of emulsions was not significant. In conclusion, the combination of HIU and H2O2 treatment is a promising approach to suppress heat-induced MP aggregation and improve the thermal stability of corresponding emulsions.

Covalent and non-covalent interaction of myofibrillar protein and cyanidin-3-O-glucoside: focus on structure, binding sites and in vitro digestion properties

BACKGROUND

The aim of this study was to investigate the effects of covalent and non-covalent interactions between myofibrillar protein (MP) and cyanidin-3-O-glucoside (C3G) on protein structure, binding sites, and digestion properties. Four methods of inducing covalent cross-linking were used in the preparation of MP-C3G conjugates, including tyrosinase-catalyzed oxidation, alkaline pH shift treatment, free radical grafting, and ultrasonic treatment. A comparison was made between MP-C3G conjugates and complexes, and the analysis included sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), C3G binding ratio, liquid chromatography-tandem mass spectrometry (LC-MS/MS), protein side-chain amino acids, circular dichroism spectroscopy, three-dimensional fluorescence, particle size, and in vitro simulated digestion.

RESULTS

Covalent bonding between C3G and amino acid side chains in MP was confirmed by LC-MS/MS. In covalent bonding, tryptophan residues, free amino groups and sulfhydryl groups were all implicated. Among the 22 peptides covalently modified by C3G, 30 modification sites were identified, located in lysine, histidine, tryptophan, arginine and cysteine. In vitro simulated digestion experiments showed that the addition of C3G significantly reduced the digestibility of MP, with the covalent conjugate showing lower digestibility than the non-covalent conjugate. Moreover, the digestibility of protein decreased more during intestinal digestion, possibly because covalent cross-linking of C3G and MP further inhibited trypsin targeting sites (lysine and arginine).

CONCLUSION

Covalent cross-linking of C3G with myofibrillar proteins significantly affected protein structure and reduced protein digestibility by occupying more trypsin binding sites. © 2023 Society of Chemical Industry.

Improving stability and bioavailability of curcumin by quaternized chitosan coated nanoemulsion

This study aims to enhance the stability and bioavailability of curcumin (Cur) using nanoemulsion coating technology. The nanoemulsion system was developed by encapsulating Cur with quaternized chitosan (QMNE), and the nanoemulsion containing Cur and medium-chain triglyceride (MCT) oil (MNE) was used as control sample. The microstructure of the nanoemulsion was examined using Dynamic light scattering (DLS), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The storage, thermal, ionic strength, and pH stability of QMNE were also evaluated, respectively. The results indicate that QMNE demonstrates superior stability, in vitro gastric fluid stability, bioavailability compared to MNE. QMNE exhibits excellent emulsification activity and stability. In addition, QMNE shows significant protection against oxidation in both emulsion systems after different heat treatments. The antimicrobial activity results reveal that QMNE exhibits greater efficacy than that of MNE. Consequently, this study provides valuable insights into the formulation of a system to encapsulate Cur and the improvement of its stability and bioavailability.

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

The quality deterioration of low-salt meat products has been gained ongoing focus of researchers. In this study, konjac glucomannan (KGM) was used to alleviate the finiteness of ultrasound treatment on the quality improvement of low-salt myofibrillar protein (MP), and the modification sequence was also investigated. The results revealed that the single and double sequential modification by utilizing KGM and ultrasound significantly influenced the gelation behavior of low-salt MPs. The uniform MP-KGM mixture formed by a single ultrasound treatment had limited protein unfolding, resulting in relatively weak intermolecular forces in the composite gel. Importantly, ultrasound pre-treatment combined with KGM modification promoted the unfolding and moderate thermal aggregation of proteins and remarkably improved the rheological behaviors and gel strength of the composite gel. This result could also be corroborated by the highest percentage of trans-gauche-trans conformation of SS bridges and maximum β-sheet proportion. Furthermore, molecular dynamic simulation and molecular docking elucidated that the hydrogen bond length between protein and KGM was shortened after ultrasound pre-treatment, which was the molecular basis for the enhanced intermolecular interactions. Therefore, ultrasound pre-treatment combined with KGM can effectively improve the gelling properties of low-salt MPs, providing a practical method for the processing of low-salt meat products.

Mono-frequency ultrasonic-assisted thawing of frozen goose meat: Influence on thawing efficiency, product quality and microstructure

This study aimed to investigate the influences of mono-ultrasound assisted thawing on the thawing efficiency, product quality and conformational characteristics of frozen goose meat. The thawing time, thawing loss, muscle quality, and microstructure of frozen goose meat were studied. The results displayed that ultrasonic-assisted thawing effectively reduced the thawing time by 45.37-57.58% compared with non-sonicated group, and significantly decreased the thawing loss. For the quality properties of goose meat tissue, ultrasound-assisted thawing with single-frequency of 50 kHz indicated a lower protein turbidity; meanwhile, hardness values were also significantly increased, and displayed a higher springiness, gumminess and chewiness of goose meat tissue. The microstructure analysis exhibited that the conformation of goose myofibrillar protein (MP) was modified following ultrasonic-assisted thawing, and became closer and more irregular. Therefore, ultrasound-assisted thawing treatments at 50 kHz mono-frequency (temperature 25℃) have a high potential application value in the thawing research of frozen goose meat, and lay a theoretical foundation for use in the meat process industries.

Emulsifying properties of wheat germ protein: Effect of different ultrasonic treatment

The effect of ultrasonic treatment on emulsifying properties of wheat germ protein (WGP) was studied in this paper. WGP was subjected to low frequency (20 kHz), high intensity ultrasonic treatment at different power (200, 400, 600, 800 W) for 10 min, or different time (2, 4, 6, 8, 10, 15, 20 min) at 400 W. The emulsifying activity index and emulsion stability index of WGP were significantly improved, and the emulsion droplet was smaller and more uniform after ultrasound treatment. Ultrasound increased the adsorbed WGP concentration at the oil-water interface and reduced the interfacial tension, which explained the improved emulsifying properties of WGP. The investigation on molecular properties and protein conformation showed that ultrasound processing increased solubility, but decreased particle size and surface charge of WGP. Ultrasound processing resulted in the unfolding of the protein molecular structure indicated by the increase of surface hydrophobicity and surface free sulfhydryl group levels, and the decrease of intrinsic fluorescence intensity. Correlation analysis showed that the changes in WGP solubility, particle size, and surface hydrophobicity were the main driven factors for the improved emulsifying properties of WGP.

Effect of multi-mode sweep frequency ultrasound pretreatment on properties of the zeins and ACE inhibitory peptides activity of the hydrolysates

Effects of sweep frequency ultrasound (SFU) pretreatment of a new multifunctional ultrasonic equipment on hydrolysis characteristics of zeins and angiotensin-converting enzyme (ACE) inhibitory activity of zein hydrolysates were investigated. Degree of hydrolysis of zeins reached the highest of 25.93 % and 25.72 % at 40 kHz and 25/40 kHz, respectively. While 25/40 kHz increased solubility, surface hydrophobicity, particle size uniform of zeins and ACE inhibitory activities of the hydrolysates significantly. Endogenous fluorescence indicated that 25/40 kHz promoted unfolding of protein molecules and exposure of hydrophobic residues, thereby facilitating enzymatic hydrolysis. Circular dichroism spectrum and Fourier transform infrared spectrometer illustrated that 25/40 kHz unfolded protein molecules and decreased α-helical contents remarkably. Gel permeation chromatography showed that more small-molecule active peptides were obtained from hydrolysates at 25/40 kHz. In conclusion, SFU pretreatment at 25/40 kHz with the new equipment before proteolysis is an efficient method to improve ACE inhibitory activity of the hydrolysates.

Effect of polyphenolic structure and mass ratio on the emulsifying performance and stability of emulsions stabilized by polyphenol-corn amylose complexes

O/W emulsions stabilized by polyphenol/amylose (AM) complexes with several polyphenol/AM mass ratios and different polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) were prepared by a high-intensity ultrasound emulsification technique. The effect of the pyrogallol group number of polyphenols and the mass ratio of polyphenols/AM on polyphenol/AM complexes and emulsions was studied. The soluble and/or insoluble complexes gradually formed upon adding polyphenols into the AM system. However, insoluble complexes were not formed in the GA/AM systems because GA has only one pyrogallol group. In addition, the hydrophobicity of AM could also be improved by forming polyphenol/AM complexes. The emulsion size decreased with increasing pyrogallol group number on the polyphenol molecules at a fixed ratio, and the size could also be controlled by the polyphenol/AM ratio. Moreover, all emulsions presented various degrees of creaming, which was restrained by decreasing emulsion size or the formation of a thick complex network. The complex network was enhanced by increasing the ratio or pyrogallol group number on the polyphenol molecules, which was because the increasing number of complexes was adsorbed onto the interface. Altogether, compared to GA/AM and EGCG/AM, the TA/AM complex emulsifier had the best hydrophobicity and emulsifying properties, and the TA/AM emulsion had the best emulsion stability.

Improvement of the emulsifying properties of mixed emulsifiers by optimizing ultrasonic-assisted processing

Optimizing ultrasound (ULD)-assisted flavonoid modification is an important component of enhancing its application potential. In this work, diverse flavonoids, such as quercetin (Que), apigenin (Api), and morin (Mor), were used to modify protein in myofibrillar protein (MP)/cellulose nanocrystal (CN) complexes using ULD-assisted method. Compared with the MP/CNs group, the triiodide contents of MP-Que/CNs, MP-Api/CNs, and MP-Mor/CNs increased by 1175.84%, 479.05%, and 2281.50% respectively. The findings revealed that the actual intensity of ULD was drastically reduced by the molecular weight decrease of these flavonoids. For olive oil emulsions prepared with mixed emulsifiers, the low interfacial diffusion rates (0.03 mN·m·s-1/2) and weak emulsifying activity (8.33 m2/g) of the MP/CN complexes were significantly improved by the flavonoids after ULD-assisted treatment. Notably, the emulsions prepared using MP-Api/CNs contained smaller oil droplets and exhibited better emulsifying properties, compared to emulsions prepared with MP-Mor/CNs or MP-Que/CNs. This study is essential for ULD-assisted treatment since the processing impact may be increased by choosing the most suitable flavonoid.

Effects of ultrasound on the oxidation and structures of the myofibrillar protein in the presence or absence of soybean oil

BACKGROUND

Ultrasound is widely used as a novel non-thermal processing technique to improve protein properties. In recent decades, applying ultrasound-assisted emulsification (UAE) to produce protein-stabilized emulsion has attracted people's attention. Instead of applying ultrasound to treat a single protein solution, UAE treatment refers to the use of sonication to a mixture of protein and oil. The purpose of this study was to compare the different effects of ultrasound treatment on the properties of the myofibrillar protein (MP) in the presence or absence of soybean oil. A suitable sonication power was selected based on the change in emulsion properties.

RESULTS

The 300W sonication power was selected due to its most effectively decreased emulsion droplet size and increased absolute zeta potential. Sonication more significantly increased the protein carbonyl content and disulfide bonds of the MP-soybean oil sample than MP sample. Due to the existence of oil, ultrasound could unfold more protein molecules illustrated by a lower α-helix content and intrinsic fluorescence intensity, and a higher surface hydrophobicity. LC-MS/MS results illustrated that sonication enhanced the myosin heavy chain and actin content at the soybean oil interface as well as accelerated the myosin light chain to separate from myosin in the MP-soybean oil system.

CONCLUSION

In summary, ultrasound treatment could lead to a higher level of protein oxidation and more protein molecule exposure in the MP with the presence of oil system than in the oil-free MP system. This article is protected by copyright. All rights reserved.

Stabilization of Olive Oil in Water Emulsion with Dairy Ingredients by Pulsed and Continuous High Intensity Ultrasound

Application of high intensity ultrasound (HIUS) for stabilization of olive oil in water emulsion with different dairy ingredients including sodium caseinate (NaCS) and whey protein isolate (WPI) was investigated. The emulsions were prepared by homogenization with a probe and then treated with either a second homogenization or HIUS at a different power level (20 and 50%) in pulsed or continuous mode for 2 min. The emulsion activity index (EAI), creaming index (CI), specific surface area (SSA), rheological properties, and droplet size of the samples were determined. The temperature of the sample rose when HIUS was applied in continuous mode and at increasing power level. HIUS treatment increased EAI and SSA of the emulsion and decreased droplet size and CI compared with those of the double-homogenized sample. Among the HIUS treatments, the highest EAI was found in the emulsion with NaCS that was treated at a power level of 50% in continuous mode, and the lowest one was obtained by HIUS applied at a power level of 20% in pulsed mode. SSA, droplet size, and span of the emulsion were not affected by HIUS parameters. Rheological properties of HIUS-treated emulsions were not different from those of the double-homogenized control sample. Continuous HIUS at 20% power level and pulsed HIUS at 50% power level reduced creaming in the emulsion after storage at a similar level. HIUS at a low power level or in pulsed mode can be preferred for heat sensitive materials.

Effect of Thermal Processing on the Conformational and Digestive Properties of Myosin

Heat treatment affects the structural properties of meat proteins, which in turn leads to changes in their sensitivity to digestive enzymes, further affecting the nutritional value of meat and meat products. The mechanism of changes in the structure and digestive properties of myosin under different heating conditions were studied. An increase in heating temperature led to the exposure of internal groups to a polar environment, but to a decrease in the sturdy α-helix structure of myosin (p < 0.05). The results of tryptophan fluorescence verified that the tertiary structure of the protein seemed to be unfolded at 70 °C. Higher protein denaturation after overheating, as proven by the sulfhydryl contents and turbidity, caused irregular aggregate generation. The excessive heating mode of treatment at 100 °C for 30 min caused myosin to exhibit a lower degree of pepsin digestion, which increased the Michaelis constant (Km value) of pepsin during the digestion, but induced the production of new peptides with longer peptide sequences. This study elucidates the effects of cooking temperature on the conformation of myosin and the change in digestibility of pepsin treatment during heating.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated-ultrasonicated OVA (SU-OVA) had decreased by 3.0-5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of - 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Microwave processing technology influences the functional and structural properties of fish gelatin

The objective of this study was to evaluate the effects of microwave processing technology (MPT, 240-800 W, 1 and 4 min) on the functional and structural properties of fish gelatin (FG). It showed that MPT could increase gel strength and texture properties of FG, especially for 240 W. MPT greatly increased emulsifying activity index (EAI) of FG, but decreased its emulsion stability index (ESI). Rheology results showed that MPT increased viscosity of FG, but decreased gelation times. Intrinsic fluorescence and Fourier transform infrared (FTIR) spectroscopy results indicated that MPT could unfold gelatin, contributing to the formation of H-bonds. Scanning electron microscopy (SEM) analysis revealed that low power and short time of MPT-treated gelatin gels had much more dense and less voids. This work provided guidance for the applications of MPT to improve the functional properties of FG, and the results show that MPT-treated FG can replace mammalian gelatin and meet the religious requirement.

Effects of hydrodynamic cavitation on physicochemical structure and emulsifying properties of tilapia (Oreochromis niloticus) myofibrillar protein

The purpose of this research was to explore the different hydrodynamic cavitation (HC) times (0, 5, 10, 15, 20 min; power 550 W, pressure 0.14 MPa) on the emulsifying properties of tilapia myofibrillar protein (TMP). Results of pH, particle size, turbidity, solubility, surface hydrophobicity, and reactive sulfhydryl (SH) group indicated that HC changed the structure of TMP, as confirmed by the findings of intrinsic fluorescence and circular dichroism (CD) spectra. Furthermore, HC increased the emulsifying activity index (EAI) significantly (P < 0.05) and changed the emulsifying stability index (ESI), droplet size, and rheology of TMP emulsions. Notably, compared with control group, the 10-min HC significantly decreased particle size and turbidity but increased solubility (P < 0.05), resulting in accelerated diffusion of TMP in the emulsion. The prepared TMP emulsion showed the highest ESI (from 71.28 ± 5.50 to 91.73 ± 5.56 min), the smallest droplet size (from 2,754 ± 110 to 2,138 ± 182 nm) and the best rheological properties, as demonstrated by the microstructure photographs. Overall, by showing the effect of HC in improving the emulsifying properties of TMP, the study demonstrated HC as a potential technique for meat protein processing.

Application of simultaneous ultrasonic curing on pork (Longissimus dorsi): Mass transport of NaCl, physical characteristics, and microstructure

This study aimed to investigate the effect of ultrasound curing with various working modes and frequency combinations, including mono-, dual- and tri-frequency, on the content of NaCl and tenderness of pork loins (Longissimus dorsi). The physical qualities, myoglobin, moisture migration, distribution, and microstructure of pork were also evaluated. The results displayed that the NaCl content of samples cured by simultaneous ultrasound (100 W/L) working mode with a frequency combination of 20, 40, and 60 kHz was higher than that of other ultrasound working modes. The effect of ultrasonic brining was significantly better than the static curing when the saline solution was >35 mL. In addition, the samples cured by simultaneous ultrasound had better physical qualities, including more pickling absorptivity, less cooking loss, and lower hardness, tenderness, and chewiness value. The intensity of lightness was reduced, although redness and yellowness remained unaltered compared to static curing. The myoglobin content decreased drastically without changing the oxygenation level, and the relaxation time of T_2b and T₂₁ was delayed. The microstructure indicated that the ultrasonic treatment could promote changes in meat texture. Overall, the simultaneous ultrasound at various frequencies could efficiently accelerate NaCl penetration and improve pork quality.

Strategy and Mechanism of Rice Bran Protein Emulsion Stability Based on Rancidity-Induced Protein Oxidation: An Ultrasonic Case Study

To provide a strategy for improving the stability of rice bran protein emulsion (RBPE), rice bran proteins (RBPs) with different oxidation extents were prepared from fresh rice bran (RB) stored for different times (0, 1, 3, 5, 10 d), and RBPE was prepared with ultrasonic treatment. The ultrasonic conditions were optimized according to the results of the RBPE’s stability (when RB stored for 0, 1, 3, 5, 10 d, the optimal ultrasonic treatment conditions of RBPE were 500 w and 50 min, 400 w and 30 min, 400 w and 30 min, 300 w and 20 min, 500 w and 50 min, respectively). Additionally, the structural characteristics and the flexibility of RBPE interface protein were characterized, and the results showed that compared with native protein and excessive oxidized protein, the unfolded structure content and flexibility of interface protein of RBPE prepared by moderate oxidized protein under optimal ultrasonic intensity was higher. Furthermore, the correlation analysis showed that the RBPE stability was significantly correlated with the structural characteristics and flexibility of the RBPE interface protein (p < 0.05). In summary, ultrasonic treatment affected the interface protein’s structural characteristics and flexibility, improving the stability of RBPE prepared from oxidized RBP.

Effect of Ultrasound Combined with Glycerol-Mediated Low-Sodium Curing on the Quality and Protein Structure of Pork Tenderloin

Considering the hazards of high salt intake and the current status of research on low-sodium meat products, this study was to analyze the effect of ultrasound combined with glycerol-mediated low-sodium salt curing on the quality of pork tenderloin by analyzing the salt content, water activity (aw), cooking loss, and texture. The results of scanning electron microscope (SEM) analysis, Raman spectroscopy, ultraviolet fluorescence, and surface hydrophobicity were proposed to reveal the mechanism of the effect of combined ultrasound and glycerol-mediated low sodium salt curing on the quality characteristics of pork tenderloin. The results showed that the co-mediated curing could reduce salt content, aw, and cooking loss (p < 0.05), improve texture and enhance product quality. Compared with the control group, the co-mediated curing increased the solubility of the myofibrillar protein, improved the surface hydrophobicity of the protein, increased the content of reactive sulfhydryl groups (p < 0.05), and changed the protein structure. The SEM results showed that the products treated using a co-mediated curing process had a more detailed and uniform pore distribution. These findings provide new insights into the quality of ultrasonic-treated and glycerol-mediated low-salt cured meat products.

Strategies to optimize the structural and functional properties of myofibrillar proteins: Physical and biochemical perspectives

Myofibrillar protein (MP), as the main meat protein, have high nutritional value. However, the relatively poor solubility of MP at low ionic strength sometimes limits the utilization of MP to produce products rich in meat protein. Accordingly, appropriate modification of MP is needed to improve their functional properties. In general, MP modification strategies are categorized into biochemical and physical approaches. Different from other available reviews, the review focuses on summarizing the principles and applications of several techniques of physical modification, briefly depicting biochemical modification as a comparison. Modification of MP with a certain intensity of direct current magnetic field, ultrasound, high pressure, microwave, or radio frequency can improve solubility, emulsification, stability, and gel formation. Of these, magnetic field and microwave-modified MP have shown some potential in reducing salt in meat. These physical techniques can also have synergistic effects with other conditions (temperature, pH, physical or chemical techniques) to compensate for the deficiencies of individual treatment techniques. However, these strategies still need further research for practical applications.HIGHLIGHTSThe current status and findings of research on direct current magnetic field in meat processing are presented.Several physical strategies to modify the microstructure and functional properties of MPs.The synergistic effects of these techniques in combination with other methods to modify MPs are discussed.

Comparative study on the in vitro digestibility of chicken protein after different modifications

The effects of tea polyphenols (TPPs) and ultrasound treatment (UDT) on the digestibility of chicken myofibrillar protein (MPN) in anenhanced oxidation system were investigated. As observed, the original aggregates of MPN were much lower in the UDT-assisted group than in the control protein group, and the difference widened after the incorporation of TPPs. The covalent structures of the UDT-assisted oxidation groups were verified via mass spectrometry and amino acid (AAD) measurements. The peptide abundance increased after the UDT-assisted covalent reaction and most of these peptides were derived from the structural proteins of MPNs according to the results of nano-LC-ESI-MS/MS. Digestion kinetic analysis showed that the digestion level of the EGCG-treated group was better than that of the other treated groups, regardless of the UDT-assisted covalent reaction. Overall, the combination of EGCG oxidation and UDT may be an efficient way to promote the nutritional value of the final MPN products.

Physicochemical properties and microstructure of composite surimi gels: The effects of ultrasonic treatment and olive oil concentration

This study was conducted to evaluate the effects of extra virgin olive (EVO) oil incorporation on the physicochemical properties and microstructure of surimi gels subjected to ultrasound-assisted water-bath heating. As the oil content was increased from 0 to 5 g/100 g, the breaking force and gel strength of the surimi gels significantly decreased, while the whiteness level exhibited the opposite tendency irrespective of the heating method. Compared with the traditional water-bath heating method, the ultrasonic heating promoted the unfolding of the α-helix structure and intensified the formation of β-sheet content and non-covalent bonds (ionic bonds, hydrogen bonds, and disulfide bonds), especially disulfide bonds, which contributed to the further crosslinking of the proteins and to gelation, thereby improving the gels' strength. In addition, smaller cavities and compact microstructures were observed in the low-oil (≤3 g/100 g) surimi gels under ultrasonic treatment, which effectively prevented water migration in the gel network and resulted in a high water holding capacity and uniform water distribution. However, the ultrasonic treatment barely remedied the poor microstructures of the high-oil (>3 g/100 g) surimi gels owing to oil coalescence, which weakened the protein-protein interaction. In conclusion, ultrasonic treatment combined with water-bath heating significantly improved the gelation properties of the low-oil surimi gels, although it did not remarkably improve those of the high-oil gels. The choice of a suitable oil concentration could be of great importance for the production and functioning of surimi products via ultrasound-assisted treatments.

Effects of proteins on emulsion stability: The role of proteins at the oil-water interface

To obtain a stable protein-added emulsion system, researchers have focused on the design of the oil-water interface. This review discussed the updated details of protein adsorption behavior at the oil-water interface. We evaluated methods of monitoring interfacial proteins as well as their strengths and limitations. Based on the effects of structure on protein adsorption, we summarized the contribution of pre-changing methods to adsorption. In addition, the interaction of proteins and other surface-active molecules at the interface had been emphasized. Results showed that protein adsorption is affected by conformation, oil polarity and aqueous environments. The monitoring of interfacial proteins through spectroscopic properties in actual emulsion systems is an emerging trend. Pre-changing could improve the protein adsorption and the purpose of pre-changing of proteins is similar. In the interaction with other surface-active molecules, co-adsorption is desirable. By co-adsorption, the respective advantages can be exploited to obtain a more stable emulsion system.

Effect of Xanthan Gum, Kappa-Carrageenan, and Guar Gum on the Functional Characteristics of Egg White Liquid and Intermolecular Interaction Mechanism

This study evaluated the effects of three polysaccharides, xanthan gum (XG), kappa-carrageenan (CA), and guar gum (GG), on the foaming and emulsifying properties of egg white liquid (EWL) and explored the intermolecular interactions and aggregation states in the initial polysaccharide−EWL complex. The results showed that the addition of XG and GG significantly improved the foaming stability of EWL on the one hand, from 66% to 78% and 69%, respectively (p < 0.05). On the other hand, the addition of XG and GG significantly improved the foam uniformity and density, and the average foam area decreased from 0.127 to 0.052 and 0.022 mm2, respectively (p < 0.05). The addition of XG and CA significantly improved the emulsification activity index (from 13.32 to 14.58 and 14.36 m2/mg, respectively, p < 0.05) and the emulsion stability index (from 50.89 to 53.62 and 52.18 min, respectively, p < 0.05), as well as the interfacial protein adsorption at the oil−water interface; it also reduced the creaming index. However, GG negatively affected these indicators. Furthermore, the electrostatic and hydrophobic interactions among molecules in EWL due to XG and the electrostatic, hydrogen bonding, and hydrophobic interactions among molecules in EWL due to CA ultimately led to the irregular aggregation of egg white proteins. Hydrophobic interactions and disulfide bonds between molecules in EWL−containing GG formed filamentous aggregations of egg white proteins. This work reveals that molecules in the polysaccharide−egg white complexes aggregate by interaction forces, which in turn have different effects on the foaming and emulsifying properties of egg white proteins.

Ultrasound treatment can increase digestibility of myofibrillar protein of pork with modified atmosphere packaging

We explored whether ultrasound treatment affected digestibility of myofibrillar protein (MP) isolated from modified atmosphere packed (MAP, 70% N₂ and 30% CO₂) pork. MP digestibility under pepsin and pancreatin treatments decreased significantly with storage time. Ultrasound treatment increased the digestibility and produced a greater number of smaller peptides. However, the total peptide count and unique peptide counts were significantly reduced. Moreover, active sulfhydryl, total sulfhydryl, particle size, turbidity and surface hydrophobicity of MP increased with time, while protein solubility and ATPase activity decreased. Compared with the untreated samples, ultrasound treatment increased protein solubility, surface hydrophobicity, and active sulfhydryl content, but decreased total sulfhydryl content (except 10 d), particle sizes, turbidity and ATPase activity. Ultrasound treatment resulted in a decline in β-turn and α-helix contents. Therefore, ultrasound is conducive to the digestion. Additionally, structural and functional properties of protein in MAP were less stable than those in vacuum-packed pork reported before.