Recent advances in modified food proteins by high intensity ultrasound for enhancing functionality: Potential mechanisms, combination with other methods, equipment innovations and future directions

Insight into dairy casein implications that enhance egg white proteins' thermodynamic and microrheological functions

One of the critical challenges in egg white proteins (EWP) industry is its high aggregation ability during its heat pasteurization preprocess. Thus, the current study has explained the casein (CN) mechanism to improve EWP thermal stability. In the methods, EWP-CN intermolecular forces, covalent bonds, secondary structure thermal behaviors, and micro-rheology were investigated. The results showed that EWP-CN sulfhydryl bonds and hydrophobicity were enhanced significantly (p < 0.05) after dynamic heat treatment. Whereas, EWP-CN complex (2,1, v/v) demonstrated the lowest turbidity (61.6 %) and highest stability coefficient (78.2 %) at 90 °C for 20 min compared to EWP. Besides, CN (10 mg/mL) has decreased the EWP aggregated particles up to 1.8 times compared to the control. That was in harmony with viscosity, storage modulus, and thermogram patterns, indicating high heat resistance. In conclusion, this study establishes a new concept to enhance the sensitive raw protein's responses by their conjugations with potential active stabilizers.

Ultrasound-assisted covalent cross-linking of egg white protein with ferulic acid: Structure, foaming, and application in chiffon cake

Egg white protein is one of the most important functional proteins in daily life; however, owing to its slow foaming, small volume and easy instability, EWP foam has limited application in the food industry, and its foaming performance needs to be further improved. However, its foaming performance still needs further improvement due to its instability mechanism. In this study, egg white protein and ferulic acid were combined via ultrasound-assisted covalent cross-linking methods, and their structure, foaming performance, and application were studied. The results showed that the composite prepared via ultrasound-assisted covalent cross-linking methods presented an increased foaming capacity of 94 % and foaming stability of 81.6 %. The Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) spectroscopy results revealed that the secondary structure of the composite changed with increasing α-helices and β-folds and the transformation of the β-turn angle and random coil. In particular, cakes prepared with FA-EWP covalent complexes have uniform and dense bubble pore sizes. Hence, this study provides new strategic information for ultrasound-assisted covalent crosslinking of polyphenols to improve the foaming performance of egg white protein.

Effects of ultrasound-induced structural modifications on the emulsifying properties of Tenebrio molitor proteins

Ultrasonication has emerged as a promising technique for modifying physicochemical properties of proteins, enhancing their functionality in food applications. This study evaluated the effects of ultrasonic treatment on the structural and functional properties of mealworm-derived proteins (MPs) and their potential as emulsifiers. Dynamic light scattering revealed a significant reduction in MP particle size from 3464.3 nm (untreated) to 115.5 nm (30 min sonication), along with increased zeta potential, indicating improved colloidal stability. Sonication enhanced oil-holding capacity and solubility, suggesting improved interfacial adsorption and emulsification. Circular dichroism and FT-IR spectroscopy confirmed structural modifications, including increased α-helix content and enhanced hydrogen bonding interactions. Free sulfhydryl content and surface hydrophobicity analyses indicated ultrasound-induced unfolding, exposing functional groups that contribute to emulsifying properties. Sonicated MPs demonstrated superior emulsion stability under varying temperature, pH, and ionic conditions. Furthermore, digestibility analysis showed improved gastric digestion (72.7 % to 82.8 %) and enhanced lipid digestion in the small intestine (36.2 % to 47.9 %), suggesting greater bioavailability. These physicochemical modifications highlight the feasibility of using sonicated MP as natural emulsifiers with enhanced functionality. This study underscores their potential in food formulations, particularly for nutritionally fortified emulsions, contributing to sustainable and functional food ingredient development.

Effects of pulsed electric field (PEF) on the gel and protein structural properties of surimi and the underlying mechanisms

This study systematically investigated the effects of pulsed electric field (PEF) treatments on the gelation properties and protein structural modifications in surimi. Through experimental analyses complemented by molecular dynamics (MD) simulations, we elucidated the molecular mechanisms underlying these changes. Notably, moderate PEF treatment (15 kV/cm, 40 min) significantly enhanced gel strength and water-holding capacity (WHC) by 34.68 % and 11.55 %, respectively, compared to untreated samples. However, excessive parameters (> 20 kV/cm or > 60 min) induced protein over-aggregation through disulfide bond crosslinking, resulting in deteriorated gel quality. MD simulations revealed that PEF-induced alterations in molecular dipole moments accelerated conformational rearrangement of α-helical structures. The synergistic interplay between reinforced hydrogen bonding networks and optimized hydrophobic interactions was identified as the primary determinant of improved gel functionality. These findings collectively highlight the critical balance required in PEF parameter selection for surimi processing optimization.

Effect of xylose glycation and ultrasonication on the interfacial properties and physicochemical stability of silkworm pupa protein-stabilized Pickering emulsion and its applicability in emulsion-filled hydrogels

Silkworm pupa protein isolate (SPPI) has the potential of being used (as an alternative nutrient) in various food products, but it has poor emulsifying and gelling property. In this study, SPPI was modified by glycation and/or ultrasonication, and the interfacial properties and stability of Pickering emulsions stabilized by SPPI-xylose conjugates and their application in emulsion-filled hydrogels (EFHGs) were investigated. Results showed that, compared with the control, the contact angle of glycated SPPI (using 3 % xylose under ultrasonication, US-X3%) decreased from 144.6° to 110.9°, and the penetration and rearrangement rates at the water-oil interface increased by 20.76 % and 72.11 %, respectively. Pickering emulsion stabilized by US-X3% exhibited smaller droplet size, stronger electrostatic repulsion and interfacial pressure, thicker interfacial film, as well as higher elasticity-dominated viscoelastic behavior. After combined treatment, the -20 °C and - 80 °C freeze-thaw stability of SPPI emulsion was increased by 3.78 and 1.62 times, respectively, and the thermal, refrigeration and salt stability were also significantly improved (p < 0.05). By filling the conjugate-stabilized Pickering emulsion (US-X3%), the content of hydrogen and ionic bonds in EFHGs network was decreased, the hardness and chewiness of the hydrogels were reduced, and the water holding capacity was increased to 95.75 %. The results of gastrointestinal digestion (in vitro) showed that the addition of xylose and the use of sonication had no significant effect on the protein digestibility of EFHGs (p > 0.05). Thus, SPPI-xylose conjugates prepared by glycation and ultrasonication exhibited excellent application potential in emulsion/gel hybrid food system.

Synergistic Effects of Ultrasound and pH-Shifting on the Solubility and Emulsification Properties of Peanut Protein

Peanut protein is a byproduct of peanut oil extraction with limited applications within the food sector due to its low solubility and emulsifying properties. This study investigated the influences and mechanisms of high-intensity ultrasound (HIU, 200~600 W) and pH-shifting (pH 12), either individually or jointly, on the structure, solubility, and emulsifying properties of PP. Results indicated that the solubility of PP significantly increased after the combined treatment, particularly when the HIU power was 300 W (p < 0.05). Accordingly, emulsions prepared from it exhibited highest storage stability. Structural analysis indicated that the increased PP solubility (9.95% to 54.37%, p < 0.05) is mainly attributed to the structural changes that occur during protein unfolding, resulting in the uncovering of hydrophobic groups (7181.43 to 14,083.00, p < 0.05) and the reduction of α-helices (24.43% to 18.17%, p < 0.05). Moreover, confocal laser scanning microscopy of the emulsions revealed that the combination-treated PP resulted in smaller protein particle sizes (50.09 μm to 15.68 μm, p < 0.05), tighter adsorption on the oil-water interface, and a denser and more stable interfacial film compared to the native and the individual treatment, thereby enhancing the stability of the system. A rheological analysis confirmed that the combined treatment improved the interfacial properties of the protein, which was advantageous for emulsion stability. In conclusion, HIU combined with pH12-shifting can appreciably improve the solubility and emulsifying properties of PP to broaden its application prospects.

Unveiling the potential of bean proteins: Extraction methods, functional and structural properties, modification techniques, physiological benefits, and diverse food applications

Bean proteins, known for their sustainability, versatility, and high nutritional value, represent a valuable yet underutilized resource, receiving less industrial attention compared to soy and pea proteins. This review examines the structural and molecular characteristics, functional properties, amino acid composition, nutritional value, antinutritional factors, and digestibility of bean proteins. Their applications in various food systems, including baked goods, juice and milk substitutes, meat alternatives, edible coatings, and 3D printing inks, are discussed. The physiological benefits of bean proteins, such as antidiabetic, cardioprotective, antioxidant, and neuroprotective effects, are also presented, highlighting their potential for promoting well-being. Our review emphasizes the diversity of bean proteins and highlights ultrasound as the most effective extraction method among available techniques. Beyond their physiological benefits, bean proteins significantly enhance the structural, technological, and nutritional properties of food systems. The functionality can be further improved through various modification techniques, thereby expanding their applicability in the food industry. While studies have explored the impact of bean protein structure on their nutritional and functional properties, further research is needed to investigate advanced modification techniques and the structure-function relationship. This will enhance the utilization of bean proteins in innovative and sustainable food applications.

Ultrasound-induced food protein-stabilized emulsions: Exploring the governing principles from the protein structural perspective

Consumers' growing demand for healthy and natural foods has led to a preference for products with fewer additives. However, the low emulsifying properties of natural proteins often necessitate the addition of emulsifiers in food formulations. Consequently, enhancing the emulsifying properties of proteins through various modification methods is crucial to meet modern consumer demands for natural food products. High-intensity ultrasound offers a green, efficient processing technology that significantly improves the emulsifying properties of proteins. This study explores how ultrasound treatment enhances the stability of protein-based emulsions by modifying protein structures. While ultrasonic treatment does not significantly affect the primary structure of proteins, it influences the secondary, tertiary, and quaternary structures depending on the type of protein, ultrasound parameters (type, intensity, and time), and treatment conditions. The results suggest that ultrasound treatment reduces α-helix content, decreases protein particle size, and increases β-sheet content, surface hydrophobicity, free sulfhydryl groups, and zeta potential, leading to a more stable protein-based emulsion. The reduced particle size and increased flexibility of proteins induced by ultrasound enable more rapid protein adsorption at the oil-water interface, resulting in smaller emulsion droplets. This contributes to the emulsion's improved stability during storage. Future research should focus on the large-scale application of ultrasonic treatment for protein modification to produce high-quality, natural foods that meet the evolving needs of consumers.

Physicochemical, techno-functional, biochemical and structural characterization of a protein isolate from groundnut (Arachis hypogaea L.) paste treated with high-intensity ultrasound

The objective of this research was to evaluate the effect of ultrasound (HISound) (200, 400 and 600 W; 15-30 min) on the physicochemical, biochemical and structural techno-functional properties of a groundnut paste protein isolate (GPPI). HISound increased the contents of free sulfhydryls (552.22 %), total sulfhydryls (124.68 %) and α-helix (389.75 %), as well as molecular flexibility (50.91 %), hydrophobic surface (38.99 %), and particle size (171.45 %) of GPPI, which improved protein solubility by 8.05 %, oil holding capacity by 73.54 %, emulsifying stability index by 226.25 % and foaming capacity by 216.00 %, compared with non-sonicated GPPI. Also, the microstructure analysis revealed smooth structures, with molecular weights in the range of 13.88-67.07 kDa. Pearson analysis determined some highly significant correlations (r ≥ 0.90, p < 0.01) between some GPPI protein properties. The improvement of GPPI properties by HISound could contribute to its use as an ingredient for human consumption.

Ultrasound treatment on commercial pea protein isolates systems: Effect on structure, rheology and gelling properties

Pea protein has attracted great attention due to its capability to meet the growing requirements from consumers for desired nutrition and texture from plant protein. Hence, the current study aimed to investigate the effects of different ultrasonic treatment parameters (power and duration) on the gelling characteristics of commercial pea protein isolates (PPIc). The findings demonstrated that by manipulating the ultrasonic power and treatment duration, great enhancement of the solubility, adhesiveness and formation strength of PPIc gel can be realized. The reduction in particle size was positively correlated with higher power and longer treatment durations. Interestingly, no direct correlation between average particle size, solubility, turbidity, and ζ-potential was observed. Additionally, the ultrasound-modified PPIc in this study exhibited comparable characteristics to laboratory-prepared pea protein isolates, in terms of solubility, water-holding capacity, and gel strength. Overall, manipulating ultrasonic parameters presents a feasible method to customize the texture of pea-protein-based substitute.

Fabrication, modification, interaction mechanisms, and applications of fish gelatin: A comprehensive review

Fish gelatin (FG) is an essential natural biopolymer isolated from aquatic sources and has been considered as a feasible substitute for mammalian gelatins. However, its inferior mechanical and gelling properties limit its applications. Consequently, FG has been modified using various methods. This review summarizes the extraction techniques (including traditional acid and alkaline methods, as well as newer technologies such as ultrasonic-assisted and microwave-assisted extraction), modification strategies (mechanical treatments, physical mixing with polysaccharides, utilization of the Hofmeister effect, chemical modifications, etc.), along with their mechanisms of action. Additionally, we discussed the applications of FG and its modified products. Furthermore, this review highlights the safety and prospects for FG and its derivatives. The mechanical properties and biological functions of FGs are enhanced after modification. Thus, modified FG composites exhibit diverse applications in areas such as foaming agents and emulsifiers, food packaging, three-dimensional printing, drug delivery systems and tissue engineering. This paper aims to provide comprehensive information for future research on FG with the intention of broadening its applicability within the industries of food, cosmetics, and pharmaceuticals. Nevertheless, the development of tough gels, aerogels, and stimuli-responsive hydrogels based on FG requires further investigation.

A comprehensive review of effects of ultrasound pretreatment on processing technologies for food allergens: Allergenicity, nutritional value, and technofunctional properties and safety assessment

Many proteins are essential food components but also major allergens. Reducing protein allergenicity while preserving its nutritional value and technofunctional properties has always been the goal of the food industry. Ultrasound (US) is a green processing method for modifying proteins. In addition, US pretreatment combined with other processing techniques (USPCT) has been increasingly used in the food industry. Therefore, this review presents an overview of recent advances in the impact of US and USPCT (US-combined enzymatic hydrolysis [USCE], US-combined glycation [USCG], and US-combined polyphenol conjugation [USCP]) on the allergenicity, nutritional value, and technofunctional properties of food allergens. We discuss the potential mechanisms, advantages, and limitations of these technologies for improving the properties of proteins and analyze their safety, challenges, and corresponding solutions. It was found that USPCT can improve the efficiency and effectiveness of different methods, which in turn can be more effective in reducing protein allergenicity and improving the nutritional value and functional properties of processed products. Future research should start with new processing methods, optimization of process conditions, industrial production, and the use of new research techniques to promote technical progress. This paper is expected to provide reference for the development of high-quality hypoallergenic protein raw materials.

Modification of hempseed protein isolate using a novel two-stage method applying high-pressure homogenization coupled with high-intensity ultrasound

Hempseed protein isolate (HPI), a novel plant protein, possesses advantages as an alternative food protein from a nutritional and sustainable perspective. This study investigated HPI modification by examining the effects of high-pressure homogenization combined with high-intensity ultrasound (HPH + HIU) on the physicochemical and functionality of HPI. Firstly, the optimal homogenization pressure (180 MPa) was selected based on the solubility and particle size of HPI. Then, the effect of ultrasonic treatment time (2, 5, and 10 min) was studied at the optimal homogenization pressure. The results showed increased solubility of HPI after all treatments. Particularly, the HPH + HIU2min treatment had a synergistic effect that maximumly increased the solubility of HPI from 6.88 % to 22.89 % at neutral pH. This treatment significantly decreased the HPI's particle size, β-sheet and total sulfhydryl contents while maximizing the random coil level, intrinsic fluorescence intensity and surface hydrophobicity compared to the single HPH or HIU2min treatments. The protein structure was modified and unfolded, enhancing the water-protein and oil-protein interactions, as reflected in the increase in water and oil absorption, foaming and emulsifying properties. However, extending the ultrasonic time to 5 min for the HPH + HIU treatment increased protein particle size and weakened the functional properties of HPI. Further prolonging the ultrasonic time to 10 min partially loosened the protein aggregates and restored the functional properties of HPI to some extent. The findings indicate a promising application of HPH + HIU as an efficient way for HPI modification to facilitate its broader application in the food industry.

Evaluation of low-temperature ultrasonic marination of pork meat at various frequencies on physicochemical properties, myoglobin levels, and volatile compounds

This study aims to evaluate the pork meat quality after ultrasonic brining at different frequencies, thereby providing a more comprehensive understanding of the effects of ultrasound marination on meat. The texture profile analysis showed that ultrasonic curing at various frequencies significantly improved the textural properties of samples, especially at 26.8 kHz, resulting in a reduction of tenderness, hardness, and chewiness values by 44%, 43%, and 44%, respectively. The cooking loss of samples marinated by ultrasound decreased from 27% without ultrasonic treatment to 22%, indicating a significant improvement in water-holding capacity, while the changes in pH had only a subtle impact on pork quality. Meanwhile, the color of pork became more rosy hue due to decreased L⁎ values and increased a⁎ values, which was mainly attributed to an elevated proportion of oxymyoglobin and reduced metmyoglobin content. Additionally, ultrasonic marination did not exert a negative impact on the oxidation of pork protein and lipids. After roasting, samples marinated by ultrasound exhibited a significantly higher abundance of volatile flavor compounds compared to static marinated meat (with an increase of 16 flavor substances) and fresh pork (with an increase of 24 flavor substances), demonstrating the efficacy of ultrasonic marination in enhancing the overall flavor and taste profile of pork. Consequently, the application of ultrasonic technology holds great potential for the "home kitchen type" rapid marination.

The gelling properties of fish gelatin as improved by ultrasound-assisted phosphorylation

This study investigated the effects of ultrasound-assisted phosphorylation on gelling properties of fish gelatin (FG). Ultrasound-assisted phosphorylation (UP) for 60, 90, and 120 min resulted in >6.54% increase of phosphorylation degree and decreased zeta potential of FG. Atomic force microscopy revealed that UP-FGs showed larger aggregates than P-FGs (normal phosphorylation FGs). Low frequent-NMR and microstructure analysis revealed that phosphorylation enhanced water-binding capability of FG and improved the gel networks. However, UP60 had the highest gel strength (340 g), gelling (17.96 °C) and melting (26.54 °C) temperature while UP90 and UP120 showed slightly lower of them. FTIR analysis indicated thatβ-sheet and triple helix content increased but random coil content decreased in phosphorylated FGs. Mass spectrometry demonstrated phosphate groups mainly bound to serine, threonine and tyrosine residues of FG and UP-FG exhibited more phosphorylation sites. The study showed that mild phosphorylation (UP60) could be applied to improve FG gel properties.

Application of ultrasound treatment in pork marination: Effects on moisture migration and microstructure

To better understanding the effects of ultrasonic marination on the porcine tissue, the moisture migration and microstructure were investigated in this study. Additionally, the acoustic field distribution was analysis using COMSOL Multiphysics. The low-filed NMR results demonstrated that ultrasonic curing induced a leftward shift in T21 and a rightward shift in T22, accompanied by a significant reduction in A22, thereby enhancing the water-holding capacity of pork. The SEM and TEM observation showed that the presence of larger interstitial gaps between muscle fibers facilitated the diffusion of NaCl. The simulation analysis revealed that the acoustic field at 26.8 kHz showed minimal standing wave effects and more pronounced cavitation, which was the main reason for the best curing effect at this frequency. The scale-up test showed the NaCl content in pork reached 1% after ultrasound curing, indicating the potential application of ultrasonic marination technology in domestic refrigerators.

Effect of Multi-Mode Divergent Ultrasound Pretreatment on Hardness, Microstructure and Digestion of Acid-Induced Whey Protein Gels

Whey protein was pretreated with multi-frequency ultrasound in mono-, dual-, and tri-frequency modes. The effect of multi-frequency ultrasound pretreatment on the hardness, chemical forces, and microstructure of acid-induced whey protein gel was investigated. Whey protein gels pretreated with dual- and tri-frequency ultrasound showed higher hardness (p < 0.05) and a denser network than mono-frequency ultrasound and control. Moreover, they had higher hydrophobic interaction and lower disulfide bonds than the control (p < 0.05). The effect of gel properties on digestion was evaluated using an in vitro static model. Whey protein gels pretreated with dual- and tri-frequency ultrasound had a higher proportion of large fragments in the oral boluses than in the control. Large fragments (>3.35 mm) in those samples were resistant to gastric digestion. Moreover, the tri-frequency ultrasound pretreatment of whey protein gel released the least free amino group during gastric digestion. In contrast, whey protein gel with the mono-frequency ultrasound pretreatment released the highest amount of free amino acid group during intestinal digestion. Findings from this study suggests that gel hardness and network density could modulate the digestion behaviors of protein gels.

Physicochemical and functional characteristics of a gourd (Cucurbita argyrosperma Huber) seed protein isolate subjected to high-intensity ultrasound

The impact of high-intensity ultrasound (HIU, 20 kHz) on the physicochemical and functional characteristics of gourd seed protein isolate (GoSPI) was studied. GoSPI was prepared from oil-free gourd seed flour through alkaline extraction (pH 11) and subsequent isoelectric precipitation (pH 4). The crude protein concentration of GoSPI ranged from 91.56 ± 0.17 % to 95.43 ± 0.18 %. Aqueous suspensions of GoSPI (1:3.5 w/v) were ultrasonicated at powers of 200, 400, and 600 W for 15 and 30 min. Glutelins (76.18 ± 0.15 %) were the major protein fraction in GoSPI. HIU decreased the moisture, ash, ether extract, and nitrogen-free extract contents and the hue angle, available water and a* and b* color parameters of the GoSPI in some treatments. The L* color parameter increased (7.70 %) after ultrasonication. HIU reduced the bulk density (52.63 %) and particle diameter (39.45 %), as confirmed by scanning electron microscopy, indicating that ultrasonication dissociated macromolecular aggregates in GoSPI. These structural changes enhanced the oil retention capacity and foam stability by up to 62.60 and 6.84 %, respectively, while the increases in the solvability, water retention capacity, and emulsifying activity index of GoSPI were 90.10, 19.80, and 43.34 %, respectively. The gelation, foaming capacity, and stability index of the emulsion showed no improvement due to HIU. HIU altered the secondary structure of GoSPI by decreasing the content of α-helices (49.66 %) and increasing the content of β-sheets (52.00 %) and β-turns (65.00 %). The electrophoretic profile of the GoSPI was not changed by HIU. The ultrasonicated GoSPI had greater functional attributes than those of the control GoSPI and could therefore be used as a functional food component.

Modification of the physicochemical, functional, biochemical and structural properties of a soursop seed (Annona muricata L.) protein isolate treated with high-intensity ultrasound

The obtained seeds from fruit processing are considered by-products containing proteins that could be utilized as ingredients in food manufacturing. However, in the specific case of soursop seeds, their usage for the preparation of protein isolates is limited. In this investigation a protein isolate from soursop seeds (SSPI) was obtained by alkaline extraction and isoelectric precipitation methods. The SSPI was sonicated at 200, 400 and 600 W during 15 and 30 min and its effect on the physicochemical, functional, biochemical, and structural properties was evaluated. Ultrasound increased (p < 0.05) up to 5 % protein content, 261 % protein solubility, 60.7 % foaming capacity, 30.2 % foaming stability, 86 % emulsifying activity index, 4.1 % emulsifying stability index, 85.4 % in vitro protein digestibility, 423.4 % albumin content, 83 % total sulfhydryl content, 316 % free sulfhydryl content, 236 % α-helix, 46 % β-sheet, and 43 % β-turn of SSPI, in comparison with the control treatment without ultrasound. Furthermore, ultrasound decreased (p < 0.05) up to 50 % particle size, 37 % molecular flexibility, 68 % surface hydrophobicity, 41 % intrinsic florescence spectrum, and 60 % random coil content. Scanning electron microscopy analysis revealed smooth structures of the SSPI with molecular weights ranging from 12 kDa to 65 kDa. The increase of albumins content in the SSPI by ultrasound was highly correlated (r = 0.962; p < 0.01) with the protein solubility. Improving the physicochemical, functional, biochemical and structural properties of SSPI by ultrasound could contribute to its utilization as ingredient in food industry.

Modifications of whey proteins for emulsion based applications: Current status, issues and prospectives

Whey proteins are a major group of dairy proteins with high potential for various food based applications. Whey protein isolate has a limited range of functionalities. This functional range can be expanded using diverse modification methods to suit specific applications. This review summarizes the recent advances in the modifications of whey proteins using chemical, physical, and enzymatic methods and their combinations as well as the modification effects on the physicochemical properties. The uses of these modified whey proteins in emulsion based food and beverage systems are described. The limitations in the studies summarized are critically discussed, while future research directions are suggested on how to better utilize whey proteins for emulsion based uses through modifications.

Effects of ultrasound-assisted intermittent tumbling on the quality of cooked ham through modifying muscle structure and protein extraction

BACKGROUND

Tumbling treatment is widely used in the production of cooked ham. However, traditional intermittent tumbling (IT) treatment is time-consuming. To enhance the tumbling efficiency, high-intensity ultrasound was used to assist IT treatment (UIT).

RESULTS

UIT treatment reduced the tumbling time and significantly improved the water holding capacity, tenderness, sliceability and texture of cooked ham compared to IT treatment. Furthermore, more violent destruction of meat tissue was exhibited in the UIT treatment. This change facilitated extraction of more salt-soluble protein, which in turn welded meat pieces tightly and improved the quality of the cooked ham.

CONCLUSION

UIT treatment could accelerate the tumbling process and enhance the quality of cooked ham. These results may provide guidance on effective strategies for a high-quality meat production process. © 2023 Society of Chemical Industry.

How does ultrasound-assisted ionic liquid treatment affect protein? A comprehensive review of their potential mechanisms, safety evaluation, and physicochemical and functional properties

Proteins are essential to human health with enormous food applications. Despite their advantages, plant and animal proteins often exhibit limited molecular flexibility and poor solubility due to hydrogen bonds, hydrophobic interactions, and ionic interactions within their molecular structures. Thus, there is an urgent need to modify the rigid structure of proteins to enhance their stability and functional properties. Ultrasound-assisted ionic liquid (UA-IL) treatment for developing compound modification and producing proteins with excellent functional properties has received interest. However, no review specifically addresses the interactions between UA-ILs and proteins. Hence, this review focused on recent research advancements concerning the effects and potential reaction mechanisms of UA-ILs on the physicochemical properties (including particle size; primary, secondary, and tertiary structure; and surface morphology) as well as the functionality (such as solubility, emulsifying properties, and foaming ability) of proteins. Moreover, the safety evaluation of modified proteins was also discussed from various perspectives, such as acute and chronic toxicity, genotoxicity, cytotoxicity, and environmental and microbial toxicity. This review demonstrated that UA-IL treatment-induced protein structural changes significantly impact the functional characteristics of proteins. This treatment approach efficiently promotes protein structure stretching and spatial rearrangement through cavitation, thermal effects, and ionic interactions. As a result, the functional properties of modified proteins exhibited an obvious enhancement, thereby bringing more opportunities to utilize modified protein products in the food industry. Potential future directions for protein modification using UA-ILs were also proposed.

Evaluation of ultrasonic-assisted pickling with different frequencies on NaCl transport, impedance properties, and microstructure in pork

The effects of ultrasonic curing with various frequencies on sodium chloride (NaCl) mass transfer in pork muscle and its potential mechanisms were investigated. The results showed that ultrasound curing dramatically increased the NaCl content in pork compared to static curing, especially curing at 26.8 kHz. The binarized images of NaCl penetration in pork visually confirmed that ultrasound enhanced the efficiency of mass transfer. Energy dispersive spectroscopy showed that the distribution of NaCl in pork tissue cured by ultrasound was the densest compared to the static curing. According to impedance analysis and microstructure observation, the structure of cell membranes was damaged to different extents during ultrasound treatments. The potential mechanisms of low-frequency ultrasound accelerated curing are mainly attributed to the action of acoustic cavitation and the sponge effect. Overall, the low-frequency ultrasound is a promising revolutionary technology in the food industry that can speed up the curing process of meat.

Effects of limited enzymatic hydrolysis and polysaccharide addition on the physicochemical properties of emulsions stabilized with duck myofibrillar protein under low-salt conditions

This study aimed to investigate the role of hydrolysis and guar gum (GG) participation on the emulsification of the duck myofibrillar protein (MP) and the related stability of oil-in-water emulsion in low-salt condition. Emulsions were prepared using one of each or both treatments, and that prepared with trypsin hydrolysis and GG (T-GG) exhibited the highest stability. FTIR analysis confirmed the hydrogen bond interactions between the system components. T-GG treatment improved emulsion properties and decreased oil droplet size. Moreover, CLSM indicated that aggregation of T-GG oil droplets was prevented. Physical stability was assessed such as Turbiscan stability index, creaming index, and rheological properties. The adsorbed percentage for T-GG was the lowest. However, interfacial tension, droplet size, stability, and peroxide value analyses indicated that a denser interfacial membrane structure is formed with T-GG. Thus, T-GG treatment could be applied in the food industry, such as in nutrient delivery systems and fat mimetics.

Effects of basil seed and guar gums coatings on sensory attributes and quality of dehydrated orange slices using osmotic-ultrasound method

In this work, the effects of gum coating (basil seed and guar gums), ultrasonic power, sonication time, and sucrose concentration on the osmosis dehydration parameters (water loss, solid gain, and rehydration rate), sensory attributes, color changes, and surface shrinkage of dehydrated orange slices using osmotic-ultrasound method were studied. The moisture loss and sucrose gain increased when the ultrasonic duration and sucrose level increased. The edible coating reduced solids absorption, with the lowest sucrose absorption in the basil seed gum-coated slices. Also, the coating increased rehydration rate of dried orange slices, with the highest rehydration ratio in the basil seed gum-coated slices (225.91 %). Edible coating with basil seeds gum improved the sensorial attributes of dried orange slices. The total color difference (ΔE) and surface shrinkage of osmotic dehydrated, dried, and rehydrated orange slices decreased with edible coating pretreatment and increasing in the sonication intensity. As the ultrasound duration enhanced from 5 to 15 min, the average surface shrinkage values of dried and rehydrated orange slices increased from 22.74 % to 26.36 %, and 12.18 % to 15.50 %, respectively. The current work confirmed that the gum coating has the potential to enhance appearance quality and sensorial attributes of osmotic-ultrasound dehydrated orange slices.

L-histidine-assisted ultrasound improved physicochemical properties of myofibrillar proteins under reduced-salt condition - Investigation of underlying mechanisms

The effects of the L-hisdine (L-His)-assisted ultrasound on physicochemical characteristics and conformation of myofibrillar protein (MP) under reduced-salt condition were investigated using spectroscopic analysis, and the binding mechanism between L-His and MP was further elucidated through molecular docking and molecular dynamics (MD) simulations. UV second derivative spectra and intrinsic Try fluorescence spectra revealed that L-His formed a complex with MP and altered the microenvironment of MP. After L-His-assisted ultrasound treatment, MP showed smaller particle size, higher solubility, and more uniform atomic force microscopy image due to the decrease of α-helix content and the subsequent increase in zeta potential, active sulfhydryl content, and surface hydrophobicity. Molecular docking and MD simulations demonstrated the optimal docking pose (minimum binding affinity of -6.78 kcal/mol) and revealed hydrophobic interactions and hydrogen bonds as the main interaction forces between L-His and MP, with several residues (ILE-464, ILE-480, THR-483, ASN-484, GLY-466, ASP-463, PHE-246) identified as binding sites.

Regulation of Protein Flexibility and Promoting the Cod Protein Gel Formation Using Ultrasound Treatment

In order to obtain a soft-textured protein gel suitable for the elderly, the cod protein gel was prepared by improving the protein flexibility under ultrasound treatment. It has been found that the increase in ultrasonic power, protein flexibility, particle size, ζ-potential, surface hydrophobicity, and α-helix content of preheated cod protein exhibited an increasing trend. The improvement of protein flexibility promoted uniformity and density of the gel network, water retention, and texture properties. The flexibility of preheated cod protein increased to 0.189, the water holding capacity of the gel reached up to 99.41%, and the hardness increased to 49.12 g, as the ultrasonic power level increased to 400 W. Protein flexibility was correlated well with the cohesiveness of the gel. The storage modulus (G') initially decreased and then increased during the heating-cooling process. The attractive forces forming between the flexible protein molecules during cooling in the ultrasound treatment groups promoted protein self-assembly aggregation and formed the cod protein gel. The gel obtained at 100-400 W could be categorized as Level 6─soft and bite-sized according to the International Dysphagia Diet Standardization Initiative (IDDSI) framework, indicating that the cod protein gel has potential as an easy-to-swallow diet for the elderly.

Improvement of the emulsifying properties of Zanthoxylum seed protein by ultrasonic modification

The influence of ultrasonic treatment (100-500 W, 30 min) on the molecular structures and emulsifying properties of Zanthoxylum seed protein (ZSP) was explored for the first time in this work. Research results indicated that the all ultrasonic treatments at different power levels decreased the particle size but increased the surface charge of ZSP. In addition, the ultrasonic treatments induced the structural unfolding of the ZAP, as indicated by the increase in α-helix, ultraviolet-visible absorbance, surface hydrophobicity and the amount of surface free sulfhydryl groups, as well as the decrease in β-sheet and intrinsic fluorescence intensity. As a result, the significantly (p < 0.05) increased emulsifying activity index (EAI) and emulsion stability index (ESI) of ZSP were observed after ultrasonic treatment. In addition, the emulsion prepared by ultrasonically treated ZSP exhibited the smaller and more uniform droplets with significantly improved stability against environmental stress (temperature, salt concentration, pH), creaming and oxidation due to the increased ratio of interfacially adsorbed ZSP. Furthermore, ultrasonic treatment at 400 W was found to be the optimum condition for modification. These findings will provide a theoretical foundation for the utilization of ultrasound in enhancing the emulsifying properties of ZSP and promoting its application in the field of food processing.

A review of green methods used in starch-polyphenol interactions: physicochemical and digestion aspects

The interactions of starch with lipids, proteins, and other major food components during food processing are inevitable. These interactions could result in the formation of V-type or non-V-type complexes of starch. The starch-lipid complexes have been intensively studied for over five decades, however, the complexes of starch and polyphenols are relatively less studied and are the subject of recent interest. The interactions of starch with polyphenols can affect the physicochemical properties and its digestibility. The literature has highlighted several green methods such as ultrasound, microwave, high pressure, extrusion, ball-milling, cold plasma etc., to assist interactions of starch with polyphenols. However, comprehensive information on green methods to induce starch-polyphenol interactions is still scarce. Therefore, in light of the importance and potential of starch-polyphenol complexes in developing functional foods with low digestion, this review has summarized the novel green methods employed in interactions of starch with flavonoids, phenolic acids and tannins. It has been speculated that flavonoids, phenolic acids, and tannins, among other types of polyphenols, may have anti-digestive activities and are also revealed for their interaction with starch to form either an inclusion or non-inclusion complex. Further information on the effects of these interactions on physicochemical parameters to understand the chemistry and structure of the complexes is also provided.

Recent advances in soybean protein processing technologies: A review of preparation, alterations in the conformational and functional properties

Currently, growing concerns about sustainable development and health awareness have driven the development of plant-based meat substitutes. Soybean proteins (SPs) are eco-friendly and high-quality food sources with well-balanced amino acids to meet consumer demand. The functionality and physicochemical attributes of SPs can be improved by appropriate processing and modification. With the burgeoning advances of modern processing technologies in the food industry, a multitude of functional foods and ingredients can be manufactured based on SPs. This review mainly highlights the conformational changes of SPs under traditional and emerging processing technologies and the resultant functionality modifications. By elucidating the relationship between processing-induced structural and functional alterations, detailed and systematic insights are provided regarding the exploitation of these techniques to develop different nutritional and functional soybean products. Some popular methods to modify SPs properties are discussed in this paper, including thermal treatment, fermentation, enzyme catalysis, high hydrostatic pressure, high-intensity ultrasound, atmospheric cold plasma, high-moisture extrusion, glycosylation, pulsed ultraviolet light and interaction with polyphenols. Given these processing technologies, it is promising to expand the application market for SPs and boost the advancement of the soybean industry.

Impact of emerging food processing technologies on structural and functional modification of proteins in plant-based meat alternatives: An updated review

In the past decade, the plant-based meat alternative industry has grown rapidly due to consumers' demand for environmental-friendly, nutritious, sustainable and humane choices. Consumers are not only concerned about the positive relationship between food consumption and health, they are also keen on the environmental sustainability. With such increased consumers' demand for meat alternatives, there is an urgent need for identification and modification of protein sources to imitate the functionality, textural, organoleptic and nutritional characteristics of traditional meat products. However, the plant proteins are not readily digestible and require more functionalization and modification are required. Proteins has to be modified to achieve high quality attributes such as solubility, gelling, emulsifying and foaming properties to make them more palatable and digestible. The protein source from the plant source in order to achieve the claims which needs more high protein digestibility and amino acid bioavailability. In order to achieve these newer emerging non-thermal technologies which can operate under mild temperature conditions can reach a balance between feasibility and reduced environmental impact maintaining the nutritional attributes and functional attributes of the proteins. This review article has discussed the mechanism of protein modification and advancements in the application of non-thermal technologies such as high pressure processing and pulsed electric field and emerging oxidation technologies (ultrasound, cold plasma, and ozone) on the structural modification of plant-based meat alternatives to improve, the techno-functional properties and palatability for successful food product development applications.

Application of ultrasound and its real-time monitoring of the acoustic field during processing of tofu: Parameter optimization, protein modification, and potential mechanism

Tofu is nutritious, easy to make, and popular among consumers. At present, traditional tofu production has gradually become perfect, but there are still shortcomings, such as long soaking time, serious waste of water resources, and the inability to realize orders for production at any time. Moreover, tofu production standards have not yet been clearly defined, with large differences in quality between them, which is not conducive to industrialized and large-scale production. Ultrasound has become a promising green processing technology with advantages, such as high extraction rate, short processing time, and ease of operation. This review focused on the challenges associated with traditional tofu production during soaking, grinding, and boiling soybeans. Moreover, the advantages of ultrasonic processing over traditional processing like increasing nutrient content, improving gel properties, and inhibiting the activity of microorganisms were explained. Furthermore, the quantification of acoustic fields by real-time monitoring technology was introduced to construct the theoretical correlation between ultrasonic treatments and tofu processing. It was concluded that ultrasonic treatment improved the functional properties of soybean protein, such as solubility, emulsifying properties, foamability, rheological properties, gel strength, and thermal stability. Therefore, the application of ultrasonic technology to traditional tofu processing to optimize industrial parameters is promising.

Hemp seed protein and chlorogenic acid complex: Effect of ultrasound modification on its structure and functional properties

In this study, the effects of ultrasound and chlorogenic acid (CA) on the structural and functional properties of hemp seed protein (HSP) was investigated. Compared with natural HSP, the UV-vis spectra intensity of ultrasound-treated HSP (UHSP) and UHSP-CA increased, the fluorescence spectra intensity decreased with a red shift in the maximum intensity peak. The results showed that ultrasound modification and complexation with CA unfolded the structure of HSP exposing its internal groups. Fluorescence quenching analysis showed that the best binding between UHSP and CA (binding constant 2.94 × 10² L/mol) was achieved at 450 W for 15 min of ultrasound treatment. In addition, the same ultrasound conditions minimized the particle size and surface roughness of UHSP and UHSP-CA. The solubility of UHSP and UHSP-CA increased by 23.3 and 38.7 %, the emulsifying activity index increased by 16.9 and 16.2 %, and the emulsion stability index increased by 20.9 and 20.8 %, respectively. These results indicated that appropriate ultrasound treatment and complexation with CA can significantly modify the structural and functional properties of HSP, improving its application value in the food field.

Sono-activation of food enzymes: From principles to practice

Over the last decade, sono-activation of enzymes as an emerging research area has received considerable attention from food researchers. This kind of relatively new application of ultrasound has demonstrated promising potential in facilitating the modern food industry by broadening the application of various food enzymes, improving relevant industrial unit operation and productivity, as well as increasing the yield of target products. This review aims to provide insight into the fundamental principles and possible industrialization strategies of the sono-activation of food enzymes to facilitate its commercialization. This review first provides an overview of ultrasound application in the activation of food protease, carbohydrase, and lipase. Then, the recent development on ultrasound activation of food enzymes is discussed on aspects including mechanisms, influencing factors, modification effects, and its applications in real food systems for free and immobilized enzymes. Despite the far fewer studies on sono-activation of immobilized enzymes compared with those on free enzymes, we endeavored to summarize the relevant aspects in three stages: ultrasound pretreatment of free enzyme/carrier, assistance in immobilization process, and modification of the already immobilized enzyme. Lastly, challenges for the scalability of ultrasound in these target areas are discussed and future research prospects are proposed.

Protein-Based High Internal Phase Pickering Emulsions: A Review of Their Fabrication, Composition and Future Perspectives in the Food Industry

Protein-based high internal phase Pickering emulsions (HIPEs) are emulsions using protein particles as a stabilizer in which the volume fraction of the dispersed phase exceeds 74%. Stabilizers are irreversibly adsorbed at the interface of the oil phase and water phase to maintain the droplet structure. Protein-based HIPEs have shown great potential for a variety of fields, including foods, due to the wide range of materials, simple preparation, and good biocompatibility. This review introduces the preparation routes of protein-based HIPEs and summarizes and classifies the preparation methods of protein stabilizers according to their formation mechanism. Further outlined are the types and properties of protein stabilizers used in the present studies, the composition of the oil phase, the encapsulating substances, and the properties of the constituted protein-based HIPEs. Finally, future development of protein-based HIPEs was explored, such as the development of protein-based stabilizers, the improvement of emulsification technology, and the quality control of stabilizers and protein-based HIPEs.

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.

Structural characterization and angiotensin-converting enzyme (ACE) inhibitory mechanism of Stropharia rugosoannulata mushroom peptides prepared by ultrasound

To reveal the structural characteristics and angiotensin-converting enzyme (ACE) inhibition mechanism of Stropharia rugosoannulata mushroom peptides prepared by multifrequency ultrasound, the peptide distribution, amino acid sequence composition characteristics, formation pathway, and ACE inhibition mechanism of S. rugosoannulata mushroom peptides were studied. It was found that the peptides in S. rugosoannulata mushroom samples treated by multifrequency ultrasound (probe ultrasound and bath ultrasound mode) were mainly octapeptides, nonapeptides, and decapeptides. Hydrophobic amino acids were the primary amino acids in the peptides prepared by ultrasound, and the amino acid dissociation of the peptide bonds at the C-terminal under the action of ultrasound was performed mainly to produce hydrophobic amino acids. Pro and Val (PV), Arg and Pro (RP), Pro and Leu (PL), and Asp (D) combined with hydrophobic amino acids were the characteristic amino acid sequence basis of the active peptides of the S. rugosoannulata mushroom. The docking results of active peptides and ACE showed that hydrogen bond interaction remained the primary mode of interaction between ACE and peptides prepared by ultrasound. The peptides can bind to the amino acid residues in the ACE active pocket, zinc ions, or key amino acids in the domain, and this results in inhibition of ACE activity. Cation-pi interactions also played an important role in the binding of mushroom peptides to ACE. This study explains the structural characteristics and ACE inhibition mechanism used by S. rugosoannulata mushroom peptides prepared by ultrasound, and it will provide a reference for the development and application of S. rugosoannulata mushroom peptides.

Gelling Characteristics of Emulsions Prepared with Modified Whey Protein by Multiple-Frequency Divergent Ultrasound at Different Ultrasonic Power and Frequency Mode

The effect of ultrasonic frequency mode (mono, dual and tri-frequency) and ultrasonic power (0–300 W) on structural properties (intrinsic fluorescence and sulfhydryl content) of whey protein was studied. Emulsions prepared with modified whey protein were used to form the heat-set gels, and the properties of whey protein emulsion gels (WPEG) and their digestion were investigated. The textural and rheological properties of WPEG prepared using whey protein pretreated by mono and dual-frequency ultrasound at the power between 180–240 W were enhanced, while those of WPEG prepared with whey protein pretreated by triple-frequency above the power of 180 W were declined. WPEG prepared using whey protein pretreated by dual-frequency ultrasound (DFU) with the power of 240 W had the highest hardness and storage modulus which were 3.07 and 1.41 times higher than the control. The microstructure of WPEG prepared using DFU pretreated whey protein showed homogeneous and denser networks than those of the control according to the results of confocal laser scanning microscope (CLSM). The modification in the microstructure and properties of the WPEG prepared using DFU pretreated whey protein delayed the protein disintegration during the first 30 min of gastric digestion when compared with control. Whereas the release rate of free amino group of the WPEG prepared using whey protein modified by ultrasonic pretreatment increased during the intestinal phase when compared with that of control. The results indicated that using dual-frequency ultrasound to modify whey protein is more efficient in improving the properties of WPEG, and ultrasonic power should be considered during the application of ultrasound pretreatment in producing protein gels. The fine network of WPEG prepared with whey protein pretreated by ultrasound resulted in better hardness and storage modulus. Partially unfolding of the protein induced by ultrasound pretreatment might make the whey protein more susceptible to the digestive enzyme. Our results could provide new insights for using ultrasound as the potential processing tool on designing specific protein emulsion gels as the delivery system for nutrients.

Independent and combined effects of ultrasound and transglutaminase on the gel properties and in vitro digestion characteristics of bay scallop (Argopecten irradians) adductormuscle

The effects of transglutaminase (TGase) addition (0.4–1.2 g/100g), ultrasound (120–720 W, 20 min), and their combination on the gel properties and in vitro digestion characteristics of bay scallop adductor muscle were studied. The gel strength of the gel sample with TGase content of 0.8 g/100g (TG-0.8) was 58.2% higher than that of the control sample (CON). The gel sample treated with ultrasound at 480 W (UT-480) had the highest gel strength. The strength of the gel prepared by combination of 0.8 g/100g TGase and 360 W ultrasound (UT-TG) was 82.3% higher than that of CON. The whiteness and water holding capacity of the gel increased regardless of the addition of TGase or ultrasound treatment. SDS-PAGE patterns showed that the myosin heavy chain of the treated samples became thinner, and the changes of actin and tropomyosin were not significant. The scanning electron microscopy results of gel samples prepared by ultrasound combined with TGase showed a denser structure, which was related to the lowest total sulfhydryl content and TCA-soluble peptide content. The results of dynamic rheology show that the UT-TG sample had the highest G′ value, followed by TG-0.8. The in vitro digestion characteristics of the selected gel samples were also discussed. The degree of protein hydrolysis and the content of free amino acids in TG-0.8 samples were the lowest, which improved after ultrasound treatment. Overall, the combination of appropriate ultrasound treatment and TGase addition provides an effective means for improving gel properties and digestibility of scallop surimi product.

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Ultrasound and TGase enhanced gel properties of bay scallop adductor muscle (BSM).

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Ultrasound-assisted treatment promoted the cross-linking of BSM myosin by TGase.

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A denser gel network structure was formed when ultrasound combined with TGase.

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Ultrasound combined with TGase can improve the digestibility of the gel in vitro.