Effects of ultrasound on structural and physical properties of soy protein isolate (SPI) dispersions

Effects of atmospheric cold plasma and high-power sonication on rheological and gelling properties of mung bean protein dispersions

The objective of this study was to evaluate the impact of high-power sonication (HPS) and atmospheric cold plasma (ACP) on gelling and rheological properties of mung bean protein dispersions. HPS at 250 J/mL for 2 min and ACP at 80 kV for 5 min were applied to different concentrations of mung bean protein isolate (MBPI). Control and HPS-treated MBPI dispersions showed a minimum gelling concentration (MGC) of 16% w/v, while ACP-treated dispersions started to gel at 14% w/v. Dynamic rheology of dispersions at 16 % concentrations showed that HPS and ACP treatments could reduce the initial gelling temperature to 52° and 65 °C, respectively, from 75 °C for no-treatment control. ACP-treated 16% protein dispersions showed a six-fold higher storage modulus (G') than the control. In addition, ACP treatment resulted in significantly more hydrophobic bonds (∼5.0 g/L) than control (∼1.4 g/L) and HPS-treated (∼1.1 g/L) MBPI gels; however, the net interaction of ionic, hydrogen, hydrophobic, and disulfide bonds was higher in HPS-treated MBPI gels. Thus, both ACP and HPS treatments altered the gelling characteristics of mung bean protein dispersions- ACP reduced MGC and improved firmness, whereas HPS improved the springiness, cohesiveness, gumminess, chewiness, and resilience of the gels.

Improving the Functional Performance of Date Seed Protein Concentrate by High-Intensity Ultrasonic Treatment

Date kernel is a plant-derived byproduct that has the potential to be converted into a high-value-added food ingredient, such as protein concentrate, in the food industry. Ultrasound, which is an alternative method for improving the functional properties of food proteins, is an effective physical treatment for modifying protein functionality. Solubility is the main criterion that primarily affects other functional properties of protein concentrates, such as emulsification, foaming, and water and oil binding. The aim of this study is to enhance the techno-functional performance of date seed protein concentrate (DSPC) by maximizing the solubility via a high-intensity ultrasound (HIUS) treatment at a fixed frequency of 20 kHz. The effect of ultrasonic homogenization under varying amplitudes and times (amplitude of 40, 60, and 80% for 5, 10, and 15 min, respectively) on the functional properties of the DSPC was investigated by using the response surface methodology (RSM). A face-centered central composite design (FC-CCD) revealed that the optimal process conditions of HIUS were at an amplitude of 80% for 15 min. The physicochemical and functional properties of the ultrasound-applied concentrate (DSPC-US) were determined under the optimum HIUS conditions, and then these properties of DSPC-US were compared to the native DSPC. The results showed that the solubility of all DSPC samples treated by HIUS was significantly (p < 0.05) higher than that of the native DSPC. In addition, emulsion activity/stability, foaming activity/stability, and oil-binding capacity increased after HIUS homogenization treatments, whereas the water-binding capacity decreased. These changes in the techno-functional properties of the DSPC-US were explained by the modification to the physicochemical structure of the DSPC (particle size, zeta potential, SDS-PAGE, SEM, FTIR, DSC, free SH content, surface hydrophobicity, and intrinsic emission). This work revealed that HIUS could be an effective treatment for enhancing the functional properties of date seed protein concentrate.

Impact of Different Enzymatic Processes on Antioxidant, Nutritional and Functional Properties of Soy Protein Hydrolysates Incorporated into Novel Cookies

Soy protein concentrate (SPC) was hydrolyzed using several commercial food-grade proteases (Alcalase, Neutrase, papain, Everlase, Umamizyme, Flavourzyme) and their combination to obtain promising ingredients in the manufacture of functional bakery products. In all cases, the hydrolysis caused nutritional, sensory, and rheological changes in SPC, as well as protein structural changes like increased surface hydrophobicity and content of exposed SH groups with the magnitude of these changes depending on enzyme specificity. The hydrolysis with the combination of Neutrase and Flavourzyme (NeuFlav) increased essential amino acid content by 9.8% and that of Lys by 32.6% compared to SPC. This hydrolysate showed also significant antioxidant activities including ABTS and superoxide anion scavenging activity and metal-chelating ability. The addition of all hydrolysates in wheat flour decreased water adsorption and increased development time to some extent due to gluten network weakening, but also decreased the rate of starch retrogradation, contributing to the increase of the shelf-life of bakery products. The NeuFlav tasted less bitter than other hydrolysates, while E-nose provided a discrimination index of 93 between control and hydrolysates. It appeared that the addition of the NeuFlav hydrolysate in a cookie formulation improved protein content and nutritional quality and directed to its higher general consumer acceptability than cookies formulated with only wheat flour.

Ultrasound-Assisted Extraction of Protein from Pumpkin Seed Press Cake: Impact on Protein Yield and Techno-Functionality

Conventional solvent-based methods widely used for isolating plant proteins may deliver an unsatisfactory protein yield and/or result in protein degradation. The present study started with the optimization of pumpkin seed protein from press cake by alkaline extraction and subsequent isoelectric precipitation. Subsequently, extraction was supported by ultrasound under three conditions: ultrasonic treatment followed by alkaline extraction (US+AE), concomitant ultrasonic treatment and alkaline extraction (UAE), and alkaline extraction followed by ultrasonic treatment (AE+US). Compared to the control group, an increase in protein yield was achieved after ultrasonic treatment, while the highest protein yield was obtained with AE+US (57.8 ± 2.0%). Isolates with a protein content of 94.04 ± 0.77 g/100 g and a yield of 43.6 ± 0.97% were obtained under optimized conditions. Following ultrasonic treatment applied during extraction, solubility, foaming capacity, foam stability, and denaturation enthalpy of the isolated protein increased, and water binding capacity decreased as compared to non-sonicated samples. The d90 particle size percentile of the extracted suspensions was 376.68 ± 38.32 µm for the control experiments, and particle size was significantly reduced in ultrasound-assisted treatments down to d90 = 179.93 ± 13.24 µm for the AE+US treatment). Generally, ultrasonication resulted in a significant increase in protein yield and improved techno-functional properties of the isolates.

Fabrication of icariin-soymilk nanoparticles with ultrasound-assisted treatment

Ultrasound is effective to fabricate nanocomplex. Soymilk is a natural nanocarrier with good compatibility. However, information about soymilk-nutraceuticals nanocomplex is limited. In this work, soymilk was used to encapsulate icariin, a well known nutraceutical with poor bioavailability. The effect of ultrasound on the quality of icariin-soymilk nanocomplexes (ISNCs) was investigated. Ultrasound could reduce the particle size, improve the surface hydrophobicity and change the microstructure of soymilk. With increasing ultrasound treatment time, an increased surface hydrophobicity was observed. The highest encapsulation efficiency (89.67 %) and loading capacity (28.92 µg/mg) were found for USI-20, whereas the smallest particle size (132.47 nm) was observed for USI-120. USI-60 showed the lowest ζ-potential (-31.33 mV) and the highest bioaccessibility (76.08 %). Ultrasound could enhance the storage stability of ISNCs. The data of NMR and fluorescence indicated that ISNCs were mainly stabilized by hydrophobic interaction.

Physicochemical and Antioxidant Properties of Industrial Hemp Seed Protein Isolate Treated by High-Intensity Ultrasound

Ultrasound is one of the non-thermal, green, and novel technologies used to functionalize plant proteins. We recently determined the optimum conditions of high-intensity ultrasound (HIUS) treatment for maximum solubility and investigated the functional properties of hemp seed protein isolate (HSPI) under the optimal conditions. In this study, we analyzed changes in primary, secondary, and tertiary structures, physical microstructures, thermal stability, and antioxidant capacity of ultrasound-applied hemp protein isolate (HSPI-HIUS). The free SH group content (+59%) and zeta potential (+25%) increased upon ultrasound treatment. The electrophoretic protein patterns of HSPI showed no significant change after HIUS treatment. The FTIR spectrum revealed the wavenumber shifts in Amid 1 and 2 regions of protein. The denaturation temperature and the ratio of β-structure increased after sonication. Antioxidant properties of hemp seed protein isolates were increased by 38% by ultrasound treatment. The obtained data in this study showed that HIUS treatment would be promising for improving the functional, physicochemical, and antioxidant properties of HSPI.

Impacts of sonication and high hydrostatic pressure on the structural and physicochemical properties of quinoa protein isolate dispersions at acidic, neutral and alkaline pHs

Herein, 1 wt% quinoa protein isolate (QPI) was exposed to sonication using a 20 kHz ultrasonicator equipped with a 6 mm horn (14.4 W, 10 mL, up to 15 min) or high hydrostatic pressure (HHP, up to 600 MPa, 15 min) treatments at pH 5, pH 7, and pH 9. The changes to physicochemical properties were probed by SDS-PAGE, FTIR, free sulfhydryl group (SH), surface hydrophobicity (H0), particle size and solubility. As revealed by SDS-PAGE, substantial amounts of 11S globulin participated in the formations of aggregates via SS bond under HHP, particularly at pH 7 and pH 9. However, protein profiles of QPI were not significantly affected by the sonication. Free SH groups and surface hydrophobicity were increased after the sonication treatment indicating protein unfolding and exposure of the embedded SH and/or hydrophobic groups. An opposite trend was observed in HHP treated samples, implying aggregation and reassociation of structures under HHP. HHP and sonication treatments induced a decrease in ordered secondary structures (random coil and β-turn) accompanied with an increase in disordered secondary structures (α-helix and β-sheet) as probed by FTIR. Finally, the sonication treatment induced a significant improvement in the solubility (up to ∼3 folds at pH 7 and ∼2.6 folds at pH 9) and a reduction in particle sizes (up to ∼3 folds at pH 7 and ∼4.4 folds at pH 9). However, HHP treatment (600 MPa) only slightly increased the solubility (∼1.6 folds at pH 7 and ∼1.2 folds at pH 9) and decreased the particle size (∼1.3 folds at pH 7 and ∼1.2 folds at pH 9). This study provides a direct comparison of the impacts of sonication and HHP treatment on QPI, which will enable to choose the appropriate processing methods to achieve tailored properties of QPI.

Effect of Ionic Strength on Heat-Induced Gelation Behavior of Soy Protein Isolates with Ultrasound Treatment

This study investigated the effect of ultrasound on gel properties of soy protein isolates (SPIs) at different salt concentrations. The results showed that ultrasound could significantly improve the gel hardness and the water holding capacity (WHC) of the salt-containing gel (p < 0.05). The gel presents a uniform and compact three-dimensional network structure. The combination of 200 mM NaCl with 20 min of ultrasound could significantly increase the gel hardness (four times) and the WHC (p < 0.05) compared with the SPI gel without treatment. With the increase in NaCl concentration, the ζ potential and surface hydrophobicity increased, and the solubility decreased. Ultrasound could improve the protein solubility, compensate for the loss of solubility caused by the addition of NaCl, and further increase the surface hydrophobicity. Ultrasound combined with NaCl allowed proteins to form aggregates of different sizes. In addition, the combined treatment increased the hydrophobic interactions and disulfide bond interactions in the gel. Overall, ultrasound could improve the thermal gel properties of SPI gels with salt addition.

Drying methods affect physicochemical and functional characteristics of Clanis Bilineata Tingtauica Mell protein

Clanis Bilineata Tingtauica Mell Protein (CBTMP) was a kind of natural full-price protein which has a bright application prospect in the food industry. Since the functional properties of protein can be significantly affected by drying method, this study aims to explore the effect of different drying methods, namely freeze drying (FD), vacuum drying (VD),and hot-air drying (HD) on the structure and functional properties of CBTMP. The results showed that the degree of oxidation of CBTMP was found to be in the following order: HD &gt; VD &gt; FD. Functional characteristics revealed that the CBTMP prepared by VD had relatively high foaming ability (150.24 ± 5.34°C) among three drying methods. However, the stability of emulsion and rheological properties prepared by FD was superior to other samples. Differential scanning calorimeter (DSC) showed CBTMP made by HD had the relatively good thermal stability (Tp = 91.49 ± 0.19 °C), followed by VD and FD. Digestive properties reflected that heating treatment could significantly increase its degree of hydrolysis in vitro. To sum up, the research could provide experimental guidance and theoretical support for the preparation method and utilization of CBTMP.

The Effects of Ethanol and Rutin on the Structure and Gel Properties of Whey Protein Isolate and Related Mechanisms

The effects of different levels of rutin (0, 0.05%, 0.1%, 0.2% and 0.3% w/v) and ethanol on the structure and gel properties of whey protein isolate (WPI) were examined. The results showed that the addition of ethanol promoted the gel formation of WPI. The addition of rutin increased the gel strength of WPI and maintained the water-holding capacity of the gel. Ethanol caused an increase in thiol content and surface hydrophobicity, but rutin decreased the thiol content and surface hydrophobicity of WPI. The particle size, viscosity and viscoelasticity of WPI increased at rutin levels of 0.2% and 0.3%, indicating that rutin caused cross-linking and aggregation of WPI, but rutin had no significant effect on the zeta-potential, indicating that electrostatic interactions were not the main force causing the changes in protein conformation and gel properties. Ethanol and rutin improved the gel properties of WPI possibly by inducing cross-linking of WPIs via hydrophobic and covalent interactions.

Dual improvement in curcumin encapsulation efficiency and lyophilized complex dispersibility through ultrasound regulation of curcumin-protein assembly

Ultrasound has a recognized ability to modulate the structure and function of proteins. Discovering the influential mechanism of ultrasound on the intramolecular interactions of egg-white protein isolate-curcumin (EPI-Cur) nanoparticles and their intermolecular interaction during freeze drying and redispersion is meaningful. In this study, under the extension of pre-sonication time, the protein solubility, surface hydrophobicity, and curcumin encapsulation rate showed an increasing trend, reaching the highest value at 12 min of treatment. However, the values decreased under the followed extension of ultrasound time. After freeze drying and redispersion were applied, the EPI-Cur sample under 12 min of ultrasound treatment exhibited minimal aggregation degree and loss of curcumin. The retention and loading rates of curcumin in the lyophilized powder reached 96 % and 33.60 mg/g EPI, respectively. However, under excessive ultrasound of >12 min, scanning electron microscopy showed distinct blocky aggregates. Overexposure of the hydrophobic region of the protein triggered protein-mediated hydrophobic aggregation after freeze drying. X-ray diffraction patterns showed the highest crystallinity, indicating that the free curcumin-mediated hydrophobic aggregation during freeze drying was enhanced by the concentration effect and intensified the formation of larger aggregates. This work has practical significance for developing the delivery of hydrophobic active substances. It provides theoretical value for the dynamic dispersity change in protein-hydrophobic active substances during freeze drying and redissolving.

Effects of ultrasound pretreatment on functional property, antioxidant activity, and digestibility of soy protein isolate nanofibrils

Nanofibrils, an effective method to modulate the functional properties of proteins, can be promoted by ultrasound pretreatment. This study investigated the effect of ultrasound pretreatment on the structure, functional property, antioxidant activity and digestibility of soy protein isolate (SPI) nanofibrils. The results showed that high amplitude ultrasound had a significant effect on structure of SPI nanofibrils. SPI nanofibrils pretreated by 80% amplitude ultrasound showed a blueshift of the amide II band in Fourier transform infrared spectroscopy (FTIR), resulted in more tryptophan residues being buried and increased the crystallinity. Low amplitude ultrasound (20%) pretreatment significantly improved the solubility, emulsifying activity index (EAI) and water absorption capacity (WAC) of SPI nanofibrils, but 80% amplitude ultrasound pretreatment of SPI nanofibrils reduced emulsifying stability index (ESI). High amplitude ultrasound (60% and 80%) pretreatment of SPI nanofibrils improved the foaming capacity and foaming stability and decreased denaturation temperature. DPPH radical scavenging activity of SPI nanofibrils were significantly improved by ultrasound pretreatment. 20% amplitude ultrasound pretreatment improved DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power of SPI nanofibrils. The digestion rate of 80% amplitude ultrasound-pretreated nanofibrils were consistently higher, and SPI nanofibrils pretreated by ultrasound were more fragmented and shorter after simulating gastrointestinal digestion. This study would expand the application of food-grade protein nanofibrils in the food industry.

Improvement in Emulsifying Capacity of Goose Liver Protein Treated by pH Shifting with Addition of Sodium Tripolyphosphate and Its Proteomics Analysis

Goose liver isolate treated by pH shifting and pH shifting/non-enzyme phosphorylation with goose liver isolate was used as a control. The functional property differences in the protein and proteins involved in the interfacial layer treated with pH shifting and non-enzyme phosphorylation were studied. Compared with the goose protein isolates (GPIs) at pH 7.0, the GPIs treated by pH shifting was not a good choice to be an emulsifier in a neutral environment, and non-enzyme phosphorylation inhibited the negative effects of pH shifting treatment and improved protein properties. The results of proteomics showed that the identified proteins in the interfacial layer belong to hydrophilic proteins. Non-enzyme phosphorylation increased the abundances of most proteins due to ion strength, including some phosphorylated proteins. Correlation analysis indicated that protein solubility was highly positively related with S₀, intrinsic fluorescence, total sulfhydryl, free sulfhydryl, A0A0K1R5T3, R0KA48, R0KFP7, U3J1L1, P01989, R0JSM9, and R0LAD1, and was also highly negatively related with particle size and R0M210, R0M714, and R0LFA3. The emulsifying activity index (EAI) demonstrated highly positive correlation with protein solubility, and was correlated with R0JKI4, R0KK84, R0L1Y3, R0LCM7, A0A068C605, and U3IW62.

Ultrasound-assisted modification of gelation properties of proteins: A review

Protein gels have diverse applications in the food, pharmaceutical, and cosmetic sectors due to their affordability, biodegradability, and edibility. However, the inherent properties of some native proteins have a few drawbacks that have to be tailored to meet the needs of specific functions as the food ingredients. The protein gelation properties mainly depend on the protein molecular structure, primarily the folding and unfolding of secondary structural elements (α-helix and β-sheets) with distinctive functions. In the past, a great amount of work (thermal, chemical, and enzymatic methods) has been carried out to enhance the gelation and functional properties of proteins. Recently, the traditional methods have been replaced with non-thermal physical methods that enhance the properties for better applications. One such approach is the use of ultrasonic technology as a low-cost green technology to modify the molecular orientation attributed to the native chemistry and functionality of that proteins. Ultrasonic technology is important in food systems and can be effectively used as an alternative method to improve the protein gelling characteristics to form high-quality gels. This article is aimed to comprehensively collate some of the vital information published on the mechanism of protein gelation by ultrasonication and review the effects of ultrasound-assisted extraction and treatments on gelation properties of different proteins. The enhanced gelation properties by the ultrasound application open a new stage of technology that enables the proteins for better utilization in the food processing sector.

Ultrasound-assisted preparation of lactoferrin-EGCG conjugates and their application in forming and stabilizing algae oil emulsions

The aim of this study was to prepare lactoferrin-epigallocatechin-3-gallate (LF-EGCG) conjugates and to determine their ability to protect emulsified algal oil against aggregation and oxidation. LF-EGCG conjugates were formed using an ultrasound-assisted alkaline treatment. The ultrasonic treatment significantly improved the grafting efficiency of LF and EGCG and shortened the reaction time from 24 h to 40 min. Fourier transform infrared spectroscopy and circular dichroism spectroscopy analyses showed that the covalent/non-covalent complexes could be formed between LF and EGCG, with the CO and CN groups playing an important role. The formation of the conjugates reduced the α-helix content and increased the random coil content of the LF. Moreover, the antioxidant activity of LF was significantly enhanced after conjugation with EGCG. LF-EGCG conjugates as emulsifiers were better at inhibiting oil droplet aggregation and oxidation than LF alone. This study demonstrates that ultrasound-assisted formation of protein-polyphenol conjugates can enhance the functional properties of the proteins, thereby extending their application as functional ingredients in nutritionally fortified foods.

Multi-mode S-type ultrasound-assisted protein extraction from walnut dregs and in situ real-time process monitoring

This study aimed to investigate the impact of multi-mode S-type ultrasound treatment on the protein extraction level of walnut dregs. The structural properties of the walnut protein (WP) were characterized, and the correlation between protein structure and extraction level was analyzed. The in situ real-time monitoring model for the ultrasound-assisted WP extraction process was established by a miniature fiber near-infrared (NIR) spectrometer. Results showed that the protein yield, purity, and comprehensive extraction index (CEI) of extracted WP were 71.07 %, 72.69 %, and 71.72, respectively, under optimal conditions (dual-frequency 20/28 kHz, ultrasonic treatment duration 30 min, and ultrasound power density 120 W/L). The secondary structure of extracted WP displayed that the proportion of α-helix and β-sheet reduced, while the contents of β-turn and random coil increased after ultrasonic treatment. Besides, sonication decreased the disulfide bond content and increased free sulfhydryl (-SH) and surface hydrophobicity compared to the control. The microstructures of WP confirmed that appropriate sonication could unfold the protein aggregates and reduce the particle size. The extraction level of WP is positively correlated with the -SH content (p < 0.01). The quantitative prediction model of Si-PLS for -SH content in the ultrasound-assisted WP extraction process was established and performed a good correction and prediction performance (Rc = 0.9736; RMSECV = 0.446 μmol/L; Rp = 0.9342; RMSEP = 0.807 μmol/L). This study exploited a high-efficiency way for the WP extraction industry, and provided theoretical support for the development of the intelligent system in industrial protein extraction process.

Ultrasonic-assisted pH shift-induced interfacial remodeling for enhancing the emulsifying and foaming properties of perilla protein isolate

In order to expand the applications of plant protein in food formulations, enhancement of its functionalities is meaningful. Herein, the effects of ultrasonic (20 KHz, 400 W, 20 min)-assisted pH shift (pH 10 and 12) treatment on the structure, interfacial behaviors, as well as the emulsifying and foaming properties of perilla protein isolate (PPI) were investigated. Results showed that the solubility of PPI treated by ultrasonic-assisted pH shift (named UPPI-10/12) exceeded 90 %, which was at least 2 and 1.4 times that of untreated PPI and ultrasound-based PPI. Meanwhile, UPPI-10/12 possessed higher foamability (increasing by at least 1.2 times) and good emulsifying stability. Ultrasonic-assisted pH shift treatment decomposed large PPI aggregates into tiny particles, evident from the dynamic light scattering (DLS) and atomic force microscopy results. Besides, this approach induced a decrease in α-helix of PPI and an increase in β-sheet, which might result in the exposure of the hydrophobic group on the structural surface of PPI, thus leading to the increase of surface hydrophobicity. The smaller size and higher hydrophobicity endowed UPPI-10/12 faster adsorption rate, tighter interfacial structure, and higher elastic modulus at the air- and oil-water interfaces, evident from the cryo-SEM and interfacial dilatational rheological results. Thus, the emulsifying and foaming properties could evidently enhance. This study demonstrated that ultrasonic-assisted pH shift technique was a simple approach to effectively improve the functional performance of PPI.

Effect of Different Thawing Methods on the Physicochemical Properties and Microstructure of Frozen Instant Sea Cucumber

To provide recommendations to users regarding which thawing method for frozen instant sea cucumbers entails lower quality losses, in this study we compared the water retention, mechanical properties, protein properties, and microstructures of frozen instant sea cucumbers post-thawing by means of different thawing approaches, including refrigerator thawing (RT), air thawing (AT), water immersion thawing (WT), and ultrasound-assisted thawing (UT). The results indicated that UT took the shortest time. RT samples exhibited the best water-holding capacity, hardness and rheological properties, followed by UT samples. The α-helix and surface hydrophobicity of WT and AT samples were significantly lower than those of the first two methods (p < 0.05). The lowest protein maximum denaturation temperature (Tmax) was obtained by means of WT. AT samples had the lowest maximum fluorescence emission wavelength (λmax). Based on these results, WT and AT were more prone to the degradation of protein thermal stability and the destruction of the protein structure. Similarly, more crimping and fractures of the samples after WT and AT were observed in the sea cucumbers’ microstructures. Overall, we observed that UT can be used to maintain the quality of frozen instant sea cucumbers in the shortest time.

Ultrasound Treatment Enhanced Semidry-Milled Rice Flour Properties and Gluten-Free Rice Bread Quality

The structural and functional properties of physical modified rice flour, including ultrasound treated rice flour (US), microwave treated rice flour (MW) and hydrothermal treated rice flour (HT) were investigated with wet-milled rice flour (WF) used as a positive control. The results showed the presence of small dents and pores on the rice flour granules of US and MW while more fragments and cracks were showed in HT. XRD and FTIR revealed that moderate ultrasonic treatment promoted the orderly arrangement of starch while hydrothermal treatment destroyed the crystalline structure of rice flour. In addition, the significant decrease of gelatinization enthalpy and the narrowing gelatinization temperature were observed in US. Compared to that of SF, adding physical modified rice flour led to a batter with higher viscoelasticity and lower tan δ. However, the batter added HT exhibited highest G' and G″ values and lowest tan δ, which led to a harder texture of bread. Texture analysis demonstrated that physical modified rice flour (except HT) reduced the hardness, cohesion, and gumminess of rice bread. Especially, the specific volume of bread with US increased by 15.6% and the hardness decreased by 17.6%. This study suggested that ultrasound treatment of rice flour could improve texture properties and appearance of rice bread.

Effects of ultrasonic pretreatment of soybean protein isolate on the binding efficiency, structural changes, and bioavailability of a protein-luteolin nanodelivery system

The combination of protein and flavonoids can ameliorate the problems of poor solubility and stability of flavonoids in utilization. In this study, soybean protein isolate pretreated by ultrasonication was selected as the embedding wall material, which was combined with luteolin to form a soybean protein isolate-luteolin nanodelivery system. The complexation effect and structural changes of soybean protein isolate (SPI) and ultrasonic pretreatment (100 W, 200 W, 300 W, 400 W and 500 W) of soybean protein isolate with luteolin (LUT) were compared, as well as the changes in digestion characteristics and antioxidant activity in vitro. The results showed that proper ultrasonic pretreatment increased the encapsulation efficacy, loading amount and solubility to 89.72%, 2.51 μg/mg and 90.56%. Appropriate ultrasonic pretreatment could make the particle size and the absolute value of ζ-potential of SPI-LUT nanodelivery system decrease and increase respectively. The FTIR and fluorescence results show that appropriate ultrasonic pretreatment could reduce α-helix, β-sheet and random coil, increase β-turn, and enhance fluorescence quenching. The thermodynamic evaluation results indicate that the ΔG < 0, ΔH > 0 and ΔS > 0, so the interaction of LUT with the protein was spontaneous and mostly governed by hydrophobic interactions. The XRD results show that the LUT was amorphous and completely wrapped by SPI. The DSC results showed that ultrasonic pretreatment could improve the thermal stability of SPI-LUT nanodelivery system to 112.66 ± 1.69 °C. Digestion and antioxidant analysis showed that appropriate ultrasonic pretreatment increased the LUT release rate and DPPH clearance rate of SPI-LUT nanodelivery system to 89.40 % and 55.63 % respectively. This study is a preliminary source for the construction of an SPI nanodelivery system with ultrasound pretreatment and the deep processing and utilization of fat-soluble active substances.

Improved effect of ultrasound-assisted enzymolysis on egg yolk powder: Structural properties, hydration properties and stability characteristics

Preparation of egg yolk powder (EYP) with excellent hydration properties and dissolution stability is important for the efficient utilization of its functional properties and nutritional properties in food. In this work, a new method utilizing ultrasound-assisted enzymolysis (UP-EM) was investigated to obtain EYP. Compared to enzymolysis-alone treated (EM), ultrasonic pre-treatment (UP) significantly increased the enzymatic hydrolysis rate by 106.28%. In particular, the UP 60 W 20 min-EM group obtained the desired solubility and coefficient of stability. The observed microstructure of EYP showed that the egg yolk particles obtained by UP-EM were more uniformly distributed and smaller in particle size. The protein structure was confirmed by Fourier transform infrared spectrum, which showed that UP enhanced the hydrogen bonding force between egg yolk proteins. Therefore, it can be believed that UP-EM can significantly improve the hydration properties and dispersion stability of EYP, laying the foundation for its wide applications in food industry.

Physicochemical, structural and functional properties of protein isolates and major protein fractions from common vetch (Vicia sativa L.)

Common vetch (CV), a leguminous crop cultivated for green manure and fodder rich in protein and starch, is widespread over much area of the northern hemisphere. Its seeds can be used as a protein source to human consumption. CV protein isolates (CVPI) and major protein fractions (CV albumin protein, CVAP; CV globulin protein, CVGP; CV glutelin protein, CVGTP) from 4 samples were investigated the properties to facilitate full use of protein resources. Protein comprises 27.70 %-32.14 % of the dry CV seed weight, which is mainly composed by CVAP (26.79 %-56.12 %) and CVGP (22.78 %-52.42 %). CVPI, CVAP and CVGP mainly presented 7S and 11S components. CVGTP mainly contained the 11S component. They showed difference in thermal properties and surface hydrophobicity. Circular dichroism data showed that α-helix was their major secondary structure. CVPI and major protein fractions exhibited a U-shape protein solubility. CVPI and CVAP had advantages in emulsifying and foaming properties. This study provided novel insights on unexploited sources of CV proteins with interesting characteristics in terms of potential uses as protein-based foods.

Effect of ultrasound on functional properties, flavor characteristics, and storage stability of soybean milk

The effects of different ultrasound treatments (20 kHz at 400 W for 0 to 9 min) on the functional properties, flavor characteristics, and storage stability of soybean milk at 4 °C were investigated. Results indicated that non-sonicated soymilk had the maximum particle size D4, 3 of 2.47 ± 0.47 µm, while 9 min high intensity ultrasound (HIU) decreased D4, 3 to 0.44 ± 0.01 µm. 9 min of HIU decreased the total number of microorganisms in soymilk from 4.51 to 3.95 Log (CFU/mL). Moreover, 9 min HIU increased the absolute value of ζ-potential from 36.43 to 34.13 mV. Turbiscan test showed that 9 min HIU decreased the instability index of soymilk from 0.78 to 0.65. Furthermore, sensory analysis, electronic nose, electronic tongue, and gas chromatography-mass spectrometry showed that 7 min HIU decreased the content of aldehydes, furans, ketones, and alcohols by 52.09%, 75.01%, 56.79%, and 57.27%, respectively.

A combined approach for modifying pea protein isolate to greatly improve its solubility and emulsifying stability

Pea protein-based delivery systems have drawn much attention in the food and pharmaceutical fields in recent years. However, its broad application faces great limitations because of the low solubility. Here, we present a novel and effective approach to overcome this difficulty and enhance the techno-functional characteristics, especially emulsifying stability, of the pea protein isolate (PPI). By combining pH-shifting with ultrasound and heating (PUH), we concluded that the solubility of PPI greatly increased from 29.5 % to 90.4 %, whereas its surface hydrophobicity increased from 1098 to 3706. This was accompanied by the changes of PPI structure, as shown by circular dichroism and scanning electron microscopy. In addition, the modified PPI was applied to stabilize sunflower oil-in-water emulsions. The droplet size of the emulsion with PUHP was reduced and its emulsion stability was significantly elevated. Taken together, we propose a novel combined approach to prepare modified PPI with high solubility and emulsion stability. We expect our method will have a wider application in modifying plant proteins and improving their industrial processing.