High intensity ultrasound modified ovalbumin: Structure, interface and gelation properties

Physicochemical and emulsifying properties of mussel water-soluble proteins as affected by lecithin concentration

The effects of lecithin addition at different concentrations (0-2.0%) on the physicochemical and emulsifying properties of mussel water-soluble proteins (MWP) were investigated. In solution system, low lecithin concentration (0.5%-1.0%) induced the aggregation and increased turbidity of composite particles. Lecithin addition caused changes in secondary structure and induced partial unfolding of MWP. Hydrophobic interactions between MWP and lecithin may contribute to the exposure of chromophores and hydrophobic groups of MWP. The interfacial tension decreased with lecithin addition. However, at a high lecithin concentration (1.5%-2.0%), the degree of aggregation and state of unfolding alleviated due to competitive adsorption. In emulsion system, with the low concentration of lecithin addition (0.5%-1.0%), droplet size and surface charge of emulsion decreased. The emulsion activity index, emulsion stability index, percentage of adsorbed protein increased. Both creaming stability and viscoelastic properties improved. At an intermediate lecithin concentration (1.0%), the emulsion showed the highest physical stability, while further addition of lecithin caused a slight deterioration in emulsifying properties. Overall, these results indicated the possibility that the lecithin-MWP mixed emulsifiers can be used to obtain emulsions with desirable properties.

High-Intensity Ultrasound Treatment on Soy Protein after Selectively Proteolyzing Glycinin Component: Physical, Structural, and Aggregation Properties

In this study, a novel method called selective proteolysis was applied to the glycinin component of soy protein isolate (SPI), and a degraded glycinin hydrolysate (DGH) was obtained. The effects of high-intensity ultrasound (HIU) treatment (20 kHz at 400 W, 0, 5, 20, and 40 min) on the physical, structural, and aggregation properties of DGH were investigated with the aim to reveal the influence of the selectively hydrolyzing glycinin component on the HIU treatment of soy protein. The effects of HIU on DGH and a control SPI (CSPI) were both time-dependent. HIU induced the formation of soluble aggregates in both samples at an early stage, while it dissociated these newly formed aggregates after a longer duration. Selectively hydrolyzing glycinin contributed to the soluble aggregation by exposing the compact protein structure and producing small protein fractions. The larger extent of hydrophobic interactions and disulfide bonds imparted a higher stability to the soluble protein aggregates formed in DGH. As a result, DGH displayed more ordered secondary structures, a higher solubility, and better gelling properties after the HIU treatment, especially at 20 min. The results of this study will be beneficial to the scientific community as well as industrial application.

Structural and functional modification of food proteins by high power ultrasound and its application in meat processing

In the field of agricultural and food processing, high power ultrasound (HPUS) is recognized as a green, physical and non-thermal technology in improving the safety and quality of foods. The functional properties of food proteins are responsible for texture, yield and organoleptic of food products which are the theoretical basis for food processing optimizing. HPUS treatment could provide the possibility for creating novel functional properties of new foods with desirable properties due to the modification of protein structure. In this article, an overview of the previous studies and recent progress of the relationship between structure modification and functional properties of food proteins using the HPUS technique were presented. The research results revealed that HPUS could significantly affect the conformation and structure of protein due to the cavitation effect resulting in the improvement of solubility, interfacial, viscosity, gelation and flavor binding properties of proteins. During meat processing, HPUS can modify the structure and thereby improve the functional properties of myofibrillar protein (MP), leading to the quality enhancement, low fat and/or salt products development and the shelf life extending. In view of this review, the recent findings of applications of HPUS in the production of meat products based on the modification of MP including curing, freezing/thawing and thermal processing have been summarized. Finally, the future considerations were presented in order to facilitate the progress of HPUS in meat industry and provided the suggestions based on the advanced protein modification by HPUS for the commercial utilization of HPUS in producing the innovative meat products.

Ferulic acid-ovalbumin protein nanoparticles: Structure and foaming behavior

Egg white was known for its excellent foaming properties, and some reports had studied the effect of polyphenol such as green tea on the foaming properties. However, ovalbumin, as the most abundant component of egg white protein, few literatures have reported the effects of polyphenols on its structure and foam property. In this study, ferulic acid (FA) was selected to explore the influence of polyphenol on the structure and foaming properties of ovalbumin (OVA). Results showed that hydrophobic interaction and hydrogen chemical bonds were the main driving force. FA could induce a significant decrease of free-SH content (12.76-3.72 μmol/g), a slight decline of surface hydrophobicity (716.39-577.65). Meanwhile, combined with the results of fluorescence spectroscopy and circular dichroism spectroscopy, we conclude that FA changed the structures and molecular flexibility of OVA. The increase of particle size and absolute zeta-potential showed there was a little aggregation between OVA molecules, proved FA could act as a cross-linker between OVA proteins. This behavior makes the adjacent films more firm and stable, therefore improved the foaming properties. This study suggested that FA could be a potential foaming agent to modify the foaming properties of OVA in the foam-related food industry.

Molecular aggregation and property changes of egg yolk low-density lipoprotein induced by ethanol and high-density ultrasound

Solvent and physical treatment are widely used in egg yolk processing, but the detailed changes in the molecular structure of egg yolk proteins during processing are unclear. The aim of this study was to investigate the effects of ethanol and ultrasonic treatments on chicken egg yolk low-density lipoprotein (LDL). The solubility, emulsifying activity and emulsifying stability decreased by 74.75%, 46.91%, and 81.58% after ethanol treatment, respectively. The average particle size of ethanol-treated LDL increased 13.3-fold to 937.85 nm. These results suggested that ethanol treatment induced wide-ranging aggregation of LDL. In contrast to ethanol treatment, ultrasonic treatment promoted the solubility and emulsifying stability of LDL and enhanced its zeta-potential (119.56%) and surface hydrophobicity (10.81%). Based on particle size analysis and transmission electron microscopy, approximately 34.65% of LDL had undergone aggregation and the molecular interface became more flexible after ultrasonic treatment. These results revealed the detailed changes in egg yolk LDL structure and properties during solvent (ethanol) and physical (ultrasound) processing.

Effect of ultrasound on the techno-functional properties of food components/ingredients: A review

Ultrasound (US) has been used in many food systems and model systems, such as starch, whey protein concentrates and soy, to modify their chemical and techno-functional properties. At present, the use of ultrasound has yielded diverse results, ranging from potentiating the technological and functional properties of various foods to different operating conditions. Similarly, the results that were obtained vary according to the ultrasonic equipment used and the power, frequency and times of sonication, as well as the characteristics of the food system used. However, not all results have been favourable because US can cause damage to the structure of some food components, such as starch, and affect the technological and functional properties of the food. In the literature, there is little research on the effect of sonication on fibre; this gap in the literature is worrisome because fibre is found in a wide variety of foods and provides health benefits. Such research would represent an opportunity for researchers to make use of this technology for the generation of knowledge and improve the techno-functional properties in fibre, which could benefit the human population and the food industry. In this review, we present current results obtained with US in different treatments affecting processes of strong importance in the food industry, emphasizing the effects in the different model systems.

Ultrasound-Assisted Mild Heating Treatment Improves the Emulsifying Properties of 11S Globulins

Ultrasonic technology is often used to modify proteins. Here, we investigated the effects of ultrasound alone or in combination with other heating methods on emulsifying properties and structure of glycinin (11S globulin). Structural alterations were assessed with Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), intrinsic fluorescence spectroscopy, ultraviolet (UV) absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The size distribution and zeta-potential of 11S globulin were evaluated with a particle size analyzer. An SDS-PAGE analysis showed no remarkable changes in the primary structure of 11S globulin. Ultrasound treatment disrupted the 11S globulin aggregates into small particles with uniform size, narrowed their distribution and increased their surface charge density. Fluorescent spectroscopy and second-derivative UV spectroscopy revealed that ultrasound coupled with heating induced partial unfolding of 11S globulin, increasing its flexibility and hydrophobicity. FTIR further showed that the random coil and α-helix contents were higher while β-turn and β-sheet contents were lower in ultrasound combined with heating group compared to the control group. Consequently, the oil-water interface entirely distributed protein and reduced the surface tension. Moreover, ultrasound combined with heating at 60 °C increased the emulsifying activity index and emulsifying stability index of 11S globulins by 6.49-folds and 2.90-folds, respectively. These findings suggest that ultrasound combined with mild heating modifies the emulsification properties of 11S globulin.

Effects of high-intensity ultrasonic (HIU) treatment on the functional properties and assemblage structure of egg yolk

The effects of high-intensity ultrasonic (HIU) treatment on the functional properties of egg yolk were studied in the present work. After HIU treatment, the emulsifying, foaming and gel properties of the egg yolk solution significantly increased, but the foam stability decreased. SDS-PAGE results showed that there was no obvious change in the protein bands of egg yolk, indicating that the yolk proteins did not undergo covalent crosslinking or degradation. HIU treatment enhanced the zeta potential of egg yolk components in solution and increased the free sulfhydryl content of egg yolk proteins. Moreover, the particle size distribution of egg yolk components in solution changed markedly, and these changes demonstrated that HIU treatment caused the aggregation of yolk low-density lipoprotein and the partial dissociation of yolk granules. These results revealed that HIU treatment could change the aggregation of yolk components, which in turn could influence the solution characteristics of egg yolk, finally resulting in changes to the functional properties of egg yolk.

Effects of Ultrasonic-Assisted Extraction on the Physicochemical Properties of Different Walnut Proteins

The effects of ultrasonic-assisted extraction (UAE, 200 W, 20 min) on the yield and physicochemical properties of different walnut proteins (WNPs, including albumin, globulin, and glutelin) were investigated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that UAE could result in protein molecular fragmentation of albumin, but did not affect the major bands of globulin and glutelin. The CD spectra demonstrated that different WNPs obtained by UAE had different changes in their secondary structure. Under UAE, there was an increase in surface hydrophobicity (H₀) of albumin and gluten and no change in the fluorescence intensity, while decreases were observed in the H₀ and fluorescence intensity of globulin; and the contents of total and surface free sulfhydryl in albumin dramatically decreased. UAE reduced the size of the particles and the dimension of the microstructures in albumin and gluten, indicating that ultrasound could unfold protein aggregates. In addition, UAE increased the solubility, emulsifying activity (EA), foaming capacity (FC), and foam stability (FS) of the obtained proteins. The above results indicate that ultrasound extraction is a promising approach to improve the extraction yield and properties of walnut proteins.

Study on structural, rheological and foaming properties of ovalbumin by ultrasound-assisted glycation with xylose

This study was to evaluate the effect of ultrasound-assisted glycation with xylose on the foaming properties, physicochemical and structural characteristics of ovalbumin (OVA). The number of free amino groups in the glycated OVA (sOVA-X) significantly decreased with the increase of treatment time. The results obtained by circular dichroism (CD) and spectrofluorimetric measurements showed that there were slight changes on the subunits and secondary structure of OVA, indicating that the tertiary structure became more flexible and loose after the sonicated glycation treatment. The glycated OVA had higher solubility and foaming properties than the untreated samples. Therefore, ultrasound improved the glycation extent, and the changes in molecular structure were responsible for their different foaming ability and foaming stability. Our study also provided principle knowledge to understand how the viscosity and rheology were related to the foaming properties of OVA glycation by xylose. The results indicated that ultrasound-assisted glycation could be an excellent approach to improve the functional properties of OVA and promote its application in food industry.

Sonochemically modified ovalbumin enhances enantioenrichment of some amino acids

As part of our efforts to develop a new method for chiral resolution of amino acids with sonochemically modified proteins, we present result that indicates how ovalbumin microspheres (OAMS) interact specifically with l-amino acids from a racemate in solution, leaving an excess of d-enantiomer in the permeate solution. Among different amino acids that interacted with the OAMS, tryptophan (Trp) was the most successfully resolved with 65% enantiomeric excess. A control experiment with native ovalbumin in solution did not show any chiral resolution of amino acids. Interestingly, when the OAMS were pretreated with racemic lysine (Lys) solution and then used for resolution of tryptophan the enantiomeric enrichment of d-tryptophan was raised to 98%. This unanticipated positive effect is discussed in terms of the structural correlation between Trp and Lys, which is less apparent in other amino acids such as phenylalanine.

Structural modification of quinoa seed protein isolates (QPIs) by variable time sonification for improving its physicochemical and functional characteristics

High intensity ultrasound treatment (HIUS) by probe method is a novel technique to impart desirable physical, structural and functional characteristics to the native proteins structures. In this concern, effect of HIUS treatment at variable intervals from 5 to 35 min on quinoa seed protein isolates (QPIs) characteristics was analyzed. A typical dynamic rheological characteristic curve of QPIs had been obtained as a result of HIUS treatments at variable time intervals. Higher sonication resulted in the formation of large protein aggregates with higher particle size which increased QPIs turbidity. Temperature and frequency sweep tests had shown dominance of storage modulus over loss modulus, thus described strong gelling behavior of treated QPIs. HIUS treatment reduced particle size of QPIs with improved its flow properties. No splitting of bands had occurred due to sonication, whereas, more intensity of bands of treated QPIs depicted its greater water solubility. HIUS treatment decreased fluorescence intensity of QPIs whereas, no significant changes in Amide-II & III regions of QPIs occurred except decrease in wave number. The effects of HIUS on QIPs isolates had shown completely different response than those of results of quinoa protein extracts. Moreover, the studies conducted on quinoa protein extracts provided detailed information about the effect of HIUS on structural changes and its impact on physicochemical, functional and rheological characteristics.

Dispersible Biopolymer Particles Loaded with Lactase as a Potential Delivery System To Control Lactose Hydrolysis in Milk

To deliver lactase in milk, dispersible capsules were fabricated by anti-solvent precipitation of zein to form a zein-lactase core and a shell of low-methoxyl sugar beet pectin cross-linked by Ca²⁺, involving electrostatic, hydrophobic, hydrogen-bonding, and Ca²⁺-bridging forces. At optimal conditions, an encapsulation efficiency of 93.0% and Z-average diameter of 652.7 nm were observed, and spherical particles smaller than 200 nm were observed in scanning electron microscopy. Contrasting with complete hydrolysis within 1 week by unencapsulated lactase, 50 units/mL encapsulated lactase resulted in 33.1 and 40.0% lactose hydrolysis in whole and skim milk, respectively, after 3 weeks of storage at 4 °C. In separate in vitro digestion assays, 50 units/mL encapsulated lactase resulted in 100% lactose hydrolysis in milk, contrasting with negligible activity by free lactase. These findings suggest the potential of the studied biopolymer particles to incorporate lactase in milk, prevent lactose hydrolysis during storage, and hydrolyze lactose in milk after ingestion.

Effect of different time of ultrasound treatment on physicochemical, thermal, and antioxidant properties of chicken plasma protein

The aim of present study was to investigate the effect of different times (5 min (UCPP-5), 10 min (UCPP-10), 20 min (UCPP-20), and 30 min (UCPP-30)) of ultrasound treatment on physicochemical, thermal, and antioxidant properties of chicken plasma protein (CPP). UCPP-20 had the highest fluorescence intensity and the lowest particle size. However, no major changes in the subunit compositions and the secondary structure of UCPPs were presented in SDS-PAGE and circular dichroism. The surface hydrophobicity and sulfhydryl content of UCPPs increased significantly (P < 0.05) as compared to those of CPP. With the increasing time of ultrasound treatment, there were more and deeper holes on the protein surfaces. Furthermore, protein modification by ultrasound could improve the thermal properties of UCPPs. Additionally, UCPPs showed a significant increase in antioxidant properties over CPP, especially UCPP-20. These observations indicated that ultrasound treatment was necessary for modification of CPP to meet the requirements for food processing.

Ultrasonic nano-emulsification - A review

The emulsions with nano-sized dispersed phase is called nanoemulsions having a wide variety of applications ranging from food, dairy, pharmaceutics to paint and oil industries. As one of the high energy consumer methods, ultrasonic emulsification (UE) are being utilized in many processes providing unique benefits and advantages. In the present review, ultrasonic nano-emulsification is critically reviewed and assessed by focusing on the main parameters such pre-emulsion processes, multi-frequency or multi-step irradiations and also surfactant-free parameters. Furthermore, categorizing aposematic data of experimental researches such as frequency, irradiation power and time, oil phase and surfactant concentration and also droplet size and stability duration are analyzed and conceded in tables being beneficial to indicate uncovered fields. It is believed that the UE with optimized parameters and stimulated conditions is a developing method with various advantages.

Structural and Functional Changes in Ultrasonicated Oyster Protein Isolates

Structural and functional changes in ultrasonicated oyster protein isolates (OPI) were investigated. Ultrasound treatments were carried out with probe (20 kHz) at 200, 400 and 600 W for 15 and 30 min. The results showed that functional properties of OPI significantly improved after sonication. Absolute zeta potential and protein solubility increased by 18.40 mV and 82.5 % at 600 W for 15 min. Oil holding capacity, emulsifying activity index, emulsion stability index, foaming ability and foaming stability increased by 300 %, 15.23 m2/g, 9.24 min, 23.9 % and 14.8 % at 600 W for 30 min. However, ultrasound treatment significantly (P < 0.05) decreased particle size and water holding capacity. The conformation of OPI became stretched and unfolded after sonication. Functional improvements resulted from stretched and unfolded conformation and reduction of particle size. Controlled condition of ultrasound can produce OPI with distinct structural and functional properties, which could meet the complex needs of manufactured food products in food industry, but further study is needed to understand the specific mechanism.

Effects of high-intensity ultrasound treatment on functional properties of plum (Pruni domesticae semen) seed protein isolate

BACKGROUND

In order to improve the functional properties of plum seed protein isolate (PSPI), the effects of high-intensity ultrasound (20 kHz) at different levels of power output (200, 400 and 600 W) on the water/oil holding, solubility, emulsifying, foaming, gel, film formation capacity and hydrolysis degrees of PSPI were investigated.

RESULTS

Compared with untreated PSPI, ultrasound treatment improved water holding capacity, solubility, emulsifying properties, foaming capacity of PSPI. The gel prepared from ultrasound treated PSPI showed the higher gel strength compared with untreated protein. The film prepared from ultrasound treated PSPI showed higher tensile strength, lower elongation and permeability, denser and more compact microstructure compared with untreated protein. Ultrasonic treatment also improved the accessibility of PSPI to the protease (Alcalase, Trypsin, Neutrase, Protamex, Papain and Flavourzyme). Furthermore, the ultrasonic treatment could induce a decrease in particle size and relative fluorescence intensity, an increase in surface hydrophobicity, and changes in secondary structure and microstructure of PSPI.

CONCLUSION

The changes in structure analysis of PSPI indicated that ultrasound treatment could induce molecular unfolding of protein, which might be helpful for improving the functional properties and efficiency of enzymatic hydrolysis. © 2018 Society of Chemical Industry.

Aggregation and conformational changes of silver carp myosin as affected by the ultrasound-calcium combination system

BACKGROUND

Ultrasound and Ca²⁺ have been used separately to increase myosin properties in fish processing. However, little is know about how myosin changes are affected by Ca²⁺ and ultrasound in combination. The present study aimed to investigate the effects of the ultrasound-calcium combination system on aggregation and conformational changes of silver carp myosin.

RESULTS

Ultrasound facilitated a Ca²⁺ -induced increase in turbidity. As the Ca²⁺ concentration increased from 0 to 100 mmol L^-1 , there was an obvious increase in the turbidity, solubility and mean hydrated particle size of myosin after ultrasound treatment compared to without treatment. Moreover, changes of total and reactive SH contents depended on the ultrasound-calcium combination conditions. Under this combination system, myosin surface hydrophobicity significantly increased for the synergistic effect of ultrasound and Ca²⁺ . Furthermore, the ultrasound-calcium combination conditions could affect myosin gelation, with better gelation properties being observed for myosin treated with a combination of 60 mmol L^-1 Ca²⁺ and 9 min of ultrasound.

CONCLUSION

The combination system reported in the present study was beneficial for myosin unfolding, facilitating intermolecular interactions between Ca²⁺ and myosin. Ultrasound treatment promoted myosin aggregation via the induction of Ca²⁺ and reduced the critical concentration of Ca²⁺ required to aggregate myosin. In the fish processing industry, this combination system can enhance the gelation properties of surimi-based products. © 2018 Society of Chemical Industry.

Bulk, Foam, and Interfacial Properties of Tannic Acid/Sodium Caseinate Nanocomplexes

For this work, the aim was to investigate the adsorption of the tannic acid (TA)/sodium caseinate (SC) nanocomplexes at the air/water interface and then to research its relationship with foam properties. First, nanocomplexes were prepared in a different mass ratio of TA and SC. The bulk behavior of nanocomplexes was evaluated by dynamic light scattering (DLS), signal-intensifying fluorescence probe (ANS), etc. As the concentration of TA increased, the z-average siameter ( D _z) of TA/SC nanocomplexes decreased gradually and the negative charge increased. Meanwhile, the surface hydrophobicity ( S_o) of the SC also decreased after the addition of TA. The interfacial properties were determined by dynamic surface tension and dilational rheology. The presence of polyphenols decreased the surface pressure (π) that resulted in poor foamability. However, the elastic ( E_d) component of the dilational modulus of films also increased as polyphenols concentration increased, which gave rise to admirable foam stability. The contribution of polyphenols to stabilize foam columns may be caused by interfacial interaction between proteins and polyphenols.

Effect of high intensity ultrasound on structure and foaming properties of pea protein isolate

The effects of high intensity ultrasound (HIUS, 20 kHz, at varying amplitude 30%, 60%, 90% for 30 min) on structure and foaming properties of pea protein isolate (PPI) were investigated. No significant change was observed from the electrophoresis profiles and circular dichroism (CD) spectrum. Analyses of fluorescence spectroscopy and the amount of free sulfhydryl groups showed that HIUS induced protein molecular partial unfolding. Furthermore, HIUS decreased particle size of PPI and increased exposed hydrophobicity, resulting in a reduction of the surface tension at the air-water interface. Therefore, the foaming ability of PPI increased from 145.6% to 200.0%. The foaming stability increased from 58.0% to 73.3% with the increasing amplitude after 10 min though all reduced to 50.0% with the extension of time. That suggested that HIUS treatment has a potential to be implemented to modify foaming properties of PPI.

Effects of thermal sterilization on soy protein isolate/polyphenol complexes: Aspects of structure, in vitro digestibility and antioxidant activity

The main purpose of this work was to investigate the influence of typical thermal sterilization approaches (pasteurization, high-temperature sterilization) on the structure, in vitro digestibility, and antioxidant activity of soy protein isolate (SPI)/black soybean seed coat extract (BE) complexes at pH 7.0. The results of zeta potential and particle size demonstrated that the addition of BE was contributed to inhibit protein thermal aggregation. Heat sterilization resulted in protein unfolding revealed by UV-Vis, circular dichroism, and fluorescence spectroscopy analysis. The increase of BE led to the reduction of fluorescence intensity and surface hydrophobicity of SPI. Moreover, the formation of SPI/BE complexes inhibited protein digestion in vitro, while thermal sterilization promoted protein digestion. The SPI/BE complexes showed a strong radical scavenging ability both before and after thermal treatment.

High intensity ultrasound treatment of faba bean (Vicia faba L.) protein: Effect on surface properties, foaming ability and structural changes

Response surface methodology was used for establishing the amplitude (72.67%) and time (17.29 min) high-intensity ultrasound (HIUS) conditions leading to an optimized faba bean protein isolate (OFPI) with lower interfacial tension, zeta potential and viscosity, and higher solubility than native faba bean protein isolate (NFPI). OFPI showed significantly higher adsorption dynamics at the air-water interface, and produced foam with significant smaller bubble diameter, higher overrun, stability and yield stress, and lower liquid drainage than NFPI. Fourier Transform Spectroscopy (FT-IR) revealed that the secondary structure of OFPI deferred from NFPI in terms of increases in β conformations (6.61% β-sheet, 19.6% β-turn, 0.8% anti-parallel β-sheet) and decreases in inter-molecular aggregates (43.54%). Multienzyme study pinpointed that the structural changes could have induced a decrease on the relative protein digestibility of OFPI respect that of NFPI. The results of this work demonstrate that HIUS technology improves the surface and foaming properties of faba bean protein isolate, which may favour the revalorisation of this crop.