Ultrasound heat treatment effects on structure and acid-induced cold set gel properties of soybean protein isolate

Structural, physicochemical and digestive properties of non-covalent and covalent complexes of ultrasound treated soybean protein isolate with soybean isoflavone

The non-covalent and covalent complexes of ultrasound treated soybean protein isolate (SPI) and soybean isoflavone (SI) were prepared, and the structure, physicochemical properties and in vitro digestion characteristics of SPI-SI complexes were investigated. Ultrasonic treatment increased the non-covalent and covalent binding degree of SPI with SI, and the 240 W ultrasonic covalent complexes had higher binding efficiency. Appropriate ultrasonic treatment caused more uniform particle size distribution, lower average particle size and higher surface charge, which enhanced the free sulfhydryl groups and surface hydrophobicity, thus improving the stability, solubility and emulsifying properties of complexes. Ultrasonic treatment resulted in more disordered secondary structure, tighter tertiary conformation, higher thermal stability and stronger SPI-SI covalent interactions of complexes. These structural modifications of particles had important effects on the chemical stability and gastrointestinal digestion fate of SI. The ultrasonic covalent complexation had a greater resistance to heat-induced chemical degradation of SI and improved its chemical stability. Furthermore, the 240 W ultrasonic covalent complexes showed lower protein digestibility during digestion, and provided stronger protection for SI, which improved the digestion stability and antioxidant activity. Therefore, appropriate ultrasound promoted SPI-SI interactions to improve the stability and functional properties of complexes, which provided a theoretical basis for the development of new complexes and their applications in functional foods.

Soy protein isolate ameliorate gel properties by regulating the non-covalent interaction between epigallocatechin-3-gallate and myofibrillar protein

This study primarily investigated the improvement of high-dose Epigallocatechin-3-Gallate (EGCG)-induced deterioration of MP gel by soy protein isolate (SPI) addition. The results showed that EGCG could interact with MP, SPI, and HSPI (heated), indicating the competitive ability of SPI/HSPI against EGCG with MP. EGCG was encapsulated by SPI/HSPI with high encapsulation efficiency and antioxidation, with antioxidant activities of 78.5% ∼ 79.2%. FTIR and molecular docking results revealed that MP, SPI, and HSPI interacted with EGCG through hydrogen bonding and hydrophobic interactions. SPI/HSPI competed with MP for EGCG, leading to the restoration of MHC and Actin bands, alleviating the aggregation caused by EGCG and oxidation. Additionally, SPI/HSPI-E significantly reduced the high cooking loss (23.71 and 26.65%) and gel strength (13.60 and 17.02%) induced by EGCG. Hence, SPI competed with MP for EGCG binding site to ameliorate MP gel properties, thereby alleviating the detrimental changes in MP caused by high-dose EGCG and oxidation.

Analyzing changes in volatile flavor compounds of soy protein isolate during ultrasonic-thermal synergistic treatments using electronic nose and HS-SPME-GC-MS combined with chemometrics

The beany flavor of soy protein isolate (SPI) creates barriers to their application in food processing. This study investigated the effect of ultrasonic-thermal synergistic treatments, combined with vacuum degassing, on the removal of volatile compounds from SPI. The results revealed that ultrasonic-thermal synergistic treatments altered protein secondary structure and increased fluorescence intensity and surface hydrophobicity, which affected the flavor-binding ability of protein, resulting in reduced electronic nose sensor response values. At synergistic treatment (350 W, 120 ℃ and 150 s), the content of hexanal, (E)-2-hexenal, and 1-octen-3-ol reduced by 70.60 %, 95.60 % and 61.23 %. (E)-2-nonenal and 2-pentylfuran were not detected. Chemometric analysis indicated significant flavor differences between control and treated SPI. Furthermore, α-helix, β-sheet, β-turn, and surface hydrophobicity highly correlated with volatile compounds through correlation analysis, indicating that altered protein structure affected interactions with volatile compounds. The study reduced beany flavor and further expanded the range of applications of plant protein in food industry.

Influence of substrate aggregation state on the enzymatic-induced crosslinking of soy protein isolate

Transglutaminase (TGase) induced-crosslinking of soy protein isolate (SPI) was markedly influenced by the substrate aggregation state. Results showed that appropriate heating significantly accelerated the TGase crosslinking, and the 7S and 11S acidic subunits were more susceptible to the enzyme than the 11S basic proteins. The content of ε-(γ-glutamyl)-lysine isopeptide bonds increased from 4.74 to 8.61 μmol/g protein when the heating intensity was increased from 75 °C for 15 min to 95 °C for 30 min, due to sufficient unfolding of the protein structure. Rheological data indicated that the gel formed from the SPI heated at 95 °C for 30 min exhibited the best properties, with a 60 % increase in the storage modulus compared with the unheated sample. However, excessive heating (95 °C, 60-120 min) caused severe aggregation of SPI and formation of insoluble aggregates, resulting in poor crosslinking efficiency and weaker gel properties.

Lentil protein isolate (Lens culinaris) subjected to ultrasound treatment combined or not with heat-treatment: structural characterization and ability to stabilize high internal phase emulsions

This study evaluated the effect of ultrasound treatment combined or not with heat treatment applied to lentil protein isolate (LPI) aiming to enhance its ability to stabilize high internal phase emulsions (HIPE). LPI dispersion (2%, w/w) was ultrasound-treated at 60% (UA) and 70% (UB) amplitude for 7 min; these samples were subjected to and then heat treatments at 70 °C (UAT70 and UBT70, respectively) or 80 °C (UAT80 and UBT80, respectively) for 20 min. HIPEs were produced with 25% untreated and treated LPI dispersions and 75% soybean oil using a rotor-stator (15,500 rpm/1 min). The LPI dispersions were evaluated for particle size, solubility, differential scanning calorimetry, electrophoresis, secondary structure estimation (circular dichroism and FT-IR), intrinsic fluorescence, surface hydrophobicity, and free sulfhydryl groups content. The HIPEs were evaluated for droplet size, morphology, rheology, centrifugal stability, and the Turbiscan test. Ultrasound treatment decreased LPI dispersions' particle size (∼80%) and increased solubility (∼90%). Intrinsic fluorescence and surface hydrophobicity confirmed LPI modification due to the exposure to hydrophobic patches. The combination of ultrasound and heat treatments resulted in a reduction in the free sulfhydryl group content of LPI. HIPEs produced with ultrasound-heat-treated LPI had a lower droplet size distribution mode, greater oil retention values in the HIPE structure (> 98%), lower Turbiscan stability index (< 2), and a firmer and more homogeneous appearance compared to HIPE produced with untreated LPI, indicating higher stability for the HIPEs stabilized by treated LPI. Therefore, combining ultrasound and heat treatments could be an effective method for the functional modification of lentil proteins, allowing their application as HIPE emulsifiers.

Enhancing the Gelation Behavior of Transglutaminase-Induced Soy Protein Isolate(SPI) through Ultrasound-Assisted Extraction

Gelation, as an important functional property of soy protein isolate (SPI), can be improved by some green technologies in food manufacturing, including ultrasound, ultrahigh pressure and microwave treatments. This work investigated the effect of an alkaline solubilisation step in SPI extraction combined with sonication on protein properties. The TGase-induced gel of the modified SPI was prepared to explore the effect of ultrasound on gel properties, including structures, strength, water-holding capacity and rheological properties. Additionally, the differences between traditional ultrasound modification of SPI and current modification methods were analyzed. The results showed that the ultrasonication-assisted extraction method could result in a significant increase in extraction rate from 24.68% to 42.25%. Moreover, ultrasound-assisted modification of SPI gels induced with transglutaminase (TGase) exhibited significant improvement in mechanical properties, such as texture, water-holding capacity and rheological properties, In particular, SPI extracted at 400 W ultrasound intensity for 180 s showed the best overall performance in terms of gel properties. Our method efficiently uniformizes gel structure, enhancing mechanical properties compared to conventional ultrasound methods, which reduced energy consumption and costs. These findings provide insights into the production of high-gelation SPI in food manufacturing.

Effects of ultrasonic treatment on the structural, functional properties and beany flavor of soy protein isolate: Comparison with traditional thermal treatment

This research explored the influences of ultrasonic and thermal treatments on the structure, functional properties, and beany flavor of soy protein isolate (SPI). In comparison with traditional thermal treatment, ultrasonic treatment effectively induced protein structural unfolding and exposure of hydrophobic groups, which reduced relative content of α-helix, increased relative content of β-turn, β-sheet and random coil, and improved the solubility, emulsifying and foaming properties of SPI. Both treatments significantly decreased the species and contents of flavor compounds, such as hexanal, (E)-2-nonenal, (Z)-2-heptenal and (E)-2-hexenal in SPI. The relative content of hexanal in the major beany flavor compound decreased from 11.69% to 6.13% and 5.99% at 350 W ultrasonic power and 150 s thermal treatment procedure, respectively. After ultrasonic treatment, structural changes in SPI were significantly correlated with functional properties but showed a weak correlation with flavor. Conversely, the opposite trend was observed for thermal treatment. Thus, using ultrasonic treatment to induce and stabilise the denatured state of proteins is feasible to improve the functional properties and beany flavor of SPI.

Effect of soy peptides with different hydrolysis degrees on the rheological, tribological, and textural properties of soy protein isolate gels

This study was performed to examine the effect of two soy peptides addition with hydrolysis degrees of 90% and 30% (hydrolysis degree (DH)90, DH30) at various concentrations (1-10 mg/mL) on soy protein isolate (SPI) gel behavior and pure SPI gel was set as control. SPI gels with adding peptides were prepared, and their rheological, textural, and tribological properties, as well as water-holding capacity, zeta potential, and particle size, were determined. During the rheological measurement, adding peptides reduced storage modulus (G') compared to the control, with larger particles formed. However, peptide addition could significantly reduce gelation time, showing a more significant effect with DH30. The gels' firmness, adhesiveness, and water-holding capacity decreased as peptide concentration increased. Syneresis was observed in gels with peptides, whereas the control sample showed no syneresis. Based on the rheological results, the shear stress in the control sample was higher than in the gels containing peptides indicating more resistance to shear. The gels with DH30 showed greater G' and G″ than DH90 at all studied concentrations. Nevertheless, there was an improvement in the lubrication behavior of SPI gels with peptide addition. DH30 showed a relatively more significant friction reduction than DH90, indicating their slightly better lubrication properties.

Flexible processing technology of coix seed prolamins by combined heat-ultrasound: Effects on their enzymatic hydrolysis characteristics and the hypoglycemic activities of derived peptides

The self-assembled structures of coix seeds affected the enzymatic efficiency and doesn't facilitate the release of more active peptides. The influence of heating combined with ultrasound pretreatment (HT + US) on the structure, enzymatic properties and hydrolysates (CHPs) of coix seed prolamin was investigated. Results showed that the structural of coix seed prolamins has changed after HT + US, including increased surface hydrophobicity, reduced α-helix and random coil content, and a decrease in particle size. So that, leads to changes in thermodynamic parameters such as an increase in the reaction rate constant and a decrease in activation energy, enthalpy and enthalpy. The fractions of <1000 Da, degree of hydrolysis and α-glucosidase inhibitory were increased in the HT + US group compared to single pretreatment by 0.68%-17.34%, 12.69%-34.43% and 30.00%-53.46%. The peptide content and α-glucosidase inhibitory activity of CHPs could be maintained at 72.21 % and 57.97 % of the initial raw materials after in vitro digestion. Thus, the findings indicate that HT + US provides a feasible and efficient approach to can effectively enhance the enzymatic hydrolysis efficiency and hypoglycaemic efficacy of CHPs.

Effect of High-Intensity Ultrasound Pretreatment on the Properties of the Transglutaminase (TGase)-Induced β-Conglycinin (7S) Gel

In this study, we investigated the effects of different high-intensity ultrasound (HIU) pretreatment times (0-60 min) on the structure of β-conglycinin (7S) and the structural and functional properties of 7S gels induced by transglutaminase (TGase). Analysis of 7S conformation revealed that 30 min HIU pretreatment significantly induced the unfolding of the 7S structure, with the smallest particle size (97.59 nm), the highest surface hydrophobicity (51.42), and the lowering and raising of the content of the α-helix and β-sheet, respectively. Gel solubility showed that HIU facilitated the formation of ε-(γ-glutamyl)lysine isopeptide bonds, which maintain the stability and integrity of the gel network. The SEM revealed that the three-dimensional network structure of the gel at 30 min exhibited filamentous and homogeneous properties. Among them, the gel strength and water-holding capacity were approximately 1.54 and 1.23 times higher than those of the untreated 7S gels, respectively. The 7S gel obtained the highest thermal denaturation temperature (89.39 °C), G', and G″, and the lowest tan δ. Correlation analysis demonstrated that the gel functional properties were negatively correlated with particle size and the α-helix, while positively with Ho and β-sheet. By contrast, gels without sonication or with excessive pretreatment showed a large pore size and inhomogeneous gel network, and poor properties. These results will provide a theoretical basis for the optimization of HIU pretreatment conditions during TGase-induced 7S gel formation, to improve gelling properties.

Multi-dimensional analysis of heat-induced soybean protein hydrolysate gels subjected to ultrasound-assisted pH pretreatment

This study aimed to evaluate the gelation characteristics of soybean protein hydrolysate (SPH) extracted by enzyme-assisted aqueous extraction. Specifically, the changes in gelation behaviors for heat-induced (95 °C, 20 min) SPH dispersions treated with pH (pH 3, 5, 9; pH 7 as control) and ultrasound (U; 240 W, 30 min) were investigated. The results showed that typical gel behavior with high elastic nature in the viscoelasticity and network structures were observed during the heating process, where the disulfide bond played a dominant role in the gel network formation of all the samples. Notably, the heat-induced aggregation in the SPH gels was mainly formed by the association of the basic B polypeptide in 11S and β subunit in 7S. The most superior SPH gel was formed at pH 7 when assisted by ultrasonication during the heating process. This as-synthesized gel showed a uniform filamentous structure and exhibited the more excellent textural, rheological and thermal properties than those of the samples formed under acidic and alkaline conditions. These results are of great value in revealing the gelation mechanism of SPH.

Interactions of soy protein isolate with common and waxy corn starches and their effects on acid-induced cold gelation properties of complexes

Soy protein isolate (SPI) was mixed with different concentrations of common starch (CS) and waxy starch (WS) from corn. The interactions of SPI with CS or WS and their effects on the acid-induced cold gelation properties of complexes were investigated. Compared with WS, SPI could bind to CS more strongly and formed a tighter SPI-CS non-covalent complex, which resulted in the increased β-sheet and a more ordered secondary structure. The gel strength, water holding capacity (WHC), viscoelasticity, hydrophobic interactions and thermal stability of SPI-CS complex gels were enhanced as increasing CS concentration, and the complex with 2% of CS had the best gelation properties. Although adding WS reduced the gel strength, rheological properties and hydrophobic interactions of SPI-WS complex gels, it improved the WHC and thermal stability of the complex gels. Therefore, CS had a broader effect on improving acid-induced cold gelation properties of SPI than WS.

Study on the Structure, Function, and Interface Characteristics of Soybean Protein Isolate by Industrial Phosphorylation

The impacts of industrial phosphorylation on the structural changes, microstructure, functional, and rheological features of soybean protein isolate (SPI) were spotlighted. The findings implied that the spatial structure and functional features of the SPI changed significantly after treatment with the two phosphates. Sodium hexametaphosphate (SHMP) promoted aggregation of SPI with a larger particle size; sodium tripolyphosphate (STP) modified SPI with smaller particle size. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) results showed insignificant alterations in the structure of SPI subunits. Fourier transform infrared (FTIR) and endogenous fluorescence noted a decline in α-helix quantity, an amplification in β-fold quantity, and an increase in protein stretching and disorder, indicating that phosphorylation treatment fluctuated the spatial structure of the SPI. Functional characterization studies showed that the solubility and emulsion properties of the SPI increased to varying degrees after phosphorylation, with a maximum solubility of 94.64% for SHMP-SPI and 97.09% for STP-SPI. Emulsifying activity index (EAI) and emulsifying steadiness index (ESI) results for STP-SPI were better than those for SHMP-SPI. Rheological results showed that the modulus of G' and G″ increased and the emulsion exhibited significant elastic behavior. This affords a theoretical core for expanding the industrial production applications of soybean isolates in the food and various industries.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

BACKGROUND

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g^-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels.

RESULTS

When κ-carrageenan concentration increased from 0 to 1.5 and 3 mg.g^-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g^-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5 mg g^-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g^-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon.

CONCLUSION

Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Walnut Protein Isolate-κ-Carrageenan Composite Gels Improved with Synergetic Ultrasound-Transglutaminase: Gelation Properties and Structure

Walnut protein is a kind of natural, high-quality plant protein resource. However, its high content of gluten, strong hydrophobicity and poor gelation ability have greatly limited its development and utilization in gel products. It was found in this experiment that ultrasonic power combined with transglutaminase (TGase) had a significant effect on the gel properties of the walnut protein isolate (WNPI)-κ-carrageenan (KC) complex. The results showed that the gel strength of the WNPI-KC complex first increased and then decreased with the increase in ultrasonic power (0-400 W). WNPI-KC composite gel had the best texture properties, rheological properties, water-holding capacity (99.41 ± 0.76%), swelling ratio (2.31 ± 0.29%) and thermal stability (83.22 °C) following 200 W ultrasonic pretreatment. At this time, the gel network was more uniform and much denser, and the water molecules were more tightly bound. Further, 200 W ultrasonic pretreatment could promote the transformation of α-helices to β-folds in protein molecules, improve the fluorescence intensity, increase the content of free sulfhydryl groups and enhance the intermolecular forces. The experimental results could provide technical support for the development of walnut protein gel food.

Ultrasound improves the physicochemical and foam properties of whey protein microgel

Whey protein microgel (WPM) is an emerging multifunctional protein particle and methods to improve its functional properties are continuously being explored. We developed a method to prepare WPM by heat-induced self-assembly under different ultrasound power (160, 320, 480, and 640 W/cm²) and characterized the particle size, surface hydrophobicity, disulfide bond, viscosity, and foam properties of WPM. Ultrasound increased the particle size of WPM-160 W to 31 μm. However, the increase in ultrasound power gradually reduced the average particle size of samples. The intrinsic fluorescence spectrum showed that ultrasound unfolded the structure of whey protein and exposed more hydrophobic groups, which increased the surface hydrophobicity of WPM. In addition, infrared spectroscopy suggested ultrasound decreased the α-helix content of WPM, implying an increase in the flexibility of protein molecules. The disulfide bond of WPM was broken by ultrasound, and the content of the-SH group increased correspondingly. The rheology indicated that the apparent viscosity decreased with the increase of ultrasonic power. Compared with the control, the ultrasonicated WPM displayed higher foam ability. Ultrasound improved the foam stability of WPM-160 W but destroyed the foam stability of other samples. These results suggest that proper ultrasound treatment can improve the physicochemical and foam properties of WPM.

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.

Recent advances in essential oil complex coacervation by efficient physical field technology: A review of enhancing efficient and quality attributes

Although complex coacervation could improve the water solubility, thermal stability, bioavailability, antioxidant activity and antibacterial activity of essential oils (EOs). However, some wall materials (such as proteins and polysaccharides) with water solubility and hydrophobic nature limited their application in complex coacervation. In order to improve the properties of EO complex coacervates, some efficient physical field technology was proposed. This paper summarizes the application and functional properties of EOs in complex coacervates, formation and controlled-release mechanism, as well as functions of EO complex coacervates. In particular, efficient physical field technology as innovative technology, such as high pressure, ultrasound, cold plasma, pulsed electric fields, electrohydrodynamic atomization and microwave technology improved efficient and quality attributes of EO complex coacervates are reviewed. The physical fields could modify the gelling, structural, textural, emulsifying, rheological properties, solubility of wall material (proteins and polysaccharides), which improve the properties of EO complex coacervates. Overall, EOs complex coacervates possess great potential to be used in the food industry, including high bioavailability, excellent antioxidant capacity and gut microbiota in vivo, masking the sensation of off-taste or flavor, favorable antimicrobial capacity.

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.

Effect of Hydrothermal Treatment on the Structure and Functional Properties of Quinoa Protein Isolate

The aim of this study was to investigate the effects of hydrothermal treatment at different temperatures and times on the structure and functional properties of quinoa protein isolate (QPI). The structure of QPI was investigated by analyzing changes in the intrinsic fluorescence spectrum, ultra-violet (UV) spectrum, and Fourier transform infrared spectrum. The solubility, water/oil-holding capacity, emulsifying activity, and emulsion stability of QPI were studied, as were the particle size and the thermogravimetric properties of QPI. The results showed that the average particle size of QPI gradually increased with the increase in hydrothermal treatment time and temperature, and reached a maximum value of 121 °C for 30 min. The surface morphology also became rough and its thermal stability also increased. The endogenous fluorescence and UV spectral intensity at 280 nm decreased gradually with increasing hydrothermal treatment time and temperature, and reduced to the minimum values at 121 °C for 30 min, respectively. After hydrothermal treatment, the secondary structure of QPI tended to be disordered. The functional properties of QPI after treatment were all superior to those of the control. The results of this study might provide a basis for the processing and utilization of QPI.

Gelling properties of black soldier fly (Hermetia illucens) larvae protein after ultrasound treatment

H. illucens, black soldier fly larvae (BSFL) is one of the sustainable sources of protein. However, the research on the functionality of BSFL proteins is limited and need to be explored to increase consumer acceptance. The aim of this study is to create a gel system from BSFL protein and evaluate the impact of ultrasound treatment at different exposure time (5, 15, 30 min) on the physicochemical properties of BSFL protein. The highest values for surface hydrophobicity, size, ζ-potential were obtained after 15 min of ultrasound treatment and the same was found for the elastic modulus. Finally, confocal laser scanning microscopy (CLSM) along with image analysis revealed the lowest pore size after 15 min of treatment. The high protein content of BSFL protein extract and its promising gel system herein created, are important features to be considered for further development of insect-based food.

Fabrication of agarose/fish gelatin double-network hydrogels with high strength and toughness for the development of artificial beef tendons

Agarose/fish gelatin (AR/FGA) double-network hydrogels (DNs) were fabricated via a one-step heating-cooling method. The structure, mechanical and textural properties, water-holding capacity, swelling behavior and sensory characteristics of the DNs were analyzed and compared with the corresponding single-network hydrogels (SNs) and beef tendons. An increase in FGA concentration (10-40 wt%) significantly enhanced the mechanical strength and toughness of DNs, while a moderate increase in AR concentration (0.5-1.5 wt%) only improved their mechanical strength. The 1.5 wt% AR/40 wt% FGA DNs attained excellent fracture stress and strain compared with the single AR and single FGA gels. This can be attributed to the energy dissipation effect, intermolecular hydrogen bond interactions and higher entanglement density of molecule chains. Furthermore, AR/FGA DNs attained a higher hardness, water holding capacity and lower swelling rate compared with SNs. The principal component analysis and correlation analysis showed that the 1.5 wt% AR/30 wt% FGA DNs displayed the most comparable correlation with beef tendons, which was consistent with the results of the sensory evaluation, showing great potential as artificial beef tendons. Our findings provide guidance for the modulation of gel properties and development of artificial foods.

Gel Property of Soy Protein Emulsion Gel: Impact of Combined Microwave Pretreatment and Covalent Binding of Polyphenols by Alkaline Method

This study investigated the effects of microwave modification, alkali polyphenol (ferulic acid) covalently combined modification, and microwave-alkali polyphenol covalently combined modification on the gel properties of soy protein emulsions. The results showed that the properties of soy protein emulsions were improved significantly by the three modification methods. After three kinds of modification, the viscoelasticity of soy protein emulsion gel increased, and a gel system with stronger elasticity was formed. The texture, water-holding, and hydration properties of the emulsion gel increased significantly. The SEM and ClSM results showed that the modified soy protein emulsion gel had a more compact and uniform porous structure, and the oil droplets could be better embedded in the network structure of the gel. Among the three modification methods, the microwave-alkali method polyphenol covalently combining the compound modification effect was best, and the microwave modification effect was least effective compared to the other two methods. Our obtained results suggested that for gel property modification of soy protein emulsion gels, microwave pretreatment combined with the covalent binding of polyphenols by an alkaline method is an effective method.

Effects of "nine steaming nine sun-drying" on proximate composition, protein structure and volatile compounds of black soybeans

Nine steaming nine sun-drying is a traditional processing technology for food or medicinal materials. The dynamic changes of the proximate composition, protein structure and volatile compounds during nine-time steaming and sun-drying of black soybeans (BS) were studied. The proximate composition results showed that the content of protein, carbohydrate and fat of BS decreased after processing, whereas the relative content of amino acids remained basically unchanged. Protein structure was evaluated using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet absorption spectroscopy (UV) and Fluorescence spectroscopy. FT-IR result revealed that the relative contents of β-sheet and β-turn of the secondary structure of black soybean protein isolate (BSPI) decreased but the relative contents of α-helix and random coil increased after steaming and sun-drying. The results of UV and fluorescence spectroscopy confirmed changes in the protein conformation. In addition, SPME-GCMS analysis demonstrated that hydrocarbons, alcohols and aldehydes were the main volatile compounds. The relative contents of 1-octen-3-ol and hexanal, which are the main sources of beany flavor decreased significantly compared with raw BS. Principal component analysis (PCA) results showed that the volatile compounds of nine steamed and nine sun-dried BS could be well distinguished during the process. These findings may therefore provide a scientific basis for the application of nine-time steamed and sun-dried BS in food industry and contribute to the understanding of process-induced chemical transformations in this ancient processing technique.

Ultrasonic pretreatment improves the gelation properties of low-salt Penaeus vannamei (Litopenaeus vannamei) surimi

The effects of different ultrasonic pretreatments (120-600 W, 20 min; 360 W, 10-30 min) on the gel properties of shrimp surimi were investigated. Gel properties and protein functional properties were analysed to clarify the mechanism of action of ultrasound. The gel strength, water holding capacity and surface hydrophobicity of shrimp surimi gel increased initially and then decreased with the increase in ultrasound power or time, but the change in total sulfhydryl content showed the opposite trend, which indicated that proper ultrasound pretreatment could improve the gel properties of shrimp surimi, expand the protein to a greater extent and expose more SH groups and hydrophobic groups. According to scanning electron microscopy observation, ultrasound made shrimp surimi gel form a denser gel network. Fourier transform infrared analysis indicated that the α-helix content in shrimp surimi gel decreased initially and then increased with the increase of in ultrasound power or time, whereas the change in β-sheet content showed the opposite trend. And the protein was the most stable in 360 W/20 min pretreatment. SDS-PAGE patterns showed that proper ultrasound inhibited the degradation of actin and troponin C. In addition, dynamic rheology illustrated that the G' values of the ultrasonic pretreatment group were higher than that of the control group, indicating that ultrasound could improve the elasticity and stability of shrimp surimi gel. The results suggested that the shrimp surimi gel pretreated by 360 W/20 min ultrasound showed the best gel properties. Furthermore, the correlation between the indexes affecting the properties of the gel was analyzed. This study provides a new technical means to improve the gel properties of shrimp surimi.

Dual-frequency multi-angle ultrasonic processing technology and its real-time monitoring on physicochemical properties of raw soymilk and soybean protein

To improve the soybean protein content (SPC), flavor and quality of soymilk, the effects of dual-frequency ultrasound at different angles (40 + 20 kHz 0°, 40 + 20 kHz 30°, 40 + 20 kHz 45°) on physicochemical properties and soybean protein (SP) structure of raw soymilk were mainly studied and compared with the conventional single-frequency (40 kHz, 20 kHz) ultrasound. Furthermore, the intensity of the ultrasonic field in real-time was monitored via the oscilloscope and spectrum analyzer. The results showed that 40 + 20 kHz 45° treatment significantly increased SPC. The ultrasonic field intensity of 40 + 20 kHz 0° treatment was the largest (8.727 × 104 W/m2) and its distribution was the most uniform. The emulsifying stability of SP reached the peak value (233.80 min), and SP also had the largest particle size and excellent thermal stability. The protein solubility of 40 + 20 kHz 30° treatment attained peak value of 87.09%. 20 kHz treatment significantly affected the flavor of okara. The whiteness and brightness of raw soymilk treated with 40 kHz were the highest and the system was stable. Hence, the action mode of ultrasonic technology can be deeply explored and the feasibility for improving the quality of soymilk can be achieved.